Plate 10 Steps in computerized data analysis. Gradient echoplanar imaging data have been acquired from three subjects under identical conditions. The time series at each voxel is analysed to estimate a measure or parameter of the experimental effect, which is represented as a parameter map. Significantly activated voxels or clusters can be identified in each individual image. Parameter maps can be averaged over individuals and generically activated voxels or clusters identified over the group of subjects. The power to detect activation is enhanced by cluster-level analysis and by combining data from several subjects.
standard Talairach-Tournoux space;12 z-coordinates for each slice are shown at the bottom left. Colour codes are the timing and power of a periodic response to a covert verbal-fluency experiment. Blue voxels show increased magnetic resonance signal during condition B (repeat a word covertly); light blue represents a greater power of response than dark blue. Red voxels show increased magnetic resonance signal during condition A (generate a word beginning with a cue letter); yellow and orange represent a greater power of response than dark red. The voxel-wise probability of a false-positive error is p = 0.0001. The main areas activated during condition A are the dorsolateral prefrontal cortex, inferior frontal gyrus, and supplementary motor area; the main areas activated during condition B are the medial parietal cortex and posterior cingulate gyrus.
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