Rhinal-hippocampal interactions during déjà vu

Non-ictal, interictal and ictal déjà vu: a systematic review and meta-analysis

Background

Déjà vu, French for "already seen," is a phenomenon most people will experience at least once in their lifetime. Emerging evidence suggests that déjà vu occurs in healthy individuals (as "non-ictal déjà vu") and in epilepsy patients during seizures (as "ictal déjà vu") and between seizures (as "interictal déjà vu"). Although the ILAE has recognized déjà vu as a feature of epileptic seizures, it is notably absent from the ICD-11. A lack of evidence-based research may account for this omission. To our knowledge, this study represents the first systematic review and meta-analysis on déjà vu experiences. Through detailed examinations of non-ictal, interictal and ictal déjà vu, we seek to highlight possible clinical implications. Rethinking the status quo of ictal déjà vu could potentially lead to earlier interventions and improve outcomes for epilepsy patients.

Methods

This study was registered in PROSPERO (ID: CRD42023394239) on 5 February 2023. Systematic searches were conducted across four databases: EMBASE, MEDLINE, PsycINFO, and PubMed, from inception to 1 February 2023, limited to English language and human participants. Studies were included/excluded based on predefined criteria. Data was extracted according to the PICO framework and synthesized through a thematic approach. Meta-analyses were performed to estimate prevalence's of the phenomena. Study quality, heterogeneity, and publication bias were assessed.

Results

Database searching identified 1,677 records, of which 46 studies were included. Meta-analyses of prevalence showed that non-ictal déjà vu was experienced by 0.74 (95% CI [0.67, 0.79], p < 0.001) of healthy individuals, whereas interictal déjà vu was experienced by 0.62 (95% CI [0.48, 0.75], p = 0.099) and ictal déjà vu by 0.22 (95% CI [0.15, 0.32], p = 0.001) of epilepsy patients. Examinations of phenomenological (sex, age, frequency, duration, emotional valence, and dissociative symptoms) and neuroscientific (brain structures and functions) data revealed significant variations between non-ictal, interictal and ictal déjà vu on several domains.

Conclusion

This systematic review and meta-analysis do not support the notion that non-ictal, interictal and ictal déjà vu are homogenous experiences. Instead, it provides insight into ictal déjà vu as a symptom of epilepsy that should be considered included in future revisions of the ICD-11.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=394239, CRD42023394239.

Towards a conflict account of déjà vu: The role of memory errors and memory expectation conflict in the experience of déjà vu

Déjà vu can be defined as conflict between a subjective evaluation of familiarity and a concurrent evaluation of novelty. Accounts of the déjà vu experience have not explicitly referred to a "conflict account of déjà vu" despite the acceptance of conflict-based definitions of déjà vu and relatively recent neuroimaging work that has implicated brain areas associated with conflict as underpinning the experience. Conflict monitoring functioning follows a similar age-related trajectory to déjà vu with a peak in young adulthood and a subsequent age-related decline. In this narrative review of the literature to date, we consider how déjà vu is defined and how this has influenced the understanding of déjà vu. We also review how déjà vu can be understood within theories of recognition memory and cognitive control. Finally, we summarise the conflict account of déjà vu and propose that this account of the experience may provide a coherent explanation as to why déjà vu experiences tend to decrease with age in the non-clinical population.

Intracranial electrical brain stimulation as an approach to studying the (dis)continuum of memory experiential phenomena

Déjà vu and involuntary autobiographical memories (IAM) can be induced by intracranial electric brain stimulation in epileptic patients, sometimes in the same individual. We suggest that there may be different types of IAM which should be taken into account and provide several ideas to test the hypothesis of a continuity between IAM and déjà vu phenomena.

Dissociation in patients with epilepsy and functional seizures: A narrative review of the literature

Dissociation is a "disruption of the usually integrated functions of consciousness, memory, identity or perception of the environment" according to DSM-5.  It is commonly seen in psychiatric disorders including primary dissociative disorders, post-traumatic stress disorder, depression, and panic disorder. Dissociative phenomena are also described in the context of substance intoxication, sleep deprivation and medical illnesses including traumatic brain injury, migraines, and epilepsy. Patients with epilepsy have higher rates of dissociative experiences as measured on the Dissociative Experiences Scale compared to healthy controls. Ictal symptoms, especially in focal epilepsy of temporal lobe origin, may include dissociative-like experiences such as déjà vu/jamais vu, depersonalization, derealization and what has been described as a "dreamy state".  These descriptions are common in the setting of seizures that originate from mesial temporal lobe epilepsy and may involve the amygdala and hippocampus. Other ictal dissociative phenomena include autoscopy and out of body experiences, which are thought to be due to disruptions in networks responsible for the integration of one's own body and extra-personal space and involve the temporoparietal junction and posterior insula. In this narrative review, we will summarize the updated literature on dissociative experiences in epilepsy, as well as dissociative experiences in functional seizures. Using a case example, we will review the differential diagnosis of dissociative symptoms. We will also review neurobiological underpinnings of dissociative symptoms across different diagnostic entities and discuss how ictal symptoms may shed light on the neurobiology of complex mental processes including the subjective nature of consciousness and self-identity.

Opening a conceptual space for metamemory experience

The experiences associated with remembering, including metamemory feelings about the act of remembering and attempts at remembering, are not often integrated into general accounts of memory. For example, David Rubin (2022) proposes a unified, three-dimensional conceptual space for mapping memory states, a map that does not systematically specify metamemory feelings. Drawing on Rubin's model, we define a distinct role for metamemory in relation to first-order memory content. We propose a fourth dimension for the model and support the proposal with conceptual, neurocognitive, and clinical lines of reasoning. We use the modified model to illustrate several cases, and show how it helps to conceptualize a new category of memory state: autonoetic knowing, exemplified by déjà vu. We also caution not to assume that memory experience is directly correlated with or caused by memory content, an assumption Tulving (1989) labeled the doctrine of concordance.

Basal temporal lobe epilepsy: SEEG electroclinical characteristics

OBJECTIVE

Temporal lobe epilepsy is the most common type of focal drug-resistant epilepsy. Seizures with predominant involvement of basal temporal regions (BTR) are not well characterized. In this stereo electroencephalography (SEEG) study, we aimed at describing the ictal networks involving BTR and the associated clinical features.

METHODS

We studied 24 patients explored with SEEG in our center with BTR sampling. We analyzed their seizures using a quantitative method: the "epileptogenicity index". Then we reported the features of the patients with maximal epileptogenicity within BTR, especially ictal network involved, ictal semiology and post-surgical outcome.

RESULTS

We found that rhinal cortex, parahippocampal cortex and posterior fusiform gyrus were the most epileptogenic structures within the BTR (mean EI: 0.57, 0.55, 0.54 respectively). Three main groups of epileptogenic zone organization were found: anterior (23% of total seizures) posterior (30%) and global (47%, both anterior and posterior). Contralateral spread was found in 35% of left seizures and 20% of right seizures. Naming deficit was more prevalent in left BTR (71% vs 29% in right seizures; p = 0.01) whereas automatic speech production was preferentially represented in right seizures (11% vs 54%; p = 0.001). Surgery was proposed for 11 patients (45.8%), leading to seizure freedom in 72% (Engel Class I). One patient presented post-operative permanent functional deficit.

CONCLUSION

Basal-temporal lobe epilepsy seems to be a specific entity among the temporal epilepsy spectrum with specific clinical characteristics. Resective surgery can be proposed with good outcomes in a significant proportion of patients and is safe provided that adequate language assessment has been preoperatively made.

Entropy, Amnesia, and Abnormal Déjà Experiences

Previous research has contrasted fleeting erroneous experiences of familiarity with equally convincing, and often more stubborn erroneous experiences of remembering. While a subset of the former category may present as nonpathological “déjà vu,” the latter, termed “déjà vécu” can categorize a delusion-like confabulatory phenomenon first described in elderly dementia patients. Leading explanations for this experience include the dual process view, in which erroneous familiarity and erroneous recollection are elicited by inappropriate activation of the parahippocampal cortex and the hippocampus, respectively, and the more popular encoding-as-retrieval explanation in which normal memory encoding processes are falsely flagged and interpreted as memory retrieval. This paper presents a novel understanding of this recollective confabulation that builds on the encoding-as-retrieval hypothesis but more adequately accounts for the co-occurrence of persistent déjà vécu with both perceptual novelty and memory impairment, the latter of which occurs not only in progressive dementia but also in transient epileptic amnesia (TEA) and psychosis. It makes use of the growing interdisciplinary understanding of the fluidity of time and posits that the functioning of memory and the perception of novelty, long known to influence the subjective experience of time, may have a more fundamental effect on the flow of time.

Insights into déjà vu: Associations between the frequency of experience and amplitudes of low-frequency oscillations in resting-state functional magnetic resonance imaging

The phenomenon of déjà vu (DV) has intrigued scientists for decades, yet its neurophysiological underpinnings remain elusive. Brain regions have been identified in which morphometry differs between healthy individuals according to the frequency of their DV experiences. This study built upon these findings by assessing if and how neural activity in these and other brain regions also differ with respect to DV experience. Resting-state fMRI was performed on 68 healthy volunteers, 44 of whom reported DV experiences (DV group) and 24 who did not (NDV group). Using multivariate analyses, we then assessed the (fractional) amplitude of low-frequency fluctuations (fALFF/ALFF), a metric that is believed to index brain tissue excitability, for five discrete frequency bands within sets of brain regions implicated in DV and those comprising the default mode network (DMN). Analyses revealed significantly lower values of fALFF/ALFF for specific frequency bands in the DV relative to the NDV group, particularly within mesiotemporal structures, bilateral putamina, right caudatum, bilateral superior frontal cortices, left lateral parietal cortex, dorsal and ventral medial prefrontal cortex, and the posterior cingulate cortex. The pattern of differences in fALFF/ALFF measures between the brains of individuals who have experienced DV and those who have not provides new neurophysiological insights into this phenomenon, including the potential role of the DMN. We suggest that the erroneous feeling of familiarity arises from a temporary disruption of cortico-subcortical circuitry together with the upregulation of cortical excitability.

Imaging the effective networks associated with cortical function through intracranial high-frequency stimulation

Direct electrical stimulation (DES) is considered to be the gold standard for mapping cortical function. A careful mapping of the eloquent cortex is key to successful resective or ablative surgeries, with a minimal postoperative deficit, for treatment of drug‐resistant epilepsy. There is accumulating evidence suggesting that not only local, but also remote activations play an equally important role in evoking clinical effects. By introducing a new intracranial stimulation paradigm and signal analysis methodology allowing to disambiguate EEG responses from stimulation artifacts we highlight the spatial extent of the networks associated with clinical effects. Our study includes 26 patients that underwent stereoelectroencephalographic investigations for drug‐resistant epilepsy, having 337 depth electrodes with 4,351 contacts sampling most brain structures. The routine high‐frequency electrical stimulation protocol for eloquent cortex mapping was altered in a subtle way, by alternating the polarity of the biphasic pulses in a train, causing the splitting the spectral lines of the artifactual components, exposing the underlying tissue response. By performing a frequency‐domain analysis of the EEG responses during DES we were able to capture remote activations and highlight the effect's network. By using standard intersubject averaging and a fine granularity HCP‐MMP parcellation, we were able to create local and distant connectivity maps for 614 stimulations evoking specific clinical effects. The clinical value of such maps is not only for a better understanding of the extent of the effects' networks guiding the invasive exploration, but also for understanding the spatial patterns of seizure propagation given the timeline of the seizure semiology.

Subjective distinguishability of seizure and non-seizure Déjà Vu: A case report, brief literature review, and research prospects

Roughly two-thirds of all people report having experienced déjà vu-the odd feeling that a current experience is both novel and a repeat or replay of a previous, unrecalled experience. Reports of an association between déjà vu and seizure aura symptomatology have accumulated for over a century, and frequent déjà vu is also now known to be associated with focal seizures, particularly those of a medial temporal lobe (MTL) origin. A longstanding question is whether seizure-related déjà vu has the same basis and is the same subjective experience as non-seizure déjà vu. Survey research suggests that people who experience both seizure-related and non-seizure déjà vu can often subjectively distinguish between the two. We present a case of a person with a history of focal MTL seizures who reports having experienced both seizure-related and non-seizure common déjà vu, though the non-seizure type was more frequent during this person's youth than it is currently. The patient was studied with a virtual tour paradigm that has previously been shown to elicit déjà vu among non-clinical, young adult participants. The patient reported experiencing déjà vu of the common non-seizure type during the virtual tour paradigm, without associated abnormalities of the intracranial EEG. We situate this work in the context of broader ongoing projects examining the subjective correlates of seizures. The importance for memory research of virtual scenes, spatial tasks, virtual reality (VR), and this paradigm for isolating familiarity in the context of recall failure are discussed.

Network of autoscopic hallucinations elicited by intracerebral stimulations of periventricular nodular heterotopia: An SEEG study

Periventricular nodular heterotopias (PVNH) are areas of neurons abnormally located in the white matter that might be involved in physiological cortical functions. Autoscopic hallucinations are changes in self-consciousness determined by a mismatch in integration of multiple sensory inputs. Our goal is to highlight the brain network involved in generation of autoscopic hallucination elicited by electrical stimulation of a PVNH in a drug resistant epilepsy patient. Our patient was explored using stereo-electroencephalography with electrodes covering the right posterior temporal PVNH and the adjacent cortex. Direct electrical high frequency stimulation of the PVNH elicited autoscopic hallucinations mainly involving the face and upper trunk. We then used multiple modalities to determine brain connectivity: single pulse electrical stimulation of the PVNH and stimulation-evoked potentials were used to highlight resting state effective connectivity. High-frequency stimulation using alternating polarity pulses enabled us to identify the network involved, time-locked to the clinical effect and to map symptom-related effective connectivity. Functional connectivity using a non-linear regression method was used to determine dependencies between different cortical regions following the stimulation. Finally, structural connectivity was highlighted using deterministic fiber tracking. Multi-modal connectivity analysis identified a network involving the PVNH, occipital and temporal neocortex, fusiform gyrus and parietal cortex.

MicroRNA-221-3p Suppresses the Microglia Activation and Seizures by Inhibiting of HIF-1α in Valproic Acid-Resistant Epilepsy

One-third of patients with epilepsy suffer from drug-resistant epilepsy (DRE). Valproic acid (VPA) is a classic anticonvulsant drug, and its resistance is a crucial predictor of DRE, but the pathogenesis remain unknown. Most patients with VPA-resistant epilepsy appear distinct inflammatory response and local hypoxia. Hypoxia-inducible factor (HIF)-1α is an essential effector molecule of hypoxia and inflammation, and may exert therefore a significant effect on the development of VPA-resistant epilepsy. We systematically assess the significance of HIF-1α on children and mice with VPA-resistant epilepsy, and investigated the micro (mi) RNAs that regulate HIF-1α expression. We established models of VPA-sensitive epilepsy and VPA-resistant epilepsy in mice, and confirmed that they had significant differences in epileptic behavior and electroencephalography data. Through proteomics analysis, we identified that HIF-1α was overexpressed in mice with VPA-resistant epilepsy, and regulated the expression of interleukin-1β and tumor necrosis factor-α. Increased expression of HIF-1α led to the increase of microglia and induced their polarization from the M2 phenotype to M1 phenotype, which triggered the release of proinflammatory mediators. Bioinformatics analysis of public databases demonstrated that miR-221-3p was reduced in VPA-resistant epilepsy, and negatively regulated HIF-1α expression. Intervention using miR-221-3p mimics reduced HIF-1α expression markedly and suppressed the activation of microglia and the release of inflammatory mediators, which relieved epileptic seizures of VPA-resistant epilepsy. These observations reveal miR-221-3p/HIF-1α as essential component in pathogenesis of VPA-resistant epilepsy which represent therapeutic antiseizure targets.

Neural networks underlying hyperkinetic seizures: A quantitative PET and SEEG study

OBJECTIVE

Hyperkinetic seizures (HKS) are characterized by complex movements that commonly occur during seizures arising from diverse cortical structures. A common semiology network may exist and analyzing the anatomo-electrical mechanisms would facilitate presurgical evaluation. Here, quantitative positron emission tomography (PET) and stereoelectroencephalography (SEEG) analysis was used to explore the underlying mechanism of HKS.

METHODS

We retrospectively collected patients with epilepsy with HKS between 2014 and 2019. The interictal PET data of patients with epilepsy with HKS were compared with those of 25 healthy subjects using statistical parametric mapping to identify regions with significant hypometabolism. Then, regions of interest (ROI) for SEEG analysis were identified based on the results of PET analysis. Patients in which the ROIs were covered by intracerebral electrodes were selected for further analysis. Stereoelectroencephalography -clinical correlations with latency measurements were analyzed, and we also performed coherence analysis among ROIs both before and during HKS.

RESULTS

Based on the inclusion criteria, 27 patients were analyzed. In the PET analysis, significant hypometabolism was observed in the ipsilateral dorsoanterior insular lobe, bilateral mesial frontal lobes (supplementary motor area/middle cingulate cortex, SMA/MCC), and the bilateral heads of the caudate nuclei in patients with HKS compared with the control group (p < 0.001). We selected dorsoanterior insula and SMA/MCC as ROIs for SEEG analysis. Eight patients with 23 HKS events were selected for further analysis. There was a linear correlation between the ictal involvement of both the dorsoanterior insula and SMA/MCC with the onset of HKS. Stereoelectroencephalography analysis indicated alpha range activity seemed more often associated with dorsoanterior insula and SMA/MCC involvement during HKS.

CONCLUSIONS

The dorsoanterior insular lobe, mesial frontal lobes (SMA/MCC), and the bilateral heads of the caudate nuclei were probably involved in the generation of HKS. The SEEG analysis further indicated that the occurrence of HKS might be partly associated with synchronized rhythmical alpha activity between dorsoanterior insula and SMA/MCC.

On seizure semiology

The clinical expression of seizures represents the main symptomatic burden of epilepsy. Neural mechanisms of semiologic production in epilepsy, especially for complex behaviors, remain poorly known. In a framework of epilepsy as a network rather than as a focal disorder, we can think of semiology as being dynamically produced by a set of interconnected structures, in which specific rhythmic interactions, and not just anatomical localization, are likely to play an important part in clinical expression. This requires a paradigm shift in how we think about seizure organization, including from a presurgical evaluation perspective. Semiology is a key data source, albeit with significant methodological challenges for its use in research, including observer bias and choice of semiologic categories. Better understanding of semiologic categorization and pathophysiological correlates is relevant to seizure classification systems. Advances in knowledge of neural mechanisms as well as anatomic correlates of different semiologic patterns could help improve knowledge of epilepsy networks and potentially contribute to therapeutic innovations.

Semi-automatic Extraction of Functional Dynamic Networks Describing Patient's Epileptic Seizures

Intracranial electroencephalography (EEG) studies using stereotactic EEG (SEEG) have shown that during seizures, epileptic activity spreads across several anatomical regions from the seizure onset zone toward remote brain areas. A full and objective characterization of this patient-specific time-varying network is crucial for optimal surgical treatment. Functional connectivity (FC) analysis of SEEG signals recorded during seizures enables to describe the statistical relations between all pairs of recorded signals. However, extracting meaningful information from those large datasets is time consuming and requires high expertise. In the present study, we first propose a novel method named Brain-wide Time-varying Network Decomposition (BTND) to characterize the dynamic epileptogenic networks activated during seizures in individual patients recorded with SEEG electrodes. The method provides a number of pathological FC subgraphs with their temporal course of activation. The method can be applied to several seizures of the patient to extract reproducible subgraphs. Second, we compare the activated subgraphs obtained by the BTND method with visual interpretation of SEEG signals recorded in 27 seizures from nine different patients. As a whole, we found that activated subgraphs corresponded to brain regions involved during the course of the seizures and their time course was highly consistent with classical visual interpretation. We believe that the proposed method can complement the visual analysis of SEEG signals recorded during seizures by highlighting and characterizing the most significant parts of epileptic networks with their activation dynamics.

Cingulate cortex function and multi-modal connectivity mapped using intracranial stimulation

The cingulate cortex is part of the limbic system. Its function and connectivity are organized in a rostro-caudal and ventral-dorsal manner which was addressed by various other studies using rather coarse cortical parcellations. In this study, we aim at describing its function and connectivity using invasive recordings from patients explored for focal drug-resistant epilepsy. We included patients that underwent stereo-electroencephalographic recordings using intracranial electrodes in the University Emergency Hospital Bucharest between 2012 and 2019. We reviewed all high frequency stimulations (50 ​Hz) performed for functional mapping of the cingulate cortex. We used two methods to characterize brain connectivity. Effective connectivity was inferred based on the analysis of cortico-cortical potentials (CCEPs) evoked by single pulse electrical stimulation (SPES) (15 ​s inter-pulse interval). Functional connectivity was estimated using the non-linear regression method applied to 60 ​s spontaneous electrical brain signal intervals. The effective (stimulation-evoked) and functional (non-evoked) connectivity analyses highlight brain networks in a different way. While non-evoked connectivity evidences areas having related activity, often in close proximity to each other, evoked connectivity highlights spatially extended networks. To highlight in a comprehensive way the cingulate cortex's network, we have performed a bi-modal connectivity analysis that combines the resting-state broadband h² non-linear correlation with cortico-cortical evoked potentials. We co-registered the patient's anatomy with the fsaverage FreeSurfer template to perform the automatic labeling based on HCP-MMP parcellation. At a group level, connectivity was estimated by averaging responses over stimulated/recorded or recorded sites in each pair of parcels. Finally, for multiple regions that evoked a clinical response during high frequency stimulation, we combined the connectivity of individual pairs using maximum intensity projection. Connectivity was assessed by applying SPES on 2094 contact pairs and recording CCEPs on 3580 contacts out of 8582 contacts of 660 electrodes implanted in 47 patients. Clinical responses elicited by high frequency stimulations in 107 sites (pairs of contacts) located in the cingulate cortex were divided in 10 groups: affective, motor behavior, motor elementary, versive, speech, vestibular, autonomic, somatosensory, visual and changes in body perception. Anterior cingulate cortex was shown to be connected to the mesial temporal, orbitofrontal and prefrontal cortex. In the middle cingulate cortex, we located affective, motor behavior in the anterior region, and elementary motor and somatosensory in the posterior part. This region is connected to the prefrontal, premotor and primary motor network. Finally, the posterior cingulate was shown to be connected with the visual areas, mesial and lateral parietal and temporal cortex.

Déjà vu and prescience in a case of severe episodic amnesia following bilateral hippocampal lesions

Several studies pertaining to déjà vu have consistently made a connection with the perirhinal region, a region located below the hippocampus. This idea is strengthened by the fact that déjà vu is an erroneous sense of familiarity and that familiarity appears to largely depend on the perirhinal region in healthy subjects. In this context, the role of the hippocampus is particularly unclear as it is unknown whether or not it plays a role in the genesis of déjà vu. We report on the case of OHVR, an epileptic patient who suffers from severe episodic amnesia related to massive isolated bilateral damage to the hippocampus. In contrast, the perirhinal region is intact structurally and functionally. This patient reports frequent déjà vu but also another experiential phenomenon with a prominent feeling of prescience, which shows some of the characteristics of déjà vécu. She clearly distinguishes both. She also developed a form of synaesthesia by attributing affective valence to numbers. This study shows that déjà vu can occur in cases of amnesia with massively damaged hippocampi and confirms that the perirhinal region is a core region for déjà vu, using a different approach from previous reports. It also provides clues about a potential influence of hippocampal alterations in déjà vécu.

Functional activity changes in memory and emotional systems of healthy subjects with déjà vu

Déjà vu (DV) is a fascinating and mysterious human experience that has attracted interest from psychologists and neuroscientists for over a century. In recent years, several studies have been conducted to unravel the psychological and neurological correlates of this phenomenon. However, the neural mechanisms underlying the DV experience in benign manifestations are still poorly understood. Thirty-three healthy volunteers completed an extensive neuropsychiatric and neuropsychological battery including personality evaluation. The presence of DV was assessed with the Inventory for Deja vu Experiences Assessment. Participants underwent episodic memory learning test, and 2 days later during event-related functional magnetic resonance imaging (fMRI), they are asked to rate old and new pictures as a novel, moderately/very familiar, or recollected. We identified 18 subjects with DV (DV+) and 15 without DV (DV-) matched for demographical, neuropsychological, and personality characteristics. At a behavioral level, no significant difference was detected in the episodic memory tasks between DV+ and DV-. Functional magnetic resonance imaging analysis revealed that DV+, independently from task conditions, were characterized by increased activity of the bilateral insula coupled with reduced activation in the right parahippocampal, both hippocampi, superior/middle temporal gyri, thalami, caudate nuclei, and superior frontal gyri with respect to DV-. Our study demonstrates that individuals who experienced DV are not characterized by different performance underlying familiarity/recollection memory processes. However, fMRI results provide evidence that the physiological DV experience is associated with the employment of different neural responses of brain regions involved in memory and emotional processes.

Illusory own body perceptions mapped in the cingulate cortex-An intracranial stimulation study

Body awareness is the result of sensory integration in the posterior parietal cortex; however, other brain structures are part of this process. Our goal is to determine how the cingulate cortex is involved in the representation of our body. We retrospectively selected patients with drug-resistant epilepsy, explored by stereo-electroencephalography, that had the cingulate cortex sampled outside the epileptogenic zone. The clinical effects of high-frequency electrical stimulation were reviewed and only those sites that elicited changes related to body perception were included. Connectivity of the cingulate cortex and other cortical structures was assessed using the h2 coefficient, following a nonlinear regression analysis of the broadband EEG signal. Poststimulation changes in connectivity were compared between two sets of stimulations eliciting or not eliciting symptoms related to body awareness (interest and control groups). We included 17 stimulations from 12 patients that reported different types of body perception changes such as sensation of being pushed toward right/left/up, one limb becoming heavier/lighter, illusory sensation of movement, sensation of pressure, sensation of floating or detachment of one hemi-body. High-frequency stimulation in the cingulate cortex (1 anterior, 15 middle, 1 posterior part) elicits body perception changes, associated with a decreased connectivity of the dominant posterior insula and increased coupling between other structures, located particularly in the nondominant hemisphere.

Déjà vu experiences in anxiety

Déjà vu occurs when a novel event is experienced with an erroneous sense of familiarity. Memory researchers theorise that this arises due to an error in the processes underlying the recognition memory system. Research has indicated that there may be a link between high levels of anxiety and increased frequency and intensity of déjà vu, however, there has been a comparatively little characterisation of déjà vu as experienced by individuals with clinical anxiety. We used an online questionnaire to collect data from individuals self-reporting a clinical diagnosis of anxiety, as well as from age-matched controls. The Anxiety Group reported a significantly higher frequency of déjà vu episodes over the previous month than controls. They also reported experiencing déjà vu more frequently and with higher intensity during periods of high anxiety. In addition, the Anxiety Group reported finding déjà vu episodes significantly more distressing than the Control Group. The findings indicate that there are differences in déjà vu experienced by people reporting high levels of anxiety compared to healthy controls without an anxiety diagnosis. We discuss structural and neural mechanisms thought to underpin déjà vu in relation to these results.

fMRI evidence supporting the role of memory conflict in the déjà vu experience

Attempts to generate déjà vu experimentally have largely focused on engineering partial familiarity for stimuli, relying on an ensuing, but unprompted evaluation of conflict to generate the experience. Without verification that experimentally-generated familiarity is accompanied by the awareness of stimulus novelty, these experimental procedures potentially provide an incomplete déjà vu analogue. We used a modified version of the Deese-Roediger-McDermott (DRM) false memory procedure to generate both familiarity and novelty within a déjà vu analogue - we coupled experimentally-generated familiarity with cues indicating that the familiarity was erroneous, using this additional source of mnemonic information to generate cognitive conflict in our participants. We collected fMRI and behavioural data from 21 participants, 16 of whom reported déjà vu. Using univariate contrasts we identified brain regions associated with mnemonic conflict, including the anterior cingulate cortex, medial prefrontal cortex and parietal cortex. This is the first experiment to image an analogue of the déjà vu experience in healthy volunteers. The increased likelihood of déjà vu reports to DRM critical lures correctly identified as "new", and the activation of neural substrates supporting the experience of cognitive conflict during déjà vu, suggest that the resolution of memory conflict may play an integral role in déjà vu.

Overcoming familiarity illusions in a single case with persistent déjà vu

While occasional déjà vu is benign in the general population, rare neuropsychological cases with persistent déjà vu have been described in the literature. We report the case of MN, a 25-year-old woman, who suffered a cerebral haemorrhage in the right thalamo-callosal region and experienced recurrent déjà vu episodes. Through clinical interviews and memory tasks related to déjà vu, we assumed that source memory errors and an inappropriate feeling of familiarity (measured by the number of false recognitions) were critically involved in MN's déjà vu. Based on this, we developed the first neuropsychological intervention dedicated to déjà vu. The rationale was to train MN to detect elements that could produce an inappropriate feeling of familiarity and to promote metacognitive awareness about déjà vu. This intervention was effective at reducing the frequency of déjà vu episodes in MN's daily life, as well as the number of false recognitions in memory tasks. In addition to its clinical contribution, this single-case study contributes to the limited literature on patients whose déjà vu is not related to epileptic abnormalities and medial temporal brain damage, and provide supportive evidence of the role of an erroneous feeling of familiarity and of metacognitive processes in déjà vu.

Déjà-rêvé: Prior dreams induced by direct electrical brain stimulation

BACKGROUND

Epileptic patients sometimes report experiential phenomena related to a previous dream they had during seizures or electrical brain stimulation (EBS). This has been alluded to in the literature as "déjà-rêvé" ("already dreamed"). However, there is no neuroscientific evidence to support its existence and this concept is commonly mixed up with déjà-vu. We hypothesized that déjà-rêvé would be a specific entity, i.e., different from other experiential phenomena reported in epileptic patients, induced by EBS of specific brain areas.

METHODS

We collected all experiential phenomena related to dreams induced by electrical brain stimulations (EBS) in our epileptic patients (2003-2015) and in a review of the literature. The content of these déjà-rêvé and the location of EBS were analyzed.

RESULTS

We collected 7 déjà-rêvé in our database and 35 from the literature, which corresponds to an estimated prevalence of 0.3‰ of all EBS-inducing déjà-rêvé. Déjà-rêvé is a generic term for three distinct entities: it can be the recollection of a specific dream ("episodic-like"), reminiscence of a vague dream ("familiarity-like") or experiences in which the subject feels like they are dreaming (literally "a dreamy state"). EBS-inducing "episodic-like" and "familiarity-like" déjà-rêvé were mostly located in the medial temporal lobes. "Dreamy states" were induced by less specific EBS areas although still related to the temporal lobes.

CONCLUSIONS

This study demonstrates that déjà-rêvé is a heterogeneous entity that is different from déjà-vu, the historical "dreamy state" definition and other experiential phenomena. This may be relevant for clinical practice as it points to temporal lobe dysfunction and could be valuable for studying the neural substrates of dreams.

Abnormal rsFC and GMV changes in parahippocampal and DLPFC for high Déjà vu experienced subjects

How déjà vu works has long been a mystery, partially because of its characteristics of unpredictable occurrences and quick disappearances, which make it difficult to be explored. Previous studies have described the anatomical structures underlying déjà vu in healthy subjects; however, the functional mechanism of déjà vu remains unclear. Therefore, this study investigated the brain structural and functional components underlying déjà vu by combining voxel-based morphometry analysis (VBM) with resting-state functional connectivity (rsFC). The VBM analysis revealed that the anterior parahippocampal gyrus (PHG) had significantly less grey matter volume (GMV) in high déjà vu group than low group, confirming previous studies. Further functional connectivity analysis revealed that the frequency of déjà vu experiences was negatively correlated with the strength of the rsFC between anterior dorsal lateral prefrontal cortex (DLPFC) and anterior PHG but positively correlated with the strength of the rsFC between posterior DLPFC and posterior PHG. Moreover, the frequency of déjà vu experiences was negatively correlated with the strength of the rsFC between the anterior and posterior regions of the PHG. These findings indicated that familiarity without recollection (PHG) and superior context monitoring (DLPFC) are critical for real-life déjà vu experiences.

Looking for the Self: Phenomenology, Neurophysiology and Philosophical Significance of Drug-induced Ego Dissolution

There is converging evidence that high doses of hallucinogenic drugs can produce significant alterations of self-experience, described as the dissolution of the sense of self and the loss of boundaries between self and world. This article discusses the relevance of this phenomenon, known as “drug-induced ego dissolution (DIED)”, for cognitive neuroscience, psychology and philosophy of mind. Data from self-report questionnaires suggest that three neuropharmacological classes of drugs can induce ego dissolution: classical psychedelics, dissociative anesthetics and agonists of the kappa opioid receptor (KOR). While these substances act on different neurotransmitter receptors, they all produce strong subjective effects that can be compared to the symptoms of acute psychosis, including ego dissolution. It has been suggested that neuroimaging of DIED can indirectly shed light on the neural correlates of the self. While this line of inquiry is promising, its results must be interpreted with caution. First, neural correlates of ego dissolution might reveal the necessary neurophysiological conditions for the maintenance of the sense of self, but it is more doubtful that this method can reveal its minimally sufficient conditions. Second, it is necessary to define the relevant notion of self at play in the phenomenon of DIED. This article suggests that DIED consists in the disruption of subpersonal processes underlying the “minimal” or “embodied” self, i.e., the basic experience of being a self rooted in multimodal integration of self-related stimuli. This hypothesis is consistent with Bayesian models of phenomenal selfhood, according to which the subjective structure of conscious experience ultimately results from the optimization of predictions in perception and action. Finally, it is argued that DIED is also of particular interest for philosophy of mind. On the one hand, it challenges theories according to which consciousness always involves self-awareness. On the other hand, it suggests that ordinary conscious experience might involve a minimal kind of self-awareness rooted in multisensory processing, which is what appears to fade away during DIED.

Memory scrutinized through electrical brain stimulation: A review of 80 years of experiential phenomena

Electrical brain stimulations (EBS) sometimes induce reminiscences, but it is largely unknown what type of memories they can trigger. We reviewed 80 years of literature on reminiscences induced by EBS and added our own database. We classified them according to modern conceptions of memory. We observed a surprisingly large variety of reminiscences covering all aspects of declarative memory. However, most were poorly detailed and only a few were episodic. This result does not support theories of a highly stable and detailed memory, as initially postulated, and still widely believed as true by the general public. Moreover, memory networks could only be activated by some of their nodes: 94.1% of EBS were temporal, although the parietal and frontal lobes, also involved in memory networks, were stimulated. The qualitative nature of memories largely depended on the site of stimulation: EBS to rhinal cortex mostly induced personal semantic reminiscences, while only hippocampal EBS induced episodic memories. This result supports the view that EBS can activate memory in predictable ways in humans.

Focal drug-resistant epilepsy: Progress in care and barriers, a Morroccan perspective

INTRODUCTION

The aim of this study is to determine the clinical, paraclinical, therapeutic and outcome aspects of drug resistant patients with epilepsy in our region and consequently to discuss methods that may improve the management of these patients.

PATIENTS AND METHODS

This paper presents a retrospective study of 25 adult patients that were followed for focal drug resistant epilepsy in epileptology unit of the University Hospital of Fez, Morocco.

RESULTS

This study recorded 25 patients including 48% of males and 52% of females. The mean age of patients was 24years-old. Hippocampal sclerosis was present in 28.5% of patients (7 cases); brain malformations were found in 19% of patients (5 cases); tumors were found in 24% of patients (6 cases); post-traumatic, post-surgical and anoxic-ischemic lesions were found in 28.5% of patients (7 cases). Resective epilepsy surgery was performed in 28,5% of patients (7 cases). Post surgical outcome was good for 5/7 patients (Engel I and II).

CONCLUSION

The clinical characteristics, etiologies and clinical course of medically refractory focal epilepsy in our region are similar to that reported in the global literature. We also demonstrated a long delay between onset of seizures and surgery (15years range 8-34years) and barriers to epilepsy surgery.

[Hippocampal sclerosis: pathogenesis, clinical features, diagnosis, and treatment]

Hippocampal sclerosis, also known as Ammon horn sclerosis or mesial temporal sclerosis, is usually associated with intractable epilepsy and characterized by specific patterns of neuronal loss and gliosis in the medial temporal lobe structures. Hippocampal sclerosis manifests clinically as epilepsy, often intractable epilepsy; in most cases, this condition is surgically treatable. As the most common histological diagnosis in adult patients subjected to epilepsy surgery, hippocampal sclerosis is characterized by complex pathogenesis and requires a multidisciplinary approach to its diagnosis and treatment. This article reviews the pathologic features, natural history, pathogenesis, and electroclinical and MRI signs of hippocampal sclerosis.

Finding the self by losing the self: Neural correlates of ego-dissolution under psilocybin

Ego-disturbances have been a topic in schizophrenia research since the earliest clinical descriptions of the disorder. Manifesting as a feeling that one's "self," "ego," or "I" is disintegrating or that the border between one's self and the external world is dissolving, "ego-disintegration" or "dissolution" is also an important feature of the psychedelic experience, such as is produced by psilocybin (a compound found in "magic mushrooms"). Fifteen healthy subjects took part in this placebo-controlled study. Twelve-minute functional MRI scans were acquired on two occasions: subjects received an intravenous infusion of saline on one occasion (placebo) and 2 mg psilocybin on the other. Twenty-two visual analogue scale ratings were completed soon after scanning and the first principal component of these, dominated by items referring to "ego-dissolution", was used as a primary measure of interest in subsequent analyses. Employing methods of connectivity analysis and graph theory, an association was found between psilocybin-induced ego-dissolution and decreased functional connectivity between the medial temporal lobe and high-level cortical regions. Ego-dissolution was also associated with a "disintegration" of the salience network and reduced interhemispheric communication. Addressing baseline brain dynamics as a predictor of drug-response, individuals with lower diversity of executive network nodes were more likely to experience ego-dissolution under psilocybin. These results implicate MTL-cortical decoupling, decreased salience network integrity, and reduced inter-hemispheric communication in psilocybin-induced ego disturbance and suggest that the maintenance of "self"or "ego," as a perceptual phenomenon, may rest on the normal functioning of these systems.

Multimodal effective connectivity analysis reveals seizure focus and propagation in musicogenic epilepsy

Dynamic causal modeling (DCM) is a method to non-invasively assess effective connectivity between brain regions. 'Musicogenic epilepsy' is a rare reflex epilepsy syndrome in which seizures can be elicited by musical stimuli and thus represents a unique possibility to investigate complex human brain networks and test connectivity analysis tools. We investigated effective connectivity in a case of musicogenic epilepsy using DCM for fMRI, high-density (hd-) EEG and MEG and validated results with intracranial EEG recordings. A patient with musicogenic seizures was examined using hd-EEG/fMRI and simultaneous '256-channel hd-EEG'/'whole head MEG' to characterize the epileptogenic focus and propagation effects using source analysis techniques and DCM. Results were validated with invasive EEG recordings. We recorded one seizure with hd-EEG/fMRI and four auras with hd-EEG/MEG. During the seizures, increases of activity could be observed in the right mesial temporal region as well as bilateral mesial frontal regions. Effective connectivity analysis of fMRI and hd-EEG/MEG indicated that right mesial temporal neuronal activity drives changes in the frontal areas consistently in all three modalities, which was confirmed by the results of invasive EEG recordings. Seizures thus seem to originate in the right mesial temporal lobe and propagate to mesial frontal regions. Using DCM for fMRI, hd-EEG and MEG we were able to correctly localize focus and propagation of epileptic activity and thereby characterize the underlying epileptic network in a patient with musicogenic epilepsy. The concordance between all three functional modalities validated by invasive monitoring is noteworthy, both for epileptic activity spread as well as for effective connectivity analysis in general.

Emergence of semiology in epileptic seizures

Semiology, the manifestation of epilepsy, is dependent upon electrical activity produced by epileptic seizures that are organized within existing neural pathways. Clinical signs evolve as the epileptic discharge spreads in both time and space. Studying the relation between these, of which the temporal component is at least as important as the spatial one, is possible using anatomo-electro-clinical correlations of stereoelectroencephalography (SEEG) data. The period of semiology production occurs with variable time lag after seizure onset and signs then emerge more or less rapidly depending on seizure type (temporal seizures generally propagating more slowly and frontal seizures more quickly). The subset of structures involved in semiological production, the "early spread network", is tightly linked to those constituting the epileptogenic zone. The level of complexity of semiological features varies according to the degree of involvement of the primary or associative cortex, with the former having a direct relation to peripheral sensory and motor systems with production of hallucinations (visual and auditory) or elementary sensorimotor signs. Depending on propagation pattern, these signs can occur in a "march" fashion as described by Jackson. On the other hand, seizures involving the associative cortex, having a less direct relation with the peripheral nervous system, and necessarily involving more widely distributed networks manifest with altered cognitive and/or behavioral signs whose neural substrate involves a network of cortical structures, as has been observed for normal cognitive processes. Other than the anatomical localization of these structures, the frequency of the discharge is a crucial determinant of semiological effect since a fast (gamma) discharge will tend to deactivate normal function, whereas a slower theta discharge can mimic physiological function. In terms of interaction between structures, the degree of synchronization plays a key role in clinical expression, as evidenced, for example, by studies of ictal fear-related behavior (decorrelation of activity between structures inducing "release" phenomena) and of déjà vu (increased synchronization). Studies of functional coupling within networks underlying complex ictal behavior indicate that the clinical semiology of a given seizure depends upon neither the anatomical origin of ictal discharge nor the target areas of its propagation alone but on the dynamic interaction between these. Careful mapping of the ictal network in its full spread offers essential information as to the localization of seizure onset, by deducing that a given network configuration could only be generated by a given area or group of areas.

How functional coupling between the auditory cortex and the amygdala induces musical emotion: a single case study

Music is a sound structure of remarkable acoustical and temporal complexity. Although it cannot denote specific meaning, it is one of the most potent and universal stimuli for inducing mood. How the auditory and limbic systems interact, and whether this interaction is lateralized when feeling emotions related to music, remains unclear. We studied the functional correlation between the auditory cortex (AC) and amygdala (AMY) through intracerebral recordings from both hemispheres in a single patient while she listened attentively to musical excerpts, which we compared to passive listening of a sequence of pure tones. While the left primary and secondary auditory cortices (PAC and SAC) showed larger increases in gamma-band responses than the right side, only the right side showed emotion-modulated gamma oscillatory activity. An intra- and inter-hemisphere correlation was observed between the auditory areas and AMY during the delivery of a sequence of pure tones. In contrast, a strikingly right-lateralized functional network between the AC and the AMY was observed to be related to the musical excerpts the patient experienced as happy, sad and peaceful. Interestingly, excerpts experienced as angry, which the patient disliked, were associated with widespread de-correlation between all the structures. These results suggest that the right auditory-limbic interactions result from the formation of oscillatory networks that bind the activities of the network nodes into coherence patterns, resulting in the emergence of a feeling.

The entropic brain: a theory of conscious states informed by neuroimaging research with psychedelic drugs

Entropy is a dimensionless quantity that is used for measuring uncertainty about the state of a system but it can also imply physical qualities, where high entropy is synonymous with high disorder. Entropy is applied here in the context of states of consciousness and their associated neurodynamics, with a particular focus on the psychedelic state. The psychedelic state is considered an exemplar of a primitive or primary state of consciousness that preceded the development of modern, adult, human, normal waking consciousness. Based on neuroimaging data with psilocybin, a classic psychedelic drug, it is argued that the defining feature of "primary states" is elevated entropy in certain aspects of brain function, such as the repertoire of functional connectivity motifs that form and fragment across time. Indeed, since there is a greater repertoire of connectivity motifs in the psychedelic state than in normal waking consciousness, this implies that primary states may exhibit "criticality," i.e., the property of being poised at a "critical" point in a transition zone between order and disorder where certain phenomena such as power-law scaling appear. Moreover, if primary states are critical, then this suggests that entropy is suppressed in normal waking consciousness, meaning that the brain operates just below criticality. It is argued that this entropy suppression furnishes normal waking consciousness with a constrained quality and associated metacognitive functions, including reality-testing and self-awareness. It is also proposed that entry into primary states depends on a collapse of the normally highly organized activity within the default-mode network (DMN) and a decoupling between the DMN and the medial temporal lobes (which are normally significantly coupled). These hypotheses can be tested by examining brain activity and associated cognition in other candidate primary states such as rapid eye movement (REM) sleep and early psychosis and comparing these with non-primary states such as normal waking consciousness and the anaesthetized state.

Is there anything distinctive about epileptic deja vu?

BACKGROUND

Déjà vu can occur as an aura of temporal lobe epilepsy and in some psychiatric conditions but is also common in the general population. It is unclear whether any clinical features distinguish pathological and physiological forms of déjà vu.

METHODS

50 epileptic patients with ictal déjà vu, 50 non-epileptic patients attending general neurology clinics and 50 medical students at Edinburgh University were recruited. Data were collected on demographic factors, the experience of déjà vu using a questionnaire based on Sno's Inventory for Déjà Vu Experiences Assessment, symptoms of anxiety and depression using the Hospital Anxiety and Depression Scale as well as seizure characteristics, anti-epileptic medications, handedness, EEG and neuroimaging findings for epileptic patients.

RESULTS

73.5% of neurology patients, 88% of students and (by definition) all epilepsy patients had experienced déjà vu. The experience of déjà vu itself was similar in the three groups. Epileptic déjà vu occurred more frequently and lasted somewhat longer than physiological déjà vu. Epilepsy patients were more likely to report prior fatigue and concentrated activity, associated derealisation, olfactory and gustatory hallucinations, physical symptoms such as headaches, abdominal sensations and fear. After controlling for study group, anxiety and depression scores were not associated with déjà vu frequency.

CONCLUSIONS

Déjà vu is common and qualitatively similar whether it occurs as an epileptic aura or normal phenomenon. However ictal déjà vu occurs more frequently and is accompanied by several distinctive features. It is distinguished primarily by 'the company it keeps'.

Electrical engram: how deep brain stimulation affects memory

Deep brain stimulation (DBS) is a surgical procedure involving implantation of a pacemaker that sends electric impulses to specific brain regions. DBS has been applied in patients with Parkinson's disease, depression, and obsessive-compulsive disorder (among others), and more recently in patients with Alzheimer's disease to improve memory functions. Current DBS approaches are based on the concept that high-frequency stimulation inhibits or excites specific brain regions. However, because DBS entails the application of repetitive electrical stimuli, it primarily exerts an effect on extracellular field-potential oscillations similar to those recorded with electroencephalography. Here, we suggest a new perspective on how DBS may ameliorate memory dysfunction: it may enhance normal electrophysiological patterns underlying long-term memory processes within the medial temporal lobe.

Epilepsy, behavior, and art (Epilepsy, Brain, and Mind, part 1)

Epilepsy is both a disease of the brain and the mind. Brain diseases, structural and/or functional, underlie the appearance of epilepsy, but the notion of epilepsy is larger and cannot be reduced exclusively to the brain. We can therefore look at epilepsy from two angles. The first perspective is intrinsic: the etiology and pathophysiology, problems of therapy, impact on the brain networks, and the "mind" aspects of brain functions - cognitive, emotional, and affective. The second perspective is extrinsic: the social interactions of the person with epilepsy, the influence of the surrounding environment, and the influences of epilepsy on society. All these aspects reaching far beyond the pure biological nature of epilepsy have been the topics of two International Congresses of Epilepsy, Brain, and Mind that were held in Prague, Czech Republic, in 2010 and 2012 (the third Congress will be held in Brno, Czech Republic on April 3-5, 2014; www.epilepsy-brain-mind2014.eu). Here, we present the first of two papers with extended summaries of selected presentations of the 2012 Congress that focused on epilepsy, behavior, and art.

Déjà experiences in temporal lobe epilepsy

Historically, déjà vu has been linked to seizure activity in temporal lobe epilepsy, and clinical reports suggest that many patients experience the phenomenon as a manifestation of simple partial seizures. We review studies on déjà vu in epilepsy with reference to recent advances in the understanding of déjà vu from a cognitive and neuropsychological standpoint. We propose a decoupled familiarity hypothesis, whereby déjà vu is produced by an erroneous feeling of familiarity which is not in keeping with current cognitive processing. Our hypothesis converges on a parahippocampal dysfunction as the locus of déjà vu experiences. However, several other temporal lobe structures feature in reports of déjà vu in epilepsy. We suggest that some of the inconsistency in the literature derives from a poor classification of the various types of déjà experiences. We propose déjà vu/déjà vécu as one way of understanding déjà experiences more fully. This distinction is based on current models of memory function, where déjà vu is caused by erroneous familiarity and déjà vécu by erroneous recollection. Priorities for future research and clinical issues are discussed.