Investigating attentional demands of a continuous primary motor task using probe reaction time and measures of corticospinal excitability


The performance of a secondary motor task during an ongoing motor task can require attention; however, it is unclear how the attentional demands of the ongoing task may affect the preparation and execution of the secondary task. Previously, probe reaction time (RT) tasks have been used as secondary tasks to investigate the attentional demands of various primary tasks. The purpose of the present experiment was to investigate whether the attentional demands of a cyclical primary motor task vary with location within a movement cycle, and whether these variations are reflected as differences in probe RT and/or measures of corticospinal excitability. Participants performed a continuous tracking task involving cycles of wrist flexion and extension with their left hand. A probe RT task involving isometric force production was performed with the right hand in response to auditory stimuli (80 dB and 120 dB) that occurred as the left hand cycled through one of five locations. Additionally, on separate trials, transcranial magnetic stimulation was applied over the left primary motor cortex to assess corticospinal excitability associated with the probe RT task. Generally, probe RT latencies were shorter following a reversal in direction of the left hand (i.e., after the left wrist cycled from flexion to extension) and there were no differences in corticospinal excitability. These results suggest that the attentional requirements for a continuous motor task vary across locations within a movement cycle, and these variations are reflected behaviourally as differences in probe RT.

Acknowledgments: Supported by NSERC and the Ontario Ministry of Research, Innovation and Science