Date of Award

1964

Document Type

Senior Scholars Paper (Colby Access Only)

Department

Colby College. Biology Dept.

Advisor(s)

Paul P. Perez

Second Advisor

James M. Gillespie

Abstract

The consolidation theory of memory assumes that a neural fixation process goes on when a subject is confronted with a stimulus to be learned; and, most important, this fixation process continues after the subject is no longer confronted with the stimulus. Interference of some sort with this fixation or perseveration process is presumed to have an adverse effect on the remembering of the stimulus. This entire learning and fixation process is referred to as consolidation, and the theory that neural interference disrupts the memory trace is called consolidation theory. The importance of the genetic factors of behavior are mentioned as a caution for any experiment and the ones in this paper in particular. One must always remember that behaviour is an interaction between environment and heredity. Also the physiological effects of electro-shock convulsions on rats and mice are discussed especially in relation to fear of ECS. The general conclusion is that animals don't seem to be emotionally upset by ECS, although there are contradictory views here. The convulsion includes both tonic and clonic stage at its level of maximum effect on the memory trace, and greatly resembles the convulsion experienced by humans. In humans, if a blow or electric shock throws the brain into sudden subnormal condition, the effects of any immediately preceding learning appear to be obliterated. This type of phenomenon led to the human consolidation experiments which used ECS as a disrupting agent with the ECS immediately following a learning task, and which were performed only on mental patients already undergoing electro-convulsive therapy. Approximately half of the experiments in the field favor a consolidation theory of memory and half favor other theories of interpretations, especially interpretations involving the disruption effects of ECS immediately following a learning task, and which were performed only on mental patients already undergoing electro-convulsive therapy. Approximately half of the experiments in the field favor a consolidation theory of memory and half favor other theories or interpretations, especially interpretations involving the disruption effects of ECS on material learned in the distant past, far beyond the twenty minutes proposed for a perseveration or consolidation period. Because of the problems of human studies, the main evaluation of the effects of ECS on retention has centered on animal experiments, most of them being done with rats. Generally the procedure in these experiments has been to (1) train normal animals (2) derive paired groups (3) subject one group to ECS and (4) test for retention and/or retrain. The "classical" consolidation experiment by Duncan shows that animals receiving immediate ECS in an avoidance conditioning situation made less avoidances than non-shocked and foot shocked controls. Miller and Coons advanced the fear of ECS or double avoidance theory as an explanation for this apparent anti-consolidative phenomenon. The entire animal-ECS literature leans heavily toward a consolidation theory of retention with approximately fifty published articles fitting the consolidation hypothesis as opposed to six which are against this interpretation. Anoxia was also reported as an excellent disruptive agent for retention by three or four psychologists. The author's experiments also confirmed a consolidation interpretation of the memory problem as opposed to a double avoidance theory, thereby agreeing with the literature consensus. This consensus of both author and literature also was against the few other alternate explanations for retention deficits proposed by some psychologists. The journal literature and the author reviewed the use of drugs instead of ECS as a disruptive agent. The experimental procedures here were generally along the same lines as the ECS-animal experiments. The conclusions in this area varied from drug to drug - some interfering with or aiding consolidation as explained by Hebb's dual trace theory and others having no effect at all. In general the drug effects, whether helpful or disruptive to consolidation, were not as strong as the ECS effects. The most interesting medium here was ether. Bures and Burresova reported one experiment where ether had no effect on consolidation and Jarvik and Essman reported one where ether seemed to disrupt the memory trace. The author, on the other hand, using the Jarvik-Essman device and the jumping box found that ether seemed to facilitate consolidation. This is a contradiction which should be examined again in future experiments. McDougall, Mayer-Goss and others proposed that consolidation theory which seemed to explain retrograde amnesia could also perhaps explain the phenomenon of retroactive inhibition. Retroactive inhibition occurs when a piece of information learned immediately after another piece - the information, in both cases, very often being nonsense syllables - seems to in some way disrupt retention of the original learning. The connection proposed between retroactive inhibition and consolidation theory is probably the weakest theoretical stand taken in the paper. The evidence in the literature seems to favor other theories - especially an associational confusion theory supported by the discovery that usually the more alike the original and interpolated tasks are, the more retroactive inhibition that will appear - although there are experiments showing a disruptive effect of dissimilar interpolated material. The author also proposes a possible consolidation explanation even for the experiment which favor the similarity and associational views. The author's two experiments in this field tend to support consolidation theory especially the second which produces retroactive inhibition using a light, a totally dissimilar stimulus, as the interpolated task. A general summary seems to be fairly strong in its support of a consolidation view of memory and retention with the possible exception of the retroactive inhibition experiments. Several experiments are proposed which, if carried out, would aid the making of an even more conclusive theoretical stand on this consolidation interpretation in all of these areas.

Keywords

Behavior Genetics, Consolidation theory of memory, genetics, ECS

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