AVOIDANCE LEARNING ON THE TAIL-FLICK TEST. T.E. King*, J.W. Grau. Department of Psychology, Texas A&M Univeristy, College Station, TX 77843.
Prior work suggested that different neural circuits mediated tail-withdrawal from radiant heat depending on test intensity; high intensities evoke a spinal reflex while low intensities depdend on supraspinal mechansims. However, results from our lab indicate that the tail-flick response is spinally mediated over a wide range of test conditions (King, et al., Neurosci Abs, 19, 965). The experiments reported here show that this is only true if subjects are shielded from cues that predict impending pain. When such cues are present 8-12 s before heat reaches nociceptive thresholds, intact rats rapidly learn to flick before the stimulus becomes painful.
In all experiments, subjects were held in a covered tube, and tail heat was adjusted to produce tail-flick latencies between 3.5 to 4.5-s. In Exp. 1, rats were tested a day after they experienced a spinal transection (at T2) or a sham operation. Subjects were trained with a long signal (a visual cue was presented 4-s before radiant heat), a short signal (the cue was only presented during the ITI). When the long signal was presented, sham rats, but not spinals, rapidly learned to exhibit a tail movement to avoid the noxious heat. The short signal did not support learning. Exp. 2 showed that auditory and tactile cues also support avoidance learning on the tail-flick test, with significant learning occurring within the first 3 trials. Exp. 3 explored the relation between signal duration and learning. We found that an avoidance response was rapidly acquired when the signal was presented 8-12 s before radiant heat reached nociceptive thresholds. Both shorter and longer signal durations led to poorer learning. Supported to MH48994 to J.W.G.
Published in Society for Neuroscience Abstracts, 21, 1995, 388.