- Title
- The timing of activity in motor neurons that produce radula movements distinguishes ingestion from rejection in Aplysia
- Author
- Morton, Douglas Wilson
- Degree
- Doctor of Philosophy, Case Western Reserve University,
Neuroscience and Bioengineering, 1993.
- Advisor
- Hillel J. Chiel
- Pages
- 175p.
- Abstract
- The marine mollusc Aplysia californica carries out biting, swallowing, and rejection responses using different movements of its radula, a structure that is used to grasp and move food. Video records during feeding show that the timing of radula closure during the radula protraction-retraction cycle constitutes a major difference between ingestion (biting or swallowing) and rejection. During ingestion, the radula is closed as it retracts. During rejection, the radula is closed as it protracts. Using in vivo cuff electrodes, one can observe two different patterns of activity on nerves that are likely to mediate these radula movements. Patterns I and II are associated with ingestion and rejection, respectively, and are distinguished by the timing of radula nerve (RN) activity relative to the onset of buccal nerve 2 (BN2) activity. During these patterns, BN2 activity is temporally related to protraction and retraction movements, while RN activity is temporally related to radula closure. Three buccal ganglion motor neurons have been characterized that are likely to contribute to these patterns. Neurons B8a and B8b project through the RN and act to close the radula. Neuron B10 projects through BN2 an d acts to retract the radula. The timing of activity in these neurons can be used to distinguish the ingestion-like and rejection-like motor patterns produced by a reduced preparation. B8a, B8b and B10 are active together during the ingestion-like pattern. Activity in B8a and B8b ends prior to the onset of activity in B10 during the rejection-like pattern. During both feeding-like patterns, the activity and peripheral actions of B8a, B8b, and B10 are consistent with the neural activity and radula movements observed in vivo during ingestion and rejection. These results suggest that the timing of activity in B8a and B8b relative to activity in B10 can be used to distinguish ingestion from rejection, and that this difference may contribute to the different radula movements underlying these responses. Studying the neural circuitry that mediates activity in B8a, B8b, and B10 could provide insights into how animals produce multiple behavioral responses, as well as how they decide which response to produce.
- Keywords
- timing activity motor neurons radula movements ingestion rejection Aplysia
Document number: case1057178515.
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