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Modeling direction discrimination thresholds for yaw rotations around an earth-vertical axis for arbitrary motion profiles.

Soyka F, Giordano PR, Barnett-Cowan M, Bülthoff HH - Exp Brain Res (2012)

Bottom Line: In accordance with previous research, thresholds decreased with shortening period length (from ~2 deg/s for 6.7 s to ~0.8 deg/s for 0.3 s).These measurements were used to fit a novel model based on a description of the firing rate of semi-circular canal neurons.In accordance with previous research, the estimates of the model parameters suggest that velocity storage does not influence perceptual thresholds.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Spemannstrasse 38, 72076 Tübingen, Germany. florian.soyka@tuebingen.mpg.de

ABSTRACT
Understanding the dynamics of vestibular perception is important, for example, for improving the realism of motion simulation and virtual reality environments or for diagnosing patients suffering from vestibular problems. Previous research has found a dependence of direction discrimination thresholds for rotational motions on the period length (inverse frequency) of a transient (single cycle) sinusoidal acceleration stimulus. However, self-motion is seldom purely sinusoidal, and up to now, no models have been proposed that take into account non-sinusoidal stimuli for rotational motions. In this work, the influence of both the period length and the specific time course of an inertial stimulus is investigated. Thresholds for three acceleration profile shapes (triangular, sinusoidal, and trapezoidal) were measured for three period lengths (0.3, 1.4, and 6.7 s) in ten participants. A two-alternative forced-choice discrimination task was used where participants had to judge if a yaw rotation around an earth-vertical axis was leftward or rightward. The peak velocity of the stimulus was varied, and the threshold was defined as the stimulus yielding 75 % correct answers. In accordance with previous research, thresholds decreased with shortening period length (from ~2 deg/s for 6.7 s to ~0.8 deg/s for 0.3 s). The peak velocity was the determining factor for discrimination: Different profiles with the same period length have similar velocity thresholds. These measurements were used to fit a novel model based on a description of the firing rate of semi-circular canal neurons. In accordance with previous research, the estimates of the model parameters suggest that velocity storage does not influence perceptual thresholds.

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Upper row gyroscope measurements (dots) at threshold level intensity together with the commanded motions (solid lines). Lower row: Power spectra of the measured and the commanded signals. The insets show a zoom of the 2nd, 3rd, and 4th harmonic. It can be seen that the 3-Hz profiles are not correctly reproduced. Note that this figure is best viewed in color 273 × 193 mm (300 × 300 DPI)
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Fig2: Upper row gyroscope measurements (dots) at threshold level intensity together with the commanded motions (solid lines). Lower row: Power spectra of the measured and the commanded signals. The insets show a zoom of the 2nd, 3rd, and 4th harmonic. It can be seen that the 3-Hz profiles are not correctly reproduced. Note that this figure is best viewed in color 273 × 193 mm (300 × 300 DPI)

Mentions: High-frequency motions are difficult to reproduce with any type of simulator. In order to assess the actual motion of the device, a gyroscope (Analog Devices ADXRS150) was attached to the seat of the simulator and yaw velocity was measured at 1,000 Hz. The nine conditions were measured at threshold level intensity and averaged over 40 trials. The averaged measured yaw velocities and their power spectra (Hsu 1995) are plotted in Fig. 2 against the commanded velocities. Although the expected differences between velocity profile shapes are small, it can be seen from both the averaged velocities and the spectra that the profiles are very well reproduced for the 0.15-Hz stimuli. For the 0.7-Hz stimuli, the commanded peak velocities are well reproduced, but the profile shapes exhibit slight distortions. However, the 3-Hz profiles are clearly distorted and the commanded peak velocities are also not correctly reproduced.Fig. 2


Modeling direction discrimination thresholds for yaw rotations around an earth-vertical axis for arbitrary motion profiles.

Soyka F, Giordano PR, Barnett-Cowan M, Bülthoff HH - Exp Brain Res (2012)

Upper row gyroscope measurements (dots) at threshold level intensity together with the commanded motions (solid lines). Lower row: Power spectra of the measured and the commanded signals. The insets show a zoom of the 2nd, 3rd, and 4th harmonic. It can be seen that the 3-Hz profiles are not correctly reproduced. Note that this figure is best viewed in color 273 × 193 mm (300 × 300 DPI)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3375416&req=5

Fig2: Upper row gyroscope measurements (dots) at threshold level intensity together with the commanded motions (solid lines). Lower row: Power spectra of the measured and the commanded signals. The insets show a zoom of the 2nd, 3rd, and 4th harmonic. It can be seen that the 3-Hz profiles are not correctly reproduced. Note that this figure is best viewed in color 273 × 193 mm (300 × 300 DPI)
Mentions: High-frequency motions are difficult to reproduce with any type of simulator. In order to assess the actual motion of the device, a gyroscope (Analog Devices ADXRS150) was attached to the seat of the simulator and yaw velocity was measured at 1,000 Hz. The nine conditions were measured at threshold level intensity and averaged over 40 trials. The averaged measured yaw velocities and their power spectra (Hsu 1995) are plotted in Fig. 2 against the commanded velocities. Although the expected differences between velocity profile shapes are small, it can be seen from both the averaged velocities and the spectra that the profiles are very well reproduced for the 0.15-Hz stimuli. For the 0.7-Hz stimuli, the commanded peak velocities are well reproduced, but the profile shapes exhibit slight distortions. However, the 3-Hz profiles are clearly distorted and the commanded peak velocities are also not correctly reproduced.Fig. 2

Bottom Line: In accordance with previous research, thresholds decreased with shortening period length (from ~2 deg/s for 6.7 s to ~0.8 deg/s for 0.3 s).These measurements were used to fit a novel model based on a description of the firing rate of semi-circular canal neurons.In accordance with previous research, the estimates of the model parameters suggest that velocity storage does not influence perceptual thresholds.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Spemannstrasse 38, 72076 Tübingen, Germany. florian.soyka@tuebingen.mpg.de

ABSTRACT
Understanding the dynamics of vestibular perception is important, for example, for improving the realism of motion simulation and virtual reality environments or for diagnosing patients suffering from vestibular problems. Previous research has found a dependence of direction discrimination thresholds for rotational motions on the period length (inverse frequency) of a transient (single cycle) sinusoidal acceleration stimulus. However, self-motion is seldom purely sinusoidal, and up to now, no models have been proposed that take into account non-sinusoidal stimuli for rotational motions. In this work, the influence of both the period length and the specific time course of an inertial stimulus is investigated. Thresholds for three acceleration profile shapes (triangular, sinusoidal, and trapezoidal) were measured for three period lengths (0.3, 1.4, and 6.7 s) in ten participants. A two-alternative forced-choice discrimination task was used where participants had to judge if a yaw rotation around an earth-vertical axis was leftward or rightward. The peak velocity of the stimulus was varied, and the threshold was defined as the stimulus yielding 75 % correct answers. In accordance with previous research, thresholds decreased with shortening period length (from ~2 deg/s for 6.7 s to ~0.8 deg/s for 0.3 s). The peak velocity was the determining factor for discrimination: Different profiles with the same period length have similar velocity thresholds. These measurements were used to fit a novel model based on a description of the firing rate of semi-circular canal neurons. In accordance with previous research, the estimates of the model parameters suggest that velocity storage does not influence perceptual thresholds.

Show MeSH
Related in: MedlinePlus