22 November 1999
Smart drugs who needs em (not mice)?
by Kate Melville 
Should you exercise before studying? Yes, according to a new study by Salk Professor Fred Gage that shows exercise stimulates chemical changes in the brain that induces learning (in mice). This new work by Professor Gage builds on previous research that showed how exercise boosted the number of brain cells in the hippocampus - the section of the brain that controls memory and learning. "The question remained, though, whether the addition of neurons correlated with increased brain function," said Professor Gage, "The new study indicates that two measures of brain activity are changed; one behavioral, the other electrophysiological." In this new research two groups of mice were studied; one group lived in standard cages with only food and water and the second group had use of a running wheel (mice apparently love to run with those in the study averaged five kilometers per night). The mice in each group were genetically identical, so that any differences should be entirely due to differing environments. After six weeks in the two environments, the mice were then measured for their ability to learn, in this case they had to find a hidden platform in a water maze. The mice who had run regularly performed (i.e. learned) considerably better than their sedentary counterparts. Next the brains from both groups of mice were studied for their abilities to undergo LTP (long term potentiation) a measure of the way that cells communicate with each other. Salk Professor Terrence Sejnowski, co-author of the study belives that, "LTP may be the molecular basis for how long-term memories are initiated. So the discovery that running mice are capable of sustaining stronger LTP than sedentary mice may be one of the reasons they learn more readily." When their brains were examined for new cell growth in the hippocampus, the mice on the move had grown more cells than their sedentary litter mates.
In an analysis Professor Gage noted that, "As expected from the previous work, we saw abundant production of new cells, and importantly, this time we showed that many of those cells are neurons, the class specialized to transmit messages throughout the brain." So it's seems clear that something interesting is happening but the question is then what exactly is the connection between exercise and smarts? In 1998 Gage's team published a report (in collaboration with Swedish scientists) that showed that adult humans grow new brain cells, overturning years of doctrine that stated humans are born with all the brain cells we will ever have and only lose cells during our lives. One possible explanation is that exercise affects steroid hormone and stress levels and so Salk's team looked at levels of corticosterone in the blood in the mice. This investigation of a possible physiological link did not work as no differences were seen in the corticosterone levels. "What I find most exciting," Gage adds, "is that taken together the studies suggest that throughout one's life, one's behavior can change the structure of the brain, and that these changes can in turn affect how we behave in our environment."
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