FIGURE 4.

Lymnaea’s central nervous system and its identified neurons. (A) Lymnaea’s central nervous system (CNS) is comprised of a circumesophagal ganglionic ring made up of nine ganglia plus two buccal ganglia that are not part of the inner ganglionic ring (LCe, left cerebral ganglion; RCe, right cerebral ganglion; LPe, left pedal ganglion; RPe, right pedal ganglion; LPl, left pleural ganglion; RPl, right pleural ganglion; LPa, left parietal ganglion; RPa, right parietal ganglion; Vi, visceral ganglion; the paired left and right buccal ganglia are not shown in this image. To expose location of neurons discussed in this paper, the cerebral commissure connecting LCe and RCe has been cut and LCe and RCe have been folded out laterally). Inside the ganglia somata of many neurons can be recognized. Many of these neurons are individually identifiable. (B) Enlargement of the boxed area in (A) showing the location of the two identified neurons that are the main focus of the paper. Right pedal dorsal 1 (RPeD1), located on dorsal surface of the RPe ganglion is a multi-modal neuron involved in the control of Lymnaea’s aerial respiration and an important locus of operant-conditioning induced plasticity of the animals’ respiratory behavior. The cerebral giant cell (GCG) indicated here is one of a bilaterally symmetrical pair of interneurons instrumental in the control of Lymnaea’s feeding behavior. The CGCs are important loci of reward-conditioning of the animals feeding behavior. These composite images were generated from 15–20 images taken at different focal depths using DMap focus stacking algorithm in Zerene Stacker build T201404082055 (Zerene Systems, Richland, WA, USA).