Characteristics of Near-Death Experiences Memories as Compared to Real and Imagined Events Memories

in PLoS ONE (2013), 8(3),

Since the dawn of time, Near-Death Experiences (NDEs) have intrigued and, nowadays, are still not fully explained. Since reports of NDEs are proposed to be imagined events, and since memories of imagined ... [more ▼]

Since the dawn of time, Near-Death Experiences (NDEs) have intrigued and, nowadays, are still not fully explained. Since reports of NDEs are proposed to be imagined events, and since memories of imagined event have, on average, fewer phenomenological characteristics than real events memories, we here compared phenomenological characteristics of NDEs reports with memories of imagined and real events. We included three groups of coma survivors (8 patients with NDE as defined by the Greyson NDE scale, 6 patients without NDE but with memory of their coma, 7 patients without memories of their coma) and a group of 18 age-matched healthy volunteers. Five types of memories were assessed using Memory Characteristics Questionnaire (MCQ – Johnson et al., 1988): target memory (NDE for NDE memory group, coma memory for coma memory group, and first childhood memory for no memory and control groups), old and recent real event memories and old and recent imagined event memories. Since NDEs are known to have high emotional content, participants were requested to choose the most emotionally salient memories for both real and imagined recent and old event memories. Results showed that, in NDE memories group, NDE memories have more characteristics than memories of imagined and real events (p<0.02). NDE memories contain more self-referential and emotional information and have better clarity than memories of coma (all p<0.02). The present study showed that NDE memories contain more characteristics than real event memories and coma memories. Thus, this suggests that they cannot be considered as imagined event memories. On the contrary, their physiological origins could lead them to be really perceived although not lived in the reality. Further work is needed to better understand this phenomenon. [less ▲]

Memories of Near-Death experiences are they memories of imagined events?

Poster (2012, October 27)

Background: The phenomenon of Near-Death Experiences (NDEs) has always intrigued but is still not fully explained despite numerous theories and studies. Since reports of NDEs are proposed to be imagined ... [more ▼]

Background: The phenomenon of Near-Death Experiences (NDEs) has always intrigued but is still not fully explained despite numerous theories and studies. Since reports of NDEs are proposed to be imagined events (French, 2001), and since memories of imagined events have, on average, fewer phenomenological characteristics than real event memories (e.g. Johnson et al., 1988), we here compared phenomenological characteristics of NDEs reports with memories of imagined and real events. Methods: We included 3 groups of coma survivors (8 patients with NDE as defined by the Greyson NDE scale – the “NDE memory group”- , 6 patients without NDE but with memory of their coma – the “coma memory group” – and 7 patients without memories of their coma – the “no memory group”) and a group of 18 age-matched healthy volunteers. Five memories were assessed using Memory Characteristics Questionnaire (MCQ – Johnson et al., 1988): target memory (NDE for NDE memory group, coma memory for coma memory group, and first childhood memory for no memory and control groups), old and recent real event memories and old and recent imagined event memories. Results: In NDE group, NDE memories showd more characteristics than memories of imagined and real events (p<0.02). These memories contain more self-referential and emotional information and have better clarity than memories of coma (all p<0.02). Conclusion: The present study showed that NDE memories contain more characteristics than real event memories and coma memories. Thus, they cannot be considered as classic imagined event memories. On the contrary, their physiological origins could lead them to be really perceived although not lived in the reality. Further work is needed to better understand this phenomenon [less ▲]

Metabolic activity in external and internal awareness networks in severely brain-damaged patients.

in Journal of Rehabilitation Medicine (2012), 44(6), 487-94

OBJECTIVE: An extrinsic cerebral network (encompassing lateral frontoparietal cortices) related to external/sensory awareness and an intrinsic midline network related to internal/self-awareness have been ... [more ▼]

OBJECTIVE: An extrinsic cerebral network (encompassing lateral frontoparietal cortices) related to external/sensory awareness and an intrinsic midline network related to internal/self-awareness have been identified recently. This study measured brain metabolism in both networks in patients with severe brain damage. DESIGN: Prospective [18F]-fluorodeoxyglucose-positron emission tomography and Coma Recovery Scale-Revised assessments in a university hospital setting. SUBJECTS: Healthy volunteers and patients in vegetative state/unresponsive wakefulness syndrome (VS/UWS), minimally conscious state (MCS), emergence from MCS (EMCS), and locked-in syndrome (LIS). RESULTS: A total of 70 patients were included in the study: 24 VS/UWS, 28 MCS, 10 EMCS, 8 LIS and 39 age-matched controls. VS/UWS showed metabolic dysfunction in extrinsic and intrinsic networks and thalami. MCS showed dysfunction mostly in intrinsic network and thalami. EMCS showed impairment in posterior cingulate/retrosplenial cortices. LIS showed dysfunction only in infratentorial regions. Coma Recovery Scale-Revised total scores correlated with metabolic activity in both extrinsic and part of the intrinsic network and thalami. CONCLUSION: Progressive recovery of extrinsic and intrinsic awareness network activity was observed in severely brain-damaged patients, ranging from VS/UWS, MCS, EMCS to LIS. The predominance of intrinsic network impairment in MCS could reflect altered internal/self-awareness in these patients, which is difficult to quantify at the bedside. [less ▲]

Functional imaging and impaired consciousness

in Schnakers, Caroline; Laureys, Steven (Eds.) Coma and disorders of consciousness (2012)

Désordres de la conscience : aspects éthiques.

in Schnakers, Caroline; LAUREYS, Steven (Eds.) Comas et états de conscience altérée (2011)

L’apparition de la ventilation mécanique dans les années cinquante et le développement des soins intensifs dans les années soixante ont permis à de nombreux patients de survivre à de graves lésions ... [more ▼]

L’apparition de la ventilation mécanique dans les années cinquante et le développement des soins intensifs dans les années soixante ont permis à de nombreux patients de survivre à de graves lésions cérébrales. Bien que ces avancées technologiques soient étonnantes, de nombreux patients vont alors se retrouver dans des états cliniques critiques peu rencontrés auparavant (1). L’impact éthique de ces états d’inconscience se reflète lors de la rédaction des premiers comités de bioéthique et lors de l’apparition du concept d’acharnement thérapeutique. En 1968, le comité spécial de l’école médicale de Harvard a publié un article essentiel redéfinissant la mort comme étant un coma irréversible et une perte permanente de toutes les fonctions cérébrales (2). Le comité, composé de dix médecins, d’un théologien, d’un avocat et d’un historien des sciences, a débattu des questions médicales, juridiques et sociétales quant à la prise en charge des patients en mort cérébrale. Nous donnerons ici un bref aperçu des principales questions éthiques liées à la notion de conscience et à la prise en charge médicale des patients atteints de troubles de la conscience (TDC) tels que le coma, l’état végétatif et l’état de conscience minimale. Nous mettrons également l’accent sur le problème de la gestion de la douleur et des prises de décision en fin de vie. [less ▲]

Les traitements pharmacologiques chez les patients récupérant du coma

in C Schnakers & S Laureys (Ed.) Comas et états de conscience altérée (2011)

Near-Death Experiences : Real or imagined memories?

Poster (2010, September)

Brain-computer interface in disorders of consciousness: answering simple questions with a P3 speller

Poster (2010, June)

Objective: In the recovery from coma, the acquisition of command following represents an important milestone, indicating emergence from the vegetative state (Schnakers et al., 2009). In some patients ... [more ▼]

Objective: In the recovery from coma, the acquisition of command following represents an important milestone, indicating emergence from the vegetative state (Schnakers et al., 2009). In some patients, recovery of consciousness may precede motor recovery. Brain-computer interfaces (BCI) might permit these patients to show non-motor dependent signs of awareness and in a next step might enable communication. This study aimed at testing to what extent an EEG-based BCI could help detecting signs of awareness and communication in disorders of consciousness. We employed a P300 based BCI where healthy volunteers and patients with locked-in syndrome and in a minimally conscious state were asked to answer yes or no to simple questions by paying attention to one out of four auditorily presented stimuli (‘yes’, ‘no’, ‘stop’, ‘go’). Methods: We studied 13 patients with a minimally conscious state (MCS, 5 TBI – 8 anoxic, mean time post injury 70±109 months; mean age 42 ± 21) and 2 in pseudo-coma or locked in syndrome (LIS; brainstem stroke, time post injury 26 and 46 months; aged 63 and 29)) and 16 healthy controls (aged 45±19). Patients were evaluated using the Coma Recovery Scale Revised (CRS-R). An auditory P300 four choice speller paradigm (Furdea et al., 2009) based on the BCI2000 system (Schalk et al., 2004) was used. 16-Channel EEG was recorded using a g.tec USBAmp amplifier. A trial constituted of 15 presentation of four sounds the order of presentation being pseudo-randomized (sound duration: ~400ms; inter-stimulus interval: ~600ms). After a training session of 4 trials, patients and healthy subjects were required to answer 10 or 12 questions, respectively. Questions were of the following kind: “Is your name Quentin?”, “Is your mother’s name Dorothée?”. A stepwise linear discriminant analysis based on the training session was used to classify the data and to provide online feedback. Offline, all training and testing sequences were pooled. Sequences with artifacts were discarded and a leave-one-out approach was used to classify the data. Results: Healthy subjects presented a mean correct response rate of 73% online and 93% offline. Note that online classification failed for one control subject due to a presumed change in cognitive strategy between training and testing sessions. LIS patients showed a correct response rate of 30 and 60% (online) and 36 and 79% (offline). Three MCS patients had a correct response rate of ≥50% offline (10, 18, 0% online and 50, 53, 57% offline). Two of these three patients did not show any command following at the bedside. The 10 remaining MCS cases showed online and offline correct answers <50% (mean 33±9% online and 25±13% offline). Conclusion: Our auditory P300-based BCI permitted functional interactive communication in 15/16 controls (online) and in all offline. Our data obtained in patients with locked-in syndrome and disorders of consciousness demonstrate the potential clinical usefulness of the technique following coma but also show lower accuracy in patients as compared to healthy volunteers. This might be due to fluctuating attentional levels and exhaustibility in the MCS and to the suboptimal EEG recording quality due to movement, ocular and respiration artifacts in these challenging patients. Further algorithmic developments should include automatic artifact detection and single trial classification. Despite the need for further improvement in BCI devices adapted to post-coma patients, our results already indicate that MCS patients without any clinical sign of command-following can employ a yes-no speller offering the hope of functional interactive communication and a possibility for decision making and autonomy. Bibliography Furdea A, Halder S, Krusienski DJ, Bross D, Nijboer F, Birbaumer N, Kübler A, 2009, An auditory oddball (P300) spelling system for brain-computer interfaces, Psychophysiology. May; 46(3):617-25. Schalk G., McFarland D.J., Hinterberger T., Birbaumer N., and Wolpaw J.R. 2004, BCI2000: A General-Purpose Brain-Computer Interface (BCI) System, IEEE Trans Biomed Eng, 51(6). Schnakers C, Vanhaudenhuyse A, Giacino J, Ventura; Boly M, Majerus S, Moonen G, Laureys S, 2009, Diagnostic accuracy of the vegetative and minimally conscious state: Clinical consensus versus standardized neurobehavioral assessment, BMC Neurology, 9 (35). [less ▲]

Near-death experiences: real or imagined?

Conference (2010, June)

Quelles attitudes médicales et éthiques adopter envers le patient en locked-in syndrome?

in Puybasset, Louis (Ed.) Enjeux éthiques en réanimation (2010)