Heading judgments during active and passive self-motion

Abstract

Previous studies have generally considered heading perception to be a visual task. However, since judgments of heading direction are required only during self-motion, there are several other relevant senses which could provide supplementary and, in some cases, necessary information to make accurate and precise judgments of the direction of self-motion. We assessed the contributions of several of these senses using tasks chosen to reflect the reference system used by each sensory modality. Head-pointing and rod-pointing tasks were performed in which subjects aligned either the head or an unseen pointer with the direction of motion during whole body linear motion. Passive visual and vestibular stimulation was generated by accelerating subjects at sub- or supravestibular thresholds down a linear track. The motor-kinesthetic system was stimulated by having subjects actively walk along the track. A helmet-mounted optical system, fixed either on the cart used to provide passive visual or vestibular information or on the walker used in the active walking conditions, provided a stereoscopic display of an optical flow field. Subjects could be positioned at any orientation relative to the heading, and heading judgments were obtained using unimodal visual, vestibular, or walking cues, or combined visual-vestibular and visual-walking cues. Vision alone resulted in reasonably precise and accurate head-pointing judgments (0.3 degrees constant errors, 2.9 degrees variable errors), but not rod-pointing judgments (3.5 degrees constant errors, 5.9 degrees variable errors). Concordant visual-walking stimulation slightly decreased the variable errors and reduced constant pointing errors to close to zero, while head-pointing errors were unaffected.

Visual Inertial Coherence Zone in the Perception of Heading

“…The median 50% detection threshold for non-zero heading was 15.6º. Although there is no comparison data available for the incongruent stimuli, the median 50% threshold for congruent stimuli was 5.9º, which is in the same order of magnitude as earlier observations 8 . Whether or not the second requirement was met was assessed from congruency judgments.…”

“…We refer to a straight ahead heading as 'zero heading'. We did not expect consistent differences in the thresholds for detection of non-zero heading for left or rightward stimuli 8 . Therefore, only rightward motion was presented, which reduced the number of trials.…”

Path integration in mammals

“…According to converging behavioral data from humans (Kearns et al, 2002;Telford et al, 1995;Harris et al, 2000), and single-cell recordings in rats (Sharp et al, 1995;Blair and Sharp, 1996), the contribution of visual flow to PI is much less obvious than the role played by non-visual feedback from locomotion in conditions where both categories of route-based information are available.…”

Hippocampal spatial representations require vestibular input

“…Therefore, internal self-motion cues also play an important role in influencing the spatial firing properties of hippocampal neurons (Foster et al, 1989;Taube and Burton, 1995;Knierim et al, 1998). Indeed, vestibular stimulation activates the hippocampal formation (Horii et al, 1994;Vitte et al, 1996), influences hippocampal place cell activity (Sharp et al, 1995), and influences navigation in humans (Telford et al, 1995). Finally, lesions of the vestibular apparatus abolish the directional firing of anterior thalamic neurons and impair spatial memory, as outlined above.…”