Neural mechanisms of motor program switching in the mollusc Pleurobranchaea. III: Role of the paracerebral neurons and other identified brain neurons

Identified neurons in the cerebropleural ganglion (brain) of the mollusc Pleurobranchaea were stimulated and recorded from intracellularly while recording the identified motor program from buccal muscles (reduced preparation) or nerves (isolated central nervous system). Neurons studied included the metacerebral giant neurons (MCGs), phasic paracerebral neurons (PC sub(p)'s), polysynaptic excitors of the PC sub(p)'s (PSEs), type II electrotonic neurons (ET sub(d)IIs)) type I electrotonic neurons (ET sub(I)'s) and several other identified neurons or neuronal classes. This study is consistent with the view that an interrelated cluster of brain neurons is specialized to command the ingestion motor program. A neural model of motor program switching in the buccal motor system is formulated, comprising separate command pathways for ingestion and egestion that converge on a common central pattern generator(s).