AUTHOR=Evans Colin G. , Barry Michael A. , Jing Jian , Perkins Matthew H. , Weiss Klaudiusz R. , Cropper Elizabeth C. TITLE=The Complement of Projection Neurons Activated Determines the Type of Feeding Motor Program in Aplysia JOURNAL=Frontiers in Neural Circuits VOLUME=15 YEAR=2021 URL=https://www.frontiersin.org/journals/neural-circuits/articles/10.3389/fncir.2021.685222 DOI=10.3389/fncir.2021.685222 ISSN=1662-5110 ABSTRACT=

Multiple projection neurons are often activated to initiate behavior. A question that then arises is, what is the unique functional role of each neuron activated? We address this issue in the feeding system of Aplysia. Previous experiments identified a projection neuron [cerebral buccal interneuron 2 (CBI-2)] that can trigger ingestive motor programs but only after it is repeatedly stimulated, i.e., initial programs are poorly defined. As CBI-2 stimulation continues, programs become progressively more ingestive (repetition priming occurs). This priming results, at least in part, from persistent actions of peptide cotransmitters released from CBI-2. We now show that in some preparations repetition priming does not occur. There is no clear seasonal effect; priming and non-priming preparations are encountered throughout the year. CBI-2 is electrically coupled to a second projection neuron, cerebral buccal interneuron 3 (CBI-3). In preparations in which priming does not occur, we show that ingestive activity is generated when CBI-2 and CBI-3 are coactivated. Programs are immediately ingestive, i.e., priming is not necessary, and a persistent state is not induced. Our data suggest that dynamic changes in the configuration of activity can vary and be determined by the complement of projection neurons that trigger activity.