Figure 3. Motor unit recordings during active movement in primates.

(a) An injectable version of the Myomatrix array (Figure 1—figure supplement 1g) was inserted percutaneously (Figure 1—figure supplement 1i) into the right biceps of a rhesus macaque performing a cued reaching task. Green and red dots: reach start and endpoints, respectively; gray regions: start and target zones. (b) Recording from 5 of 32 unipolar channels showing spikes from three individual motor units isolated from the multichannel recording (Figure 1—figure supplement 2). (c) At trial onset (dotted line), a sudden force perturbation extends the elbow, signaling the animal to reach to the target. (d) Spike times (tick marks) from 13 simultaneously recorded motor units. (e) Example voltage data from a Myomatrix array (top) and traditional fine-wire EMG (middle, bottom) collected from the same biceps muscle in the same animal performing the same task, but in a separate recording session. Gray traces (bottom) show smoothed EMG data from the fine-wire electrodes in all trials, orange trace shows trial-averaged smoothed fine-wire EMG, and dark gray trace represents smoothed data from the example fine-wire trace shown above it. (f) Spike times of four motor units (of the 13 shown in d) recorded simultaneously over 144 trials.