Pulling an all-night study marathon may be tempting, but students would do well to study, then rest. The old-fashioned advice now has some research to back it up, thanks to a computer simulation showing the long branched dendrites of pyramidal neurons in the cerebral cortex.
According to a report, Wenbiao Gan of the Langone Medical Center at New York University, and his colleagues, trained mice to run backwards or forwards on a rotating rod, then left some of them to sleep while keeping the rest awake, using confocal and two-photon microscopy to monitor the motor cortex, which is involved in controlling movement, through ‘windows’ scraped into animals’ skulls.
“We found that about 5% of spines in the motor cortex were formed anew in response to the learning task over 8-24 hours,” says Gan, “and our previous studies show that a fraction of these rapidly formed new spines – about 10% – are maintained over the subsequent weeks to months.”
The experiments also showed that the same neurons that were activated during learning of the task were reactivated during sleep, and this apparently stablized the newly-formed spines, because no new spines were seen when reactivation was blocked with a drug.
The researchers reportedly did not re-test learning behavior after blocking spine formation, however, or determine whether the new spines actually paired up with nerve terminals to form functioning synapses. Even if they did form synapses, it’s not clear that such a small number of them could contribute to information processing, so more work is needed to confirm that the new spines that sprout during sleep are indeed involved in memory.
