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Inhibition of retrieval in hypnotic amnesia: dissociation by upper-alpha gating.

ABSTRACT: Hypnotic amnesia is a functional dissociation from awareness during which information from specific neural processes is unavailable to consciousness. We test the proposal that changes in topographic patterns of cortical oscillations in upper-alpha (10-12?Hz) band selectively inhibit the recall of memories during hypnotic amnesia by blocking availability of locally processed information at specific points in retrieval. Participants were prescreened for high or low hypnotic susceptibility. Following hypnotic induction, participants were presented with a series of 60 face stimuli and were required to identify affective expressions. Participants received a suggestion for amnesia for these faces. They were then presented with a set of 30 old and 30 new faces and identified each as old or new. Amnesia suggestion was lifted and recall tested using the remaining 30 old faces and another 30 new faces. Exact Low Resolution Brain Electromagnetic Tomography source analyses are reported for 64 channel event-related electroencephalogram recorded from highs showing reversible amnesia to old faces. For high-susceptible participants, the amnesia suggestion significantly increased old faces wrongly identified while for low-susceptible participants amnesia suggestion increased the new faces wrongly identified. There were no differences between high- and low-susceptible participants following reversal of the suggestion. For previously seen faces which were wrongly identified, compared to new faces correctly identified, (late) evoked upper-alpha is significantly higher in right BA7 in a region implicated in top-down executive control to assist recall of visual information. Lagged nonlinear connectivity between cortical sources in upper-alpha in the same condition showed significantly increased connectivity between right BA34 (parahippocampal gyrus) and right BAs 7, 20 and 22. Integration between these regions is essential for recall of recent faces. During amnesia, spatial and temporal coordination of upper-alpha appears to suppress integrated functioning of these regions (hence recall). These patterns were absent after reversal of amnesia suggestion.

SUBMITTER: Jamieson GA

PROVIDER: S-EPMC6007141 | biostudies-other | 2017

REPOSITORIES: biostudies-other

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Inhibition of retrieval in hypnotic amnesia: dissociation by upper-alpha gating.

Jamieson Graham A GA Kittenis Marios D MD Tivadar Ruxandra I RI Evans Ian D ID

Neuroscience of consciousness 20170419 1

Hypnotic amnesia is a functional dissociation from awareness during which information from specific neural processes is unavailable to consciousness. We test the proposal that changes in topographic patterns of cortical oscillations in upper-alpha (10-12 Hz) band selectively inhibit the recall of memories during hypnotic amnesia by blocking availability of locally processed information at specific points in retrieval. Participants were prescreened for high or low hypnotic susceptibility. Followi ...[more]

PMID: 30042839

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Project description:BackgroundLong-term memory formation is generally assumed to involve the permanent storage of recently acquired memories, making them relatively insensitive to disruption, a process referred to as memory consolidation. However, when retrieved under specific circumstances, consolidated fear memories are thought to return to a labile state, thereby opening a window for modification (e.g., attenuation) of the memory. Several interventions during a critical time frame after this destabilization seem to be able to alter the retrieved memory, for example by pharmacologically interfering with the restabilization process, either by direct protein synthesis inhibition or indirectly, using drugs that can be safely administered in patients (e.g., propranolol). Here, we find that, contrary to expectations, systemic pharmacological manipulations in auditory fear-conditioned rats do not lead to drug-induced post-retrieval amnesia.ResultsIn a series of well-powered auditory fear conditioning experiments (four with propranolol, 10 mg/kg, two with rapamycin, 20-40 mg/kg, one with anisomycin, 150 mg/kg and cycloheximide, 1.5 mg/kg), we found no evidence for reduced cued fear memory expression during a drug-free test in adult male Sprague-Dawley rats that had previously received a systemic drug injection upon retrieval of the tone fear memory. All experiments used standard fear conditioning and reactivation procedures with freezing as the behavioral read-out (conceptual or exact replications of published reports) and common pharmacological agents. Additional tests confirmed that the applied drug doses and administration routes were effective in inducing their conventional effects on expression of fear (propranolol, acutely), body weight (rapamycin, anisomycin, cycloheximide), and consolidation of extinction memories (cycloheximide).ConclusionsIn contrast with previously published studies, we did not find evidence for drug-induced post-retrieval amnesia, underlining that this effect, as well as its clinical applicability, may be considerably more constrained and less readily reproduced than what the current literature would suggest.

Project description:Variation of information in the firing rate of neural population, as reflected in different frequency bands of electroencephalographic (EEG) time series, provides direct evidence for change in neural responses of the brain to hypnotic suggestibility. However, realization of an effective biomarker for spiking behaviour of neural population proves to be an elusive subject matter with its impact evident in highly contrasting results in the literature. In this article, we took an information-theoretic stance on analysis of the EEG time series of the brain activity during hypnotic suggestions, thereby capturing the variability in pattern of brain neural activity in terms of its information content. For this purpose, we utilized differential entropy (DE, i.e., the average information content in a continuous time series) of theta, alpha, and beta frequency bands of fourteen-channel EEG time series recordings that pertain to the brain neural responses of twelve carefully selected high and low hypnotically suggestible individuals. Our results show that the higher hypnotic suggestibility is associated with a significantly lower variability in information content of theta, alpha, and beta frequencies. Moreover, they indicate that such a lower variability is accompanied by a significantly higher functional connectivity (FC, a measure of spatiotemporal synchronization) in the parietal and the parieto-occipital regions in the case of theta and alpha frequency bands and a non-significantly lower FC in the central region's beta frequency band. Our results contribute to the field in two ways. First, they identify the applicability of DE as a unifying measure to reproduce the similar observations that are separately reported through adaptation of different hypnotic biomarkers in the literature. Second, they extend these previous findings that were based on neutral hypnosis (i.e., a hypnotic procedure that involves no specific suggestions other than those for becoming hypnotized) to the case of hypnotic suggestions, thereby identifying their presence as a potential signature of hypnotic experience.

Dataset Information

Inhibition of retrieval in hypnotic amnesia: dissociation by upper-alpha gating.

Publications

Inhibition of retrieval in hypnotic amnesia: dissociation by upper-alpha gating.

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