Influence of Tactile Flow on Visual Heading Perception

Abstract

The integration of information from different sensory modalities is crucial for successful navigation through an environment. Among others, self-motion induces distinct optic flow patterns on the retina, vestibular signals and tactile flow, which contribute to determine traveled distance (path integration) or movement direction (heading). While the processing of combined visual–vestibular information is subject to a growing body of literature, the processing of visuo-tactile signals in the context of self-motion has received comparatively little attention. Here, we investigated whether visual heading perception is influenced by behaviorally irrelevant tactile flow. In the visual modality, we simulated an observer’s self-motion across a horizontal ground plane (optic flow). Tactile self-motion stimuli were delivered by air flow from head-mounted nozzles (tactile flow). In blocks of trials, we presented only visual or tactile stimuli and subjects had to report their perceived heading. In another block of trials, tactile and visual stimuli were presented simultaneously, with the tactile flow within ±40° of the visual heading (bimodal condition). Here, importantly, participants had to report their perceived visual heading. Perceived self-motion direction in all conditions revealed a centripetal bias, i.e., heading directions were perceived as compressed toward straight ahead. In the bimodal condition, we found a small but systematic influence of task-irrelevant tactile flow on visually perceived headings as function of their directional offset. We conclude that tactile flow is more tightly linked to self-motion perception than previously thought.

Visuo-tactile heading perception

“…Nevertheless, tactile stimuli were also clearly considered for heading perception. In sum, Bayes-nonoptimal multisensory integration as found in the present study was also reported in previous work ( 30 – 33 ) and can also be found in the case that tactile stimuli are not task relevant ( 15 ).…”

“…The bias of perceived heading toward straight ahead is in line with results from the literature [Refs. 15 , 19 – 22 , but see also Ref. 8 , which found priors to the side (±90°)] and consistent with Bayesian accounts that have proposed a prior for straight ahead as the most common heading direction ( 21 , 23 ).…”

“…Finally, in a recent study, we were able to show that tactile heading stimuli (airflow), despite being behaviorally irrelevant, were capable of biasing visually perceived heading. In that study, visual and tactile flow could be either spatially congruent or incongruent ( 15 ). Results showed a small but significant attraction toward the tactile flow (distractor), which peaked for an angular separation of 10° between visual and tactile self-motion direction.…”

Rats rely on airflow cues for self-motion perception

“…With a unique apparatus to provide airflow to the forehead in humans, the Bremmer group recently found that these airflow cues are integrated (sub-optimally) with visual cues of self-motion perception (Rosenblum, Grewe, et al, 2022;Rosenblum, Kreß, et al, 2022).…”

“…Despite evidence that airflow facilitates the feeling of vection (the sensation of movement of one’s body in space) even in humans (Seno et al, 2011; Murata et al, 2014; Kurosawa et al, 2017), the question whether, and to what extent, land animals use and integrate airflow information for self-motion perception has been little studied. With a unique apparatus to provide airflow to the forehead in humans, the Bremmer group recently found that these airflow cues are integrated (sub-optimally) with visual cues of self-motion perception (Rosenblum, Grewe, et al, 2022; Rosenblum, Kreß, et al, 2022). Whether more naturalistic airflow (e.g., that could be sensed across the whole body) would be integrated in line with Bayesian predictions of optimality remains an open question.…”