Repetitive training of a perceptual task leads to performance enhancement on that task. This so-called perceptual learning is regarded as a manifestation of neural plasticity in the sensory/perceptual system. It has been found that after training completion the brain continues a process of strengthening learning and memory for long term retention of the learned task. This process is called consolidation. Recent research results have led some researchers to suggest that consolidation occurs during sleep after training. However, that sleep plays a role at all in consolidation is doubted by a considerable number of researchers, and among studies that advocate a role of consolidation in sleep there is controversy regarding during which stage of sleep consolidation occurs. In this proposal, specifically, we will conduct experiments in which fMRI brain activity will be measured during sleep after subjects perform a visual training task that leads to learning of the task. It has been found that some types of visual tasks involve a highly local neural circuit in a low-level stage of visual processing. If fMRI activity changes are observed specifically in the trained region during sleep after training of a visual task and performance is higher after the sleep, this would be strong direct evidence that consolidation of PL occurs during sleep. In the proposed research, a new technology will be used that allows us to simultaneously measure polysomnogram (PSG) while using functional magnetic resonance imaging (fMRI), so that we can objectively determine the onset/offset of sleep and sleep stages using the most standard method in sleep studies. This will enable us to indicate during which stage of sleep, if any, consolidation occurs. The proposed study is highly novel and successful results would not only allow us to reveal the role of sleep in consolidation of PL but also to resolve some serious controversies about the role of sleep in learning and memory that has attracted attention of researchers in the fields of memory, learning and sleep in general. At the same time, the proposal contains highly risky and exploratory natures. This proposal has potential for generalization to applied clinical fields. Recovery and rehabilitation from damages of visual function depend on plasticity and reorganization of remaining neural structures. However, the degree of plasticity and reorganization that take place in the brain is yet unknown. Positive findings from our studies may be applied to the development of better rehabilitation programs and better evaluation of the role of sleep in the recovery and rehabilitation process for a number of neurological conditions.
The primary goal of the proposed research is to test whether sleep plays an important role in consolidation of visual learning. For this purpose, it will be examined whether or not activity in the region of a visual area that is involved in the learning is changed during sleep after training, by means of functional magnetic resonance imaging (fMRI). Successful research results will provide a base of knowledge from which new visual functions and recovery from damages of a visual function are effectively obtained.
