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Explicit and implicit memory

In many situations we need to consciously recall information we have received. For example, if I asked someone where they went for their summer holidays last year, and they could tell me, they would be using explicit memory as they could consciously recall the information wanted. If, on the other hand, asked someone when and where they learned to ride a bicycle, and the steps by which they gained expertise, they would probably find this difficult. They might demonstrate how to ride a bicycle without much trouble, that is they would have implicit memory of this skill, they would remember how to do it even if they were unable to explain it with any great ease or remember when and how they learned the skill. Like procedural memory, implicit memory is usually intact or relatively intact in people with organic memory impairment.

Reference Working Memory Tasks

This design often utilizes mazes with more than eight arms.112627 Typically, at least four of the arms are never rewarded across trials (the reference memory component) while the remaining (often eight) arms are rewarded for initial entries. Thus, within a given session the animal must remember which arms are never baited (reference memory) and those arms which are rewarded but have been previously entered during that session (working memory). Please refer to previous sections regarding these designs and also to the Additional Methodological Issues section below.

Working Memory Procedures

Working memory procedures in the MWM (sometimes referred to as spatial matching to sample procedures) generally involve a two trials day paradigm in which a hidden platform is located in one of four quadrants and randomly relocated on each of several subsequent days of testing. The assumption drawn is that each rat will obtain information regarding the location of the platform on the first trial which will be of benefit for discerning its position on Trial 2. The intertrial interval can be manipulated in order to alter the difficulty of the task.

Working Memory vs Reference Memory

Impairments in RAM performance have been interpreted as deficits in working memory since, it is argued, subjects must retain an updated list of visited and non-visited arms during a given session.2 Variations of the basic procedure have included procedures in which food is never available in certain arms of the maze.112627 In these paradigms, animals learn not to enter these unreinforced maze arms. This invariant aspect of the procedure is interpreted to reflect reference memory. It is sometimes overlooked that in procedures where reinforcement is available in all maze arms, there are aspects of the task that can still be ascribed to reference memory. It should also be recognized that although it is commonly interpreted that working memory is selectively impaired in many conventional RAM paradigms, this is in part due to the relative ease of the working memory component of the task. When the working memory component of a different task (e.g., split-stem T-maze) is made more difficult...

Working memory

'Working memory' is one of the most important and exciting concepts in modern neuroscience, and rightly so. It refers to a cognitive faculty that is essential for mentation and complex behaviour. This faculty subserves much of our ability to interact with the world in a flexible and intelligent manner, and is essential for thought, planning, and language. For example, reading these lines and combining them into a meaningful message, requires working memory. It is doubtful whether without working memory there would have been a Homer, a Shakespeare, a Mozart, or a Newton, and an audience to appreciate them. A mind without working memory is thus expected to be a rather dull place. The idea that there should be a cognitive faculty that 'holds things in mind' temporarily, probably occurred long ago to thoughtful individuals while practising their own working memory. The term 'working mem-ory'itself was introduced by Miller et al. (1960) in referring to a postulated quick-access brain space...

Non Human Primate Models of Distractibility Task Irrelevant Stimuli

The products of selective attention and distractibility were assessed in these studies by exposing animals to additional stimuli during delay intervals, the time at which selective attention and consolidation operate in concert to produce working memory. Thus, presentation of stimuli during delays may best be characterized as disrupting formation of the product of selective attention (i.e., the interaction of these two cognitive processes). It is this product whose characteristics are grouped or consolidated to represent a single salient stimulus, the stimulus that is to be remembered (this process is illustrated in Figure 8.1).

Delayed Matchingto Sample DMTS Task Relevant Stimuli

The DMTS model employed in our laboratory is an adaptation and elaboration of that developed by Bartus and colleagues.21 Regarding the mnemonic functions that may be assessed using this model, some uncertainty likely exists. Clearly, standard DMTS or delayed matching-to-location tasks require the function of working memory, defined as retention of information needed to complete a given task at a given time. A large body of work conducted by Goldman-Rakic and others has identified many of the anatomical and neurochemical underpinnings of working memory12-14 and performance on these tasks is, indeed, altered by manipulation of these systems. However, the distinction between working and other complex forms of memory in completing these tasks is unclear. The complexity of most delayed recall task rules, as well as the extensive baseline training regimen in both rodents22 and non-human primates19,23 implies the involvement of reference memory in completion of each individual task. This is...

Delay Non MatchtoSample Dnmts Procedure

This procedure allows for greater experimental control over the animal's performance in that the set of arms accessible during the pre-delay session are under the control of the experimenter. Therefore, particular response patterns that the animal might use are not beneficial for accurate responding. In addition, this version of the RAM task represents a delayed non-match-to-sample task which can be used to specifically assess working memory processes.

Different Types of Errors in the RAM

In this task, the rat must remember a specific array of cues within an episode to correctly perform the task. The pattern of open and closed arms varies in a random manner from day to day. Therefore, the animal confronts a new working memory problem each day. This repeated acquisition feature promotes the use of within-subjects crossover designs in which a single rat can receive different doses of a given drug and or vehicle and serve as its own control. Furthermore, performance on non-injection days gives an index of proactive and or persistent drug effects on performance. This task maximizes the data obtained from a single rat. The task is sensitive to age-related cognitive impairments9 and to damage to the HPC,19 areas of the temporal cortex23 and to the cholinergic septohippocampal pathway.19

Non MatchtoSample Free Choice

Perhaps the most commonly used RAM paradigm is one in which the animal is free to select any arm, initial arm entries are rewarded, and no delay is imposed between any choices. As detailed elsewhere in this chapter, this paradigm suffers from the potential development of a constant sequence of arm visitation, resulting in the use of reference memory rather than working memory to perform the task. Introducing a forced choice component to this task would make it trial dependent and therefore working memory would be required to perform the task.

Chlordiazepoxide Modulation

These studies examined the time-dependence, site-specificity, and potential mechanism of action of CDP. Rats injected with CDP into the medial septum, but not the lateral septum, amygdala, or nucleus basalis, exhibited dose-dependent deficits in DNMTS performance. Furthermore, there was a distinct time-dependent profile with deficits observed when CDP was injected immediately, but not 15, 30, or 45 min after the pre-delay session. Rats injected with CDP immediately after training were able to acquire and use information during the post-delay session, but they were unable to utilize information from the pre-delay session to guide performance. They exhibited a significant decrease in CC and an increase in RE, but no alterations in PE. These rats exhibited impaired memory of the arms entered in the pre-delay session but they could acquire and retain new information during the post-delay session. CDP disrupted working memory (i.e., retrograde amnesia) but did not produce an anterograde...

Cholinergic Modulation

Cholinergic antagonists also impair spatial memory in a wide variety of cognitive paradigms across several species, including humans.15 Systemic and intra-hippo-campal administration of the muscarinic cholinergic antagonist, scopolamine, prior to training impairs working memory performance of rats in the RAM.37,38 Using a RAM paradigm similar to the DNMTS task described above,39 it was found that scopolamine (1) injected prior to training increased the number of RE but not PE and (2) injected immediately prior to testing increased both RE and PE. The effects of pre-training and pre-testing scopolamine are further support for the involvement of cholinergic-dependent processes in the encoding and retrieval of working memory.

Advantages and Disadvantages

The RAM task offers a variety of experimental advantages for the study of cognitive function in rodents. For example, its behavioral substrates and its temporal dynamics are now well characterized. The task assesses working memory and is sensitive to parametric manipulations which vary the demand on memory processes. Furthermore, there is an extensive literature regarding the brain areas and neurotransmitter systems that are critical for its performance. The RAM has been successfully used to study normal cognition in rodents and the changes in Advantages Performance in radial mazes is based on natural foraging behaviors of rats and therefore generalization of results to the behavioral repertoire of the animal may be more accurate than those based on non-natural behaviors. Once animals have been trained to a baseline criterion, the task requirements can be changed for each session, thereby allowing the use of within-subject designs. This reduces the number of animals required for...

Working Reference Memory

The radial-arm maze can be used to distinguish between working memory, defined as memory with changing contents, as opposed to reference memory, defined as memory with fixed contents. The procedure is to leave some arms of the maze without bait. Entries into these arms would be reference memory errors since their status as unbaited arms is unchanging. The task for the animal is to retrieve the baits from the other arms which are baited once at the beginning of the session. Re-entries into these arms are working memory errors since their status has changed from

Operant Analysis of Striatal Lesions Deficits in Cognitive Tasks

It was Rosvold's experimental work in the 1950s that seriously challenged the concept of the striatum as a structure involved purely in motor function. Based on the topographical nature of projections from prefrontal cortex to the caudate nucelus, it was shown that caudate lesions in monkeys produced impairments on the same tasks that were known to be sensitive to frontal lesions.70 In particular, bilateral lesions of the caudate nucelus were seen to impair accuracy on Jacobsen's classic tasks of frontal function designed to assess spatial working memory, such as spatial alternation and delayed response.71-73

Delayed Matching Tasks

The automation of delayed matching procedures represented one such attempt to assess the impact of striatal lesions on working memory. This requires an animal to be presented initially with a sample stimulus, and then after a variable delay, to be presented with a choice between two stimuli, one being the earlier sample and the other novel. Remembrance of the earlier stimulus presentation is then tested by requiring the animal to choose either the initial sample (delayed-matching-to-sample DMTS) or the novel stimulus (Delayed-non-matching-to-sample DNMTS). Correct responses result in the delivery of food rewards, whereas an incorrect response is signalled by time out or some other error signal. The introduction of a variable delay between sample presentation and choice response allows the rate of forgetting to be determined from the plot of decline in choice as the length of the delay interval increases. DMTS was first developed for assessing memory in primates, and required monkeys...

Introduction and Overview

Although the majority of studies dealing with the phenomenon of autoshaping have used a procedure whereby delivery of reinforcers was not contingent upon a specified response, my own laboratory has taken advantage of the automaticity and lack of experimenter-induced bias conveyed by autoshaping and we too have utilized a response-contingent component whereby the subject (normally a rat but we, as others4 have, used autoshaping with chickens as well) is given the opportunity to manipulate its environment (e.g., touching the extended lever, initiating its retraction earlier than programmed to do so noncontingently) leading to the delivery of a reinforcing stimulus (e.g., food) slightly sooner than its delivery in the absence of an operant (lever touch) response. For protocols we generally use, the subject cannot earn more reinforcers during a daily session in which 12 to 30 or more trials are presented and their session lengths cannot be shortened by more than a fraction, thereby most...

Working and Reference Memory

Working memory is involved in temporarily maintaining representations of previously experienced events or episodes, whereas reference memory contributes to the performance of well-learned responses in the presence of an appropriate discriminative stimulus.15 This component theory of memory serves to provide a conceptual framework for interpreting the dissociation in memory processes observed in both humans and animals following damage to the hippocampus (HPC) or its cholinergic innervation. While several nomenclatures have been introduced to describe this behavioral dissociation, the working memory-reference memory distinction is attractive since each of these processes can be operationally defined within given experimental contexts. We will use this terminology throughout this chapter.

Delayed Alternation Tasks

The spatial delayed alternation task (DA) is another task that involves short-term working memory and requires animals to alternate their responding between two spatially distinct locations. Like the DMTP task, it is very sensitive to damage of the mPFC. Indeed, deficits in delayed alternation in Wisconsin boxes (for monkeys) and in T mazes (for rats) were among the defining features of the prefrontal deficit described by Jacobsen in his classic primate studies in the 1930s,89,90 and replicated many times since.21,91,92 Rats similarly exhibit clear deficits in delayed alternation after prefrontal lesions when tested in a T maze.88,93-95

Trimethyltin Neurobehavioral Toxicity and the Learning Performance Distinction

What we had concluded by the end of the 1980s was that doses of TMT that had the greatest effect upon binding of 3H-corticosterone to hippocampal cytosolic receptors interfered most with acquisition of autoshaping with a working memory component (i.e., a reinforcement delay after lever retraction), without apparently affecting acquisition or performance of the same task, in the same chambers, using the same reinforcers, and under the same level of food deprivation but without a substantial working memory component. In other words, such outcomes led us to conclude that moderate doses of TMT (e.g., 3 to 6mg kg) most likely did not interfere with sensorimotor integration, reinforcement efficacy, and basic association processes, but rendered the rats less capable or incapable of learning or performing as control subjects when there was temporal discontiguity between the CS (lever retraction) and the UCS (food pellet delivery). Higher doses of TMT cause a larger lesion (measured by...

Summary and Conclusions

The Morris Water Maze (MWM) equipped with a video tracking system has become a commonly used and well-accepted behavioral task for rodents. It is quite easy to set up in a relatively small laboratory, is comparatively less expensive to operate than many types of behavioral tasks, and is easy to master by research and technical personnel. It utilizes a number of mnemonic processes in rats that are relevant to the study of human learning and memory and disorders thereof. In addition, it is a very versatile paradigm, which can be used to study both spatial and non-spatial (discriminative) learning as well as working memory processes, and offers several means of delineating and dissociating confounding non-mnemonic processes.

Vasopressin and Enhanced Cognition or Arousal

From a physiological and pharmacological viewpoint, it is interesting to note that the des-gly analog, which is virtually devoid of both pressor and endocrine properties, nevertheless enhanced autoshaping in a less ambiguous fashion when used with a 6 s delayed reinforcement variation, compared with a 0 s delay variation,27 which allowed acquisition to proceed at a considerably faster rate (and without a working memory component, which we believe is introduced by the delay of reinforcement). By introducing the delay of reinforcement, we were not only able to more assuredly detect the facilitatory effect of the des-gly vasopressin upon learning and or memorial processes,25 we were starting to realize that superstitious or adventitiously reinforced behaviors directed toward the retracting and retracted lever (mostly as nose-pokes, although observation of rats' behaviors during the reinforcement delays and inter-trial-intervals via closed circuit TV also revealed substantial numbers of...

Response Patterning

In versions of the RAM task that involve a design in which all arms are accessible and rewarded, the subject must visit each arm once to obtain a reward subsequent visits are not rewarded and are scored as errors. Results obtained using this design may be confounded due to the subject not employing a spatial strategy to optimize its search for reward. Subjects may use an algorithmic pattern of arm selections, such as always visiting the immediately neighboring arm to the left thus the subject would not make any errors. (Actually, in our experience, a common strategy used by rats in the RAM is to choose every second arm moving clockwise or anticlockwise until an error i.e., no food reward occurs, then to select the immediately adjacent arm and continue to visit every second arm.) However, the adoption of such an egocentric behavioral strategy resembles what is defined as skill or reference memory and minimizes or eliminates the working memory aspect of the task. These egocentric...


Schematic representation of working memory formation. At each stage of the process, cognitive resources are allotted to attend to both relevant and non-relevant extraneous stimuli and target stimulus encoding can be diminished by increasing the salience of these non-target stimuli.

Bdnmts Free Choice

This task24 is similar to the one that we have used, the DNMTS forced choice. Animals, in a preliminary training phase, have learned the win-shift rule that reentries into an arm are not rewarded during the DNMTS task the animal visits a subset of the total arms (e.g., 4 of 8 arms), and then a delay is interposed (seconds to hours). Subsequently, the animal is permitted to continue selecting arms but is rewarded only for first entries into arms that were not selected in the pre-delay. The difference from the forced choice paradigm described above is that the animal is free to select the arms to visit during the pre-delay portion of the task no barriers or doors are utilized to determine the arm selection for the animal. A problem with this task can occur if an individual animal consistently chooses either the same arms or the same pattern of arms during the pre-delay session. This consistent pattern of choices would suggest that the animal is not using spatial working memory, but...

Figure 122

Although some investigators test working and reference memory on an 8-arm maze with four baited and four unbaited arms, this lessens the sensitivity of the task as the memory demands for the location of four baits is low. We have found that use of a 16-arm maze with 12 baited and 4 unbaited arms provides a useful measure of working vs. reference memory while keeping task demands high. Figure 12.3 shows an example of working and reference memory performance on a 16-arm radial maze with the muscarinic antagonist scopolamine causing a selective impairment in working memory performance.

B HD Symptomatology

Moreover, it has become obvious that HD patients express a profile of neuro-psychological deficits not dissimilar to those seen in patients with prefrontal cortical damage.20 This includes impairments in learning21,22 and working memory,21,23 as well as deficiencies in executive tasks that assess planning and attentional con-trol.14,23,24 A number of psychiatric symptoms are also present in HD, such as depression and anxiety.25

Figure 146

Probable that limbic structures (e.g., the hippocampus, amygdaloid complex, fimbria-fornix) are important for the formation and or use of spatial information or spatial mapping, it should be remembered that time is passing between the insertion of the experimental subject into the start area of the maze and its discovery of the reinforcer (food or platform). If there is a so-called working memory-consolidation dysfunction and the subject cannot bridge the temporal gap between the start area and goal because of a working memory defect, it most probably will be interpreted as a spatial mapping defect. Depending upon the specific experimental question being asked, this may or may not be an important distinction. It was because of this potential confound that we chose to use a procedure (autoshaping in an operant chamber) which did not require as much motoric behaviors as do mazes, and at the same time allowed us to control the magnitude of the temporal gap, and to measure motoric...

Figure 151

A typical session might have a two-second cue period and a five-second delay, although manipulating the cue duration and delay duration will influence the atten-tional and short-term memory components of the task, respectively. Arnsten10 has described a modified version of the delayed response task in which five different delay lengths (arrived at empirically, depending on abilities of individual monkeys) are quasi-randomly distributed over the 30 trials that make up a daily test session. Arnsten has also described a variation of this task that included the introduction of distractors.11 Other variations of the delayed response task have the monkey face a panel containing lighted stimulus response buttons12 (Figure 15.2) or a touch-sensitive computer monitor13 instead of using the WGTA. Non-automated and automated tests each have their relative strengths and weaknesses. In general, monkeys seem to learn tasks quicker when there is interaction with an experimenter rather than...

Figure 172

D) Scope and limitations The bar-pressing task described above is specifically tailored to evaluate procedural memory. This form of memory predominantly engages neuronal circuitry linking the neocortex and the basal ganglia and does not require the participation of the hippocampal formation, which has in fact been shown to interfere with acquisition of the task. Indeed, hippocampal-lesioned animals were shown to display better retention scores than controls when tested 24 hours following a partial acquisition session.17 Similarly, post-training sub-seizure electrical stimulation of the hippocampus was demonstrated to produce a time-dependent enhancement of retention performance, thus suggesting that hippocampal dysfunction actually facilitates procedural memory consolidation processes. Consequently, this bar-pressing task is not pertinent for studies of the hippocampal's role in memory processes. b) Basic procedures We currently use two basic spatial discrimination procedures to...

Figure 176

Navigation task (Spatial reference memory). B. Repeated acquisition task (Spatial working memory). Repeated acquisition task Two days after the reference memory task (acquisition and probe trial tests), we usually perform a 5-day spatial working memory (repeated acquisition) test. Each day the platform is placed in a new location, and mice must find it across four successive trials (10-min inter-trial interval). The apparatus, room setup, and lighting are the same as in the reference memory version of the water maze task. Animals are released from the same starting position in all trials on all days. On each of the 5 days, the platform is relocated to a different point. If an animal does not locate the platform (by chance) on the first trial, it is guided to the platform by the experimenter and allowed to remain there for 15 sec. Animals spend an equal amount of time resting on the platform for all trials followed by an intertrial interval of 10 min in a holding cage. If the animal...

D AF64A Impairment

One of our laboratories initiated a series of studies to determine whether AF64A produced a dissociation of memory in which working memory was compromised and reference memory was spared. In the first set of studies rats were trained in the DNMTS task prior to surgery. After acquisition they were bilaterally injected icv with either CSF or 3.0 nmoles of AF64A and given a 14-day recovery period before being retested. Following recovery, rats were returned to the DNMTS task and tested in 30 sessions with random delays of 0, 0.5, 1, 5, 15, or 30 mins imposed between the fourth and fifth arm choices. Rats injected with vehicle (CSF) exhibited excellent performance at each of the delay intervals (80 to 85 correct). However, the AF64A-injected group was performing at approximately chance levels (50 to 60 ) of accuracy regardless of delay condition. Despite the impairments in the DNMTS task, the AF64A group was able to acquire a reference memory task (i.e., position discrimination) in which...

Pharmacology I Introduction

How are you to know this information about drugs Certainly you have had instruction which presented the basics of anatomy, physiology, and pharmacology. This instruction has given you a sound foundation for learning more in these areas. This subcourse will present instruction in anatomy, physiology, and pharmacology. The material in anatomy and physiology is included to refresh your memory or to give you additional information so you can better understand the pharmacology material.

Disorder of the thinking process

Association psychology indicates that the semantic memory is organized in the form of a network. This means that each representation is linked with a number of other notions, related closely as well as distantly. In rational thinking, a 'determining tendency' (49 guides the flow of ideas in the chosen direction and excludes associations which do not conform with this goal. This procedure can be disturbed in various ways which are commonly grouped together under the heading of 'formal thought disorder'.

The Neuroanatomy and Neuropsychology of Declarative and Nondeclarative Memory

This chapter describes recent studies that illuminate the function of the medial temporal lobe and the relationship between declarative and nondeclarative memory. Three findings will be emphasized 1) the capacity for learning new factual information (semantic memory) is always dependent on the medial temporal lobe 2) remote memory for autobiographical events (episodic memory) is independent of the medial temporal lobe and 3) humans have a robust capacity for habit memory that can operate independently of declarative memory and independently of the medial temporal lobe.

Genes the brain and the mind

It is also becoming clear that the learning experiences and hence memories are not confined to a single set of synapses in a defined brain locus, but as long-term memory is formed, they become widely distributed across several brain regions and therefore become a distributed property of a definite neuronal system. (1,8) It is in this way that a unique individual brain is constructed in continual contact with the environment.

Spared memory for remote autobiographical events following damage to the medial temporal lobe

Earlier studies suggested that remote autobiographical memories were intact after damage to the hippocampal region and surrounding cortex. For example, patient R.B., who had histologically identified lesions restricted to the CA1 field of the hippocampus bilaterally, was as good as controls at recalling autobiographical memories from his earlier life (Zola-Morgan et al. 1986). Similarly, patients L.M. and W.H. were unimpaired when asked to recall remote autobiographical memories (MacKinnon and Squire 1989). These two patients had histologically identified damage to all the CA fields of the hippocampus, as well as damage to the dentate gyrus, the subiculum (W.H. only), and some cell loss in the entorhinal cortex (Rempel-Clower et al. 1996). In these studies, the autobiographical memories were assessed using a 0-3 scoring system. In contrast to these findings, other patients have been described who appear to have difficulty recalling autobiographical episodes from all periods of their...

The Emergence Of Executive Skills

A related problem stems from the finding that executive tasks that do relate strongly to ToM require not only inhibitory skill but also working memory. Tasks that make working memory demands but not inhibitory demands, or that make inhibitory demands but not working memory demands, tend not to relate to ToM (Carlson et al., 2002 Hala et al., 2003). However, while Perner's account explains how ToM might be necessary for the development of inhibitory skill, it is not at all clear how advances in ToM could generate working memory advances.

Proposal 3 Executive Functioning Affects The Emergence Of Theoryofmind Concepts

In addition to influencing the expression of ToM, however, advances in EF might also be critical for the acquisition of ToM concepts themselves (Moses, 2001 Russell, 1996). If so, that would also be a potential explanation for why EF-ToM relations are observed. How could EF play a role in concept acquisition Imagine a creature entirely devoid of executive skills. Such a creature's behavior would be driven by innate tendencies and learned habits, and would largely be at the mercy of external stimuli. A creature of this kind would be captured by whatever was most salient in the current context and would never be able to distance itself from that context in order to reflect on the possibility of alternative perspectives. Intangible, unobservable entities such as mental states would be inaccessible to it. Some degree of inhibitory capacity would thus seem to be necessary to form mental state concepts (and any other abstract concepts for that matter). Working memory would also seem to be...

Neurobiology of learning and memory

It is now clear that the same pathway is used by other organisms mutations in PKA or its subunits disrupt olfactory learning in the fruitfly Drosophila 71) Two forms of CREB have been identified that have complementary effects on olfactory learning in Drosophila, just as they do in Aplysia. The situation in mammals is more complex, but CREB has been identified as a key molecule in learning. Mice with a targeted mutation in the CREB gene have spatial memory deficits. (72) The animals could be conditioned to a tone and could learn to find a hidden platform in a water bath, but both skills were lost after 30 min. In other words, the deficit specifically affected long-term memory. Successful short-term training ruled out motivational sensory or motor deficits as an explanation. The involvement of CREB in long-term memory in molluscs, flies, and mice indicates the existence of an evolutionary conserved pathway that operates in neurones. There seems little doubt that what applies at the...

Ways of understanding memory Length of storage

The working memory model of Baddeley and Hitch subdivides memory into three main types depending both on time-based and conceptual differences. The first system, sensory memory, is a brief and rather literal trace that results from a visual, auditory, or other sensory event, probably lasting no longer than a quarter of a second. This is the system we use to make sense of moving pictures (visual sensory memory) or language (auditory sensory memory). Most people with damage to this system would present with perceptual or language disorders and we would not normally think of them as having memory problems. The second system, working memory, is considered to have two main components or functions. The first of these is short-term or immediate memory, which lasts for several seconds. This period of time can be extended to several minutes if the person is rehearsing or concentrating on the particular information. Unlike sensory memory, information in working memory has already undergone...

Type of information to be remembered

In 1972 Tulving(2) produced an influential paper distinguishing two types of memory semantic and episodic. Semantic memory is memory for our knowledge about the world, for example remembering that Dublin is the capital of Eire, or that a fox has a bushy tail. Semantic memory is also concerned with our knowledge of social A third system that operates differently from either semantic or episodic memory is procedural memory, the system used for learning skills such as riding a bicycle or learning to type. People get better with practice and can demonstrate the skill even though they may not remember how they learned to ride a bicycle or type. JC, a young amnesic patient of mine, successfully learned to type even though he had no conscious recollection of learning. In his words, 'Practical skills developed without me being aware of how this came about. I could do things without being able to explain how'. Procedural memory is typically normal or nearly normal in amnesic patients.

Conditions that give rise to memory problems and typical presentations

Whatever the cause of the organic memory impairment, certain characteristics tend to be seen in survivors. People with a classic amnesic syndrome show an anterograde amnesia, that is they have great difficulty learning and remembering most kinds of new information. Immediate memory, however, is normal when this is assessed by forward digit span or the recency effect in free recall. There is usually a period of retrograde amnesia. This gap or period of retrograde amnesia is very variable in length and may range from a few minutes to decades. Previously acquired semantic knowledge and implicit memory (remembering without awareness or conscious recollection) are typically intact in amnesic subjects. Other cognitive skills, apart from memory, are normal or nearly normal. As the majority of patients with severe memory disorders present with additional cognitive problems such as attention deficits, word-finding problems, or slowed information processing, those with a

Less common manifestations of memory disorders

Despite the typical picture of organic memory impairment described above, other manifestations are possible and are encountered every now and again. Returning for a moment to the working memory model of Baddeley and Hitch( referred to earlier, one can find patients with deficits in the short-term or immediate (that is to say a few seconds) memory system. Baddeley and Hitch subdivide this system into several 'slave' systems that aid the central executive in its role as co-ordinator of temporary storage systems. Two of these slave systems have been studied in detail. One is the phonological loop that utilizes subvocal speech and is involved in many short-term verbal memory tasks. The second system is the visuospatial sketchpad a temporary system used in creating and manipulating visual images. Patients with phonological loop or verbal short-term memory difficulties have been reported, (7) and visuospatial sketchpad or visual short-term memory deficits have also been reported 8.) Wilson...

Chapter References

Autobiographical memory and emotional disorders. In The handbook of emotion and memory. Research and theory (ed. S.A. Christianson), pp. 451-77. Erlbaum, Hillsdale, NJ. 81. Evans, J., Williams, J.M.G., O'Loughlin, S., and Howless, K. (1992). Autobiographical memory and problem solving strategies of parasuicide patients. Psychological Medicine, 22, 399-405. 82. Brittlebank, A.D., Scott, J., Williams, J.M., and Ferrier, I.N. (1993). Autobiographical memory in depression state or trait marker British Journal of Psychiatry, 162, 118-21. 83. Kuyken, W. and Brewin, C.R. (1995). Autobiographical memory functioning in depression and reports of early abuse. Journal of Abnormal Psychology, 104, 585-91. 85. Roediger, H.L. (1990). Implicit memory. Retention without remembering. American Psychologist, 45, 1043-56.

Further Behavioral Tests

Supplied with a piece of food at the beginning of any one trial. The most efficient performance for the rat is to visit each arm only once. This seems a very simple behavioral pattern insofar as these results can be achieved by a rule such as turn sharp left as you come out of each arm . In practice, rats do not solve the task in this way, but tend to choose arms roughly opposite to the one which they have visited before, a behavior that indicates a considerable amount of working memory information (possibly spatial information).

Synapse Specific Protein Synthesis Gene Induction and Synaptic Plasticity

In Lymnaea, the synaptic plasticity-induced formation of long-term memory (LTM) in the intact animals is both transcription and translation dependent38. Interestingly, the locus for this transcription and translation-dependent process is confined to one single neuron termed RPeD1. Ablation of its cell body in the intact animals completely blocks memory formation39. Similarly, long-term facilitation (LTF), which is thought to be the underlying mechanism for LTM in Aplysia, has also been extensively studied and a variety of molecules and underlying mechanisms identified. One of the key issues is to define the precise locus for new protein synthesis during plasticity. For instance, how is a single synaptic connection subjected to modification in a neuron that has multiple synaptic connections To

Mental status examination

Frequently a more detailed neuropsychological test is needed. It should cover the main cognitive domains including memory functions (short- and long-term memory), abstract thinking, judgement, aphasia, apraxia, agnosia, orientation, attention, executive functions, and speed of information processing. (4 58

Serving as a standard or a model

It is anchored in the concepts and measures of information theory, and demonstrates that the brain is an information processing system of limited capacity. Although Miller's intention was not to determine a precise value, his estimate of short-term memory capacity of seven-plus-or-minus-two chunks became almost a mantra (not without challenges e.g. Baddeley 1994). 10. This place is reserved to three papers, each published by an independent research team. These papers promoted what was later to become a most productive chapter in the molecular biology of learning investigation of the role of macromolecular synthesis and growth in consolidation and long-term memory. Taken together, the studies of Flexner et al. (1963), Agranoff and Klinger (1964), and Barondes and Cohen (1966), have demonstrated that inhibition of protein synthesis during or immediately after training prevents the formation of long-term memory, without affecting short-term memory. These...

Distinctions Within Long Term Memory

Although long-term memory was treated as a single type of memory in these early psychological accounts, neuroscientists soon found that memory for different kinds of information could be differentially affected by brain damage. In an attempt to control severe epileptic seizures in a patient designated H.M., William Scoville removed much of his medial temporal lobe.4 The surgery was successful in relieving H.M.'s epilepsy, but left him severely amnesic (Scoville & Milner, 1957). In particular, after the surgery he was not able to learn new information or remember events in his life since the surgery (anterograde amnesia). Moreover, he experienced graded loss of memory for several years of his life preceding the surgery (retrograde amnesia). Nonetheless, H.M.'s short-term memory was unimpaired if not distracted he could retain information for several minutes. One result of the line of research that began with H.M., to which I will return below, was the hypothesis that the hippocampus...

Neuropsychological deficits

Many individuals with a history of chronic excessive alcohol consumption show evidence of moderate impairment in short- and long-term memory, learning, visuoperceptual abstraction, visuospatial organization, the maintenance of cognitive set, and impulse control. (35) This tendency for alcoholics to show proportionally greater visuospatial than language-related impairments suggests that alcohol might have a selective effect on the right hemisphere the so-called 'right hemisphere hypothesis'.(36) However, right hemisphere functions also decline with ageing and the current view is that the functional lateralities of 'alcoholics' and ageing individuals are similar to normal controls.(36)

Neuropsychological aspects

The terms 'short-term' and 'long-term' memory should be abolished from psychiatric discourse, as they cause confusion across disciplines. It is more useful to consider current or recent memory versus remote or autobiographical memory. In addition, 'prospective memory' refers to remembering to do something. Concepts of memory are considered in Ch.a.2t 1 2 5.2,. As described in that chapter, a distinction is generally drawn between so-called 'working memory', which holds information for brief periods (a matter of several seconds) and allocates resources, and secondary memory, which holds different types of information on a permanent or semipermanent basis. Secondary memory, in turn, can be subdivided into an episodic (or 'explicit') component, semantic memory, and implicit memory. Episodic memory refers to incidents or events from a person's past, and is characteristically severely affected in the amnesic syndrome. As mentioned previously, semantic memory refers to a knowledge of facts,...

Mechanistic Decomposition Of Memory Into Component Processesoperations

11 In large part, Kolers construed his process approach as opposed to a structuralist approach in which memory was viewed as involving stored representations, and the mind was populated with different structural components. Kolers and Roediger (1984) stated We will show in some detail that distinctions between mental representation and mental process, between 'symbol' and 'skill,' are of questionable worth for psychology and may indeed actually misrepresent psychological processes (p. 429). Instead of drawing a dichotomy between structuralist and proceduralist accounts, however, it is perhaps more fruitful to construe Kolers' project as recommending a corrective in the symbolic linguistic account of mental representations and recognizing a broader range of mental representations and processes on them. Kolers and Roediger's positive statement of their view, in fact, maintains the distinction between representations and operations, but shifts the focus to operations (skills) We will...

The seahare a marine snail


Because of lack of space, we will not concern ourselves here with the fine details of the Aplysia story, but rather with a few generalizations only. The cellular analysis of Aplysia reflexes has shown that a significant component of the circuit that subserves simple learning could be pinned down to the level of identified neurons and synapses. This analysis was the first to demonstrate the central role of cyclic adenosine monophosphate in memory (Cedar et al. 1972 CREB), and the multiplicity of time- and context-dependent mechanisms of plasticity in a single cell. It has also demonstrated that at least part of the loci that subserve short-term memory also subserve long-term memory. Further, analysis of plasticity in the GSWR has provided much support for the zeitgeist proposal that long-term memory storage relies on modulation of gene expression (Goelet et al. 1986 Martin et al. 1997a,b consolidation, immediate early genes, protein synthesis). It is noteworthy that in recent years,...

Identifying the Operations Performed by Medial Temporal Lobe Structures

One of the intriguing questions that emerged from studies of H.M. and other patients with hippocampal damage is why they experienced graded retrograde amnesia, severely affecting memory for events up to a few years preceding damage. The phenomenon suggested that the hippocampus was not just a gateway to long-term memory but played a more extended role in creating long-term memories, a process referred to as consolidation. Why should the process of laying down long-term memories occur on a timescale of years James McClelland, Bruce McNaughton, and Randall O'Reilly (1995) proposed that the answer had to do with the way in which information is stored in neocortical areas (likely in the other parts of the temporal lobe than the MTL). They proposed that the neocortex works much like a standard feed-forward connectionist network. Although such networks can be trained to perform any task (as long as sufficient hidden units are available), they suffer what is known as catastrophic...

A type of protein that regulates the expression of genes and fulfils a key role in neuronal plasticity

In recent years, multiple lines of evidence have shown that (a) the cAMP cascade is stimulated in learning (e.g. Aplysia, Drosophila), and (b) protein synthesis and modulation of gene expression are required for consolidation. CREB links these two lines of evidence. The first to implicate CREB in neuronal plasticity were Dash et al. (1990), in Aplysia neurons. Subsequent studies in a variety of species have indicated that the involvement of CREB, and CRE-regulated gene expression in general, in neuronal plasticity and memory formation, is possibly universal, and that CREB activation is correlated with, and necessary for, the formation of long-term memory (e.g. Bourtchuladze et al. 1994 Bartch et al. 1995 Yin et al. 1995 Bito et al. 1996 Impey et al. 1996,1998 Guszowski and McGaugh 1997 Lamprecht et al. 1997).2 The experience-dependent balance between the activator and repressor isoforms of CREB may be critical in determining the fate of a memory....

Illnessrelated deficits

Again, the question arises, are these deficits generalized or specific Different studies provide different answers. All show deficits across the board including visual perception, recognition memory, motor skills, language comprehension and expression, episodic memory, and planning. However, some authors point out that some test scores seem to be disproportionately impaired and other relatively spared this gives rise to the claim for specific neuropsychological deficits in schizophrenia. Visual perception, recognition, naming, and procedural or motor learning are relatively spared while executive functions (including tasks of set shifting, ignoring irrelevance, doing more than one thing simultaneously, forward planning) and learning and semantic memory tend to be the functions more obviously affected.

Acondition considered a priori to provide reliable evidence for something else

Does the mechanism suffice for memory formation In practice, this criterion is more difficult to satisfy than the previous ones. It requires mapping candidate loci of the engram. The methodology involves mimicry experiments, resembling those mentioned in 3 above. It is common practice to infer that if event A is both necessary and sufficient for event B to take place, B is caused by A.2 The following examples illustrate the use of this criterion induction of conditioned phototaxis in the mollusc Hermissenda by altering membrane properties of photoreceptors in vivo (Farley et al. 1983) microinfusion of the neurotransmitter octopamine into the brain to show that octopamine encodes the unconditioned stimulus in classical conditioning of the honeybee (Hammer and Menzel 1998) a similar experiment with serotonin and long-term facilitation in Aplysia (Sun and Schacher 1998) switching on gluatamtergic N-methyl-d-aspartate receptors in the mouse in an attempt to prove that this...

Revising Initial Decompositions Of Memory Processes

An important merit of Tulving's HERA model is that it provides a strong set of claims about the operations localized in different brain areas. It is an exemplar of a heuristic identity claim. One of the virtues of advancing such claims is that researchers expand the body of relevant evidence that can be used in assessing the functional decomposition employed in their mechanistic models. In this case cognitive psychologists had long differentiated the operations of encoding and retrieval and, as I have detailed in earlier sections, had phenomenally decomposed memory into different phenomena short-term or working memory and four types of long-term memory procedural, perceptual, semantic, and episodic. HERA is specifically a heuristic identity claim about encoding and retrieval of episodic memory representations. Do these mental activities really rely on distinct mental operations In this section, I will begin by discussing challenges specifically to Tulving's HERA model. The strategy...

Do Episodic and Semantic Memories Rely on Different Systems

Although HERA is presented as advancing a contrast between encoding and retrieval of episodic memory, the encoding studies used to defend HERA require semantic memory retrieval. Hence, the results can be interpreted as supporting an asymmetry between semantic and episodic retrieval, with semantic retrieval being localized to left prefrontal cortex and episodic retrieval to right prefrontal cortex. This distinction between semantic and episodic memory is fundamental to the memory systems approach that Tulving and others have defended, with the hippocampus and right prefrontal cortex being claimed as central contributors to the episodic encoding system. Recently, a variety of types of evidence have been advanced challenging the sharpness of the distinction and especially the idea that different memory systems are involved. Typically, hippocampal damage does manifest itself primarily in failure of episodic memory. However, children who suffer hippocampal damage early in life exhibit...

The Effects of Potassium Channel Blockers on Cognitive Impairment

Rossini and co-workers (2001) reported a study of the effects of AP on neurocognitive dysfunction using a larger, more generalized battery of tests. A total of 60 primary and secondary progressive patients with MS were randomized in a double-blind, placebo-controlled, crossover trial of oral AP using 6-month treatment periods. A total of 49 patients completed the study. The testing battery included tests for sustained attention (the Auditory Attention test), short-term memory (the Forward Digit and Corsi's Block Span tests), long-term memory (the 15' Delayed Recall of Rey's 15-Words List and the 15' Delayed Recall of Rey's Figure A tests), visual perception (Benton's Line Orientation test), language (Token test), executive function (Wisconsin Card Sorting test), general intelligence (Raven's Progressive Maticies test), and depression (Hamilton's scale). Neither the study group as a whole nor a subgroup analysis based on serum AP levels showed any treatment-related changes. Studies to...

Closing the Assembly of Consciousness

Rise of the core consciousness over a fraction of a second, but before that pulse of core consciousness decays, another object causes another pulse of core consciousness to begin. The apparent continuity of core consciousness comes from the abundant production of such pulses along with the fact that we have no device to detect the breaks. Neither conventional long-term memory nor language is needed for this process.

Are Short and Long Term Memory Really Distinct

One of the earliest distinctions in modern memory research is that between short- and long-term memory. Although H.M. had exhibited severe deficits in encoding new long-term explicit memories, he performed normally on short-term memory tasks requiring delays of only a few seconds. Other patients were identified who exhibited impaired short-term memory but intact long-term memory (Shallice & Warrington, 1970). This suggested that there are distinct short- and long-term memory systems (or in more recent formulations, distinct working memory and long-term memory systems). However, there remained a contingent of investigators who rejected the construal of short-term or working memory as a separate system (Cowan, 1995), and recent studies have suggested that short- and long-term memory rely on some of the same brain areas and, hence, presumably similar operations. From the initial studies of H.M., areas in the MTL, including not just the hippocampus but also the perirhinal,...

The smallest number of coordinates needed to specify uniquely a point in space

Determined within 10-1-100s ( attention, perception, phase). Working memory lasts 101-102s. Cellular consolidation of long-term memory takes place over 102-104s system consolidation in the mammalian brain requires 103-106s and possibly even more (Dudai 1996).All this means that critical events in the biology of acquisition should be addressed by biophysics (Dudai 1997&). Practically, most of the current research on acquisition actually addresses events that take place long after initial critical decisions have been made, and some even forgotten. This is especially true for molecular studies, which deal with processes and mechanisms in the 102-105s range. These are hence expected to tap after-effects of initial encoding and registration, consolidation, and homeostasis.

Tests of the Hypothesis That Protein Synthesis Is Required for Memory Storage

Tests of the protein-synthesis hypothesis of memory formation were initiated by Flexner and associates in the early 1960s (e.g., Flexner, Flexner, de la Haba, & Roberts, 1965 Flexner, Flexner, Stellar, de la Haba & Roberts, 1962), and much research followed their design (1) giving animal subjects brief training that, without further treatment, would yield evidence of retention at a test a few days later (2) administering to experimental subjects an inhibitor of protein synthesis at various times close to training, while control subjects received an inactive substance and (3) comparing test performance of experimental and control subjects. By the early 1970s considerable evidence indicated that protein synthesis during or soon after training is necessary for formation of long-term memory (LTM), but the interpretation of the findings was clouded by serious problems such as the following (1) The inhibitors of protein synthesis then available for research (such as puromycin and...

An open problem a mystery

These changes are obligatory for long-term memory Many alterations are detected in the brain after training, at the molecular, synaptic, cellular, and system levels. Yet some of these alterations may not directly relate to experience-dependent modifications in internal representations (e.g. some could subserve homeostasis). Are we currently pursuing the processes and mechanisms that are really relevant ( criterion) skills, for space, for language, for facts, for events, for the self ( taxonomy). Some of these systems may have evolved at first in response to a certain selective pressure but later became adapted to new needs or even paved the way to new faculties and capabilities. Will new memory systems emerge to cope with the new technological environment, what will their capabilities be, and which new opportunities will they open for brain and behaviour 10. And, finally What is consciousness ( conscious awareness) Similarly to enigma 1 above, this issue definitely transcends memory...

The brain system that endows the subject with the capacity to perform 12 above

Research on the different categories of human knowledge. The new computer era opened new vistas for understanding the storage and retrieval of knowledge, which infiltrated human memory research. In the mid-1960s, Quillian proposed a method by which meaning could be stored optimally in a computer program, and his postulates were adapted by psychologists in their attempt to account for the storage of knowledge in real brains (Collins and Quillian 1969 Tulving and Donaldson 1972). This type of knowledge encoding was termed 'semantic memory' ( declarative memory, taxonomy). Tulving (1972, 1983) went on to distinguish semantic memory, which he dubbed 'mental thesaurus', from another type of knowledge that humans have about the world, which is about temporally dated events, describable in terms of their perceptible attributes, and the spatiotemporal relations of these events to each other. This memory he termed 'episodic'. The term is now used, depending on the context of discussion, to...

Polymethodological Study Of Creativity

Perhaps the most comprehensive study of the neurophysiology of creative processes has been conducted by researchers at the institute of the human brain at the Russian Academy of Science. Four tasks of varying creative content were specifically developed for EEG and PET analysis. The first task (D Difficult) consisted of composing a mental story from words spanning several different semantic areas (e.g. to begin, glass, to want, roof, mountain, to keep silence), which was designed to induce subjects to give up stereotyped ways of thinking. The second task (E Easy) consisted of composing a mental story from words from the same semantic area (e.g. school, to understand, task, to learn, lesson), which was considered to involve more stereotyped thinking than the first task. While the first and second tasks involved making a story out of as many of the listed words as possible, in any order, the third task (R Reconstruction) consisted of making a mental story out of the listed words without...

Can Parts of the Neurochemical Cascade Be Related to Different Stages of Memory Formation

Some of the difficulty in attempting to relate parts of the neurochemical cascade to different stages of memory formation comes from problems of defining stages of memory, as discussed more fully elsewhere (Rosenzweig, Bennett, Colombo, Lee, & Serrano, 1993). Consider, for example, some very different attempts to state the duration of STM. Early investigators of human STM (Brown, 1958 Peterson & Peterson, 1959) reported that it lasts only about 30 sec if rehearsal is prevented. Agranoff, Davis, & Brink (1966) reported that in goldfish, if formation of LTM is prevented by an inhibitor of protein synthesis, STM can last up to 3 days, although normally LTM forms within an hour after training. Kandel et al. (1987) wrote that in Aplysia, A single training trial produces short-term sensitization that lasts from minutes to hours (p. 17) and that long-term memory is memory that lasts more than one day (p. 35). Rose (1995) suggests that, in the chick, memories that persist only a few hours...

Is Learning Induced Neuroanatomical Plasticity Necessary for Storage of Long Term Memory

Whether learning-induced anatomical changes in the nervous system are necessary for storage of long-term memory has been discussed by several authors, including Morris (1989), Greenough, Withers, and Wallace (1990), Martinez and Derrick (1996), Black and Greenough (Chapter 2), and Martinez, Barea-Rodriguez, and Derrick (Chapter 6). Greenough et al. (1990, pp. 162 165) note several observations that relate number of synapses and degree of dendritic branching to the amount and sites oflearning or experience in some cases I augment the statements of Greenough, et al. (a) The amount of dendrite per neuron in the occipital cortex of the rat reflects the amount of stimulation or complexity in the environment for example, the measures are greatest in EC rats, least in those from IC, and intermediate in those from SC. (b) Similar effects of training or experience occur in young,

Features Of The Invertebrate Rsar

The RSAR of invertebrates is rapid, effective and adaptive. In contrast to the broad-spectrum innate immunity in Drosophila and mosquitoes (Christophides et al., 2002 Hoffmann, 2003), RSAR has features similar to the peptide-based adaptive immunity in vertebrates (Whitton & Oldstone, 2001). The specificity determinants of RSAR are siRNAs, which are derived and processed from the invading virus. After being uploaded into RISC, these virus-specific siRNAs selectively recruit target viral genomic and or messenger RNAs by base-pairing for RISC-mediated destruction. At the whole-organism level, RNA silencing may also provide a long-term memory, analogous to the lifetime maintenance of specific virus resistance in plants recovered from a virulent primary infection (Covey et al., 1997 Ratcliff et al., 1997, 1999 Xin & Ding, 2003). However, while the peptide-based immunity in vertebrates usually takes more than a week to respond (Whitton & Oldstone, 2001), the RNA-silencing response in fruit...

Cerebral Localization Of Learning And Memory Processes Using Dissociation Designs

Knowlton, Mangels, and Squire (1996) start their review article by stating, Students of brain and behavior have long recognized that double dissociations references to Teuber (1955) and later authors provide the strongest evidence for separating the functions of brain systems (p. 1399). They present evidence for a double dissociation between human brain regions and kinds of memory amnesic patients, with damage to the limbic-diencephalic regions, show impaired formation of declarative but not of nondeclarative memories, whereas patients with Parkinson's disease, who have damage to the neostriatum (caudate nucleus and putamen), show impaired formation of habits but not of declarative memories. Kesner, in a series of studies summarized in Chapter 10, has found evidence of double and triple dissociations between brain regions involved in working memory for different attributes of the learning situation. A similar research project in another laboratory also found a triple dissociation,...

Neurosteroids in Learning Memory and Brain Aging

Deterioration of cognitive functions typically accompanies aging. The role of GABA in learning and memory is evidenced by the fact that GABA antagonists facilitate the hippocampal long-term potentiation (LTP) (51) LTP is a synaptic process mediated via excitatory neurotransmitters, believed to be fundamental for long-term memory. Because an inhibitory input provided by the GABAergic interneurons sets a threshold for postsynaptic modification of excitatory inputs (52), the GABAergic steroids are likely to influence memory. In this context, DHEAS, DHEA, and PREGS, as GABA-antagonists, are expected to enhance learning and memory, and the GABA-agonistic steroids are expected to impair memory, in an analogous manner, as barbiturates and benzodiazepines produce amnesia (53), whereas GABA antagonists, picrotoxin and pentylenetetrazol, reverse amnesia and improve memory (54,55). Pentylenetetrazol was even used with some success in treatment of geriatric patients with impaired memory (56)....

Some repercussions of the PAS hypothesis On static vs dynamic models of memory

Hebb, the most influential guide of modern dual-trace models, presented a dynamic universe of neuronal ensembles that encode internal representations (1949), but subsequent accounts of the Hebbian universe too often tended to depict the consolidated long-term trace as a relatively immutable mnemonic unit, falling for the lures of erroneous storage metaphors of memory persistence (discussed in Roediger 1980 Dudai 2004). The PAS hypothesis clearly argues for a dynamic view of long-term memory, in which internal representations are in continual flux furthermore, it argues that the magnitude of this flux over time is proportional to the extent the representation is used. It is noteworthy that, in theory, flux doesn't necessarily imply significant change in content. Consider, for example, the classical Ship of Theseus problem, sometimes invoked in discussions of memory persistence (Dudai 2002a,b). The ship of the mythical Greek hero was placed on display in Athens, and with time, parts of...

Genes whose products are induced rapidly and transiently in response to extracellular stimulation

Ample data show that the induction of IEGs is correlated with, and sometimes obligatory for, long-term (but not short-term) plasticity and memory (e.g. Impey et al. 1996 Yin and Tully 1996). This is construed within the prevailing conceptual framework ( Zeitgeist), which describes the consolidation of long-term memory as a growth process that endows the memory with immunity to molecular turnover (Goelet et al. 1986 Dudai 1989 Milner et al. 1998 development, protein synthesis). The idea is that, whereas weak training results in only transient post-translational modifications in the neurons, training that involves repetitive or coincident stimuli induces IEGs, culminating in long-term circuit alterations and therefore long-term memory. The products of the IEGs, or at least of those IEGs that encode TFs, are hence regarded as intracellular switches that transform short-term into long-term plasticity. IEGs have also become a major focus of research in developmental neurobiology (Curran...

Studies Using Noninvasive Brain Imaging

Neuroimaging techniques have recently been used to study cognitive processes, and since the early 1990s they have been used to study brain processes in learning and memory. This is a field of research on learning and memory that clearly could not have taken place without the discovery of brain-imaging techniques. An early review of this area was that of McCarthy (1995) it included material on 14 brain-imaging studies using working memory tasks and six studies investigating processes involved in long-term memory. Another review focused on hemispheric asymmetry in encoding and retrieval (Nyberg, Cabeza, & Tulving, 1996). It showed that encoding involves especially activation of the left prefrontal cortex, whereas retrieval involves especially activation of the right prefrontal cortex. More reports are continuing to appear, and the next edition of this book may very well include a chapter devoted to such studies.

The Traditional Theoryreduction Perspective

For purposes of discussing the theory-reduction model, I will assume that the knowledge achieved within a given discipline can be stated in a set of laws (a view that the mechanistic perspective rejects). In order to carry out deductions between sets of laws, two challenges have to be overcome. First, typically laws in different sciences employ different terminology. Laws in physics, for example, might employ terms such as mass and attractive force, whereas those in chemistry would involve names of elements and molecules and types of chemical bonds. Neuroscience accounts might refer to increased rates of spiking whereas psychological accounts might refer to retrieving a representation from a working memory buffer. But one cannot logically deduce a conclusion that uses terms that are not in the premises. To address this issue, advocates of the theory-reduction model appealed to bridge principles (Nagel called them rules of correspondence) that equated vocabulary in the two laws. The...

The lack of recall of autobiographical memories dating to infancy

One class of explanations suggests that the problem lies already at the acquisition phase early personal memories are not retained to begin with, because the brain systems that are required for autobiographical, episodic memory simply do not mature before the age of 3-4 years (Nadel and Zola-Morgan 1984 Nelson 1998 declarative memory). A related suggestion implicates both acquisition and retention and rests on cognitive rather than neurological arguments. It claims that the infant's mind cannot form the appropriate mental structures that serve as inner frameworks for organizing new information in a sensible manner. The generic term for such abstract mental structures is 'schemata' (Bartlett 1932 Piaget 1969 Cohen 1996). In the absence of mature schemata, so goes the argument, autobiographical experiences cannot be stored in an effective, retrievable form. A version of this argument considers the intense episodes of infantile memory inconsistent with the categories of the adult...

Syndromes related to acculturative stress Brain fag

The term brain fag, coined by Nigerian students, refers to a condition first reported in 1959 by Prince among this population. (36 Since then the brain fag syndrome has been recognized in many Nigerian students at home and abroad, and also in students of other African countries who are exposed to the acculturative stress of a Western-type education system emphasizing theoretical book knowledge, quite different from the practical know-how and tribal lore acquired through oral traditions by older generations in Africa. Nevertheless, the older generations expect their students to achieve academic and socio-economic success in modern society and these parental expectations are increasing the emotional pressure on the students. The clinical picture of brain fag is characterized by a variety of symptoms (36 bothering sensations on or in the head and body, especially aches, burning, and crawling eye trouble and visual disturbances, especially blurred vision and tears when reading impaired...

Nicotinic Antagonists

Nicotine-induced memory improvements can be blocked by the nicotinic antagonist mecamylamine.435 43 Interestingly, the muscarinic antagonist scopolamine also can reverse memory enhancement induced by nicotine in rats.43 The effects of mecamy-lamine also appear to be related to task difficulty and dose, since some studies have not found mecamylamine-induced deficits,14 and have even found paradoxical improvements in performance.35 3654 As discussed later, these effects may be due to the degree of proactive interference involved in the task.

Behavioral Specification

Working memory is defined as memory with changing contents, as opposed to reference memory, which is defined as memory with fixed contents. Working memory can be differentiated from reference memory in the radial-arm maze by always baiting the same arms and not the others at the beginning of each session. Entries into baited arms are considered working memory and entries into unbaited arms are considered reference memory. Usually a 16-arm radial maze is used for assessing working and reference memory. This technique has been used to show the relative specificity of nicotine-induced improvement in working but not reference memory.29 Baiting 12 of the 16 arms presents a difficult working memory task, while still leaving 4 arms never baited allows for the assessment of reference memory. This technique has been used to show the relative specificity of nicotine-induced improvement in working but not reference memory.29 30 The specificity of the cognitive effects of nicotinic treatments can...

Nicotinic Receptor Subtype Involvement In Memory Function

In the central nervous system, although other prominent subunit combinations including the a4p2, a3p4, and a7 exist as well. The functional roles played by these subtypes are being discovered. Hippocampal a4p2, a3p4, and a7 receptors appear to be important for working memory functions. Studies have shown that most hippocampal neurons have nicotinic receptors that respond to nicotine with a Type IA nicotinic current characterized by rapid desensitization and blockade by MLA,2,13 a selective a7 nicotinic receptor antagonist.59 Fewer neurons have receptors that respond with Type II currents and are blocked by DHpE and Type III currents, which are blocked by mecamylamine and are more slowly desensitized.2 Some neurons show a mixed response termed Type IB which is partially blocked by either MLA or DHpE, but completely blocked by both antagonists.2 The pharmacological and kinetic properties of these currents support their correspondence to a7 (Type 1A), a4p2 (Type II), and a3p4 (Type III)...

Magnetic resonance imaging and movement disorders

In an event-related fMRI study comparing PD patients to control subjects, PD patients in the ''off-levodopa'' state showed decreased activation of the supplementary motor area, but increased activation in the primary motor cortex and the lateral premo-tor cortex bilaterally (Haslinger et al., 2001). Following oral levodopa replacement, there was partial normalization of the abnormal patterns of cortical activation. In another fMRI study, the effects of dopaminergic therapy on cognitive and motor functions in PD patients were evaluated (Mattay et al., 2002). Motor tasks activated the supplementary motor area, lateral premotor cortex, sensorimotor cortex, parietal cortex, and cerebellum bilaterally. The cortical activations were greater in the on-levodopa state, and the increase in activation correlated with better motor performance. Working memory tasks activated the prefrontal cortex, pericin-gulate cortex, anterior cingulate cortex, and parietal cortex bilaterally. The cortical...

Traumatic Brain Injury

Our recent studies with children have utilized Spectroscopic Imaging (SI), rather than the single voxel methodology described above 25 . A spectroscopic imaging slice was selected above the lateral ventricles to extend from the frontal lobe to the occipital and parietal lobes sampling both white and gray matter. Water suppressed PRESS localization with outer voxel suppression bands was used to excite parenchyma and avoid lipid artifact from the skull. See Figure 2 (panel A) for an example MRI image with superimposed SI grid. Patient recruitment and data analyses are ongoing. Here we report on NAA Cre ratios averaged across many voxels (predominantly white matter), with separate estimates for anterior and posterior halves of the data matrix. A large battery of cognitive tests was administered individual scores were standardized and averaged into these composites overall cognitive (as above), motor, language, visuo-motor, and working memory. The TBI children (N 28, mean age 13.6, SD...

Topographical Changes

Prabhakaran (1997) used functional magnetic resonance imaging (fMRI) to investigate cortical activity during the performance of the Standard and Advanced Progressive Matrices (SPM and APM) in order to assess the cortical activation of fluid intelligence and reasoning. The participants attempted to solve three types of problems from the SPM and APM, one requiring analytic reasoning, another requiring figural or visuo-spatial reasoning and the third type involving simple pattern matching. When comparing the analytic and figural reasoning problems Prabhakaran (1997) found activation in both the right and left frontal areas and a predominantly left hemispheric activation in the parietal, temporal and occipital areas, which was associated with analytical reasoning. When comparing the figural and the matching problems, figural reasoning was associated with an increase in activation mainly in the right hemisphere in the frontal, parietal and temporal areas that was proposed to be associated...

Question And Answer Session

WEINBERGER Well, again I think that is a whole other symposium, and there have been many. But our application of blood flow measurements was as another physiological assay of neuronal function. So the blood flow measurements I showed you were acquired during the specific cognitive processing of a working memory task and a sensory motor control task.

Performance Deficits By Nicotinic Drugs

Abnormalities that occur in aged humans and AD patients. This assertion is based on observations that they begin to encounter learning and memory deficits during the second decade of life, with more substantial deficits apparent by the mid- to late 20s. With age, nonhuman primates have been shown to develop abnormal neurites, amyloid deposition, altered levels of neurotransmitters, and reductions in synaptic densities and pyramidal neurons with age. They also express the apoenzyme E isoform that is analogous to the human apoE4 isoform implicated as a risk factor in AD.59 60 Furthermore, improvements in DMTS performance by nicotine may be especially relevant since this working memory task engages many of the same neuronal substrates in monkeys as in humans (e.g., prefrontal cortex, hippocampus, etc.). A modified version of the DMTS paradigm has been used to study cognitive ability and impairment in AD patients, and delay dependent deficits in DMTS performance have been documented in...

Cognitive Impairment and Dementia

The second theory is that the EDS contributes to the cognitive impairment found in patients with SDB. It is well known that one of the primary symptoms of SDB is EDS, and that EDS can impair cognitive functioning including auditory verbal learning (47), executive functioning, and working memory (48). It is also possible that the cognitive deficits found in SDB patients are a product of multiple factors, which may include both hypoxia and EDS. In addition, there is evidence that many of the progressive dementias involve degenerative pathologies in brainstem regions, areas that are responsible for regulating respiration and other autonomic functions relevant to sleep maintenance (49). Therefore, because many older adults suffer from dementia, it is possible that sleep disorders such as SDB may be more likely to occur in this group of patients.

Administration pharmacokinetics and dosage Administration

However, the improvement in positive symptoms which is often achievable with the typical antipsychotic drug is only one element in the treatment of schizophrenia and is not sufficient grounds for judging response to be adequate. Additional efficacy factors of major importance are improvement in negative symptoms, depression, suicidality, anxiety, and especially cognitive function. (31,) Tolerability and safety factors, such as compliance, tardive dyskinesia, weight gain, and medical morbidity are also major elements in outcome and are influenced by the choice of a typical or atypical antipsychotic drug. Typical neuroleptic drugs do not significantly improve the negative symptoms of schizophrenia in the majority of patients ,3 ,36) There is a consensus that typical neuroleptic drugs can improve negative symptoms that are secondary to positive symptoms and depression while at the same time possibly causing negative symptoms due to their ability to produce extrapyramidal side-effects.(36...

Plasticity Of Olfactory Microcircuits

If newborn interneurons are necessary for bulbar function or plasticity, disruption of cell migration in the rostral migratory stream would be expected to affect olfactory processing or learning. Indeed, in PSA-NCAM-mutant mice, the number of newborn granule cells is reduced by 40 and odor discrimination is impaired (Gheusi et al. 2000). One hypothesis is that the impairment is due to reduced GABAergic inhibition of mitral cells by granule cells, which is likely to play a role in the function of interglomerular microcircuits (see above). Furthermore, the rate of apoptosis is reduced in animals exposed to an enriched olfactory environment. This effect is associated with more robust and extended long-term memory measured in a simple task. In general, these results suggest a relationship between interneuron number and system performance.

The set of procedures and techniques that guide the planning execution and analysis of a type of tasks

The field of memory research is equipped with its own special repertoire of methods. These are exemplified in classical conditioning, cue revaluation, delay task, fear conditioning, habituation, instrumental conditioning, LTP, maze, priming, real-life memory, sensitization, transfer, and working memory. But brain research in general is in a special situation. It is a truly multidisciplinary enterprise. The more it advances, the more it is quick to incorporate knowledge and methods from a great variety of other disciplines. These range from molecular, cellular, and developmental biology, via physiology and anatomy, clinical neurology and neuroimaging, psychology, and ethology, to computational science and information theory (Dudai 1989 Martin and Bateson 1993 Baddeley 1997 Manning and Dawkins 1998 Zigmond et al. 1999 Kandel et al. 2000). Not surprisingly, a recent textbook in the neurosciences is authored by no less than 150

The Hippocampus As A Sex Hormonesensitive Limbic Brain Region Involved In Cognition And The Cognitive Aspects Of Emotion

The hippocampus is implicated in spatial and explicit memory functions (28) and is part of the limbic system and therefore a participant in the affective and vegetative states (29). It is a brain region that provides context and cognitive meaning to many appetitive and aversive events (30,31), and it is a major target for circulating adrenal steroids and or for their actions during stress and in the diurnal sleep-waking cycle (32). Sex differences have been described in hippocampal morphology involving the size of the dentate gyrus (33-35), and spatial learning with global spatial cues is faster in males than in females (7). This trait can be reduced in newborn male rats by castration, and it is enhanced in newborn female rats by neonatal treatment with estrogens (7) this may be the pathway for sexual differentiation, because the hippocampus transiently expresses estrogen receptors and aromatizing enzymes during the first 2 wk of neonatal life (36,37). Estrogen receptors are largely...

Management following hospital discharge

An important consideration in SAH survivors is the disease's neuropsychiatric sequelae.225,226 Even patients with good Glasgow Outcome Scores will have deficits 12 months posthaemorrhage. Short term memory is reduced in 53 and long term memory is reduced in 21 . Visuospatial construction and memory, mental flexibility, and psychomotor speed remain abnormal in 28-62 . Ten per cent have dysphasic language performance and up to 50 remain unemployed.

Memories Of Past Attitudes

We have immediate access only to our current attitudes. Past attitudes must be retrieved from memory. The question is what sort of memory could do this job. Young children have good memory for things, events, and situations. This is semantic memory. It retrieves only content, without its actual experience. Another sort of memory, called episodic, retrieves experiential details of past contents, linked to spatiotemporal contexts, and vivid reactions and emotions. Episodic memory also operates in young children and perhaps some nonhuman species (Clayton, Griffiths, Emery, & Dickenson, 2002). Episodic memories are represented in the same brain areas as are actual experiences (Conway, 2002). This is significant because it suggests that, like ongoing mentation, episodic memory accesses only past experiences or their contents but not past self-representingness. Furthermore, the reliving of past experiences or contents may re-create a vivid sense of having seen or desired something but not...

S Evidence statements

Four RCTs examined the efficacy of cognitive remediation programs for cognitive dysfunction. The first trial assessed the effectiveness of cognitive training and neuropsychotherapy in comparison to non-specific mental stimulation. The results showed no overall beneficial effect for the intervention at six month follow-up.407 The second trial examined the use of cognitive assessment plus remediation, compared to assessment alone, or no treatment. The results indicated no significant differences between the groups on any of the outcomes measures.408 The third study assessed the use of cognitive remediation strategies in patients who were resident in long-term nursing facilities. The results showed no beneficial effect for the intervention as compared to the no treatment control group.409 The last study compared the use of the story memory technique to no intervention. The results showed positive effects on three out of five of the outcomes assessed, including patients self report of...

Binding Mechanism for Large Scale Neuronal Assemblies

Following the activation by glutamate, the NMDA receptor channel complex remains in an activated state for several hundred milliseconds. This endows the postsynaptic membrane with a relatively long memory for the detection of correlated activity. The receptor, therefore, plays a role not only in the initiation of long-term memory but also in working memory, the ability to store and manipulate information over periods of time ranging from seconds to minutes. A large time window is also necessary for detecting widely distributed correlated activity, and consequently for establishing Hebbian assemblies that connect very distant neurons. The concept of the cell assembly is one of the most commonly used in brain theory. Hebb's (1959) central idea was that the spatiotemporal activity of a cell assembly is identical with the physiological instantiation of a mental representation. In his words, T he assembly activity is the simplest case of an image or an idea a representative process.''

Clinicopathological correlations

Premotor signs of mild executive cognitive dysfunction are seen in nearly all PD patients and might be explained by the stage 2 nor-adrenergic and serotoninergic neuronal degeneration with sleep fragmentation as well as daytime sleepiness with inattention. Executive functions represent a range of cognitive functions under the control of the frontal lobes and generally require some sort of working memory and optimal attention. Degeneration of the ascending cholinergic and catechola-minergic neuronal systems may contribute, at least in part, to the occurrence of frontal-lobe-like symptomatology associated with PD (Fantini, 2005).

Increases in Synapse Number Associated with Learning and Memory

Observed in the cerebellar cortex of acrobatic rats persist for at least 4 weeks after completion of training18 and may, therefore, represent a substrate of long-term memory storage. number are associated with a more traditional, associative form of learning. Adult rats were given five daily training sessions, each one consisting of 100 paired presentations of a tone conditioned stimulus and periorbital shock unconditioned stimulus. During each presentation, the commencement of the conditioned stimulus preceded that of unconditioned one after which the stimuli were paired and then co-terminated. One group of control animals received explicitly unpaired presentations of the stimuli while the other was not stimulated. Synapses were quantified in the interpositus nucleus of the cerebellum, which is known to support long-term retention of the delayed eyeblink conditioned response. The numerical density of synapses and neurons was estimated in the anterior part of the interpositus nucleus...

The Neuronal Workspace Hypothesis And The Mechanisms For Access To Consciousness

Long-term memory (PAST) Long-term memory (PAST) The central proposition of the hypothesis is the neural distinction in the brain of two main computational spaces. The first is a processing network composed of parallel, distributed, and functionally encapsulated processors organized from cortical microcircuits. These processors range from primary (or even heteromodal) sensory processors, motor processors, long-term memory stores including semantic database, the self, autobiographical and personal data, attentional and evaluative systems including motivation, reward, and, in general terms, the emotions. The second computational space is referred to as a global workspace and it is assumed to consist of a distributed set of cortical neurons, which physically integrate the multiple processors by their ability to receive from and send back to homologous neurons in other cortical areas through long-range excitatory axons. These horizontal projections interconnect at the brain-scale distant...

Bodis Wollner and MY Jo

Language deficits in non-demented PD patients can include impairments in comprehension, verbal fluency, and naming. Comprehension deficits become evident when patients are required to process sentences with non-canonical, irregular grammatical structures. Semantic memory deficits may result in the impairments in category fluency and confrontational naming. Selective language deficits may be due to impaired dynamics of the ''phonological loop'' connecting the pre-frontal cortex and the basal ganglia. A more encompassing linguistic and functional model of PD specific language impairments would be useful for evaluating language deficits in the context of motor dysfunction.

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