Fig. 3. Sensory-induced activity in the intact animal. (A) Extracellular recordings of the ivn and the dvn before and after food injection. Top: ivn recording close to the brain. Middle: recording of the ivn close to the STNS. Bottom: pyloric rhythm on the dvn. Each dot labels the beginning of a new pyloric cycle. The pyloric period increased from 1.06 s before feeding to 0.77 s after feeding. (B) Left: phase plot of the pyloric neurons PD and LP before (open boxes) and after feeding (filled boxes). Medians of the beginning and end of the activity phase are given for each neuron. Black boxes show upper and lower quartiles. ^*P<0.05; ^**P<0.01 (Wilcoxon signed-rank test). Right: number of spikes per bin (250 ms) of the IV neurons before (open boxes) and after (filled boxes) feeding. (C) Extracellular recordings of ivn and dvn before (left) and after (right) chemosensory stimulation (upper two traces). In the two lower traces ivn activity was separated into the descending and ascending neurons by computer analysis. After chemosensory stimulation the descending (IV) neurons started to burst, whereas the activity of the ascending neurons appeared to remain unchanged. The bursts of the descending neurons were time locked with LG neuron bursts on the dvn. (D) Box plots (minimum, lower quartile, median, upper quartile, maximum) of period, burst duration and mean intraburst spike frequency of the rhythmic activity of the descending neurons. The square represents the mean. (E) Extracellular recordings of dvn and ivn in vivo (two bottom traces) during rhythmic IV neuron activity (top trace). LG neuron bursts coincided with each burst of the IV neurons that possessed a spike frequency of 30 Hz or more. The firing frequencies of LG and the IV neurons were measured as a sliding average with a bin width of 1 s (top two traces).