Vestibular thresholds for yaw rotation about an earth-vertical axis as a function of frequency
Grabherr, Luzia ; Nicoucar, Keyvan ; Mast, Fred ; Merfeld, Daniel
In: Experimental Brain Research, 2008, vol. 186, no. 4, p. 677-681
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- 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 5Hz) 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 2.8degs−1 for 0.05Hz, 2.5degs−1 for 0.1Hz, 1.7degs−1 for 0.2Hz, 0.7degs−1 for 0.5Hz, 0.6degs−1 for 1Hz, 0.4 degs−1 for 2Hz, and 0.6degs−1 for 5Hz. The results show that motion thresholds increase at 0.2Hz and below and plateau at 0.5Hz and above. Increasing velocity thresholds at lower frequencies qualitatively mimic the high-pass characteristics of the semicircular canals, since the increase at 0.2Hz 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 0.71degs-1 and a cut-off frequency of 0.23Hz, which corresponds to a time constant of approximately 0.70s. These findings provide no evidence for an influence of velocity storage on perceptual yaw rotation thresholds