Models of posthypnotic amnesia.

The term " posthypnotic amnesia " refers to the temporary inability of the hypnotized subject to remember, after hypnosis, the events that had transpired while he or she was hypnotized. Over the years, several parallels have been drawn between posthypnotic amnesia and other disorders of memory that are observed in the psychological clinic and the experimental laboratory, and in the psychopathology of everyday life. In each case, the person finds it difficult or impossible to gain access to certain critical memories through the ordinary process of active recall. Nevertheless, it is apparent that the critical memories are stored essentially intact, because the amnesia can be lifted and accurate recall restored. Even during the amnesic period itself, the unrecalled memories can be observed to affect behavior and experience, if only indirectly. All of this takes place in the apparent absence of any defect or alteration in central nervous system functioning. These broad phenotypic similarities uniting the various functional amnesias may imply genotypic similarities as well. Thus, the study of posthypnotic amnesia may serve as an important avenue of approach to a variety of topics in normal and pathological memory functioning. Since the development of standardized hypnotic procedures for laboratory has yielded a great deal of information concerning the major parameters of posthypnotic amnesia (see the reviews by Cooper l4 and Hilgard 32, 3 3). We know, for example, that posthypnotic amnesia is temporary and can be can-celed or lifted by the administration of a prearranged reversibility cue.42, 4 3 * 48 Furthermore, the extent of the initial amnesia and the degree to which the lost memories can be recovered after the suggestion has been canceled, are both highly correlated with hypnotic susceptibility; 32* 428 48 factor-analytic studies suggest, in fact, that amnesia lies at the core of the domain of hypnosis.32 Moreover, the quantitative differences in recall observed during amnesia are matched by qualitative differences between the vague and fragmentary memory of subjects with complete or partial posthypnotic amnesia and the clearly detailed memories of those who are not amnesic.21. 4 0 Finally, posthypnotic amnesia must be specifically suggested to the subject: in contrast to many other functional amnesias, it rarely occurs in a truly spontaneous In attempting to understand the phenomenon of posthypnotic amnesia, a number of conceptual models of the amnesic process have been developed. 285 Analogies to posthypnotic amnesia have been drawn from ordinary forgetting, the withholding of …