A 'beta' approach to learning.

A "beta' approach to learning

Benzodiazepines, a group of antianxiety and anticonvulsant drugs that include diazepam (better known as Valium), have been found to interfere with recent memory and learning. French scientists now report that an anxiety-promoting drug-- one of a group of chemical compounds shown to have properties opposite to those of benzodiazepines--enhances performance on three learning and memory tasks, at least among mice and chicks. Human trials have not yet been conducted.

The memory effects of methyl -carboline-3-carboxylate ( -CCM) were compared with those of diazepam. In the first experiment, mice deprived of food for 24 hours were placed in an unfamiliar cage containing an unlimited food supply. Mice injected with -CCM (in doses much lower than those that produce anxiety or convulsions) or diazepam just before entering the cage behaved the same as controls who received no injections, exploring the surroundings but eating practically nothing during the 30-second exposure. Four days later, the same mice were again placed in the cage after a 24-hour fast. The control group ate much more, presumably because they had become somewhat accustomed to the enclosure. Mice given -CCM ate about twice as much as the controls, and diazepamtreated animals consumed much less than controls. Food intake did not surpass that of controls, however, when -CCM was administered in high doses.

Moderate injections of -CCM similarly improved the avoidance behavior of mice who had previously entered a dark box where mild electric foot shocks were delivered. In contrast, diazepam-treated mice had difficulty avoiding such a box even if previously exposed to high-intensity shock.

The investigators then found that -CCM enhances the retention of imprinting (time spent following a moving decoy) in newborn chicks, while diazepam interferes with imprinting.

-CCM may increase an animal's level of arousal and thus improve learning during a training session, Patrice Venault of the French National Center for Scientific Research in Gif-sur-Yvette and her colleagues report in the June 26 NATURE. Conversely, they say, diazepam may reduce arousal. But the precise way in which benzodiazepines interfere with both learning and retention of short-term memories in humans, note the researchers, remains unknown.