Dissociating the causal role of DLPFC and PMd in preparing and executing a bimanual coordination task – a neuro-navigated rTMS study

Abstract

Background: Previous neural imaging studies have shown that the dorsolateral prefrontal cortex (DLPFC) and dorsal premotor cortex (PMd) are active during complex bimanual tasks. Objective: This study used disruptive repetitive transcranial magnetic stimulation (rTMS) to further explore (1) if respective correlational evidence is a representation of a causal relationship and (2) if DLPFC and PMd show a differential causal contribution to specific task outcome measures. Methodology: A total of 41 young healthy adults (mean age: 22.20 years ± 2.95 SD) were enrolled in this study. We applied disruptive short-train rTMS (5 pulses, 10 Hz) on either DLPFC or PMd during either the preparation or execution of a complex bimanual tracking task (BTT). Specifically, we examined the effect of disruption on two BTT performance measures: task accuracy (TE) and movement stability (MI). While TE is assumed to measure the conscious monitoring of the task, MI measures only the stability (smoothness) of the bimanual movement. Results: DLPFC disruption during motor preparation had a short detrimental effect on TE, while MI was unaffected. There was no effect of DLPFC disruption during motor execution on either TE or MI. In contrast, PMd disruption during motor preparation and execution had a short detrimental effect on MI, while TE was unaffected. Conclusion: The current findings revealed a differential causal involvement of DLPFC and PMd in preparing and executing a complex bimanual coordination task. More specifically, DLPFC is suggested to be more involved in the conscious monitoring of the task and these cognitive operations of movement control were most crucial during motor preparation. In contrast, the role of PMd is restricted to the integration of two unimanual movements into a single control structure for both hands during both motor preparation and execution.