Figure 4
Efferent-mediated fast and slow excitation may be distinguished based on response activation and duration. (a) Ensemble mean response histograms (100 ms bins) were generated for irregular afferents during ipsilateral (red, 18 units, 108 trials) or midline efferent stimulation (black, 18 units, 74 trials). (b) Time course of efferent-mediated fast excitation is shown after subtracting the midline ensemble histogram from the ipsilateral ensemble histogram in panel (a). (c) Ensemble mean response histograms from panel (a) were replotted using a smaller 12.5-ms bin size. The first 500-ms of the ensemble histograms are shown. Rise times constants were derived from exponential fits. (d) Expansion of panel (a) demonstrates that estimates of slow excitation at t = 6–7 s (orange bar) exclude contributions from fast excitation. (e) Mean efferent-mediated fast excitation for ipsilateral and midline stimulation are plotted against CV*. (f) Mean efferent-mediated slow excitation for ipsilateral and midline stimulation are plotted against CV*. Total number of afferents for midline and ipsilateral stimulation are 144 (n = 65 regular, 79 irregular) and 120 (n = 34 regular, 86 irregular), respectively. Vertical dashed line separates regular from irregular afferents. Indicated p values in panels (e,f) are from comparisons of response amplitudes in regular or irregular afferents with midline vs. ipsilateral stimulation using Mann Whitney.
