Visual vs. Auditory Landmark for Vestibular Self-motion Perception

Abstract

Spatial navigation requires us to precisely perceive our position and the spatial relationships between our own and environmental objects’ location in space. As we move through the environment, multiple cues convey congruent spatial information: indeed, we rely both on inertial vestibular self-motion information and on visual and auditory landmarks. Here we directly investigate the perceptual interaction between inertial cues and environmental landmarks. Twenty-six healthy participants sat on a chair in a darkened room, leaning on a chin rest. On each trial, to test for self-motion detection, we delivered Galvanic Vestibular Stimulation (GVS) or sham stimulation pulse (0.7 mA of amplitude and 250 ms of duration). Critically, GVS activates the peripheral vestibular organs, i.e., the otoliths and semicircular canal afferents, eliciting a self-motion sensation (a roll tilt sensation). However, the chosen stimulation parameters induce a relatively weak virtual sensation of roll rotation. To test whether self-motion sensitivity could be aided by the environmental cue, participants performed the detection task with or without external visual (LED red light) or auditory landmark (pink noise sound emitted by a loudspeaker) both placed in front of them, in different blocks of trials. Participants’ ability to detect virtual vestibular-induced self-motion sensation with and without a landmark was measured using a signal detection approach. We computed the d prime as a measure of participants’ sensitivity and the criterion as an index of their response bias. Results showed that the sensitivity to detect self-motion was higher in the presence of the visual landmark, but not in the presence of the auditory one. The response bias remained unaffected. This finding shows that visual signals coming from the environment provide relevant information to enhance our ability to perceive inertial self-motion cues, suggesting a specific interaction between visual and vestibular systems in self-motion perception.