Shahar Arzy

The Out-of-Body Experience: Disturbed Self-Processing at the Temporo-Parietal Junction

Folk psychology postulates a spatial unity of self and body, a “real me” that resides in one’s body and is the subject of experience. The spatial unity of self and body has been challenged by various philosophical considerations but also by several phenomena, perhaps most notoriously the “out-of-body experience” (OBE) during which one’s visuo-spatial perspective and one’s self are experienced to have departed from their habitual position within one’s body. Here the authors marshal evidence from neurology, cognitive neuroscience, and neuroimaging that suggests that OBEs are related to a failure to integrate multisensory information from one’s own body at the temporo-parietal junction (TPJ). It is argued that this multisensory disintegration at the TPJ leads to the disruption of several phenomenological and cognitive aspects of self-processing, causing illusory reduplication, illusory self-location, illusory perspective, and illusory agency that are experienced as an OBE.

Subjective mental time: the functional architecture of projecting the self to past and future

Human experience takes place in the line of mental time (MT) created through ‘self‐projection’ of oneself to different time‐points in the past or future. Here we manipulated self‐projection in MT not only with respect to one’s life events but also with respect to one’s faces from different past and future time‐points. Behavioural and event‐related functional magnetic resonance imaging activity showed three independent effects characterized by (i) similarity between past recollection and future imagination, (ii) facilitation of judgements related to the future as compared with the past, and (iii) facilitation of judgements related to time‐points distant from the present. These effects were found with respect to faces and events, and also suggest that brain mechanisms of MT are independent of whether actual life episodes have to be re‐experienced or pre‐experienced, recruiting a common cerebral network including the anteromedial temporal, posterior parietal, inferior frontal, temporo‐parietal and insular cortices. These behavioural and neural data suggest that self‐projection in time is a fundamental aspect of MT, relying on neural structures encoding memory, mental imagery and self.

Self in time: imagined self-location influences neural activity related to mental time travel

Conscious awareness of the self as continuous through time is attributed to the human ability to remember the past and to predict the future, a cogitation that has been called “mental time travel” (MTT). MTT allows one to re-experience ones own past by subjectively “locating” the self to a previously experienced place and time, or to pre-experience an event by locating the self into the future. Here, we used a novel behavioral paradigm in combination with evoked potential mapping and electrical neuroimaging, revealing that MTT is composed of two different cognitive processes: absolute MTT, which is the location of the self to different points in time (past, present, or future), and relative MTT, which is the location of ones self with respect to the experienced event (relative past and relative future). These processes recruit a network of brain areas in distinct time periods including the occipitotemporal, temporoparietal, and anteromedial temporal cortices. Our findings suggest that in addition to autobiographical memory processes, the cognitive mechanisms of MTT also involve mental imagery and self-location, and that relative MTT, but not absolute MTT, is more strongly directed to future prediction than to past recollection.

Brain system for mental orientation in space, time, and person

Significance Processing of spatial, temporal, and social relations relies on mental cognitive maps, on which the behaving self is oriented relative to different places, events, and people. Using high-resolution functional MRI scanning in individual subjects, we show that mental orientation in space, time, and person produces a sequential posterior–anterior pattern of activity in each participant’s brain. These activations are adjacent and partially overlapping, highlighting the relation between mental orientation in these domains. Furthermore, the activity is highly overlapping with the brain’s default-mode network, a system involved in self-referential processing. These findings may shed new light on fundamental cognitive processing of space, time, and person and alter our understanding of disorientation phenomena in neuropsychiatric disorders such as Alzheimer’s disease. Orientation is a fundamental mental function that processes the relations between the behaving self to space (places), time (events), and person (people). Behavioral and neuroimaging studies have hinted at interrelations between processing of these three domains. To unravel the neurocognitive basis of orientation, we used high-resolution 7T functional MRI as 16 subjects compared their subjective distance to different places, events, or people. Analysis at the individual-subject level revealed cortical activation related to orientation in space, time, and person in a precisely localized set of structures in the precuneus, inferior parietal, and medial frontal cortex. Comparison of orientation domains revealed a consistent order of cortical activity inside the precuneus and inferior parietal lobes, with space orientation activating posterior regions, followed anteriorly by person and then time. Core regions at the precuneus and inferior parietal lobe were activated for multiple orientation domains, suggesting also common processing for orientation across domains. The medial prefrontal cortex showed a posterior activation for time and anterior for person. Finally, the default-mode network, identified in a separate resting-state scan, was active for all orientation domains and overlapped mostly with person-orientation regions. These findings suggest that mental orientation in space, time, and person is managed by a specific brain system with a highly ordered internal organization, closely related to the default-mode network.

Illusory reduplications of the human body and self.

Publisher Summary This chapterreviews phenomenological, functional,and anatomical similarities and differences of the three main forms of visual reduplication: out-of-body experience, autoscopic hallucination, and heautoscopy. Illusory reduplications of the patients own body refer to complex manifestations during which patients experience a second own body or self in their environment. Further, the chapter reviews the rarer forms of autoscopic phenomena including multiple visual doubles (polyopic heautoscopy) and inner visual doubles (inner heautoscopy). The description of the visual doubles is followed by a discussion of sensorimotor doubles (feeling of a presence), auditory doubles (hearing of a presence), and negative doubles (negative heautoscopy) due to neurological disease. Although several patients with the feeling of a presence due to focal brain damage are described, the feeling of a presence as an autoscopic phenomenon is considered because it is characterized by a nonvisual body reduplication as opposed to the three main forms of autoscopic phenomena that are all characterized by a visual body reduplication. It is believed that the investigation of the phenomenological, functional, and neural mechanisms leading to the experience of a double in neurological patients (and healthy subjects) is likely to improve self-related neuroscientific models of embodiment, selfhood, and subjectivity.

In-vivo magnetic resonance imaging of the structural core of the Papez circuit in humans

Papez circuit is one of the major pathways of the limbic system, and it is involved in the control of memory and emotion. Structural and functional alterations have been reported in psychiatric, neurodegenerative, and epileptic diseases. Despite the clinical interest, however, in-vivo imaging of the entire circuit remains a technological challenge. We used magnetic resonance diffusion spectrum imaging to comprehensively picture the Papez circuit in healthy humans: (i) the hippocampus–mammillary body pathway, (ii) the connections between the lateral subiculum and the cingulate cortex, and (iii) the mammillo–thalamic tract. The diagnostic and therapeutic implications of these results are discussed in the context of recent findings reporting the involvement of the Papez circuit in neurological and psychiatric diseases.

Reversible functional connectivity disturbances during transient global amnesia.

Transient global amnesia (TGA), an abrupt occurrence of severe anterograde episodic amnesia accompanied by repetitive questioning, has been known for more than 50 years. Despite extensive research, there is no clear evidence for the underlying pathophysiological basis of TGA. Moreover, there is no neuroimaging method to evaluate TGA in real time.

Deficient mental own-body imagery in a neurological patient with out-of-body experiences due to cannabis use

In the present work, we report repeated out-of-body experiences (OBEs) in a patient with tetraplegia and severe somatosensory loss due to multiple sclerosis and predominant involvement of the cervical spinal cord. OBEs were experienced on a daily basis and induced by cannabis treatment that was started for severe spasticity with painful cramps and cloni. In order to investigate the link between OBEs and mental own-body imagery, the patient was asked to imagine himself in the position and visual perspective that is generally reported during OBEs, using front- and back-facing schematic human stimuli. Performance was measured before and after cannabis consumption. First, our data reveal that the patient was less accurate for back-facing than front-facing stimuli. This was found before and after cannabis consumption and is the opposite pattern to what is generally observed in healthy participants and in our control subjects (who did not use cannabis). We refer to this as lesion effect and argue that this relative facilitation for stimuli reflecting the position and visual perspective that is generally reported during OBEs might be due to recurrent and spontaneous own-body transformations during the patients frequent OBEs. Secondly, we found a cannabis effect, namely a performance improvement in the back-facing condition while performance in the front-facing condition remained unchanged, after cannabis administration. We argue that cannabis administration may interfere with own-body imagery when reflecting the actual body position and only when associated with brain damage. Based on these data we propose an extended neurological model for own-body illusions including multisensory and sensorimotor mechanisms, cannabis consumption, and cortical and subcortical processing.

Antiepileptic drugs modify power of high EEG frequencies and their neural generators

Background:  The clinical and molecular effects of antiepileptic drugs (AEDs) have been extensively investigated. Much less is known about their effects on human electrophysiology.

Psychogenic amnesia and self-identity: a multimodal functional investigation

Background:  Patients with psychogenic amnesia generally suffer from episodic memory deficits associated with an impairment of self‐identity. While the first is generally attributed to limbic dysfunction, the latter might be related to posterior parietal cortex.