TEMPORAL LOBE FUNCTION
1. The auditory cortex lies on the upper surface of the superior temporal gyrus, buried in the lateral sulcus (Heschl's gyrus).
The dominant hemisphere is important in the hearing of language. The non-dominant hemisphere is important in the hearing of sounds, rhythm and music. Close to the auditory cortex labyrinthine function is represented.
2. The middle and inferior temporal gyri are concerned with learning and memory (see later).
3. The limbic lobe: the inferior and medial portions of the temporal lobe, including the hippocampus and parahippocampal gyrus.
The sensation of olfaction is mediated through this structure as well as emotional/ affective behaviour.
Olfactory fibres terminate in the uncus.
The limbic lobe or system also incorporates inferior frontal and medial parietal structures and will be discussed later.
4. The visual pathways pass deep in the temporal lobe around the posterior horn of the lateral ventricle.
IMPAIRMENT OF TEMPORAL LOBE FUNCTION
1. Auditory cortex
Cortical deafness: Bilateral lesions are rare but may result in complete deafness of which the patient may be unaware.
Lesions which involve surrounding association areas may result in difficulty in hearing spoken words (dominant) or difficulty in appreciating rhythm/music (non-dominant) -AMUSIA. Auditory hallucinations may occur in temporal lobe disease.
2. Middle and inferior temporal gyri
Disturbance of memory/learning will be discussed later.
Disordered memory may occur in complex partial seizures either after the event - postictal amnesia - or in the event - deja vu, jamais vu.
3. Limbic lobe damage may result in: Olfactory hallucination with complex partial seizures Aggressive or antisocial behaviour. Inability to establish new memories (see later).
4. Damage to optic radiation will produce an upper homonymous quadrantanopia. Dominant hemisphere lesions are associated with Wernicke's dysphasia.
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