Frontal lobe contribution to voluntary movements in humans.

We assessed the contribution of human prefrontal cortex to movement related potentials (MRPs) generated prior to voluntary movements. MRPs were recorded during self-paced movements of the right thumb (experimental condition I), the left thumb (experimental condition II) and both thumbs (experimental condition III) from patients with focal lesions centered in dorsolateral frontal association cortex (PFCx, n = 11) and in age matched controls (n = 11). Controls generated a slowly rising readiness potential (RP) beginning at about 1000 ms prior to movement. A negative shift (NS') began at about 450 ms and a motor potential (MP) appeared at about 100 ms prior to movement. Both the NS' and MP were maximal over scalp sites contralateral to movements. Unilateral PFCx lesions preferentially reduced the RP and NS' components of the MRP. This indicates that PFCx is involved in a neural network beginning at least 1000 ms prior to movement. The differential PFCx effects on the early (RP, NS') and late components (MP) suggest that these MRPs index different movement-related circuits.