Human perception of self-motion and orientation during galvanic vestibular stimulation and physical motion

Galvanic vestibular stimulation (GVS) is an emergent tool for stimulating the vestibular system, offering the potential to manipulate or enhance processes relying on vestibular-mediated central pathways. However, the extent of GVS’s influence on the perception of self-orientation pathways is not understood, particularly in the presence of physical motions. Here, we quantify roll tilt perception impacted by GVS during passive whole-body roll tilts in humans (N = 11). We find that GVS systematically amplifies and attenuates perceptions of roll tilt during physical tilt, dependent on the GVS waveform. Subsequently, we develop a novel computational model that predicts 6DoF self-motion and self-orientation perceptions for any GVS waveform and motion by modeling the vestibular afferent neuron dynamics modulated by GVS in conjunction with an observer central processing model. This effort provides a means to systematically alter spatial orientation perceptions using GVS during concurrent physical motion, and we find that irregular afferent dynamics alone best describe resultant perceptions.Author summary: Vestibular-mediated deficits are a primary concern for astronauts, aviators, and individuals on Earth. These deficits include loss of spatial orientation, impaired postural control and locomotion, loss of fine motor control, and motion sickness. Further, vestibular dysfunction negatively impacts aging adults, affecting more than a third of US adults over 40. One promising means of reducing these vestibular-mediated deficits is through applied Galvanic Vestibular Stimulation (GVS). GVS affects vestibular sensory information through current applied via skin-surface electrodes, most commonly situated over the mastoid processes, behind the ears. However, the full extent that GVS may be utilized for these purposes has remained unknown. Here, we empirically quantify the influence of GVS on roll perception during dynamic, passively-applied, whole-body roll motions. To extend our understanding further, we develop and validate a computational model from this data that can predict spatial orientation perceptions across any applied current or passively applied physical motion profile.