Feeding neural networks in the mollusc Aplysia.
Aplysia feeding is striking in that it is executed with a great deal of plasticity. At least in part, this flexibility is a result of the organization of the feeding neural network. To illustrate this, we primarily discuss motor programs triggered via stimulation of the command-like cerebral-buccal interneuron 2 (CBI-2). CBI-2 is interesting in that it can generate motor programs that serve opposing functions, i.e., programs can be ingestive or egestive. When programs are egestive, radula-closing motor neurons are activated during the protraction phase of the motor program. When programs are ingestive, radula-closing motor neurons are activated during retraction. When motor programs change in nature, activity in the radula-closing circuitry is altered. Thus, CBI-2 stimulation stereotypically activates the protraction and retraction circuitry, with protraction being generated first, and retraction immediately thereafter. In contrast, radula-closing motor neurons can be activated during either protraction or retraction. Which will occur is determined by whether other cerebral and buccal neurons are recruited, e.g. radula-closing motor neurons tend to be activated during retraction if a second CBI, CBI-3, is recruited. Fundamentally different motor programs are, therefore, generated because CBI-2 activates some interneurons in a stereotypic manner and other interneurons in a variable manner.
Cropper
Elizabeth C
EC
Department of Physiology and Biophysics, Mt. Sinai School of Medicine, New York, NY 10029, USA. elizabeth.cropper@mssm.edu
Evans
Colin G
CG
Hurwitz
Itay
I
Jing
Jian
J
Proekt
Alex
A
Romero
Adarli
A
Rosen
Steven C
SC
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001048:Aplysia / Q000502:physiology*; D001522:Behavior, Animal; D004068:Digestive System Physiological Phenomena; D005246:Feedback; D005247:Feeding Behavior / Q000502:physiology*; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000502:physiology; D009043:Motor Activity; D009415:Nerve Net / Q000166:cytology / Q000502:physiology*; D009433:Neural Inhibition; D016571:Neural Networks, Computer; D009474:Neurons / Q000145:classification / Q000502:physiology*