Movement-related potentials with reference to isometric force output in discrete and repetitive tasks.

This study investigates whether different speed and accuracy constraints in discrete and repetitive index finger isometric force-production tasks influence the characteristics of the movement-related potentials (MRP) preceding and accompanying these tasks. Three components of MRP (Bereitschaftspotential, BP, motor potential, MP, and movement-monitoring potential, MMP) associated with isometric force output were identified and examined. Our principal finding for the MRP amplitude showed that only MMP, not BP and MP, was enhanced at higher rates of force development for both speed and accuracy tasks. That is to say, there was a high correlation between MMP peak amplitude and the rate of force development for both repetitive and discrete force-production tasks. Additionally, the amplitude of MMP was consistently higher for fast, rather than accurate, force outputs. Moreover, the results from analysis of MRP onset times suggest that, in general, the MRP begin earlier for the fast force output than for the accurate force output.