Human discrimination of head-centred visual–inertial yaw rotations

Abstract

To successfully perform daily activities such as maintaining posture or running, humans need to be sensitive to self-motion over a large range of motion intensities. Recent studies have shown that the human ability to discriminate self-motion in the presence of either inertial-only motion cues or visual-only motion cues is not constant but rather decreases with motion intensity. However, these results do not yet allow for a quantitative description of how self-motion is discriminated in the presence of combined visual and inertial cues, since little is known about visual–inertial perceptual integration and the resulting self-motion perception over a wide range of motion intensity. Here we investigate these two questions for head-centred yaw rotations (0.5 Hz) presented either in darkness or combined with visual cues (optical flow with limited lifetime dots). Participants discriminated a reference motion, repeated unchanged for every trial, from a comparison motion, iteratively adjusted in peak velocity so as to measure the participants’ differential threshold, i.e. the smallest perceivable change in stimulus intensity. A total of six participants were tested at four reference velocities (15, 30, 45 and 60 °/s). Results are combined for further analysis with previously published differential thresholds measured for visual-only yaw rotation cues using the same participants and procedure. Overall, differential thresholds increase with stimulus intensity following a trend described well by three power functions with exponents of 0.36, 0.62 and 0.49 for inertial, visual and visual–inertial stimuli, respectively. Despite the different exponents, differential thresholds do not depend on the type of sensory input significantly, suggesting that combining visual and inertial stimuli does not lead to improved discrimination performance over the investigated range of yaw rotations.

A Circuit for Integration of Head- and Visual-Motion Signals in Layer 6 of Mouse Primary Visual Cortex

“…Although we cannot say which specific features of the rotation velocity mice used to perform the task (e.g., peak versus range), this approach allowed us to generate a psychometric curve using increasingly similar stimulus pairs. These data indicate that, despite having vestibular afferent fibers displaying lower sensitivity to head velocity ( Cullen, 2014 ), mice nevertheless exhibit relative discrimination thresholds similar to those reported by humans ( Nesti et al., 2015 ).…”

A review of human sensory dynamics for application to models of driver steering and speed control

“…( 2013 ) only found results that fit the MLE model for 3 out of 8 participants and Nesti et al. ( 2015 ) found that combined visual-inertial thresholds were higher than predicted by a MLE model. Butler et al.…”

Accumulation of Inertial Sensory Information in the Perception of Whole Body Yaw Rotation

“…A comparison of self-motion DTs for different stimulus durations was, to the best of our knowledge, never performed before. However, previous studies did measure DTs for supra-threshold yaw discrimination using a 2IFC experimental paradigm and 5 s long stimuli [ 6 , 9 , 16 ]. Nesti and colleagues [ 6 ] reported an average DT of 3.6 deg/s for a 15 deg/s reference stimulus amplitude, while Mallery and colleagues [ 16 ] measured an average DT of 2.26 deg/s for reference stimulus amplitudes of 20 deg/s.…”

“…However, previous studies did measure DTs for supra-threshold yaw discrimination using a 2IFC experimental paradigm and 5 s long stimuli [ 6 , 9 , 16 ]. Nesti and colleagues [ 6 ] reported an average DT of 3.6 deg/s for a 15 deg/s reference stimulus amplitude, while Mallery and colleagues [ 16 ] measured an average DT of 2.26 deg/s for reference stimulus amplitudes of 20 deg/s. Results from the present study, with an average DT of 2.6 deg/s for a 5 s long stimulus with amplitude of 15 deg/s, are thus consistent with previous literature–minor discrepancies are attributable to inter-individual differences and to differences in the employed motion simulators.…”

“…Experimentally measuring DTs has been a powerful tool for the study of different aspects related to self-motion perception, such as the relationship between physical and perceived motion intensity [ 6 , 14 – 18 ] or the processes underlying multisensory integration [ 1 , 4 – 6 , 9 ]. However, to the best of our knowledge, it remains an open question how DTs are affected by the stimulus duration, a relationship that might shed light on how sensory evidence in self-motion is accumulated by the CNS over time.…”