A brief temporal gradient of retrograde amnesia independent of situational change.

Rats were given a single electroconvulsive shock at varying intervals after receiving a punishing shock to the feet immediately after stepping into a compartment. Significant amounts of retrograde amnesia for the memory of the punishment was shown when electroconvulsive shock was administered up to and including 30 seconds after the punishment but not at 60 seconds. This brief temporal gradient cannot be explained in ternis of changed stimulus cues or learned interference analogouS to retroactive inhibition.