Activity of a monkey PTN during precision and power grip, (a): Response averages for a PTN and for the muscle (1DI) in which it produced a PSF, showing activity before and during a precision grip task. Histograms of PTN discharges for 16 repetitions of the task with either light (above) or heavy force were constructed in relation to the earliest detectable lever movement (time zero). The gross EMG recorded at the same time with percutaneous wire electrodes was rectified and averaged (shown at right), (b): Corresponding task-related analysis for the same PTN and muscle during the power grip. Time zero represents the earliest detectable pressure increase in the rubber cylinder. This cell was almost completely deactivated during the power grip, despite the fact that its target muscle showed increased activity during this task.