The Role of Beta Oscillations in Mental Time Travel.

The brain processes short-interval timing but also allows people to project themselves into the past and the future (i.e., mental time travel [MTT]). Beta oscillations index seconds-long-interval timing (i.e., higher beta power is associated with longer durations). Here, we used parietal transcranial alternating current stimulation (tACS) to investigate whether MTT is also supported by parietal beta oscillations and to test the link between MTT and short intervals. Thirty adults performed a novel MTT task while receiving beta and alpha tACS, in addition to no stimulation. Beta tACS corresponded to a temporal underestimation in past but not in future MTT. Furthermore, participants who overestimated seconds-long intervals also overestimated temporal distances in the past-projection MTT condition and showed a stronger effect of beta tACS. These data provide a unique window into temporal perception, showing how beta oscillations may be a common mechanism for short intervals and MTT.

Time Interaction With Two Spatial Dimensions: From Left/Right to Near/Far.

In this study, we explored the time and space relationship according to two different spatial codings, namely, the left/right extension and the reachability of stimulus along a near/far dimension. Four experiments were carried out in which healthy participants performed the time and spatial bisection tasks in near/far space, before and after short or long tool-use training. Stimuli were prebisected horizontal lines of different temporal durations in which the midpoint was manipulated according to the Muller-Lyer illusion. The perceptual illusory effects emerged in spatial but not temporal judgments. We revealed that temporal and spatial representations dynamically change according to the action potentialities of an individual: temporal duration was perceived as shorter and the perceived line's midpoint was shifted to the left in far than in near space. Crucially, this dissociation disappeared following a long but not short tool-use training. Finally, we observed age-related differences in spatial attention which may be crucial in building the memory temporal standard to categorize durations.

Embodying an invisible face shrinks the cone of gaze.

The possibility of being invisible has long fascinated people. Recent research showed that multisensory illusions can induce experiences of bodily invisibility, allowing the psychological consequences of invisibility to be explored. Here, we demonstrate an illusion of embodying an invisible face. Participants received touches on their face and simultaneously saw a paintbrush moving synchronously in empty space and defining the shape of an invisible face. Using both explicit questionnaire measures (Experiment 1) and implicit physiological measures (Experiment 2), we show that such invisible enfacement induces a sense of ownership. We further demonstrate that embodying an invisible face shrinks the width of the cone of gaze (i.e., the range of eye deviations people judge as directed toward themselves; Experiments 3 and 4). These results suggest that the experience of invisibility affects the way in which we process the attention of others toward the self, starting from the perception of gaze direction. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The illusion of having a tall or short body differently modulates interpersonal and peripersonal space.

The brain constructs a functional representation of the space around the body, the so called peripersonal space (PPS), which is a sensorimotor interface used to ensure suitable motor acts. However, this sector of space is also involved in social interactions. Individuals indeed, maintain an interpersonal space (IPS) indicating how close they prefer to stand relative to others. Here, we investigated whether a change in one's own body height representation can differently modulate action and social space. To this aim, we measured IPS and PPS in a similar way through a Reaching-distance and a Comfort-distance task, respectively, before and after participants experienced the illusion of having a tall (Experiment 1), or a short (Experiment 2), body. The illusion of having a tall body significantly reduced the IPS and enlarged PPS. On the other hand, the illusion of having a short body contracted the IPS, leaving the PPS intact. A further experiment (Experiment 3), showed that the illusory ownership for the tall or short body is a necessary condition to update the participants' height representation. Thus, a change in body height representation was effective to reveal a dissociation in the representation of the space around the body, depending on whether this sector of space is used for programming actions, or for regulating social interactions.

The sense of agency shapes body schema and peripersonal space.

Body schema, a sensorimotor representation of the body used for planning and executing movements, is plastic because it extends by using a tool to reach far objects. Modifications of peripersonal space, i.e., a functional representation of reach space, usually co-occur with body schema changes. Here, we hypothesized that such plastic changes depend on the experience of controlling the course of events in space trough one's own actions, i.e., the sense of agency. In two experiments, body schema and peripersonal space were assessed before and after the participants' sense of agency over a virtual hand was manipulated. Body schema and peripersonal space enlarged or contracted depending on whether the virtual hand was presented in far space, or closer to the participants' body than the real hand. These findings suggest that body schema and peripersonal space are affected by the dynamic mapping between intentional body movements and expected consequences in space.

Invisible body illusion modulates interpersonal space.

Interpersonal space (e.g., IPS) refers to the physical distance individuals maintain from others during social interactions, and into which intrusion by others can cause discomfort. Here, we asked whether the size of IPS is affected by manipulation of one's own body representation. To address this issue, in Experiment 1, IPS was measured through a comfort-distance task, before and after eliciting the illusion of owning an invisible body. To rule out a general, nonspecific change in space perception consequent the illusion, we also assessed peripersonal space, e.g., PPS, the area around the body used to act on nearby objects, through a reaching-distance task. Results showed that the experience of invisibility induces a selective contraction of IPS, without affecting the perceived reaching space around the body. In Experiment 2, a tool-use manipulation produced the opposite dissociation, modifying the boundaries of PPS, but leaving IPS distance unaltered. Collectively, these findings support a close relationship between IPS and the conscious representation of the body external appearance, i.e. the body image, and suggest the existence of two functionally separate representations of the space immediately surrounding the body in humans, which may form the basis of distinct processes engaged for different behavioural contexts.