Delayed development of amnesia following electroconvulsive shock

Mice in Experiment 1 were given ECS either 8 sec or 20 sec following 1 training trial on an inhibitory avoidance task. A retention test was given 1, 6 or 24 hr later. In the 20 sec ECS delay groups retention performance was high at the 1 hr test but low at the 6 and 24 hr tests. In the 8 sec ECS delay group the retention performance was low at both the 1 hr and 24 hr tests. Response latencies 1 hr following treatments were not increased by ECS only or ECS following a noncontingent footshock. Experiment 2 examined state-dependency interpretations of these effects. Mice received either ECS or no ECS 20 sec after a training trial. One week later the mice received either an ECS or no ECS 1 hr prior to a retention test. Reinstatement of the ECS state did not enhance retention: the second ECS did not produce high retention latencies in mice given posttraining ECS. The findings are consistent with the view that amnesia develops as short term memory processes decline following ECS.