Brain activity related to consolidation of perceptual learning during sleep

Abstract

Recently, a large number of studies have suggested that sleep plays an important role in learning consolidation, although it is still controversial. In the present study, we examined consolidation-related brain activity during sleep after perceptual training. We measured brain activity in sleep for about an hour using simultaneous EEG and fMRI technique. First, subjects underwent the adaptation protocol in which they slept inside the MRI scanner with electrode attached so that they familiarized themselves to fall asleep inside the scanner. Then, we measured BOLD signals in the visual cortex before and after training of a texture discrimination task. Perceptual learning of this task is known to be locationally specific and may involve the primary visual cortex (V1) (Karni & Sagi, 1991). Stimulus targets were presented only in the upper left visual field. The post learning sleep session was conducted at the same night as the training. Relative BOLD changes in brain activity in both the trained and untrained regions in V1 during sleep compared to that in the wake period before the sleep onset were calculated. Sleep stages were determined by EEG signals using a standard method. Visual areas in each subject's brain had been localized in advance in a separate fMRI session. Results indicate that in the post learning sleep period, the relative brain change for the trained region in V1 was significantly different from the untrained region and for the trained region during the sleep before the learning. In addition, before the training, there was no significant difference between relative brain changes in the untrained and trained regions in V1. These results indicate that sleep consolidation process occurs in a highly localized circuit specific to the location of a trained stimulus.

Footnotes

 NIH; NSF; ERATO Shimojo Implicit Brain Function, JST NCRR; The MIND institute; MGH