Whole body motion-detection tasks can yield much lower thresholds than direction-recognition tasks: implications for the role of vibration

Abstract

Earlier spatial orientation studies used both motion-detection (e.g., did I move?) and direction-recognition (e.g., did I move left/right?) paradigms. The purpose of our study was to compare thresholds measured with motion-detection and direction-recognition tasks on a standard Moog motion platform to see whether a substantial fraction of the reported threshold variation might be explained by the use of different discrimination tasks in the presence of vibrations that vary with motion. Thresholds for the perception of yaw rotation about an earth-vertical axis and for interaural translation in an earth-horizontal plane were determined for four healthy subjects with standard detection and recognition paradigms. For yaw rotation two-interval detection thresholds were, on average, 56 times smaller than two-interval recognition thresholds, and for interaural translation two-interval detection thresholds were, on average, 31 times smaller than two-interval recognition thresholds. This substantive difference between recognition thresholds and detection thresholds is one of our primary findings. For motions near our measured detection threshold, we measured vibrations that matched previously established vibration thresholds. This suggests that vibrations contribute to whole body motion detection. We also recorded yaw rotation thresholds on a second motion device with lower vibration and found direction-recognition and motion-detection thresholds that were not significantly different from one another or from the direction-recognition thresholds recorded on our Moog platform. Taken together, these various findings show that yaw rotation recognition thresholds are relatively unaffected by vibration when moderate (up to ≈ 0.08 m/s(2)) vibration cues are present.

Visual and vestibular perceptual thresholds each demonstrate better precision at specific frequencies and also exhibit optimal integration

“…For roll tilt in the dark, the average thresholds for total vestibular loss patients were significantly greater than normal for the frequency range tested herein, which suggests that, for this task in the dark, vestibular cues predominate over all other cues combined. Finally, another recent report suggests that motion direction recognition thresholds are relatively unaffected by device vibration, providing further support for the importance of vestibular cues in motion direction recognition (Chaudhuri et al 2013).…”

“…Similar reasoning applies to other artifacts that would result in inflated vestibular thresholds. For example, there is evidence that external "noise" may raise thresholds for nonvestibular perception (e.g., Watamaniuk and Heinen 1999), although a recent study showed that increased device vibration did not significantly change yaw rotation direction recognition thresholds (Chaudhuri et al 2013). Experimental procedure.…”

Determining thresholds using adaptive procedures and psychometric fits: evaluating efficiency using theory, simulations, and human experiments

“…The study was approved by the local institutional review board and was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki. Each subject was screened using a detailed, standard vestibular diagnostic clinical exam to confirm the absence of undiagnosed vestibular disorders (Grabherr, Nicoucar, Mast, and Merfeld 2008;Valko, Priesol, Lewis, and Merfeld 2012;Chaudhuri, Karmali et al 2013;Karmali, Lim, and Merfeld 2014). Screening included Hallpike tests, angular vestibuloocular reflex (VOR) evoked via rotation, caloric testing, and posture control measures.…”

“…did I move left or right?) in response to upright whole-body yaw rotation, using methods similar to those used in previous studies (Grabherr, Nicoucar, Mast, and Merfeld 2008;Valko, Priesol, Lewis, and Merfeld 2012;Chaudhuri, Karmali, and Merfeld 2013). An adaptive, one-interval, two-alternative, categorical, forced-choice procedure (Treutwein 1995;Leek 2001) was used.…”

“…We attempted to minimize the influence of non-vestibular cues using the same approaches previously used (Grabherr, Nicoucar, Mast, and Merfeld 2008;Valko, Priesol, Lewis, and Merfeld 2012;Chaudhuri, Karmali, and Merfeld 2013;Karmali, Lim, and Merfeld 2014). Briefly, subjects were secured with a five-point harness in a racing-style chair, with their head fixed relative to the chair and platform with a vacuum cushion snugly pressed between two adjustable plates.…”