PUB - Publikationen an der Universität Bielefeld

Sensory systems adjust their sensitivity through adaptation, i.e., a history-dependent shift of the stimulus-response characteristic. For example, in motion-encoding proprioceptors, adaptation to constant stimulation during continuous active movement could ensure high responsiveness to changes in movement speed. In the stick insect Carausius morosus, continuous active movement occurs during active tactile exploration movements of the antennae. As walking stick insects reliably respond to antennal tactile cues with targeted leg movements, adaptation of neurons of the antennal-mechanosensory pathway should affect the information transfer from the head to the legs. Here, we measure adaptation in an identified descending interneuron that conveys antennal proprioceptive information to the thoracic ganglia: The contralateral ON-type velocity-sensitive (cONv) interneuron. This interneuron encodes antennal-joint velocity as well as substrate vibration (Ache et al., 2015, J.Neurosci., 35:4081). Preliminary results showed that cONv reduces its response to repeated antennal deflection suggesting adaptation. Here, we ask whether multimodal activation of cONv can lead to a change in response intensity of the neuron when compared to unimodal stimulation. Using hook-electrode connective recordings, we examined the responses of the bilateral pair of cONv interneurons to antennal ramp-and-hold deflections at one of two ramp velocities. We found that cONv reached the same level of adaptation after 20 ramps irrespective of the velocity imposed, implying faster adaptation at higher velocity. Imposed movements of the opposite antenna did not affect the level of adaptation of cONv, while substrate vibration delivered at a rate comparable to footfall during walking set cONv into the adapted state, suggesting cross-modal adaptation