How brain uses sleep for visual task learning

Evidence is mounting that while sleeping the brain employs neural oscillations - brainwaves - of particular frequencies to consolidate learning in specific brain regions.

In August, Brown University scientists reported that two specific frequencies, fast-sigma and delta, that operated in the supplementary motor area of the brain were directly associated with learning a finger-tapping task akin to typing or playing the piano.

The new results show something similar with a visual task in which 15 volunteers were trained to spot a hidden texture amid an obscuring pattern of lines. Takeo Watanabe, professor of cognitive, linguistic, and psychological sciences at Brown, said that perceptual learning in general has been found to improve the visual ability of patients who have some decline of function due to aging.

In this case the researchers, led by graduate student Ji Won Bang, devised an experiment to see how sleep may help such training take hold. They measured the brainwaves of the participants during sleep before and the training, and they measured the volunteers' performance on the task before and after.

The researchers saw significant increases in sigma brainwave power after sleep compared to before in the visual cortical area in the occipital lobe of the volunteers' brains.

To ensure they were measuring activity related to learning the task, the researchers purposely put the stimulus of the discrimination task in a particular quadrant of the subjects' field of view. That position corresponds to an anatomically distinct part of the visual cortical area. The team saw that the measured gain in sigma wave power was greater specifically in that trained part of the visual cortical area rather than in the untrained parts.

They also saw that the difference of power increase between trained and untrained regions of the visual cortical area was correlated with each individual's performance improvement on the task.

The study has been published in the Journal of Neuroscience.