Uncovering the drivers of human sensorimotor learning: EEG oscillatory manifestations of error, repetition and reward processing.

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Sensorimotor learning is at the heart of humans' capacity to acquire and maintain efficient motor behaviour across the lifespan. Computational modeling work has highlighted the contributions of sensory prediction errors and target errors to the acquisition of a new motor behaviour, as well as the contributions of movement repetitions and rewards to the long-term retention of motor memories. Still, there remains an important gap in our understanding of how these processes manifest in the brain, and in particular how functional interactions between brain regions change during learning. In this light, the long-term objective of my research is to study learning-related neuroplasticity at the systems levels within the human sensorimotor network. Interestingly, there is growing evidence that rhythmic brain activity plays a key role in computations involved in learning and plasticity. Specifically, neural oscillations in the theta-band (3-7 Hz) have been shown to be modulated by sensory prediction errors and target errors, whereas oscillations in the beta-band (15-30 Hz) have been shown to be modulated by movement repetitions and rewards. The short-term objective of my program is to test the hypothesis that theta and beta oscillations instantiate functional communication in distinct brain networks mediating errors vs. repetitions and rewards, with the important implication that they respectively relate to acquisition and retention of motor behaviours. In Theme 1, experiments will test the hypothesis that theta-band oscillations i) covary with the size of sensory prediction errors, ii) causally relate to acquisition of a new motor behaviour, and iii) depend upon the cerebellum. In Theme 2, experiments will test the hypothesis that beta-band oscillations i) reflect the degree of plasticity induced by repetitions and rewards, ii) causally relate to retention of a new motor behaviour, and iii) are modulated by sensory prediction errors. A key element is to bridge the gap between brain and behaviour, relating neural responses incurred by errors, repetitions and rewards to rates of acquisition and retention of motor memories. Paradigms of visuomotor adaptation of goal-directed reaching movements will be used while electroencephalography (EEG) is recorded. To establish a causal link between neural responses and motor behaviour, non-invasive brain stimulation techniques will be used to influence cortical activity, including single-pulse transcranial magnetic stimulation (TMS), repetitive TMS (rTMS) and transcranial alternating current stimulation (tACS). At a time where we are garnering the tools to alter neural rhythms in a circumscribed manner through non-invasive neuromodulatory interventions, there is a need for fundamental research to provide reliable biomarkers of known mediators of learning. The present research looks to fill that gap, with the ultimate hope of optimizing motor learning and performance in both healthy and brain-injured populations.