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Amphetamines Activate a Task-Specific Response
Aug 13, 1996
WESTPORT, Aug 13 (Reuters) - In the current issue of The Journal of Neuroscience, NIH scientists "...uncover the phenomenon of amphetamines."

Dr. Daniel R. Weinberger and colleagues report the surprising finding that amphetamines do not stimulate activity nonspecifically throughout the brain as was previously thought. Amphetamines, they have discovered, stimulate only the areas necessary to pe rform the task at hand.

Dr. Weinberger's group used positron emission tomography to analyze brain activity in eight normal men and women. The clinicians administered either placebo or dextroamphetamine to the subjects, and 2 hours later asked each subject to perform one of two t asks: an abstract reasoning test or a nonverbal intelligence test.

Under normal conditions, the NIH group explained, the abstract reasoning task would stimulate activity in the dorsolateral prefrontal cortex, and the intelligence test would activate the posterior cortex.

Dr. Weinberger reports that, "...during the [abstract reasoning task], there was increased 'signal' relative to the control the superior portion of the left inferior frontal gyrus...and relatively decreased activation of the right hippocampus." The NIH group observed the opposite pattern of activation during the nonverbal intelligence test, "...increased right hippocampal 'signal' and decreased activation in the left inferior frontal gyrus."

The patterns observed were similar to those noted previously in studies of normal, untreated subjects.

J Neurosci 1996;16:4816-4822.