Experiences de mort imminente: phenomenes paranormaux ou neurologiques?

in Revue Médicale de Liège (2008), 63(5-6), 438-44

Seeing a bright light at the end of a tunnel or having a sense of being out of the physical body are phenomena that some patients report after having been close to death. Some spiritual and psychological ... [more ▼]

Seeing a bright light at the end of a tunnel or having a sense of being out of the physical body are phenomena that some patients report after having been close to death. Some spiritual and psychological theories have been developed in order to explain these near-death-experiences. Clinical studies have aimed to determine their frequency and to assess their precipitating factors. Recent neuroimaging studies, however, have shown the involvement of the temporo-parietal cortex in the generation of out-of-body experiences and are offering a physiological, neurological account for the phenomenon, rebuffing dualistic, non-physical explanations. [less ▲]

Voluntary brain processing in disorders of consciousness

in Neurology (2008), 71(20), 1614-1620

Background: Disentangling the vegetative state from the minimally conscious state is often difficult when relying only on behavioral observation. In this study, we explored a new active evoked related ... [more ▼]

Background: Disentangling the vegetative state from the minimally conscious state is often difficult when relying only on behavioral observation. In this study, we explored a new active evoked related potentials paradigm as an alternative method for the detection of voluntary brain activity. Methods: The participants were 22 right-handed patients (10 traumatic) diagnosed as being in a vegetative state (VS) (n 8) or in a minimally conscious state (MCS) (n 14). They were presented sequences of names containing the patient’s own name or other names, in both passive and active conditions. In the active condition, the patients were instructed to count her or his own name or to count another target name. Results: Like controls, MCS patients presented a larger P3 to the patient’s own name, in the passive and in the active conditions. Moreover, the P3 to target stimuli was higher in the active than in the passive condition, suggesting voluntary compliance to task instructions like controls. These responses were even observed in patients with low behavioral responses (e.g., visual fixationand pursuit). In contrast, no P3 differences between passive and active conditions were observed for VS patients. Conclusions: The present results suggest that active evoked-related potentials paradigms may permit detection of voluntary brain function in patients with severe brain damage who present with a disorder of consciousness, even when the patient may present with very limited to questionablyany signs of awareness. [less ▲]

Revelations from the unconscious: studying residual brain function in coma and related states.

in Bulletin et Mémoires de l'Académie Royale de Médecine de Belgique (2008), 163(7-9), 381-8388-90

The purpose of our research is to contribute to a better understanding of the residual brain function of patients who survive an acute brain damage but remain in a coma, vegetative state, minimally ... [more ▼]

The purpose of our research is to contribute to a better understanding of the residual brain function of patients who survive an acute brain damage but remain in a coma, vegetative state, minimally conscious state or locked-in syndrome. The diagnosis, prognosis, therapy and medical management of these patients remain difficult. These studies are also of interest scientifically, as they help to elucidate the neural correlates of human consciousness. We here review our studies on bedside behavioral evaluation scales, electrophysiology and functional neuroimaging in these disorders of consciousness and conclude by discussing methodological and ethical issues and current concepts of the standards for care and quality of life in these challenging conditions. [less ▲]

Comment prédire l'évolution du coma post-anoxique?

in Revue Médicale de Liège (2008), 63(5-6), 263-268

Spontaneous neural activity during human slow wave sleep.

in Proceedings of the National Academy of Sciences of the United States of America (2008), 105(39), 15160-5

Slow wave sleep (SWS) is associated with spontaneous brain oscillations that are thought to participate in sleep homeostasis and to support the processing of information related to the experiences of the ... [more ▼]

Slow wave sleep (SWS) is associated with spontaneous brain oscillations that are thought to participate in sleep homeostasis and to support the processing of information related to the experiences of the previous awake period. At the cellular level, during SWS, a slow oscillation (<1 Hz) synchronizes firing patterns in large neuronal populations and is reflected on electroencephalography (EEG) recordings as large-amplitude, low-frequency waves. By using simultaneous EEG and event-related functional magnetic resonance imaging (fMRI), we characterized the transient changes in brain activity consistently associated with slow waves (>140 microV) and delta waves (75-140 microV) during SWS in 14 non-sleep-deprived normal human volunteers. Significant increases in activity were associated with these waves in several cortical areas, including the inferior frontal, medial prefrontal, precuneus, and posterior cingulate areas. Compared with baseline activity, slow waves are associated with significant activity in the parahippocampal gyrus, cerebellum, and brainstem, whereas delta waves are related to frontal responses. No decrease in activity was observed. This study demonstrates that SWS is not a state of brain quiescence, but rather is an active state during which brain activity is consistently synchronized to the slow oscillation in specific cerebral regions. The partial overlap between the response pattern related to SWS waves and the waking default mode network is consistent with the fascinating hypothesis that brain responses synchronized by the slow oscillation restore microwake-like activity patterns that facilitate neuronal interactions. [less ▲]

Que mesure la neuro-imagerie fonctionnelle: IRMf, TEP & MEG?

in Revue Médicale de Liège (2008), 63(5-6), 231-7

Functional cerebral imaging techniques allow the in vivo study of human cognitive and sensorimotor functions in physiological or pathological conditions. In this paper, we review the advantages and ... [more ▼]

Functional cerebral imaging techniques allow the in vivo study of human cognitive and sensorimotor functions in physiological or pathological conditions. In this paper, we review the advantages and limitations of functional magnetic resonance imaging (fMRI), positron emission tomography (PET) and magnetoencephalography (MEG). fMRI and PET measure haemodynamic changes induced by regional changes in neuronal activity. These techniques have a high spatial resolution (a few millimeters), but a poor temporal resolution (a few seconds to several minutes). Electroencephalogram (EEG) and MEG measure the neuronal electrical or magnetic activity with a high temporal resolution (i.e., milliseconds) albeit with a poorer spatial resolution (i.e., a few millimeters to one centimeter). The combination of these different neuroimaging techniques allows studying different components of the brain's activity (e.g., neurovascular coupling, electromagnetic activity) with both a high temporal and spatial resolution. [less ▲]

Quelle vie apres le Locked-In syndrome?

in Revue Médicale de Liège (2008), 63(5-6), 445-51

The Locked-In Syndrome (LIS) is classically caused by an anterior pontine vascular lesion and characterized by quadriplegia and anarthria with preserved consciousness and intellectual functioning. We here ... [more ▼]

The Locked-In Syndrome (LIS) is classically caused by an anterior pontine vascular lesion and characterized by quadriplegia and anarthria with preserved consciousness and intellectual functioning. We here review the definition, etiologies, diagnosis and prognosis of LIS patients and briefly discuss the few studies on their quality of life and the challenging end-of-life decisions that can be encountered. Some clinicians may consider that LIS is worse than being in a vegetative or in a minimally conscious state. However, preliminary data from chronic LIS survivors show a surprisingly preserved self-scored quality of life and requests of treatment withdrawal or euthanasia, though not absent, are infrequent. [less ▲]

A french validation study of the Coma Recovery Scaled-Revised (CRS-R)

in Brain Injury (2008), 22(10), 786-792

What is it like to be vegetative or minimally conscious?

in Current Opinion in Neurology (2007), 20(6), 609-613

Purpose of review Patients in a vegetative or minimally conscious state continue to pose problems in terms of diagnosis, prognosis and treatment. Despite recent waves of international media attention ... [more ▼]

Purpose of review Patients in a vegetative or minimally conscious state continue to pose problems in terms of diagnosis, prognosis and treatment. Despite recent waves of international media attention following Terri Schiavo's death and the 'miracle recovery' of Terry Wallis, research efforts aimed at increasing our knowledge about brain function in these conditions remain scarce and must address a series of difficulties, including financial and ethical barriers. Here we review current possibilities and limitations of clinical and para-clinical assessment of chronic disorders of consciousness. Recent findings During the past year the field has witnessed publication of significant, yet isolated, case reports in top-ranking journals, including Science and Nature. Such milestone reports and other impressive recent technological advances in the study of vegetative and minimally conscious patients reveal enthralling areas of science that must find their way to clinical medical reality. Summary Consciousness is a subjective experience whose study has remained within the purview of philosophy for millennia. That has finally changed, and empirical evidence from functional neuroimaging offers a genuine glimpse at a solution to the infamous mind-body conundrum. New technological and scientific advances offer the neurological community unique ways to improve our understanding and management of vegetative and minimally conscious patients. [less ▲]

When thoughts become action: An fMRI paradigm to study volitional brain activity in non-communicative brain injured patients

in NeuroImage (2007), 36(3), 979-992

The assessment of voluntary behavior in non-communicative brain injured patients is often challenging due to the existence of profound motor impairment. In the absence of a full understanding of the ... [more ▼]

The assessment of voluntary behavior in non-communicative brain injured patients is often challenging due to the existence of profound motor impairment. In the absence of a full understanding of the neural correlates of consciousness, even a normal activation in response to passive sensory stimulation cannot be considered as proof of the presence of awareness in these patients. In contrast, predicted activation in response to the instruction to perform a mental imagery task would provide evidence of voluntary task-dependent brain activity, and hence of consciousness, in non-communicative patients. However, no data yet exist to indicate which imagery instructions would yield reliable single subject activation. The aim of the present study was to establish such a paradigm in healthy volunteers. Two exploratory experiments evaluated the reproducibility of individual brain activation elicited by four distinct mental imagery tasks. The two most robust mental imagery tasks were found to be spatial navigation and motor imagery. In a third experiment, where these two tasks were directly compared, differentiation of each task from one another and from rest periods was assessed blindly using a priori criteria and was correct for every volunteer. The spatial navigation and motor imagery tasks described here permit the identification of volitional brain activation at the single subject level, without a motor response. Volunteer as well as patient data [Owen, A. M., Coleman, M.R., Boly, M., Davis, M.H., Laureys, S., Pickard J.D., 2006. Detecting awareness in the vegetative state. Science 313, 1402] strongly suggest that this' paradigm may provide a method for assessing the presence of volitional brain activity, and thus of consciousness, in non-communicative brain-injured patients. (c) 2007 Elsevier Inc. All rights reserved. [less ▲]