"We found that the brain does a pretty good job at compensating for the effect that alcohol has on the brain's ability to process the visual information needed to adjust motor commands," says John D. Van Horn, a research associate professor of psychological and brain sciences and the lead author on the paper. "Alcohol selectively suppresses the brain areas needed to incorporate new information into subsequent and correct motor function."
For the study, eight people, ranging in age from 21-25, were asked to maneuver a joy stick both while sober and when experiencing a blood alcohol level of 0.07 percent (just below the legal definition of intoxicated). Brain activity during this task was captured using functional magnetic resonance imaging, known as fMRI. The study was published online in the journal NeuroImage on March 6, 2006.
The study found that alcohol selectively suppresses cognitive activity in the frontal and posterior parietal brain regions; these are regions most commonly associated with the brain's ability to monitor and process visuomotor feedback. Van Horn explains that this study is one of the first ever to directly illustrate this suppression effect in the brain in humans using neuroimaging.
"We know that alcohol has a global effect on the brain. This study was unique in that it isolated the specific network that underlies the processing and translation of visual and motor commands. The poor coordination one feels after a couple of drinks is due to the poor feedback processing in brain areas critical for updating the mental models for motor action. While this idea is not entirely new, our demonstration, using functional neuroimaging is a first and likely the start of a more extensive neuroimaging research paradigm into the effects of alcohol on the brain," says Van Horn.
Van Horn's coauthors on the study are Melana Yanos, a member of the Dartmouth class of 2004, Paul Schmidt, a 2003 Dartmouth graduate, and Scott Grafton, the John Sloan Dickey Third Century Professorship in the Social Sciences and a professor of psychological and brain sciences.
The study was funded by the National Science Foundation, the National Institute of Neurological Disorders and Stroke, and a Dartmouth College sponsored Richter Grant, Marie A. Center 1982 Memorial Fund Award, and Susan L. Burkhardt 1982 Award.