Figure 2

Typical responses of a single unit under anesthesia with isoflurane only. Top: Raster plots of the responses to 50-Hz stimulation in first (left) and second (right) blocks. Each row on the raster plots represents the spike train of the single unit corresponding to a given stimulus lasting for 2 seconds. Stimuli were presented ten times at each of five amplitudes (each indicated by a different color; at this frequency, the faintest stimulus did not elicit a response in this afferent). Bottom: Mean firing rates as a function of amplitude at the three frequencies tested. Each point indicates the average firing rate over 10 repetitions of each stimulus. Error bars denote the standard deviation. Note that we observed entrainment plateaus in a subset of fibers [14], but these were relatively uncommon given how sparsely amplitudes were sampled at each frequency.