On the relation between genuine and simulated amnesia

When claims of amnesia are made in legal cases, it is necessary to determine whether they are genuine or simulated. This article assesses current knowledge of the relation between genuine and simulated amnesia and discusses issues that are critical to understanding of the problem. It is argued that there are few well established facts regarding the nature of simulated amnesia, and no evidence that experts can distinguish accurately between genuine and simulated amnesia. Suggestions are made for future research that draw upon recent advances in cognitive psychology, social psychology, and neuropsychology.     

The neural correlates of movement intentions: A pilot study comparing hypnotic and simulated paralysis

The distinct feeling of wanting to act and thereby causing our own actions is crucial to our self-perception as free human agents. Disturbances of the link between intention and action occur in several disorders. Little is known, however, about the neural correlates of wanting or intending to act. To investigate these for simple voluntary movements, we used a paradigm involving hypnotic paralysis and functional magnetic resonance imaging. Eight healthy women were instructed to sequentially perform left and right hand movements during a normal condition, as well as during simulated weakness, simulated paralysis and hypnotic paralysis of the right hand. Right frontopolar cortex was selectively hypoactivated for attempted right hand movement during simulated paralysis while it was active in all other conditions. Since simulated paralysis was the only condition lacking an intention to move, the activation in frontopolar cortex might be related to the intention or volition to move.     

Developmental amnesia

The concept of developmental amnesia is proposed to describe the impairment of normal memories during a person's school age life. One hundred psychotherapy patients were interviewed and the age of earliest memories ranged from 1–12 years, with a mode of 5 years. Memory was continuous for 53% of patients by 1st grade, while 18% reported life memory was still episodic at age 18 or later. Parental alcohol problems were associated with delay of continuous memories.     

Transient global amnesia

Transient global amnesia (TGA) is a memory dysfunction characterized by a sudden onset of dense anterograde amnesia (AA) that gradually resolves across several hours. TGA is typically accompanied by repeated questions (concerning present circumstances) with retrograde amnesia for events preceding the attack, and it usually strikes individuals in their late 50s and early 60s. The etiology of TGA remains unclear, although it probably reflects a temporary disruption of the blood supply to the temporal lobe. The physical and psychological events preceding the attack are diverse, but they often include acute emotional and physical stressors. TGA appears to be benign, with low risk for recurrence or residual complications. While systematic memory research on TGA patients is rare, these individuals present a unique opportunity to study amnestic behaviors in otherwise normal individuals. A guide to conducting future research is provided.     

Creating false memories of infancy with hypnotic and non‐hypnotic procedures

This study was designed to test the conditions under while false memory reports are likely to be elicited from hypnotic and non‐hypnotic participants. Low, medium and high hypnotizables were administered either a hypnotic or non‐hypnotic suggestion for regression to the day after birth. False memories of infancy were generated in 68 of 78 age‐regressed participants, nearly half of whom reported strong beliefs in the reality of their recovered ‘memories’. Non‐hypnotic participants were slightly but significantly more likely to report infancy experiences than were hypnotic participants. However, hypnotizability did not have a significant effect on the classification of these experiences as memories or as fantasies. Implications for the experimental and clinical contexts are discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Multiple predictors of hypnotic susceptibility

In this article, we report two experiments in which various measures thought to be related to hypnotizability were analyzed by stepwise discriminant analysis techniques. Absorption (Tellegen, 1981, 1982; Tellegen & Atkinson, 1974) and preference for an imagic style of thinking (Isaacs, 1982) were robust predictors of hypnotizability; each variable accounted for significant variance in hypnotizability at their respective steps in two samples and correctly classified a significant proportion of low- and high-hypnotizable subjects in the discriminant analyses. The addition of two other variables in Experiment 2--a Sleep-Dream score derived from Evans's (1977) Cognitive Control of Sleep Mentation subscale and Gibson's (1985) Dream Questionnaire, and the Belief in the Supernatural subscale of the Taft (1969) Experience Questionnaire--increased the correct classification of the medium-hypnotizable subjects from chance levels to 74%. It is argued that a confirmatory and hierarchical approach is needed in future studies to explore correlates of hypnotizability more fully.     

Alcohol increases hypnotic susceptibility

One approach to hypnosis suggests that for hypnotic experience to occur frontal lobe activity must be attenuated. For example, cold control theory posits that a lack of awareness of intentions is responsible for the experience of involuntariness and/or the subjective reality of hypnotic suggestions. The mid-dorso-lateral prefrontal cortex and the ACC are candidate regions for such awareness. Alcohol impairs frontal lobe executive function. This study examined whether alcohol affects hypnotisability. We administered 0.8 mg/kg of alcohol or a placebo to 32 medium susceptible participants. They were subsequently hypnotised and given hypnotic suggestions. All participants believed they had received some alcohol. Participants in the alcohol condition were more susceptible to hypnotic suggestions than participants in the placebo condition. Impaired frontal lobe activity facilitates hypnotic responding, which supports theories postulating that attenuation of executive function facilitates hypnotic response, and contradicts theories postulating that hypnotic response involves enhanced inhibitory, attentional or other executive function.     

The many faces of amnesia

Results from studies of retrograde amnesia provide much of the evidence for theories of memory consolidation. Retrograde amnesia gradients are often interpreted as revealing the time needed for the formation of long-term memories. The rapid forgetting observed after many amnestic treatments, including protein synthesis inhibitors, and the parallel decay seen in long-term potentiation experiments are presumed to reveal the duration of short-term memory processing. However, there is clear and consistent evidence that the time courses obtained in these amnesia experiments are highly variable within and across experiments and treatments. The evidence is inconsistent with identification of basic temporal properties of memory consolidation. Alternative views include modulation of memory and emphasize the roles that hormones and neurotransmitters have in regulating memory formation. Of related interest, converging lines of evidence suggest that inhibitors of protein synthesis and of other biochemical processes act on modulators of memory formation rather than on mechanisms of memory formation. Based on these findings, memory consolidation and reconsolidation studies might better be identified as memory modulation and "remodulation" studies. Beyond a missing and perhaps unattainable time constant of memory consolidation, some current views of memory consolidation assume that memories, once formed, are generally unmodifiable. It is this perspective that appears to have led to the recent interest in memory reconsolidation. But the view adopted here is that memories are continually malleable, being updated by new experiences and, at the same time, altering the memories of later experiences. Studies of memory remodulation offer promise of understanding the neurobiological bases by which new memories are altered by prior experiences and by which old memories are altered by new experiences.     

Nonverbal priming in amnesia

In this experiment, we examined whether a group of well-characterized amnesic patients would exhibit normal priming for novel nonverbal materials after a single exposure. Both amnesic patients and normal control subjects studied line figures and were then given a priming test in which they were asked to reproduce both old (studied) and new (unstudied) figures after a brief exposure. The measure of priming was the number of old patterns drawn correctly relative to the number of new patterns drawn correctly. Both subject groups reproduced more old patterns than new patterns, and the effect was similar in the two groups. In contrast, amnesic patients were significantly impaired on a recognition memory test for the items that had been presented. This study contributes to recent evidence that implicit memory can support the rapid acquisition of novel verbal and nonverbal information. Perceptual priming for such material is independent of the structures damaged in amnesia.     

The fractionation of retrograde amnesia

This single case study describes our investigations of the retrograde memory deficit of a patient who became severely and selectively amnesic after an encephalitic illness. On clinical assessment his retrograde deficit for both personal and public events appeared to encompass his entire adult life. However, he retained knowledge of words introduced into the vocabulary during the retrograde period. The experimental investigation documented his inability to recall, recognize, and place in temporal order the names and faces of famous people for all time periods sampled. By contrast, his recall of either a famous face or a famous name was significantly facilitated by the verbal cue of the person's first name and initial of the surname (i.e., Margaret T...). His performance on a test of "familiarity" that required him to select the famous name or the famous face from two distractors (unknown) was within normal limits. It is argued that names and faces of famous people are represented in more than one system: both in a vocabulary-like fact memory system that is preserved and also in a congnitively mediated schemata that in this case is functionally inoperative.     

Detection and identification of words and letters in simulated visual search of word lists

Ss were shown a rapid sequence of words and had to (a) make a speeded response to the presentation of a predefined target and (b) report a "response word" which they thought immediately followed the target in the sequence. In Experiment I presentation rate was varied orthogonally with the number of alternative targets. Detection errors and latency increased with target set size, as did the distance of the response word from the target in the list sequence. Increases in presentation rate produced greater target-response distance without affecting detection time. In Experiment II Ss were in some conditions given only the initial letter of the targets; the response could be either the whole word following the target or only its initial letter. The results indicated that Ss could, within limits, concurrently detect initial letters and identify words. Alternatives to hierarchical-type models of stimulus processing in visual search were discussed.     

Mechanisms of hypnotic and nonhypnotic forgetting

Subjects participated in two experimental sessions designed to study laboratory-induced amnesia, one using a standard hypnosis paradigm and one using a non-hypnotic directed-forgetting paradigm. Two independent sources of variation were derived from the hypnotic amnesia data: retrieval inhibition and inhibition release. In the nonhypnotic directed-forgetting procedure, some items were cued to be forgotten shortly after presentation and some were cued to be remembered. At test, the subjects were asked to recall both the to-be-remembered and the to-be-forgotten items. Over 39% of the variance in the recall of the to-be-forgotten items could be accounted for by the inhibition and release constructs obtained with hypnosis. These relations between the two procedures were not mediated by verbal ability or cognitive style (field independence). We concluded that the mechanisms of forgetting involved in laboratory demonstrations of hypnotic and nonhypnotic amnesia are related, and the implication is that some of them are the same, namely, retrieval inhibition and inhibition release. We also argued that the possible demand characteristics that accompany the hypnosis procedure are not apparent with the nonhypnotic procedure. Therefore, the relationships observed in the present results were taken as evidence that hypnotically induced amnesia is not entirely the result of subjects' reactions to demand characteristics.