The Journal of Neuroscience, July 1, 2002, 22(13):5265-5270
BRIEF COMMUNICATION
Spatial Transformations in the Withdrawal Response of the Tail in
Intact and Spinalized Rats
Corey L.
Cleland and
Ross E.
Bauer
Department of Biology, James Madison University, Harrisonburg,
Virginia 22807
Previous studies of spatial transformations between sensory input
and motor output in escape responses have suggested two alternative
patterns of spatial integration. The continuous pattern corresponds to
withdrawal movements directed 180° away from the location of the
stimulus, whereas the categorical pattern corresponds to movements that
are biased toward a limited number of preferred directions. The goal of
these experiments was to determine which pattern best describes the
tail withdrawal response in spinalized and intact rats by applying
pinpoint heat stimuli at eight points distributed circumferentially
around the tail and measuring the direction and speed of the resulting
withdrawal response. Our results are consistent with a novel, hybrid
continuous-categorical movement strategy. In the spinalized animal,
responses were primarily away from the stimulus (the continuous
component) but exhibited a pronounced ventral bias (the categorical
component). In addition, stimuli delivered to the ventral surface,
which would be expected to evoke a dorsally directed response (opposite
to the preferred ventral direction), instead evoked responses that were
markedly variable and clustered in the left and right directions.
Intact rats showed a similar pattern of response, except reversed; the bias was in the dorsal direction, and the response to dorsal
stimulation was now highly variable and lateral in direction. These
results reveal a complex tail withdrawal strategy that is modulated by descending supraspinal pathways to adapt the response to the
biomechanical and environmental constraints imposed on movement of the
rat tail.
Key words:
spinal; reflex; pain; nociception; thermal; flexion
Copyright © 2002 Society for Neuroscience 0270-6474/02/22135265-06$05.00/0