Vulnerability of skeletal and autonomic manifestations of memory in the rat to electroconvulsive shock.

A series of experiments was performed to probe the phenomenon of sparing of memory by electroconvulsive shock (ECS) when amnesia is assessed by autonomic indices. Differential vulnerability of memory as indexed by skeletal and autonomic responses was determined to be a function of a higher threshold to disruption for autonomically indexed memories. Autonomic responses spared by ECS were found to reflect underlying memory rather than artifact produced by nonassociative factors arising from the interaction of conditioned stimulus (CS), unconditioned stimulus (US), and ECS. Furthermore, retrograde amnesia gradients of different slopes were observed with skeletal and autonomic measures. Two interpretations of these phenomena are discussed. One hypothesis suggests that individual components of a memory are consolidated at different rates, whereas the other concerns the differentail sensitivity of various measures in assessing memory.