Neural correlates of habituation of the proleg withdrawal reflex in larvae of the hawk moth, Manduca sexta |
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Authors: | E R Wood D E Wiel J C Weeks |
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Institution: | (1) Institute of Neuroscience, University of Oregon, Eugene, Oregon 97403-1254, USA, Tel.: +1-541/346-4517, Fax: +1-541/346-4548, e-mail: weeks@uoneuro.uoregon.edu, US |
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Abstract: | The larval proleg withdrawal reflex of the hawk moth, Manduca sexta, exhibits robust habituation. This reflex is evoked by deflecting one or more mechanosensory planta hairs on a proleg tip.
We examined neural correlates of habituation in an isolated proleg preparation consisting of one proleg and its segmental
ganglion. Repeated deflection of a single planta hair caused a significant decrease in the number of action potentials evoked
in the proleg motor nerve (which carries the axons of proleg retractor motor neurons). Significant response decrement was
seen for interstimulus intervals of 10 s, 60 s and 5 min. Response decrement failed to occur in the absence of repetitive
stimulation, the decremented response recovered spontaneously following a rest, and electrical stimulation of a body wall
nerve facilitated the decremented response (a neural correlate of dishabituation). Adaptation of sensory neuron responses
occurred during repeated hair deflections. However, when adaptation was eliminated by direct electrical stimulation of sensory
neurons, the response in the proleg motor nerve still decreased significantly. Muscle recordings indicated that the response
of an identified proleg retractor motor neuron decreased significantly during habituation training. Thus, habituation of the
proleg withdrawal reflex includes a central component that is apparent at the level of a single motor neuron.
Accepted: 20 December 1996 |
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Keywords: | Habituation Dishabituation Manduca sexta Learning Invertebrate |
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