Evolution of cognitive function via redeployment of brain areas

(SD 21.5) of activations are in categories other than the category with the highest number
of activations.

Using the measure of population diversity among categories discussed above shows that
the 86 brain regions have a mean category diversity of 0.76 (SD 0.11); ignoring the
medial/lateral division gives 0.81 (SD 0.09). As shown in Table 1, an average category
diversity of 0.81 suggests a fairly high degree of redeployment throughout the brain.

Table 1: Illustrations of the category diversity of some Brodmann areas. The table shows some
examples of the diversity of activations across categories for three Brodmann areas.

These results are perhaps even more striking when put in graphical form. Figure 2
represents activations of Brodmann areas in the left hemisphere, in each of the four task
domains, by both color and intensity. The color represents the task domain, and the
intensity indicates the number of tasks in the category that activate the area. I use the
colors cyan (language), magenta (attention), yellow (perception) and black (imagery) so
that these colors can be mixed using standard CMYK 4-color printing methods.

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