Figure 1.
The stomatogastric nervous system (STNS) of crabs. A, Schematic of the STNS of the crab C. borealis. Neurons of the pyloric circuit are located in the stomatogastric ganglion (STG). They receive input from neuromodulatory projection neurons that originate in the paired commissural ganglia (CoG) and the unpaired esophageal ganglion (OG) and send their axons through the stomatogastric nerve (stn). Pyloric motor neurons project their axons through the lateral ventricular (lvn), pyloric dilator (pdn), and pyloric constrictor (pyn) nerves. The extracellular recording sites are indicated by circles. B, The core pyloric circuit consists of a group of pacemaker neurons: the anterior burster (AB) and two pyloric dilator (PD) neurons. They inhibit their followers, the lateral pyloric (LP) and 3–5 pyloric constrictor (PY) neurons. Inhibitory synapses are shown as circles, and electrical connections are depicted with resistor symbols. C, The pyloric rhythm and rhythm parameters. The activity of the PD neurons from the pacemaker group is recorded from the pdn. Activity of all neurons can be recorded from the lvn, where LP is typically the largest unit, PD is mid-sized, and PY are the smallest units. In addition, PD and PY activity are also recorded from the pdn and pyn, respectively. Cycle period is defined as the time from the beginning of one PD burst (PDon) to the next. Fcycle is the inverse of cycle period (P). Burst start (on) and end (off) for each neuron is calculated by dividing the latency with respect to PDon by the cycle period. In addition, we counted the number of spikes per burst (#spks) and calculated the average spike frequency (Fspks) by dividing #spks-1 by burst duration (off-on).