Visuo-vestibular interaction in the reconstruction of travelled trajectories

We recently published a study of the reconstruction of passively travelled trajectories from optic flow. Perception was prone to illusions in a number of conditions, and not always veridical in the others. Part of the illusionary reconstructed trajectories could be explained by assuming that subjects base their reconstruction on the ego-motion percept built during the stimulus' initial moments . In the current paper, we test this hypothesis using a novel paradigm: if the final reconstruction is governed by the initial percept, providing additional, extra-retinal information that modifies the initial percept should predictably alter the final reconstruction. The extra-retinal stimulus was tuned to supplement the information that was under-represented or ambiguous in the optic flow: the subjects were physically displaced or rotated at the onset of the visual stimulus. A highly asymmetric velocity profile (high acceleration, very low deceleration) was used. Subjects were required to guide an input device (in the form of a model vehicle; we measured position and orientation) along the perceived trajectory. We show for the first time that a vestibular stimulus of short duration can influence the perception of a much longer lasting visual stimulus. Perception of the ego-motion translation component in the visual stimulus was improved by a linear physical displacement: perception of the ego-motion rotation component by a physical rotation. This led to a more veridical reconstruction in some conditions, but to a less veridical reconstruction in other conditions

Reconstructing passively travelled manoeuvres: Visuo-vestibular interactions.

We recently published a study of the reconstruction of passively travelled trajectories from optic flow. Perception was prone to illusions in a number of conditions, and not always veridical in the other conditions. Part of the illusionary reconstructed trajectories could be explained if we assume that the subjects based their reconstruction on the ego-motion percept obtained during the stimulus' initial moments. In the current paper, we test this hypothesis using a novel paradigm. If indeed the final reconstruction is governed by the initial percept, then additional, extra-retinal information that modifies the initial percept should predictably alter the final reconstruction. We supplied extra-retinal stimuli tuned to supplement the information that was underrepresented or ambiguous in the optic flow: the subjects were physically displaced or rotated at the onset of the visual stimulus. A highly asymmetric velocity profile (high acceleration, very low deceleration) was used. Subjects were required to guide an input device (in the form of a model vehicle; we measured position and orientation) along the perceived trajectory. We show for the first time that a vestibular stimulus of short duration can influence the perception of a much longer lasting visual stimulus. Perception of the ego-motion translation component in the visual stimulus was improved by a linear physical displacement; perception of the ego-motion rotation component by a physical rotation. This led to a more veridical reconstruction in some conditions, but it could also lead to less veridical reconstructions in other conditions

Visuo-vestibular interaction in the reconstruction of travelled trajectories

We recently published a study of the reconstruction of passively travelled trajectories from optic flow. Perception was prone to illusions in a number of conditions, and not always veridical in the others. Part of the illusionary reconstructed trajectories could be explained by assuming that subjects base their reconstruction on the ego-motion percept built during the stimulus' initial moments . In the current paper, we test this hypothesis using a novel paradigm: if the final reconstruction is governed by the initial percept, providing additional, extra-retinal information that modifies the initial percept should predictably alter the final reconstruction. The extra-retinal stimulus was tuned to supplement the information that was under-represented or ambiguous in the optic flow: the subjects were physically displaced or rotated at the onset of the visual stimulus. A highly asymmetric velocity profile (high acceleration, very low deceleration) was used. Subjects were required to guide an input device (in the form of a model vehicle; we measured position and orientation) along the perceived trajectory. We show for the first time that a vestibular stimulus of short duration can influence the perception of a much longer lasting visual stimulus. Perception of the ego-motion translation component in the visual stimulus was improved by a linear physical displacement: perception of the ego-motion rotation component by a physical rotation. This led to a more veridical reconstruction in some conditions, but to a less veridical reconstruction in other conditions

Motor processes in mental rotation

Much indirect evidence supports the hypothesis that transformations of mental images are at least in part guided by motor processes, even in the case of images of abstract objects rather than of body parts. For example, rotation may be guided by processes that also prime one to see results of a specific motor action. We directly test the hypothesis by means of a dual-task paradigm in which subjects perform the Cooper-Shepard mental rotation task while executing an unseen motor rotation in a given direction and at a previously learned speed. Four results support the inference that mental rotation relies on motor processes. First, motor rotation that is compatible with mental rotation results in faster times and fewer errors in the imagery task than when the two rotations are incompatible. Second, the angle through which subjects rotate their mental images, and the angle through which they rotate a joystick handle are correlated, but only if the directions of the two rotations are compatible. Third, motor rotation modifies the classical inverted V-shaped mental rotation response time function, favoring the direction of the motor rotation; indeed, in some cases motor rotation even shifts the location of the minimum of this curve in the direction of the motor rotation. Fourth, the preceding effect is sensitive not only to the direction of the motor rotation, but also to the motor speed. A change in the speed of motor rotation can correspondingly slow down or speed up the mental rotation

Combined Induction of Rubber-Hand Illusion and Out-of-Body Experiences

The emergence of self-consciousness depends on several processes: those of body ownership, attributing self-identity to the body, and those of self-location, localizing our sense of self. Studies of phenomena like the rubber-hand illusion (RHi) and out-of-body experience (OBE) investigate these processes, respectively for representations of a body-part and the full-body. It is supposed that RHi only target processes related to body-part representations, while OBE only relates to full-body representations. The fundamental question whether the body-part and the full-body illusions relate to each other is nevertheless insufficiently investigated. In search for a link between body-part and full-body illusions in the brain we developed a behavioral task combining adapted versions of the RHi and OBE. Furthermore, for the investigation of this putative link we investigated the role of sensory and motor cues. We established a spatial dissociation between visual and proprioceptive feedback of a hand perceived through virtual reality in rest or action. Two experimental measures were introduced: one for the body-part illusion, the proprioceptive drift of the perceived localization of the hand, and one for the full-body illusion, the shift in subjective-straight-ahead (SSA). In the rest and action conditions it was observed that the proprioceptive drift of the left hand and the shift in SSA toward the manipulation side are equivalent. The combined effect was dependent on the manipulation of the visual representation of body parts, rejecting any main or even modulatory role for relevant motor programs. Our study demonstrates for the first time that there is a systematic relationship between the body-part illusion and the full-body illusion, as shown by our measures. This suggests a link between the representations in the brain of a body-part and the full-body, and consequently a common mechanism underpinning both forms of ownership and self-location

Lausanne medical dispatch centre's response to COVID-19.

The COVID-19 crisis is an unprecedented event. It is therefore essential for dispatch centres to share their experiences while the crisis is underway, similar to hospitals, so that we will all benefit from feedback.This letter to the editor describes the Lausanne dispatch centre response to COVID-19 and the lessons learned so far

The validity of using self-reports to assess emotion regulation abilities in adults with autism spectrum disorder

Purpose. – The current paper focused on the validity of using self-reports to assess emotion regulation abilities in autism spectrum disorders (ASD). To assess this we sought responses to two alexithymia self-reports and a depression self-report at two time points from adults with and without ASD. Materials and methods. – An initial sample of 27 adults withASD and 35 normal adults completed the 20-item Toronto alexithymia scale (TAS-20), the Bermond and Vorst alexithymia questionnaire-form B (BVAQ-B), and the Beck depression inventory (BDI), at test time 1. Of these individuals, 19 ASD and 29 controls participated again after a period ranging from 4 to 12 months. Results. – ASD participants were able to report about their own emotions using self-reports. BVAQ-B showed reasonable convergent validity and test–retest reliability in both groups. Scores on both alexithymia scales were stable across the two participant groups. However, results revealed that although the TAS-20 total score discriminated between the two groups at both time points, the BVAQ-B total score did not. Moreover, the TAS-20 showed stronger test–retest reliability than the BVAQ-B. Conclusion. – ASD participants appeared more depressed and more alexithymic than the controls. The use of the BVAQ-B, as an additional assessment of alexithymia, indicated that ASD patients have a specific type of alexithymia characterised by increased difficulties in the cognitive domain rather than the affective aspects of alexithymia