Duke Neurobiology Invited Seminar: Daniel Colon-Ramos: Electrical synapses create a high-pass filter to modulate sensory information processing and action selection in C. elegans
Daniel Colon Ramos
Abstract: Animals perform specific behaviors in response to specific sensory information from their environment. Yet, similar sensory stimuli can trigger distinct behaviors depending on the context, a process known as "action selection". How animals select which context-dependent behavior to perform? We examined this question in the nematode C. elegans. C. elegans can learn to prefer a temperature, and when in a gradient, will move across the gradient towards their preferred temperature (a behavior known as gradient migration). Upon encountering their preferred temperature, they switch their behavioral strategy to track the temperature (a behavior known as isothermal tracking). From forward genetic screens we uncovered a role for the innexin/inx-1 gene in action selection during thermotaxis: mutants for inx-1 display reduced gradient migration and abnormally perform isothermal tracking at incorrect temperatures. We discovered that inx-1 is specifically required in the AIY interneurons, a pair of first-layer interneurons of the thermotaxis circuit. Inx-1 forms an electrical synapse that couples the bilaterally symmetric AIY interneurons. The coupling of the interneurons reduces input resistance and excitability, altering sensory information processing. The AIY interneurons control persistent forward movement in response to a stimulus, and their reduced excitability affects persistence of thermotaxis behavior as it senses temperature changes in the gradient, and thereby, action selection in response to specific temperatures. Our findings identify a specific role for electrical synapses in sustaining electrophysiological circuit properties that then enable context-dependent action selection based on experience.