Practice and neural efficiency: An fMRI study of the influence of expertise on working memory processes

This project examined the effects of practice on brain activity during the performance of different kinds of working memory tasks. The development of expertise in a particular skill has a number of known cognitive effects, including faster and more efficient performance. Little is known, however, about how the development of expertise is represented in the brain. Previous neuroimaging studies of practice and learning have proposed a distinction between 'fast' and 'slow' learning mechanisms that may correspond to different patterns of neural activation. 'Fast' changes result from repetitive practice on a task over the course of minutes or hours and may involve habituation-like response within a fixed brain network. 'Slow' changes, on the other hand, occur with more gradual performance improvements and may result in functional reorganization of neural activity due to a shift in the underlying processes subserving task performance. In this project we tested the hypothesis that fast changes, occurring over the course of an fMRI scanning session, could be observed across different working memory (WM) processes and domains. We also predicted that fast changes could be distinguished from slow changes based on a comparison of experts in the motor domain (pianists) and non-experts (individuals with no piano training).; In Experiments 1 and 2, we examined practice-related changes in brain activation over the course of a scanning session during performance of delayed recognition tasks. We used event-related fMRI in order to examine the influence of practice on separate WM processes associated with different trial periods (cue, delay, probe). In Experiment 1, during performance of a face WM task, we observed practice-related decreases, and not increases, over the course of the session. Importantly, these decreases in neural activation occurred during the cue only. Furthermore, these decreases occurred without improvements in performance, suggesting that practice-related changes in activation may occur without behavioral evidence of learning. In Experiment 2, we examined further the question of whether practice differently influences domain-specific and domain-general WM networks. Participants performed two tasks that probed different WM domains (object and spatial). The influence of practice differed across levels of the cortical hierarchy such that multimodal regions showed greater practice-related decreases than primary sensory and motor regions. The influence of practice, as in Experiment 1, was most prominent during encoding. In this period only, domain-specific regions decreased to a greater extent than domain-general regions.; In Experiment 3, we examined 'fast' and 'slow' learning simultaneously by comparing short-term changes in brain activity for pianists and non-pianists during performance of a complex motor sequence learning task. All subjects demonstrated learning of the sequence, but pianists showed faster overall motor responses. Functional imaging revealed evidence of 'fast' changes within a task-active network of bilateral motor and parietal regions that decreased across the session for both groups. We also observed evidence of 'slow' changes, as demonstrated by more extensive activation for pianists, particularly in the right hemisphere, across prefrontal, motor, and parietal regions.; In all three experiments, we observed 'fast' learning, characterized by practice-related decreases in fMRI signal from early to late in the session. Additionally, in Experiment 3, we observed an expansion in the underlying network for individuals with expertise in the task. These findings suggest that 'fast' (associated with task repetition) and 'slow' (associated with the development of expertise) learning are based on different underlying mechanisms. Overall, our results suggest that an analysis of dynamic changes in brain activity provides insight into mechanisms underlying specific WM processes and domains, as well as long-term function...