Figure 1.

Overt crawling behavior after complete transection of the M2/M3 interganglionic connectives. A,B, Movement raster plots depicting elongation (E, black boxes) and contraction (C, gray boxes) movements over time for individual leeches that received a sham surgery (A) and an M2/M3 transection surgery (B). Movements are shown for time points before the surgery (Pre), 1, 7, and 21 days after surgery. C, Graph of crawling activity at several time points after surgery for a random subset of the leeches used in Figs. 2–6 (n = 10 for each group). Error bars denote the standard deviation. *, statistically significant differences (p < 0.01). D, Schematic depicting a truncated view of the CNS of a leech. All nerve recordings showing fictive locomotor activity were obtained from the dorsal posterior nerve root (DP nerve), which contains the axon of the motoneuron DE-3. Although all 21 segmental ganglia have DPs, only the DP associated with mid-body ganglion M8 (DP(8)) is illustrated here. Diagonal hash marks denote ganglia that were removed to simplify the cartoon.