Motor adaptation and internal model formation in a robot-mediated forcefield

Abstract

Background Motor adaptation relies on error-based learning for accurate movements in changing environments. However, the neurophysiological mechanisms driving individual differences in performance are unclear. Transcranial magnetic stimulation (TMS)-evoked potential can provide a direct measure of cortical excitability. Objective To investigate cortical excitability as a predictor of motor learning and motor adaptation in a robot-mediated forcefield. Methods A group of 15 right-handed healthy participants (mean age 23 years) performed a robot-mediated forcefield perturbation task. There were two conditions: unperturbed non-adaptation and perturbed adaptation. TMS was applied in the resting state at baseline and following motor adaptation over the contralateral primary motor cortex (left M1). Electroencephalographic (EEG) activity was continuously recorded, and cortical excitability was measured by TMS-evoked potential (TEP). Motor learning was quantified by the motor learning index. Results Larger error-related negativity (ERN) in fronto-central regions was associated with improved motor performance as measured by a reduction in trajectory errors. Baseline TEP N100 peak amplitude predicted motor learning (P = 0.005), which was significantly attenuated relative to baseline (P = 0.0018) following motor adaptation. Conclusions ERN reflected the formation of a predictive internal model adapted to the forcefield perturbation. Attenuation in TEP N100 amplitude reflected an increase in cortical excitability with motor adaptation reflecting neuroplastic changes in the sensorimotor cortex. TEP N100 is a potential biomarker for predicting the outcome in robot-mediated therapy and a mechanism to investigate psychomotor abnormalities in depression.

Investigating the effects of repetitive paired-pulse transcranial magnetic stimulation on visuomotor training using TMS-EEG

“…Specifically, amplitude was increased and more lateralized over ipsilateral central electrodes (Figs 5 & 8). While previous work has used TMS-EEG to investigate changes in cortical reactivity associated with visuomotor adaptation (Koch et al ., 2020; Taga et al ., 2021), effects of learning were limited to the later peaks that are associated with increased contamination from sensory input (Biabani et al ., 2019). Consequently, as far as we are aware, the current study is the first to report a modulation of the early TEP peaks following visuomotor training.…”