Coordinates of Human Visual and Inertial Heading Perception.

Benjamin Thomas Crane,Doug Wylie

doi:10.1371/journal.pone.0135539

Abstract

Heading estimation involves both inertial and visual cues. Inertial motion is sensed by the labyrinth, somatic sensation by the body, and optic flow by the retina. Because the eye and head are mobile these stimuli are sensed relative to different reference frames and it remains unclear if a perception occurs in a common reference frame. Recent neurophysiologic evidence has suggested the reference frames remain separate even at higher levels of processing but has not addressed the resulting perception. Seven human subjects experienced a 2s, 16 cm/s translation and/or a visual stimulus corresponding with this translation. For each condition 72 stimuli (360° in 5° increments) were delivered in random order. After each stimulus the subject identified the perceived heading using a mechanical dial. Some trial blocks included interleaved conditions in which the influence of ±28° of gaze and/or head position were examined. The observations were fit using a two degree-of-freedom population vector decoder (PVD) model which considered the relative sensitivity to lateral motion and coordinate system offset. For visual stimuli gaze shifts caused shifts in perceived head estimates in the direction opposite the gaze shift in all subjects. These perceptual shifts averaged 13 ± 2° for eye only gaze shifts and 17 ± 2° for eye-head gaze shifts. This finding indicates visual headings are biased towards retina coordinates. Similar gaze and head direction shifts prior to inertial headings had no significant influence on heading direction. Thus inertial headings are perceived in body-centered coordinates. Combined visual and inertial stimuli yielded intermediate results.

Highlights

Human heading estimation is multi-sensory involving visual and inertial cues[1,2,3]
The neurophysiology has not eliminated the possibility of a common coordinate system for perception of visual and vestibular headings, no such common coordinate system has been found as visual headings have only been found to be represented in retinal coordinates and vestibular headings have been found in only head and body coordinates
The large offsets in visual heading estimates with changes in gaze position were consistently observed across subjects and predicted from the known neurophysiology

Summary

Introduction

Human heading estimation is multi-sensory involving visual and inertial cues[1,2,3] These sensory modalities use different reference frames with vision represented relative to the retina[4,5,6], vestibular relative to the head[6,7,8,9], and somatosensation relative to the body[10, 11]. In VIP visual stimuli are represented in eye-centered coordinates[23, 24] while vestibular headings in VIP are in body coordinates that do not vary with changes in eye or head position[16]. The neurophysiology has not eliminated the possibility of a common coordinate system for perception of visual and vestibular headings, no such common coordinate system has been found as visual headings have only been found to be represented in retinal coordinates and vestibular headings have been found in only head and body coordinates

Methods

Results

Conclusion