Figure 1.

Pyloric activity phases are variable but not correlated with the cycle period. A, Left, Schematic diagram shows the layout of the STNS in vitro and the locations of intracellular (electrode) and extracellular (circles) recordings. OG: esophageal ganglion, CoG: commissural ganglion, STG: stomatogastric ganglion, lvn: the lateral ventricular nerve, pdn: PD nerve, pyn: pyloric nerve. Middle, Schematic diagram shows a simplified circuit diagram of the neurons recorded. Ball-and-stick symbols are inhibitory chemical synapses. Resistor denotes electrical coupling. Right, Simultaneous extracellular and intracellular recordings show the regular triphasic oscillations of the pyloric circuit. Shown are bursting activity of pacemaker neuron PD and follower neurons LP and PY. Cycle period (P) and latencies of the onset and end of each burst (arrows) are calculated from the onset of the PD burst. Extracellular recordings are from the lvn (showing the LP, PD and PY spikes), the pdn (showing the PD spikes), and pyn [showing the PY and the lateral posterior gastric (LPG) neuron spikes]. Intracellular recording from the LP neuron shows bursting activity (yellow) and slow wave oscillations, as well as timing of IPSPs from the PY (light blue) and PD (pink) neurons. B, Burst latencies of the PD and LP neuron in reference to PD burst onset, as marked in panel A, shown versus P. Quartile plot shows the distribution of P, with the dashed line indicating the mean value. Lines indicate best linear fit, showing that latencies grow proportionally with P. C, Phase values (φ = latency/P) shown versus P. Histograms show distribution of φ values. Linear fits indicate a lack of correlation between all φ values and P. D, CV of P and φ values shown to compare variability of the values within preparations (quartile plots) to their variability across preparations (circles).