Comparative characteristics of the retention of verbal information received by adult subjects in the waking and hypnotic states

Estimation of the amounts of short-term memory in adults in the waking and hypnotic states showed two relationships in its expression. If subjects memorized verbal information in the waking state and were hypnotized after that, their short-term memory was considerably impaired. After the same subjects were awakened again, this form of memory was not improved; moreover, it was further impaired. On the other hand, if adult subjects memorized verbal information in the state of hypnosis (an altered state of consciousness, ASC), their short-term memory remained almost unchanged after they returned to the original waking state.     

Brain/behaviour dissociation on old/new distinction in a patient with amnesic syndrome

Event-related potentials (ERP) were recorded in a recognition memory task in 5 healthy subjects and an amnesic patient. A list of high-imagery words with low probability in everyday language was presented visually for 200 ms each. A second list, consisting of 50% previously presented (`old') words and 50% `new' words was presented immediately after the first list. Old/new distinction was determined by the subject's motor response. For each subject single trial analysis of ERPs was performed. In each healthy subjects, correct old/new distinction was associated with significant ERP differences from 500 to 900 ms after stimulus onset. It was, therefore, assumed that task and recording procedures were appropriate for the study of ERPs with recognition memory. The main finding is a dissociation between brain activity and behaviour with old/new distinction in the patient with amnesic syndrome. Frequently, the patient incorrectly classified previously shown words (`old' words) to be presented for the first time (`new'). But ERP showed that brain processing of `old' words which had incorrectly been classified to be `new' is different from correctly classified new words. ERP differences were significant between 900 and 1200 ms after stimulus presentation. These data indicate preserved memory functions which are not assessed at the behavioural level in the memory recognition task.     

Functional neuroanatomy of the hypnotic state

The neural mechanisms underlying hypnosis and especially the modulation of pain perception by hypnosis remain obscure. Using PET we first described the distribution of regional cerebral blood flow during the hypnotic state. Hypnosis relied on revivification of pleasant autobiographical memories and was compared to imaging autobiographical material in "normal alertness". The hypnotic state was related to the activation of a widespread set of cortical areas involving occipital, parietal, precentral, premotor, and ventrolateral prefrontal and anterior cingulate cortices. This pattern of activation shares some similarities with mental imagery, from which it mainly differs by the relative deactivation of precuneus. Second, we looked at the anti-nociceptive effects of hypnosis. Compared to the resting state, hypnosis reduced pain perception by approximately 50%. The hypnosis-induced reduction of affective and sensory responses to noxious thermal stimulation were modulated by the activity in the midcingulate cortex (area 24a'). Finally, we assessed changes in cerebral functional connectivity related to hypnosis. Compared to normal alertness (i.e., rest and mental imagery), the hypnotic state, significantly enhanced the functional modulation between midcingulate cortex and a large neural network involved in sensory, affective, cognitive and behavioral aspects of nociception. These findings show that not only pharmacological but also psychological strategies for pain control can modulate the cerebral network involved in noxious perception.     

Distinct Effects of Memory Retrieval and Articulatory Preparation when Learning and Accessing New Word Forms

Temporal and frontal activations have been implicated in learning of novel word forms, but their specific roles remain poorly understood. The present magnetoencephalography (MEG) study examines the roles of these areas in processing newly-established word form representations. The cortical effects related to acquiring new phonological word forms during incidental learning were localized. Participants listened to and repeated back new word form stimuli that adhered to native phonology (Finnish pseudowords) or were foreign (Korean words), with a subset of the stimuli recurring four times. Subsequently, a modified 1-back task and a recognition task addressed whether the activations modulated by learning were related to planning for overt articulation, while parametrically added noise probed reliance on developing memory representations during effortful perception. Learning resulted in decreased left superior temporal and increased bilateral frontal premotor activation for familiar compared to new items. The left temporal learning effect persisted in all tasks and was strongest when stimuli were embedded in intermediate noise. In the noisy conditions, native phonotactics evoked overall enhanced left temporal activation. In contrast, the frontal learning effects were present only in conditions requiring overt repetition and were more pronounced for the foreign language. The results indicate a functional dissociation between temporal and frontal activations in learning new phonological word forms: the left superior temporal responses reflect activation of newly-established word-form representations, also during degraded sensory input, whereas the frontal premotor effects are related to planning for articulation and are not preserved in noise.     

Neuroelectric evidence for cognitive association formation: an event-related potential investigation

Although many types of learning require associations to be formed, little is known about the brain mechanisms engaged in association formation. In the present study, we measured event-related potentials (ERPs) while participants studied pairs of semantically related words, with each word of a pair presented sequentially. To narrow in on the associative component of the signal, the ERP difference between the first and second words of a pair (Word2-Word1) was derived separately for subsequently recalled and subsequently not-recalled pairs. When the resulting difference waveforms were contrasted, a parietal positivity was observed for subsequently recalled pairs around 460 ms after the word presentation onset, followed by a positive slow wave that lasted until around 845 ms. Together these results suggest that associations formed between semantically related words are correlated with a specific neural signature that is reflected in scalp recordings over the parietal region.     

Pain Modulation in Waking and Hypnosis in Women: Event-Related Potentials and Sources of Cortical Activity

Using a strict subject selection procedure, we tested in High and Low Hypnotizable subjects (HHs and LHs) whether treatments of hypoalgesia and hyperalgesia, as compared to a relaxation-control, differentially affected subjective pain ratings and somatosensory event-related potentials (SERPs) during painful electric stimulation. Treatments were administered in waking and hypnosis conditions. LHs showed little differentiation in pain and distress ratings between hypoalgesia and hyperalgesia treatments, whereas HHs showed a greater spread in the instructed direction. HHs had larger prefrontal N140 and P200 waves of the SERPs during hypnotic hyperalgesia as compared to relaxation-control treatment. Importantly, HHs showed significant smaller frontocentral N140 and frontotemporal P200 waves during hypnotic hypoalgesia. LHs did not show significant differences for these SERP waves among treatments in both waking and hypnosis conditions. Source localization (sLORETA) method revealed significant activations of the bilateral primary somatosensory (BA3), middle frontal gyrus (BA6) and anterior cingulate cortices (BA24). Activity of these contralateral regions significantly correlated with subjective numerical pain scores for control treatment in waking condition. Moreover, multivariate regression analyses distinguished the contralateral BA3 as the only region reflecting a stable pattern of pain coding changes across all treatments in waking and hypnosis conditions. More direct testing showed that hypnosis reduced the strength of the association of pain modulation and brain activity changes at BA3. sLORETA in HHs revealed, for the N140 wave, that during hypnotic hyperalgesia, there was an increased activity within medial, supramarginal and superior frontal gyri, and cingulated gyrus (BA32), while for the P200 wave, activity was increased in the superior (BA22), middle (BA37), inferior temporal (BA19) gyri and superior parietal lobule (BA7). Hypnotic hypoalgesia in HHs, for N140 wave, showed reduced activity within medial and superior frontal gyri (BA9,8), paraippocampal gyrus (BA34), and postcentral gyrus (BA1), while for the P200, activity was reduced within middle and superior frontal gyri (BA9 and BA10), anterior cingulate (BA33), cuneus (BA19) and sub-lobar insula (BA13). These findings demonstrate that hypnotic suggestions can exert a top-down modulatory effect on attention/preconscious brain processes involved in pain perception.     

Mesmerizing memories: brain substrates of episodic memory suppression in posthypnotic amnesia

Two groups of participants, one susceptible to posthypnotic amnesia (PHA) and the other not, viewed a movie. A week later, they underwent hypnosis in the fMRI scanner and received a suggestion to forget the movie details after hypnosis until receiving a reversal cue. The participants were tested twice for memory for the movie and for the context in which it was shown, under the posthypnotic suggestion and after its reversal, while their brain was scanned. The PHA group showed reduced memory for movie but not for context while under suggestion. Activity in occipital, temporal, and prefrontal areas differed among the groups, and, in the PHA group, between suggestion and reversal conditions. We propose that whereas some of these regions subserve retrieval of long-term episodic memory, others are involved in inhibiting retrieval, possibly already in a preretrieval monitoring stage. Similar mechanisms may also underlie other forms of functional amnesia.     

Bilingual and multilingual language processing

This chapter addresses the interesting question on the neurolinguistics of bilingualism and the representation of language in the brain in bilingual and multilingual subjects. A fundamental issue is whether the cerebral representation of language in bi- and multilinguals differs from that of monolinguals, and if so, in which specific way. This is an interdisciplinary question which needs to identify and differentiate different levels involved in the neural representation of languages, such as neuroanatomical, neurofunctional, biochemical, psychological and linguistic levels. Furthermore, specific factors such as age, manner of acquisition and environmental factors seem to affect the neural representation. We examined the question whether verbal memory processing in two unrelated languages is mediated by a common neural system or by distinct cortical areas. Subjects were Finnish-English adult multilinguals who had acquired the second language after the age of ten. They were PET-scanned whilst either encoding or retrieving word pairs in their mother tongue (Finnish) or in a foreign language (English). Within each language, subjects had to encode and retrieve four sets of 12 visually presented paired word associates which were not semantically related. Two sets consisted of highly imaginable words and the other two sets of abstract words. Presentation of pseudo-words served as a reference condition. An emission scan was recorded after each intravenous administration of O-15 water. Encoding was associated with prefrontal and hippocampal activation. During memory retrieval, precuneus showed a consistent activation in both languages and for both highly imaginable and abstract words. Differential activations were found in Broca's area and in the cerebellum as well as in the angular/supramarginal gyri according to the language used. The findings advance our understanding of the neural representation that underlies multiple language functions. Further studies are needed to elucidate the neuronal mechanisms of bi/multilingual language processing. A promising perspective for future bi/multilingual research is an integrative approach using brain imaging studies with a high spatial resolution such as fMRI, combined with techniques with a high temporal resolution, such as magnetoencephalography (MEG).     

Protein synthesis subserves reconsolidation or extinction depending on reminder duration

When learned associations are recalled from long-term memory stores by presentation of an unreinforced conditioned stimulus (CS), two processes are initiated. One, termed reconsolidation, re-activates the association between the conditioned and unconditioned stimuli and transfers it from a stable protein synthesis-independent form of storage to a more labile protein-dependent state. The other is an extinction process in which presentation of the CS alone degrades the association between CS and US. To address the mechanistic relationship between reconsolidation and extinction, we have used an invertebrate model of contextual memory, which involves an association between the learning context and a visual danger stimulus. Here, we show that re-exposure duration to the learning context acts as a switch guiding the memory course toward reconsolidation or extinction, each depending on protein synthesis. Manipulation of this variable allows findings of impaired extinction to be discriminated from those of disrupted reconsolidation.     

Post-Amputation Pain Is Associated with the Recall of an Impaired Body Representation in Dreams—Results from a Nation-Wide Survey on Limb Amputees

The experience of post-amputation pain such as phantom limb pain (PLP) and residual limb pain (RLP), is a common consequence of limb amputation, and its presence has negative effects on a person’s well-being. The continuity hypothesis of dreams suggests that the presence of such aversive experiences in the waking state should be reflected in dream content, with the recalled body representation reflecting a cognitive proxy of negative impact. In the present study, we epidemiologically assessed the presence of post-amputation pain and other amputation-related information as well as recalled body representation in dreams in a sample of 3,234 unilateral limb amputees. Data on the site and time of amputation, residual limb length, prosthesis use, lifetime prevalence of mental disorders, presence of post-amputation pain, and presence of non-painful phantom phenomena were included in logistic regression analyses using recalled body representation in dreams (impaired, intact, no memory) as dependent variable. The effects of age, sex, and frequency of dream recall were controlled for. About 22% of the subjects indicated that they were not able to remember their body representation in dreams, another 24% of the amputees recalled themselves as always intact, and only a minority of less than 3% recalled themselves as always impaired. Almost 35% of the amputees dreamed of themselves in a mixed fashion. We found that lower-limb amputation as well as the presence of PLP and RLP was positively associated with the recall of an impaired body representation in dreams. The presence of non-painful phantom phenomena, however, had no influence. These results complement previous findings and indicate complex interactions of physical body appearance and mental body representation, probably modulated by distress in the waking state. The findings are discussed against the background of alterations in cognitive processes after amputation and hypotheses suggesting an innate body model.     

Spatio-temporal activation of cyclic AMP response element-binding protein, activity-regulated cytoskeletal-associated protein and brain-derived nerve growth factor: a mechanism for pontine-wave generator activation-dependent two-way active-avoidance memory processing in the rat

The present study explored possible physiological and molecular mechanisms of pontine-wave (P-wave) generator activation-dependent memory processing in the rat using a two-way active-avoidance learning paradigm. The results show that learning training increased rapid eye movement sleep and activated brainstem cells in the P-wave generator. During this period, there was a time-dependent increase in phosphorylation of cAMP response element-binding protein (CREB) in the dorsal hippocampus and amygdala and increased synthesis of activity-regulated cytoskeletal-associated protein (Arc) in the dorsal hippocampus, amygdala, frontal cortex and occipital cortex. Learning training also increased synthesis of brain-derived nerve growth factor (BDNF) in the occipital cortex, amygdala and dorsal hippocampus at different time intervals. During this time, the levels of nerve growth factor did not change. The results also show that the increase in rapid eye movement sleep P-wave density during the post-training 3-h recording session is positively correlated with the increased levels of phosphorylated CREB, BDNF and Arc in the dorsal hippocampus. These results suggest that memory processing of two-way active-avoidance learning may involve excitation of P-wave-generating cells in the brainstem and increased expression of phosphorylated CREB, Arc and BDNF in a time-dependent manner in the forebrain. These dynamic changes in cellular and molecular features provide considerable insight into the mechanisms of the P-wave generator activation-dependent memory consolidation process.     

Acquisition of enhanced natural killer cell activity under anesthesia

An increase in natural killer (NK) cell activity can be conditioned with a one trial learning paradigm to demonstrate the interaction between the central nervous system (CNS) and the immune system. In order to demonstrate learning possibilities during ‘non-conscious’ state, mice were anesthetized with a ketamin/rompun mixture and underwent one trial learning with odor cue as the conditioned stimulus (CS) preceding the unconditioned stimulus (US). The results indicated that mice that were exposed to camphor odor cue under the influence of anesthesia can associate the signal with the poly I:C unconditioned stimulus and were able to recall the conditioned response upon reexposure to the CS. Secondly, the conditioned association made in a conscious state can be recalled by exposure to the same olfactory odor cue in a ‘non-conscious’ state. The increase in the conditioned change in NK cell activity of both situations was significantly higher than the control group. The results demonstrate that learning can take place and the learned response can be recalled under the reduced awareness caused by anesthesia. The findings we report are unusual and novel in that they demonstrate that the CNS can learn new associations under conditions where the host is apparently unaware of the signals being linked. Anesthesia combined with the long interstimulus interval indicates that certain neuronal pathways in the CNS are receptive to second signals (elicited by the US) even when the second signal is separated by one day. This means the conditioned learning of a physiological response can take place unconsciously at a separate level and under situations where the host is totally unaware of the events which the brain is processing and linking as incoming information.     

The structure of dependent relationship between neurons in the sensorimotor cortex of the left and right hemisphere in rabbits during immobilizing catatonia

Relations between activities of neurons simultaneously recorded in the left and right sensorimotor brain cortices of rabbits were analyzed in a series of experiments before the induction of the immobilization state ("animal hypnosis"), in the state of immobilization, and after its termination. The total baseline percent of significant correlations between activities of neighboring (within 50 microns) neurons in the left hemisphere was significantly lower than in the right hemisphere. This characteristic of the left hemisphere changed neither in the immobilization state nor after its termination. In the right-hemisphere cortex, the total percent of correlations between neighboring neurons significantly decreased during immobilization and returned to the baseline level after the termination of this state. In contrast, percent of correlations between the activities of remote (within 500 microns) neurons in the right-hemisphere did not change during immobilization, whereas in the left cortex it changed significantly and reached its baseline level after the normalization of rabbit's state. Further analysis showed that the revealed cortical interhemispheric asymmetry is underlain by asymmetric activities of individual neurons and small neuronal populations. Thus, for example, changes in the structure of interneuronal correlations in cortical microareas of the left and macroareas of the right hemispheres could be of different directions, whereas correlated activities in microareas of the right and macroareas of the left-hemispheres could change synergetically. In other words, asymmetry was revealed at different levels of neuronal integration (neuronal pairs, micro- or macrogroups of neurons). This finding testifies to a mosaic character of neuronal activity, which finally results in the general functional asymmetry during the "animal hypnosis". Certain changes in the structure of functional relations between neurons of the sensorimotor cortex that developed in the state of "animal hypnosis" persisted and even augmented after the termination of this state.     

Rehearsal of dreams and waking events similarly improves the quality but not the quantity of autobiographical recall.

Salient dreams are often discussed and ruminated upon over time, especially when they feature in dream work or therapy. The present study investigated the effects of rehearsal over time on dream memories, as compared to memories for waking experiences. Participants were instructed to complete a dream and waking episodic event diary over two weeks. A rehearsal group (n = 27) were instructed to read through their reports after recording them. A control group (n = 28) were instructed not to look at their reports. A surprise recall task demonstrated that rehearsal reduced significantly the detail of dream, but not waking event, reports. It maintained episodic richness for dreams. Furthermore, rehearsed dream and event reports corresponded significantly more closely with original reports than controls. These data indicate that while rehearsal may not increase dream recall over time, it may influence the phenomenology of memories that are subsequently recalled, such that a rehearsed memory is subsequently recalled, rather than the original experience. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Interregional cortical interactions at different stages of natural sleep and the hypnotic state: EEG evidence

The characteristic patterns of EEG spatial organization at different stages of natural sleep and the hypnotic state were studied in 26 volunteers aged 18–22 years. EEGs were recorded using 12 monopolar leads, and EEG cross-correlation coefficient matrices were calculated for consecutive epochs (4 and 8 s). Matrices averaged for each state were treated using factor analysis. The EEG correlation matrices were compared element by element for the states studied and the waking state. Relatively similar changes in the spatial structure of EEG correlations were observed at different stages of natural sleep, with the correlations tending to intensify, especially in the posterior temporal region of the right hemisphere. In the light and deep (somnambular) phases of hypnosis, the interaction between cortical zones that was characteristic of distant relationships of the EEGs of frontal regions, especially the posterior inferior frontal region of the right hemisphere, decreased. The systemic reorganization of the interregional EEG correlations during natural sleep was considerably more pronounced than in the hypnotic state. Notwithstanding, the highly orderly spatial organization of the cortical biopotential field that was typical of the waking state was retained at different stages of natural sleep and hypnosis. Thus, the coordination of the activities of distant nerve centers oriented to providing for a certain function or maintaining a certain functional state occurs against the background of a relatively invariant pattern of interregional integration at the level of the whole brain.Translated from Fiziologiya Cheloveka, Vol. 31, No. 2, 2005, pp. 34–48.Original Russian Text Copyright © 2005 by A. Shepovalnikov, Tsitseroshin, Rozhkov, Galperina, Zaitseva, R. Shepovalnikov.     

Polymorphism C366G of gene <Emphasis Type="Italic">GRIN2B</Emphasis> and verbal episodic memory: No association with schizophrenia

The present study searched for associations between gene GRIN2B (glutamate receptor, ionotropic, N-methyl-D-aspartate, subunit 2B) and component processes of verbal episodic memory in schizophrenic patients. The Rey Auditory Verbal Learning Test (RAVLT) as a part of a large neuropsychological battery was administered to 302 patients with schizophrenic spectrum disorders (sample PI). Also, 285 patients (sample P2) and 243 healthy controls (sample C2) performed the “10 words” test that measures short-term memory. The GRIN2B rs7301328 (C366G) polymorphism was genotyped for each subject. There were no associations between the polymorphism and any measure of the RAVLT either in the whole PI sample or in a subsample of patients with a severe cognitive deficit. The GRIN2B influenced immediate recall and proactive interference in the “10 words” test in the control group: homozygotes CC recalled fewer words and showed a lower effect of proactive interference than carriers of other genotypes. The results suggest that the C366G polymorphism could influence verbal episodic memory in the general population, but this influence is absent in schizophrenic patients.     

Effects of cholinergic enhancement on visual stimulation, spatial attention, and spatial working memory

We compared behavioral and neural effects of cholinergic enhancement between spatial attention, spatial working memory (WM), and visual control tasks, using fMRI and the anticholinesterase physostigmine. Physostigmine speeded responses nonselectively but increased accuracy selectively for attention. Physostigmine also decreased activations to visual stimulation across all tasks within primary visual cortex, increased extrastriate occipital cortex activation selectively during maintained attention and WM encoding, and decreased parietal activation selectively during maintained attention. Finally, lateralization of occipital activation as a function of the visual hemifield toward which attention or memory was directed was decreased under physostigmine. In the case of attention, this effect correlated strongly with a decrease in a behavioral measure of selective spatial processing. Our results suggest that, while cholinergic enhancement facilitates visual attention by increasing activity in extrastriate cortex generally, it accomplishes this in a manner that reduces expectation-driven selective biasing of extrastriate cortex.     

Superior serial memory in the blind: a case of cognitive compensatory adjustment

In the absence of vision, perception of space is likely to be highly dependent on memory. As previously stated, the blind tend to code spatial information in the form of "route-like" sequential representations [1-3]. Thus, serial memory, indicating the order in which items are encountered, may be especially important for the blind to generate a mental picture of the world. In accordance, we find that the congenitally blind are remarkably superior to sighted peers in serial memory tasks. Specifically, subjects heard a list of 20 words and were instructed to recall the words according to their original order in the list. The blind recalled more words than the sighted (indicating better item memory), but their greatest advantage was in recalling longer word sequences (according to their original order). We further show that the serial memory superiority of the blind is not merely a result of their advantage in item recall per se (as we additionally confirm via a separate recognition memory task). These results suggest the refinement of a specific cognitive ability to compensate for blindness in humans.     

Temporal characteristics of the initial stage of the verbal information processing in healthy subjects and in schizophrenia

The study aimed to investigate the early coding of visually presented words and pseudowords using event-related potentials (ERP). We conducted comparative analysis of the characteristics of P100 and N170 in healthy controls and in patients with the first episode of schizophrenia during passive perception of verbal stimuli as well as under conditions of relevant words and pseudowords. The latency of early ERP components P100 and N170 appeared to be shorter in comparison with healthy subjects in the temporal, parietal and occipital areas. The latency of P100 in patients was significantly shorter in the temporal, parietal and occipital areas, whereas the latency of N170 was shorter in the parietal and occipital areas than in controls. The latency of N170 in healthy subjects was significantly longer to words than to pseudowords and in patients - vice versa. The latencies of N170 in all TPO areas were equal in healthy subjects during word processing, and this equality was upset during non-word processing. In patients with schizophrenia the equality was upset, but, opposite to healthy patients, the upset of equality was more expressed during words processing. Thus, the early stage of verbal information processing in schizophrenic patients is insufficient in time. The time deficit of the automatic processes may lead to defective processing of overall information.     

Hypnotizability,Hypnosis and Prepulse Inhibition of the Startle Reflex in Healthy Women: An ERP Analysis

A working model of the neurophysiology of hypnosis suggests that highly hypnotizable individuals (HHs) have more effective frontal attentional systems implementing control, monitoring performance, and inhibiting unwanted stimuli from conscious awareness, than low hypnotizable individuals (LHs). Recent studies, using prepulse inhibition (PPI) of the auditory startle reflex (ASR), suggest that HHs, in the waking condition, may show reduced sensory gating although they may selectively attend and disattend different stimuli. Using a within subject design and a strict subject selection procedure, in waking and hypnosis conditions we tested whether HHs compared to LHs showed a significantly lower inhibition of the ASR and startle-related brain activity in both time and intracerebral source localization domains. HHs, as compared to LH participants, exhibited (a) longer latency of the eyeblink startle reflex, (b) reduced N100 responses to startle stimuli, and (c) higher PPI of eyeblink startle and of the P200 and P300 waves. Hypnosis yielded smaller N100 waves to startle stimuli and greater PPI of this component than in the waking condition. sLORETA analysis revealed that, for the N100 (107 msec) elicited during startle trials, HHs had a smaller activation in the left parietal lobe (BA2/40) than LHs. Auditory pulses of pulse-with prepulse trials in HHs yielded less activity of the P300 (280 msec) wave than LHs, in the cingulate and posterior cingulate gyrus (BA23/31). The present results, on the whole, are in the opposite direction to PPI findings on hypnotizability previously reported in the literature. These results provide support to the neuropsychophysiological model that HHs have more effective sensory integration and gating (or filtering) of irrelevant stimuli than LHs.