Event-related potentials as a function of movement parameter variations during motor imagery and isometric action

Neuroimaging and electrophysiological studies have shown that executed acti on and motor imagery activate common neuronal substrates, leading to the hy pothesis that movement preparation and motor imagery are functionally equiv alent processes. This study further tested the functional equivalence hypot hesis by determining whether electrocortical patterns associated with varia tions in motor control parameters are similar during imagined and executed actions. Event-related potentials (ERPs) were recorded from the supplementa ry motor/premotor area (SMA/PMA; FCz site) and primary motor area (M1; C3, C4 sites) during an executed and an imagined, cued, discrete isometric cont raction task while target force (TF; low, moderate) and rate of force devel opment (RFD; slow, rapid) were varied. For M1, the correlation of ERPs betw een moderate- and low force-executions was near zero and N2 amplitude was g reater for moderate than low force executions, indicating that M1 activity is related to TF. Rapid executions were greater in amplitude and longer in latency than slow executions and the ERPs for rapid- and slow-executions we re negatively correlated, indicating that M1 activity is also related to RF D. There were no differences in N2 amplitude and a zero correlation between execution and imagined actions of similar TF and RFD, indicating that neit her TF or RFD are represented in M1 activity during imagery. For SMA/PMA, t here was a moderate correlation between moderate- and low force-executions and larger N2 amplitude for moderate- than for low force-executions, indica ting that TF may be related to SMA/PMA electrocortical activity. ERP patter ns were uncorrelated between rapid- and slow-execution at FCz, but N2 ampli tude was the same, making it unclear whether the RFD parameter is represent ed in FCz activity. The correlational and N2 amplitude analyses demonstrate that patterns of electrocortical activity at SMA/PMA are nearly isomorphic during executed and imagined actions as TF and RFD are varied. These resul ts provide evidence that patterns of electrocortical activity associated wi th variations in the parameters of executed action are similar during motor imagery at SMA/PMA but not at M1. (C) 2000 Elsevier Science B.V. All right s reserved.