Evolution of cognitive function via redeployment of brain areas

AMGD = 1

AMGD = 1.5

Figure 1: Illustrations of the average minimum graph distance (AMGD). The figure shows the
average minimum graph distances between nodes in some simple graphs. Lines between nodes indicate
adjacency.

Results

On average, each of the 135 tasks activated 5.97 regions (SD 4.80). Perceptual tasks
activated 4.88 (n = 42, SD 3.55), attention 5.26 (n = 39, SD 4.23), imagery 6.39 (n = 18,
SD 3.29) and language 7.81 (n = 36, SD 6.56). More importantly, the 86 brain regions
that were activated by at least one task supported, on average, 9.36 different tasks (SD
8.62). Ignoring the division into medial and lateral regions gives an average of 13.00
tasks per area (SD 8.44), nearly one in ten of the tasks surveyed.

The activations were not limited to closely related tasks. Of the 86 regions activated in
some task, 57 (66.3%) had activations in at least three categories; 28 of these had
activations in all four categories. Only 15 regions (17.4%) had activations in just one
category. Counting the number of tasks by category that activated each region, and
normalizing the count of tasks in each category to n=42, shows that an average of 37.8%

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