Vestibular thresholds for yaw rotation about an earth-vertical axis as a function of frequency

Abstract

Perceptual direction detection thresholds for yaw rotation about an earth-vertical axis were measured at seven frequencies (0.05, 0.1, 0.2, 0.5, 1, 2, and 5 Hz) in seven subjects in the dark. Motion stimuli consisted of single cycles of sinusoidal acceleration and were generated by a motion platform. An adaptive two-alternative categorical forced-choice procedure was used. The subjects had to indicate by button presses whether they perceived yaw rotation to the left or to the right. Thresholds were measured using a 3-down, 1-up staircase paradigm. Mean yaw rotation velocity thresholds were 2.8 deg s(-1) for 0.05 Hz, 2.5 deg s(-1) for 0.1 Hz, 1.7 deg s(-1) for 0.2 Hz, 0.7 deg s(-1) for 0.5 Hz, 0.6 deg s(-1) for 1 Hz, 0.4 deg s(-1) for 2 Hz, and 0.6 deg s(-1) for 5 Hz. The results show that motion thresholds increase at 0.2 Hz and below and plateau at 0.5 Hz and above. Increasing velocity thresholds at lower frequencies qualitatively mimic the high-pass characteristics of the semicircular canals, since the increase at 0.2 Hz and below would be consistent with decreased gain/sensitivity observed in the VOR at lower frequencies. In fact, the measured dynamics are consistent with a high pass filter having a threshold plateau of 0.71 deg s(-1) and a cut-off frequency of 0.23 Hz, which corresponds to a time constant of approximately 0.70 s. These findings provide no evidence for an influence of velocity storage on perceptual yaw rotation thresholds.

Directional Asymmetries and Age Effects in Human Self-Motion Perception

“…Motion stimuli were delivered using a 6-degree-offreedom motion platform (Moog, East Aurora, NY, model 6DOF2000E) similar to that used in other laboratories for human motion perception studies (Grabherr et al 2008;Fetsch et al 2009;MacNeilage et al 2010). Subjects were seated in a padded racing seat (Corbeau, Sandy UT, model FX-1) mounted on the platform (Fig.…”

“…Other studies of vestibular perception using a similar type of motion platform have also used masking noise which was presented at 60 dB with the addition of ear plugs (Grabherr et al 2008) or via headphones (MacNeilage et al 2010). The intensity of the masking noise used in the current study varied with time as a half-sine wave so that the peak masking noise occurred at the same time the peak velocity was reached.…”

“…These results suggested motion perception thresholds may be direction specific, but no attempts to define direction specific thresholds were made (Benson et al 1986). A recent review also discusses the possibility of vestibular biases (Merfeld 2011) and mentions that two otherwise normal subjects were excluded from a prior report on vestibular thresholds due to significant asymmetries (Grabherr et al 2008).…”

“…Vestibular reflexes including the VOR (Stefansson and Imoto 1986;Tian et al 2001), spinal reflexes (Liaw et al 2009), and VEMP (Nguyen et al 2010) also decline with age. Most prior studies of motion perception have focused on a population under age 40 (Walsh 1961;Benson et al 1986Grabherr et al 2008;MacNeilage et al 2010;Mallery et al 2010;Soyka et al 2011), but when older subjects were included, advanced age was associated with higher perceptual thresholds in fore-aft motion (Kingma 2005).…”

“…Forced choice methods have now standardized threshold determination in several fields of psychophysics (Treutwein 1995;Leek 2001;Knill and Pouget 2004), and these techniques are now the standard method of assessing motion perception thresholds Grabherr et al 2008;Gu et al 2008;MacNeilage et al 2010;Mallery et al 2010). These techniques have the advantage of largely eliminating the tendency to bias one choice, but make the assumption that the choices have equal thresholds.…”