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

Olaf Blanke
2008
Journal paper

Abstract

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.

Official source

https://infoscience.epfl.ch/record/154854?ln=en

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Healthy human beings are aware of their current position space and are able to distinguish their own body from that of other persons or objects. This capability arises from a coupling of sensory information with cognitive processes, and leads to a representation of the person's self. However, in some clinical cases these processes fail and a person can feel himself to be outside of his physical body, as in the out-of-body experience. These phenomena are interesting to study as they lend insight to certain aspects of bodily self-consciousness, such as self-localization and self-attribution. These aspects can be experimentally manipulated in healthy participants through exposure to conflicting multisensory input, as has been demonstrated with the creation of an ownership's feeling with rubber hand stroked synchronously with the real hand. Here, we worked on the full body by manipulate the self-localization of healthy participants. We used similar protocols as in the study of Lenggenhager et al. (2007) and Ehrsson (2007b) but with a lying position, rather a seated or standing as in the aforementioned studies, which are the commune position when out-of-body experience occurs. Participants were put in a comfortable lying position and saw an image of their body through 3D head mounted display, recorded by a video camera located two meters above them. By providing different temporal and spatial information about a visual-tactile event (stroking on the participants' back or chest) self-localization and identification could be modified in a predictable way. We measured self-localization using a mental ball dropping task and measured phenomenological aspects using a questionnaire. The results indicated that a significant variations in self-localization occurred during the experiment. As a follow-up study, we used mental imagery (in our case we used fMRI) to study the regions of the brain involved in this illusion

2008

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

Olaf Blanke

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.

Elsevier2009

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We take the feeling that our body belongs to us for granted. However, recent research has shown that it is possible to alter the subjective sensation of body ownership (BO) by manipulating multisensory bodily inputs. Several frontal and parietal regions are known to specifically process multisensory cues presented close to the body, i.e., within the peripersonal space (PPS). It has been proposed that these PPS fronto-parietal regions also underlie BO. However, most previous studies investigated the brain mechanisms of either BO or of PPS processing separately and by using a variety of paradigms. Here, we conducted an extensive meta-analysis of functional neuroimaging studies to investigate PPS and BO processing in humans in order to: a) assess quantitatively where each one of these functions was individually processed in the brain; b) identify whether and where these processes shared common or engaged distinct brain mechanisms; c) characterize these areas in terms of whole-brain co-activation networks and functions, respectively. We identified (i) a bilateral PPS network including superior parietal, temporo-parietal and ventral premotor regions and (ii) a BO network including posterior parietal cortex (right intraparietal sulcus, IPS; and left IPS and superior parietal lobule, SPL), right ventral premotor cortex, and the left anterior insula. Co-activation maps related to both PPS and BO encompassed largely overlapping fronto-parietal networks, but whereas the PPS network was more frequently associated with sensorimotor tasks, the BO network was rather associated with attention and awareness tasks. Finally, the conjunction analysis showed that (iii) PPS and BO tasks anatomically overlapped only in two clusters located in the left parietal cortex (dorsally at the intersection between the SPL, the IPS and area 2 and ventrally between areas 2 and IPS). Distinct activations were located for PPS at the temporo-parietal junction and for BO in the anterior insula. These results in PPS and BO and provide evidence-based insight about the overlap of the two processes in the IPS region and the extensive connectivity between the two associated co-activation networks. They also show significant dissociations, with PPS fronto-parietal areas located more proximal to the central sulcus than BO areas. Such anatomical distinction may also reflect the different functions of the two processes, whereby PPS areas underlie a multisensory-motor interface for body-objects interaction and BO areas being involved in bodily awareness and self-consciousness.

Elsevier2017

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Elsevier2017