Circuit plasticity coordinates action selection and temporal compression during operant conditioning in Aplysia

A central challenge in neuroscience is to explain how reinforcement jointly shapes action selection and the temporal structure of action execution to optimize behavioral efficiency. Using an ex vivo operant conditioning paradigm in the Aplysia feeding circuit, we found that reinforcement biases selection toward ingestive motor programs and shortens their duration by advancing the transition from protraction to retraction phases of the feeding movements. Temporal compression reflected coordinated plasticity of phase-switch elements.

Operant conditioning reduced the intrinsic electrical excitability of neuron B52 and thereby weakened B52-mediated inhibition of the retraction-initiating interneuron B64, while also lowering the threshold for triggering the B64 plateau potential. Phase-restricted co-manipulation of B52 and B64 activity reproduced protraction shortening. These results provide a circuit-level framework for how reinforcement coordinates motor-pattern selection with temporal structure within identified circuitry, a form of circuit plasticity that may contribute to the efficiency of action execution.

We thank Paul Smolen for comments on an earlier draft of the manuscript and Endang Kartikaningrum and Ling Zhong for maintaining the aquaria. This work was supported by National Institutes of Health grant R01 NS101356. Present address: Kobe University Graduate School of Medicine, Department of Neurophysiology, Kobe, Japan Department of Neurobiology and Anatomy, W.M.

Keck Center for the Neurobiology of Learning and Memory, McGovern Medical School at the University of Texas Health Science Center, Houston, TX, USA Yuto Momohara, Curtis L. Byrne The authors declare no competing interests. Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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