Neural Mechanisms Underlying Functional Plasticity of the Human Brain

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Learning and skill acquisition rely to a large extent on implicit processes that occur independent of conscious awareness, both on short and long timescales. An example on a short timescale is repetition priming (RP) improved performance in identifying, producing, or classifying a stimulus upon repetition of the same or a related stimulus. Neuroimaging reveals that RP is often accompanied by repetition suppression (RS) reduced neural activation in parts of the brain that are critical for the task at hand. Despite 20 years of research, the link between RP and RS remains elusive. Many theories have focused on changes in local activity within discrete brain regions. However, an alternative explanation is that RS might be a consequence of more efficient communication across large-scale cortical networks. By this account, repetition leads to more efficient coupling across brain regions (functional connectivity: FC), which simultaneously reduces local neural activity and enhances cognitive performance. However, there is little direct evidence to support this hypothesis to date. Thus, there is a critical need for studies that directly test this hypothesis to elucidate the neural mechanism underlying this fundamental process. Regarding longer timescales, evidence demonstrates that spontaneous fluctuations of brain activity across large-scale networks play a fundamental role in learning and skill acquisition as well. While these patterns of activity persist, largely independent of ongoing thoughts, they are also modulated by experienc to some extent, and this modulation has an impact on future behaviour and performance. Little is known about how this intrinsic activity interacts with RP or RS, but this could be a fundamental mechanism underlying long-term functional plasticity in the brain; thus, there is a critical need for studies that elucidate the relationship between repeated experiences, patterns of intrinsic activity, and long-term behavioural facilitation. This research proposal has 2 primary objectives:*** 1) To determine if RP and RS reflect neural efficiency due to enhanced FC, and if they interact with long-term neurocognitive plasticity reflected by intrinsic activity, using fMRI.*** 2) To establish causal cortico-cortical and brain-behaviour relationships that lead to both short- and long-term neurocognitive plasticity by experimentally modulating brain activity using transcranial magnetic stimulation.******The long-term objective is to develop a comprehensive model that characterizes and quantifies the causal interrelationships between implicit processes acting on different timescales, to understand how neurocognitive plasticity shapes cognitive performance over time. This work will produce critically needed insight into these fundamental processes, of which we currently know little, and will have a significant impact on the fields of human learning and cognition.