Figure 9.

A, Summary of response patterns for different populations of neurons during precision grip task. Proportions are given for spinal PreM-INs, UID neurons in M1 (Wannier et al., 1991), and PTNs in M1 (Smith et al., 1975), and CM cells in M1 (Maier et al., 1993). Note that the t+ components of CM cells and PTNs include other sustained activities during a hold period, i.e., “ramp” and “decrementing” patterns. The proportion of spinal PreM-IN target muscle results is also shown. B, A schematic illustration for possible functional connections. The dashed lines indicate connections not tested in this study. The gradual increase in the proportion of a muscle-like activity pattern (p+t+) suggests that the phasic and tonic activities could be converged and integrated at each neural level.