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

Processing of social closeness in the human brain

Healthy social life requires relationships in different levels of personal closeness. Based on ethological, sociological, and psychological evidence, social networks have been divided into five layers, gradually increasing in size and decreasing in personal closeness. Is this division also reflected in brain processing of social networks? During functional MRI, 21 participants compared their personal closeness to different individuals. We examined the brain volume showing differential activation for varying layers of closeness and found that a disproportionately large portion of this volume (80%) exhibited preference for individuals closest to participants, while separate brain regions showed preference for all other layers. Moreover, this bipartition reflected cortical preference for different sizes of physical spaces, as well as distinct subsystems of the default mode network. Our results support a division of the neurocognitive processing of social networks into two patterns depending on personal closeness, reflecting the unique role intimately close individuals play in our social lives

Mental time in amnesia: evidence from bilateral medial temporal damage before and after recovery

The human mind is continuously involved in "projecting" the self in time in order to process past memories and predict future occurrences. "Self-projection" in time involves episodic and spatial memory, relying on medial-temporal structures, but also engages visuo-spatial imagery, relying on occipito-temporal structures, and self-location, relying on temporo-parietal structures. Here we had the rare opportunity to investigate the relation between self-projection in time and memory, using a novel behavioural paradigm, in a patient with subacute bilateral medial-temporal damage during a period of amnesia as well as after recovery. Despite her memory deficit the patient was able to "project" herself to past and future, yet with significant improvement after recovery. We discuss our findings with respect to the relations between episodic memory and medial-temporal structures with self-projection in time to past and future

Schizotypal Perceptual Aberrations of Time: Correlation between Score, Behavior and Brain Activity

A fundamental trait of the human self is its continuum experience of space and time. Perceptual aberrations of this spatial and temporal continuity is a major characteristic of schizophrenia spectrum disturbances – including schizophrenia, schizotypal personality disorder and schizotypy. We have previously found the classical Perceptual Aberration Scale (PAS) scores, related to body and space, to be positively correlated with both behavior and temporo-parietal activation in healthy participants performing a task involving self-projection in space. However, not much is known about the relationship between temporal perceptual aberration, behavior and brain activity. To this aim, we composed a temporal Perceptual Aberration Scale (tPAS) similar to the traditional PAS. Testing on 170 participants suggested similar performance for PAS and tPAS. We then correlated tPAS and PAS scores to participants' performance and neural activity in a task of self-projection in time. tPAS scores correlated positively with reaction times across task conditions, as did PAS scores. Evoked potential mapping and electrical neuroimaging showed self-projection in time to recruit a network of brain regions at the left anterior temporal cortex, right temporo-parietal junction, and occipito-temporal cortex, and duration of activation in this network positively correlated with tPAS and PAS scores. These data demonstrate that schizotypal perceptual aberrations of both time and space, as reflected by tPAS and PAS scores, are positively correlated with performance and brain activation during self-projection in time in healthy individuals along the schizophrenia spectrum

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 patient's 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

The mental time line: an analogue of the mental number line in the mapping of life events

A crucial aspect of the human mind is the ability to project the self along the time line to past and future. It has been argued that such self-projection is essential to re-experience past experiences and predict future events. In-depth analysis of a novel paradigm investigating mental time shows that the speed of this "self-projection" in time depends logarithmically on the temporal-distance between an imagined "location" on the time line that participants were asked to imagine and the location of another imagined event from the time line. This logarithmic pattern suggests that events in human cognition are spatially mapped along an imagery mental time line. We argue that the present time-line data are comparable to the spatial mapping of numbers along the mental number line and that such spatial maps are a fundamental basis for cognition

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 one's 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 one's 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