Human sensitivity to vertical self-motion

Abstract

Perceiving vertical self-motion is crucial for maintaining balance as well as for controlling an aircraft. Whereas heave absolute thresholds have been exhaustively studied, little work has been done in investigating how vertical sensitivity depends on motion intensity (i.e., differential thresholds). Here we measure human sensitivity for 1-Hz sinusoidal accelerations for 10 participants in darkness. Absolute and differential thresholds are measured for upward and downward translations independently at 5 different peak amplitudes ranging from 0 to 2 m/s2. Overall vertical differential thresholds are higher than horizontal differential thresholds found in the literature. Psychometric functions are fit in linear and logarithmic space, with goodness of fit being similar in both cases. Differential thresholds are higher for upward as compared to downward motion and increase with stimulus intensity following a trend best described by two power laws. The power laws’ exponents of 0.60 and 0.42 for upward and downward motion, respectively, deviate from Weber’s Law in that thresholds increase less than expected at high stimulus intensity. We speculate that increased sensitivity at high accelerations and greater sensitivity to downward than upward self-motion may reflect adaptations to avoid falling.

Eye Movements in Darkness Modulate Self-Motion Perception

“…To further investigate this effect, Figure 5 shows a linear relation ( R 2 = 0.65, p < 0.01) between the bias and precision across all participants and conditions. This effect, which follows Weber’s perceptual law (Fechner, 1860), is consistent with the signal dependence of (discrimination) precision that has been shown recently for vertical self-motion (Nesti et al, 2014). …”

“…Studies conducted to characterize vestibular-only sensitivity are often performed in complete darkness or with closed eyes (Grabherr et al, 2008; MacNeilage et al, 2010a,b; Roditi and Crane, 2012; Valko et al, 2012; Nesti et al, 2014). However, the results of our free-fixation conditions suggest that, even under these circumstances, results could easily be influenced by vestibularly driven eye movements.…”

Horizontal and Vertical Distance Perception in Altered Gravity

“…The "paternalistic vision hypothesis" of the gravity theory, which proposes that visual perception distorts the world according to the perceiver's abilities, has been strongly criticized recently 26 . An alternate interpretation for our finding is the possible differences in sensitivity to horizontal and vertical motions, and to the asymmetric sensitivity to upward and downward vertical motion 27,28 . The pioneering work of Fernandez & Goldberg 29 demonstrated that the utricular sensitivity to horizontal plane motion in monkeys was higher than the saccular sensitivity to vertical plane motion.…”

Sound-evoked vestibular stimulation affects the anticipation of gravity effects during visual self-motion

“…Thus, heading direction is monitored more robustly by integrating vestibular and visual signals, even when in conflict (Fetsch et al 2009;Butler et al 2015). Previous studies found differences in the representation of downward versus horizontal self-motion (Barnett-Cowan et al 2012;Nesti et al 2014). Moreover, functional magnetic resonance imaging (fMRI) showed that vertical visual self-motion activates a cerebral network including the parieto-insular vestibular cortex (PIVC), inferior parietal cortex, intraparietal sulcus, and cerebellar vermis (Indovina et al 2013b), a network known to process both visual and vestibular signals in humans (Indovina et al 2005;Lopez and Blanke 2011).…”