(A) Left: Representative recordings of nuchal and contralateral forelimb EMG activity to show the temporal relations among twitches in those muscles. Asterisks denote experimenter-scored twitches. Right: Cross-correlogram (5-ms bins) of nuchal muscle twitches with ipsilateral (dotted line) and contralateral (solid line) forelimb twitches. (B) Mean (+SEM) twitching per min for nuchal muscle and ipsilateral (ipsi) and contralateral (contra) forelimb muscles across 15 P8 rats. Ipsi: ipsilateral; contra: contralateral. (C) Stacked plot showing the percentage of IO units that exhibited significant activity within ±10 ms of twitch onset in relation to nuchal, ipsilateral forelimb, contralateral forelimb, and hindlimb twitches. (D) Perievent histograms (5-ms bins) showing IO unit activity in relation to nuchal, ipsilateral forelimb, and contralateral forelimb twitches. Data are pooled across 17, 9, and 10 units, respectively. Upper and lower confidence bands (p < 0.01 for each band) are indicated by horizontal dashed lines. (E) Perievent histogram (20-ms bins) showing IO unit activity in relation to peripheral limb stimulation for units that were most active within ±10 ms of twitch onset. Data are pooled across 15 units and triggered on 369 stimulations (F) Perievent histogram (5-ms bins) showing twitch-related IO unit activity for units that were most active >10 ms after twitch onset. Data are pooled across 7 units and triggered on 2059 twitches. Upper and lower confidence bands (p < 0.01 for each band) are indicated by horizontal dashed lines.