Control of memory by spreading cortical depression: A case for stimulus control.

Abstract

A stimulus-control hypothesis is offered to account for recent findings which have been taken to indicate that spreading depression prevents the neural storage of memory traces. 3 general conclusions derived from the spreading depression results are reevaluated: (a) Memory confinement to 1 cerebral hemisphere produced by training under unilateral depression is reinterpreted as a generalization-decrement phenomenon, (b) Memory transfer between cerebral hemispheres produced by a few reinforced responses with neither hemisphere depressed is reinterpreted as a stimulus-generalization phenomenon, (c) Memory storage prevented by spreading depression is reinterpreted as memory storage displaced by spreading depression from the depressed areas in the cortex to the nondepressed areas in the subcortex. Several new experiments suggested by the stimulus-control hypothesis are discussed and several old results at variance with the memory interpretations are reexamined in terms of the stimuluscontrol hypothesis.

Retrieval of memory in animals.

“…Misanin and his colleagues have made a similar point in relation to the amnestic effects of hypothermia (e.g., Misanin & Hoover, 1971). Similarly, Schneider has suggested that amnestic effects caused by the application of potassium chloride to the brain (e.g., Kapp & Schneider, 1971;Schneider, 1967) may be mediated by failure in memory retrieval, a contention he has documented with thorough supporting evidence from many sources. Schneider has made a similar suggestion concerning the amnestic effects of electroconvulsive shock (Schneider, Malter, & Advokat, 1969).…”

Asymmetrical state dependency from temporary septal area dysfunction in rats.

“…Another frequently used technique of producing reversible dysfunction of a limited area of the brain, cortical spreading depression, also appears to have state-dependent properties. Schneider (1967) presented arguments and evidence that lack of transfer of training seen when spreading depression is initiated in one hemisphere during conditioning and in the other hemisphere during testing may be a result of "generalization decrement." Generalization decrement refers to the stimulus properties of an abnormal state induced by drugs or other treatments and is one explanation of the basic dissociative or state-dependent phenomenon.…”

Spreading Depression: A Behavioral Analysis

“…Before pursuing the generalization hypothesis further, in fact in order to clarify it, it is important to add a comment about our view of memory confinement in general (Schneider, 1967). In our estimation the reason animals trained with one hemisphere depressed show no retention when tested with the opposite hemisphere depressed is not that one hemisphere stores memory and the other does not; rather, it is that depression has stimulus properties that are not the same during training and testing.…”

“…The effects have also been seen with behaviors involved in drinking and shock avoidance. Schneider (1966Schneider ( , 1967 and Thompson and Hjelle (1965), in independent studies, examined the effects of depression on learned avoidance behavior and found that the disruptive effects correlated with the motor demands of the task. That the difference in water consumption decreases as the time for drinking increases was taken as evidence that depression affects motor behavior.…”