Perceptual Learning and Consolidation Studied with Perfusion fMRI

Lay Summary

Imaging Imagery While We Sleep, with Perfusion fMRI

University of Pennsylvania researchers will study what occurs in the awake and sleeping brain while people learn to recognize faces or buildings.  The findings should help to explain the role of sleep in this essential learning function, called visual perception, and also may provide a basis for restoring visual perception capacity in people who have sustained a brain injury.

Prior research suggests that people have an initial period of fast improvement in learning to recognize a face or a building, followed by slow, step-wise, improvement seen following sleep.  Improvement is associated with the fine-tuning of an internal (mental) representation of facial appearance.  Using fMRI to provide a quantitative measure of cerebral blood flow over hours to days, the researchers will examine how the brain processes visual perception learning, and describe the role of REM (rapid eye movement) sleep in this process. (REM is the deepest stage of sleep.)  They will image the neural activity of patients as they practice identifying faces and while they sleep (in the scanner).  Then, investigators will undertake REM sleep scanning in participants who  learn to discriminate pictures of either faces or buildings.  Depending on which type of visual learning is taking place, the investigators hypothesize, specific parts of the brain will show increased neural activity, and REM sleep will play a role in the consolidation of this perceptual experience.

Significance:  The findings of how REM sleep contributes to visual perception learning should provide new information on this vital brain function, and may provide a basis for devising rehabilitation strategies for people with brain injuries that resulted in diminished visual perception capacity.

Abstract

Perceptual Learning and Consolidation Studied with Perfusion fMRI

Training on a visual discrimination task improves subject performance over several days. Behavioral studies of this perceptual learning suggest that there is an initial period of fast improvement in performance that occurs during the first training session, followed by step-wise enhancement of performance after additional training. There is evidence that rapid-eye-movement (REM) sleep is critical to this slow consolidation of learning over training periods. Behavioral studies have also characterized the systems-level changes in information processing that accompany improvement in performance. In subjects trained to discriminate faces, for example, improved performance appears driven by enhancement of the stimulus representation, as opposed to reduction of external or internal perceptual noise. Characterizing the neural basis of perceptual learning should help us understand the properties of rehabilitative therapy for recovery of visual function following brain injury.

The proposed experiments make use of a recently developed neuroimaging technique, perfusion functional magnetic resonance imaging (fMRI), that is ideally suited to the study of the long time-scale changes in neural activity presumed to accompany perceptual learning. By observing cerebral blood flow in subjects while they perform a perceptual learning task and while they sleep after training, I will test the following hypotheses: 1) different neural mechanisms underlie initial, fast improvement in task performance compared to subsequent slow improvement; 2) improved performance is manifest on a neural level by augmented responses to trained stimuli within category-specific cortical areas; and 3) step-wise improvements in performance are associated with reactivation of category-specific cortical areas during REM sleep.