Figure 4. Spikes in dINs are early relative to those in non-dINs and vrs during swimming.

A, overlapped spikes of a motoneuron (mn) and dIN aligned relative to the start of ‘adjacent’ ventral root (vr) bursts (dashed line) show that the dIN fires earlier. The inset diagram shows the typical recording arrangement (actual recording site and vr bursts, black; adjusted recording site and vr bursts, grey; see Fig. 1). B, distribution of spike peak timing for the two neurons in A. C, the relative timing of spike peaks for 16 dINs (dark bars) and 15 non-dINs (light bars), all adjusted to give timings relative to an adjacent ventral root. Distributions of spike timings for each neuron (e.g. B) were normalised (as % of the whole sample of spike times for each neuron, using 2 ms bins) and then combined to give overall spike time distributions for dINs and non-dINs.