Cortical sensorimotor activity during movement execution [M] and motor imagery [I] performed under various force-time constraints was examined.  Event-related potentials (ERPs) were obtained from the C3 scalp site during isometric muscle contractions performed with a hand dynamometer and imagined contractions of the same task, while time to percent peak force (ballistic [B]: <250 ms; slow-graded [S]: >500 ms) and percent of peak muscle force (low [L]: <20% MVC; high [H]: >60% MVC) were varied.  Males (N = 26) also completed a tone-only control condition.  Cross-correlation between difference potentials (task ERP minus tone-only ERP) were: BM-SM = 0.48; BM-BI = 0.39; SM-SI = 0.90; BI-SI = -0.06; HM-LM = 0.17; HM-HI = 0.46; LM-LI = 0.72; HI-LI = -0.28.  Moderate correlations between [M] and [I] suggests that neural processing in the sensiorimotor cortex during [M] and [I] is different.  Low correlations between [B] and [S] movements, as well as between [H] and [L] movements, indicate that neural processing in the sensorimotor cortex is different depending on the speed and force of the movements, which is also found during imagined movements.  In conclusion, sensorimotor activity may be related to variations in force-time profiles during both [M] and [I].
   Supported by a U.S. Dept. of Veterans Affairs Medical Research Grant.