Abstract
Six experiments are reported that explore the relation between a learning/performance deficit observed in signalized rats and the phenomenon of learned helplessness. Previous research in signalized rats has demonstrated that exposure to aversive events that cannot be controlled (noncontingent events) has a deleterious effect on instrumental learning, much like exposure to inescapable shock affects escape/avoidance learning in intact animals. Experiment 1 showed that noncontingent tailshock has an effect similar to noncontingent legshock, inducing a learning deficit in spinal rats. Experiment 2 showed that 6 min of intermittent tailshock at an intensity of 1.5 mA was required to induce the deficit. Previous research demonstrated that the learning deficit observed following noncontingent legshock lasted for at least 20 hrs. Experiment 3 demonstrated that the learning deficit resulting from noncontingent tailshock decays between 48 and 96 hrs. Experiment 4 demonstrated that 360 s of 1.5 mA tailshock does not induce a deficit if subjects are signalized 2 hrs after shock exposure, suggesting that brain-mediated mechanisms can inhibit the induction of the learning deficit. Experiments on learned helplessness using intact rats have demonstrated that the learning deficit can be counteracted by prior exposure to contingent shock (an "immunization" experiment) or by shaping animals to learn to respond following noncontingent shock (a "therapy" experiment). Experiments 5 & 6 showed that these procedures also attenuate the learning deficit in spinal rats.
Crown, Eric Daniel (2000). Instrumental learning within the spinal cord: further examination of the deficit observed following noncontingent shock. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2000 -THESIS -C78.