I just read an article which reviewed functional MRI (fMRI) results in autistic individuals fMRI illustrates brain activity while subjects perform a task. The "investigators found that those with autism exhibited more activity in the temporal and occipital regions and less in the frontal cortex than those without autism." Temporal and occipital regions are involved in perception, while the frontal cortex is in charge of executive function and prioritizing attention to different stimuli. The studies were performed while the subjects performed tasks including face processing, object processing and reading. "This research helps explain autistics' exceptional visual abilities, where at least 1 out of 2 excel in visuospatial tasks," said principal investigator Laurent Mottron, MD, PhD. Later, he suggests "instead of describing autism as a social deficit, "which may be true but isn't very specific," it could be described as "a condition characterized by a brain reorganization in favor of perceptual superiority." When asked about the inference that more activity indicated "superiority" Dr. Mottron said: "Sometimes that corresponds to superior performance but that may not always be true,"
Indeed, in functional imaging of subjects with ADHD, they perform poorly on tests of executive function and exhibit more activity in their prefrontal cortex than do subjects without ADHD. When they are treated with stimulants, they perform better and the amount of activity decreases to match that of someone without ADHD. It seems that this activity corresponds to an increased number of electrical signals being sent without triggering the next action. In other words, the increased activity may illustrate an ineffective "loop" where signals are sent and resent within one part of the brain and don't make it to the part which most efficiently performs the task in question.