Neural-learning ventures.

Cells in a brain area that regulates movement pool their resources flexibly and with increasing coordination as rats learn to perform a simple action in response to a signal, according to a new investigation.

Over 7 days, four adult male rats learned to press down on a lever and, upon feeling a vibration or hearing a tone, release the lever quickly. They then learned to wait longer for the stimuli before releasing the lever. Microelectrodes implanted in the motor-control area of the rats' brains allowed neuroscientist Mark Laubach of Duke University Medical Center in Durham, N.C., and his coworkers to gauge the activity of 20 to 30 randomly selected neurons in each animal during training.

As trials proceeded, a trio of activity patterns changed so that the scientists were better able to predict a rat's correct or incorrect response. The set consisted of the average rate of electrical discharges by all neurons, amount of synchronized activity among all neurons (SN: 2/20/99, p. 122), and correlated discharge rates in subgroups of neurons.

Sets of motor neurons foster learning through both the timing and synchronizing of their electrical bursts, the researchers propose in the June 1 NATURE.