The capacity of motor reflex and vocalization thresholds to support avoidance conditioning in the rat.

Unconditional responses (URs) of the rat that predict 1-trial, step-through passive avoidance conditioning were identified. The URs examined were spinal motor reflexes (SMRs) and vocalization afterdischarges (VADs) generated by tailshock. In Experiment 1, SMR and VAD thresholds were determined following systemic administration of saline or morphine sulfate. Experiment 2 revealed that the capacity of these tailshocks to support conditioning covaried with the probability that VADs were elicited and were independent of the proportion of SMRs that were generated. This pattern of conditioning was not a consequence of either morphine-induced memory deficts or its induction of state-dependent learning (Experiment 3). The results are consistent with the 2-process theories of J. Konorski (1967) and A. R. Wagner & S. E. Brandon (1989) in which the unconditional stimulus is viewed as being composed of separable but interrelated epicritic-sensory and protopathic-emotive attributes.