Dehydration alters human brain shape and activity, slackens task performance

When dehydration strikes, part of the brain can swell, neural signaling can intensify, and do monotonous tasks can get harder. With the help of brain scans and a simple, repetitive task to test responsiveness, exercise physiologists at the Georgia Institute of Technology studied volunteer subjects who sweated a lot and did not hydrate. The fluid loss led most of the subjects to make more goofs on the task, and areas of participants' brains showed conspicuous changes. The researchers also found that even without dehydration, exertion and heat put a dent in test subjects' performance, but water loss made the dent about twice as deep. "We wanted to tease out whether exercise and heat stress alone have an impact on your cognitive function and study the effect of dehydration on top of that," said Mindy Millard-Stafford, the study's principal investigator and a professor in Georgia Tech's School of Biological Sciences. "We found a two-step decline."