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1 Behavioural Brain Sciences Ctr., The University of Birmingham, School of Psychology, Birmingham, United Kingdom
* To whom correspondence should be addressed. E-mail: p.praamstra{at}bham.ac.uk.
Previous behavioral work has shown the existence of both anticipatory and reactive grip force responses to predictable load perturbations, but how the brain implements anticipatory control remains unclear. Here, we recorded EEG while participants were subjected to predictable and unpredictable external load perturbations. Participants used precision grip to maintain the position of an object perturbed by load force pulses. The load perturbations were either distributed randomly over an interval 700-4300 ms (unpredictable condition) or they were periodic with interval 2000 ms (predictable condition). Preparation for the predictable load perturbation was manifested in slow preparatory brain potentials and in EMG and force signals recorded concurrently. Preparation modulated the long-latency reflex elicited by load perturbations, with a higher amplitude reflex response for unpredictable compared to predictable perturbations. Importantly, this modulation was also reflected in the amplitude of sensorimotor cortex potentials just preceding the long-latency reflex. Together, these results support a transcortical pathway for the long-latency reflex and a central modulation of the reflex grip force response.
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