Ne 05

Body movements and EMG were observed when monkeys were at rest without any movements. Body movements evoked by oICMS or eICMS were video-recorded. The timing of oICMS/eICMS was indicated by the flash of LEDs set near the body parts recorded. When body movements were observed, a pair of surface dish electrodes (NE-05, Nihonkohden) were attached to the skin over the belly of the responsible muscle. Muscle activity was amplified (5000 times), filtered (50–3000 Hz), digitized at 50 kHz, and stored on a computer simultaneously with neuronal activity using LabView software. Although body parts in which movements and/or EMG were evoked depended on the cortical site of oICMS/eICMS, EMG of the extensor carpi radialis longus and flexor carpi radialis muscles was mainly recorded and used for further analyses.

EMGs of the biceps brachii and triceps brachii muscles were obtained using surface electrodes (NE-05, Nihon Kohden) for monkey K or chronically implanted stainless steel wire electrodes (7-stranded 25.4-μm diameter wire with Teflon coating; A-M Systems, Sequim, WA) for monkey U. Signals from the electrodes were amplified (5000×) and bandpass-filtered (150–3000 Hz) using an amplifier (MEG-5200, Nihon Kohden), digitized at 20 kHz (PCIe-6321, National Instruments), and stored on a computer. The root mean square (RMS) of each EMG was calculated with a 100-ms moving window. The RMS of the EMG was aligned with task events, and the mean and SEM were computed (Supplementary Fig. 5).