ICMS motor mapping

Intracortical microstimulation (ICMS) procedures were used to identify the caudal and rostral forelimb areas (CFA and RFA). A digital image of the cortical surface was acquired and overlaid with a 250 µm grid in order to co-register insertion sites with their corresponding cortical target. Responses at the grid intersections (avoiding surface vasculature) were noted and used to inform microelectrode array placement. Pulses trains synchronized with an audio monitor were delivered at 1-Hz, and each train consisted of bursts of 13 bi-phasic pulses at a pulse frequency of 300-Hz and phase duration of 100-ms. During data analysis, responses were grouped categorically by the following scheme: "Distal Forelimb" (DF), which included wrist extension or flexion, or digit movements; "Proximal Forelimb" (PF), which included elbow flexion; "Distal-Proximal" (DF-PF), which was assigned when an interpolated electrode site was likely to be between a Distal or Proximal site; "No Response" (NR), when threshold stimulation (up to 80 µA) did not elicit any movement; or "Other" (O), when a trunk, shoulder, neck, mouth, face, or vibrissae response was elicited.