Symposia > Barbeau

déjà vu, déjà vecu and other mnesic experiential phenomena

Chair:   Emmanuel J. Barbeau

CerCo, Toulouse, France

Abstract:

Experiential phenomena refer to a category of subjective experiences that subjects usually feel as “strange”. In this symposium, we focus on déjà vu, déjà vecu and more elaborated memory experiences. Transient experiential phenomena are sometimes reported by patients with epilepsy; however, these phenomena, in particular déjà vecu, can also be chronic in some patients with dementia, and can occur, such as déjà vu, in healthy subjects. These experiences open an exciting window into the study of memory. This symposium aims at showing how the study of such phenomena can advance our knowledge of some memory processes and clinical conditions. Two of the talks report state-of the art behavioural data in patients with déjà vu
and déjà vécu. The two others report studies of the synchronisation of intracerebral electroencephalography (EEG) signals during déjà vu and recollection of vivid memories. As will be seen from this series of talks, this field, at the interface between clinical research and basic science, appears very promising for the study of memory.

Talk 1:

Déjà vu in unilateral temporal-lobe epilepsy is associated with selective impairments in familiarity assessment

Stefan Köhler & Chris Martin
The Brain and Mind Institute, University of Western Ontario, Canada

In déjà vu, a phenomenological impression of familiarity is experienced with a sense that the current environment or situation should in fact not feel familiar. How can such a paradoxical experience arise? In the present study, we sought to elucidate the mechanisms involved in déjà vu by examining unilateral TLE patients who experience this phenomenon as part of their seizures (TLE+). Specifically, we tested whether these patients show a unique pattern of interictal memory deficits that reflects selective impairments in familiarity assessment, as defined in current dual-process models of recognition memory. Phenomenological reports confirmed that ictal déjà vu experiences reflected feelings of familiarity for the immediate
visual environment that were experienced as subjectively inappropriate. In Experiment 1, we employed a Remember-Know paradigm for visual scenes and we observed recognition impairments that were indeed limited to familiarity assessment in TLE+ patients. In Experiment 2, we administered an exclusion task for visual scenes in which both recognition processes were placed in opposition. TLE+ patients again displayed recognition impairments -but these impairments spared their ability to counteract familiarity with recollection of contextual detail. The selective pattern of deficits in TLE+ patients contrasted with the pattern we observed in our control group of TLE patients without déjà vu (TLE-), whose deficits encompassed familiarity as well as recollection. Notably, the pattern of behaviour across patient groups paralleled differences in structural integrity of the medial temporal lobes, with significantly smaller and hints of more focal volume reductions in the affected hemisphere of TLE+ patients.


Talk 2:

Forced-choice recognition in patients with chronic deja vecu

O'Connor, A.R.1, Illman, N.A.2 & Moulin, C.J.A.2
1 University of St. Andrews, Scotland
2 University of Leeds, England

We have previously reported cases of dementia who present with almost continuous deja vecu - what we have described as recollective confabulation. By our view, these patients have a fronto-temporal deficit by which they misinterpret novelty as a retrieval experience, and in this leads them to experience 'recollection' of the present moment. On formal testing, this pattern is particularly pronounced for ‘novel’ low frequency words. In a case series we present 13 patients with dementia who presented with sensations of deja vu and deja vecu, and describe the core features of their experience. In particular, these patients are significantly
more likely to assign false positives in yes/no tasks with the experience of recollection. For the first time we present an analysis of forced-choice recognition data, and find that the pattern of responses given by these deja vecu patients is no different from a group of participants with Alzheimer's disease without deja vu and deja vecu experiences. We suggest that intact familiarity processes are sufficient to overcome false sensations of recollection in this group - and this relatively normal performance establishes a boundary around recollective confabulation and its impact on recognition memory.


Talk 3:

Déjà vu induced by direct intracerebral stimulations studies

Fabrice Bartolomei
INSERM U 751, Marseille, France

The phenomenon of 'déjà vu' is caused by acute disturbance of mnemonic systems of the medial temporal lobe (MTL). In epileptic patients investigated with intracerebral electrodes, déjà vu can be more readily induced by stimulation of the rhinal cortices (RCs) than the hippocampus (H). Indeed, in a previous stimulation, study we provided evidence that the probability to induce DV was maximal after stimulation of the entorhinal cortex, while reminiscences of vivid memories were obtained after stimulation of the basal temporal cortex including the perirhinal region (Bartolomei et al, Neurology. 2004;63(5):858-64). Recently,
we analysed the synchronisation of intracerebral electroencephalography (EEG) signals recorded from RC, H and amygdala (A) in epileptic patients in whom déjà vu was induced by electrical stimulation (Bartolomei et al, Clin Neurophysiol. 2011 In press). In comparison with RC stimulations that did not lead to déjà vu (DV-), stimulations triggering déjà vu (DV ) were associated with increased broadband EEG correlation (p=0.01). Changes in correlations were significantly different in the theta band for RC-A (p=0.007) and RC-H (p=0.01) and in the beta band for RC-H (p=0.001) interactions. These findings suggest that Déjà vu is the results of changes in synchronization process between mesial temporal structures.

Talk 4:

Recollection of vivid memories following intracerebral stimulations in epileptic patients

Emmanuel J Barbeau, Jonathan Curot, Thomas Busigny
CerCo, Toulouse, France

Electrical stimulation of the temporal cortex in patients with epilepsy sometimes elicits experiential phenomena such as recollection of vivid memories. The neurophysiological substrate of such phenomena is poorly understood. Furthermore, the relation between the site of stimulation and the type of memory elicited has only recently started to be investigated. We investigated these issues in several patients and take patient FGA as an example. FGA had intracerebral electrodes stereotaxically implanted in the right temporal lobe for investigation of drug-resistant epilepsy. We report the results of electrical stimulations of the perirhinal
region. Two stimulations elicited experiential phenomena consisting of visual memories that belonged to FGA’s past, but which were not related to any particular episode (autobiographical semantic memory). These visual memories consisted of objects or of details of objects. These two stimulations were contrasted with other stimulations in the same subhippocampal region. Cross-correlation analysis of the depth-EEG signals filtered in frequency sub-bands revealed that experiential phenomena occurred only when the various
brain structures involved in the after-discharge were synchronized in the theta range. These structures included the perirhinal region, the hippocampus, other limbic structures as well as a primary visual area. Our results suggest that recollection of vivid memory after electric stimulation of the cortex may rely on wide networks of brain areas that transiently synchronize. However, the phenomenological experience could depend on the site of stimulation: context-free when subhippocampal structures are stimulated, context-rich when the amygadala/hippocampus are stimulated.
 

Talk 5:

Unveiling the mystery of déjà vu

Milan Brázdil1 Radek Mareček1Tomáš Urbánek2, Tomáš Kašpárek3, Michal Mikl4, Ivan Rektor4, Adam Zeman5  

1 Masaryk University, Brno, Czech Republic
2 Academy of Sciences of the Czech Republic, Brno
3 Faculty Hospital Brno and Medical Faculty of Masaryk University, Brno
4  Masaryk University, Brno
5  University of Exeter, Exeter


Electrical stimulation of the temporal cortex in patients with epilepsy sometimes elicits experiential phenomena such as recollection of vivid memories. The neurophysiological substrate of such phenomena is poorly understood. Furthermore, the relation between the site of stimulation and the type of memory elicited has only recently started to be investigated. We investigated these issues in several patients and take patient FGA as an example. FGA had intracerebral electrodes stereotaxically implanted in the right temporal lobe for investigation of drug-resistant epilepsy. We report the results of electrical stimulations of the perirhinal
region. Two stimulations elicited experiential phenomena consisting of visual memories that belonged to FGA’s past, but which were not related to any particular episode (autobiographical semantic memory). These visual memories consisted of objects or of details of objects. These two stimulations were contrasted with other stimulations in the same subhippocampal region. Cross-correlation analysis of the depth-EEG signals filtered in frequency sub-bands revealed that experiential phenomena occurred only when the various
brain structures involved in the after-discharge were synchronized in the theta range. These structures included the perirhinal region, the hippocampus, other limbic structures as well as a primary visual area. Our results suggest that recollection of vivid memory after electric stimulation of the cortex may rely on wide networks of brain areas that transiently synchronize. However, the phenomenological experience could depend on the site of stimulation: context-free when subhippocampal structures are stimulated, context-rich when the amygadala/hippocampus are stimulated.
 


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