Corticomotor excitability during precision motor tasks.

The aim of this preliminary study was to investigate motor cortex (cortical) excitability between a similar fine visuomotor task of varying difficulty. Ten healthy adults (three female, seven male; 20-45 years of age) participated in the study. Participants were instructed to perform a fine visuomotor task by statically abducting their first index finger against a force transducer which displayed the level of force (represented as a marker) on a computer monitor. This marker was to be maintained between two stationary bars, also displayed on the computer monitor. The level of difficulty was increased by amplifying the position of the marker, making the task more difficult to control. Cortical measures of motor evoked potential (MEP) and silent period (SP) duration in first dorsal interosseous (FDI) muscle were obtained using transcranial magnetic stimulation (TMS) while the participant maintained the "easy" or "difficult" static task. An 11.8% increase in MEP amplitude was observed when subjects undertook the "difficult" task, but no differences in MEP latency or SP duration. The results from this preliminary study suggest that cortical excitability increases reflect the demand required to perform tasks requiring greater precision with suggestions for further research discussed.