Figure 7
SCh injection for muscle spindle identification. (A) Foot displacement during the ramp-and-hold trial. (B) Histogram of firing rate changes after SCh injection for units classified as muscle spindle afferents. (C) A unit with strong SCh response that was differentially modulated by perturbation direction with a dynamic response during flexion of the leg (flexion phase bounded by dashed lines), likely representing a primary muscle spindle (type Ia) afferent. (D) A unit with modest SCh response with a small dynamic response during flexion of the leg, likely representing a secondary muscle spindle (type II) afferent. (E) A unit that responds during leg extension movements, but appears unaffected by SCh, likely representative of a cutaneous afferent. (F) A unit without response to SCh or limb motion. Firing rates are displayed as mean (line) ± standard deviation (shaded area). Unit waveforms (red, amplitude given below or above) displayed in (C–F) to show stability of signal amplitude before and after SCh injection.
