Article Figures & Data
Figures
- Figure 1.
A, The haptic stimulus in the SHV task was a bar that consisted of two pieces with parallel edges mounted on a stepper motor, and the visual stimulus was a red line in the SVV task. In both tasks, the orientation of the stimulus was reported with respect to the perceived vertical. B, Sample time course of 100 trials with responses from the paradigm used in both tasks. The y-axis shows the angle of the stimulus presented, and the color indicates the response for that trial (left, in gray; right, in black). The stimulus angles were presented randomly within a range that started at 180° and then was adjusted based on previous responses (gray sectors in the top circles). C, An example of psychometric fit to the responses in the paradigm. The bias value (SVV/SHV) is determined as the center of the curve (i.e., point of subjective equality), where the probabilities of right and left responses are equal. Precision is determined as the slope of the curve.
- Figure 2.
Raw SHV value and the task bias are shown for each hand use and three different head tilt positions. Error bars show the SEM.
- Figure 3.
A, individual SHV and SVV measurements are shown for both head tilts on the top plots (left tilt reversed) with the group means (green). The group means for the SHV task with each hand, and those for the SVV task are also shown on the bottom plots (error bars show the SEM). B, SHV and SVV spatial bias for both head tilts are shown on the top plots (left tilt reversed) with the group means (green). The group means of SVV and SHV spatial biases are shown on the bottom plots. These results show that once the effect of hand bias is removed, the SHV spatial biases measured with each hand are similar, and they also conform with the SVV spatial bias.
- Figure 4.
The effect of hand use in the haptic task can be removed when the measurements with the head upright are subtracted out from those with the head tilted. In the visual task, however, the change in eye position with head tilt cannot be subtracted out. Accordingly, a difference between SHV and SVV tasks can provide the visuospatial bias in each subject. There is a significant correlation (bottom graph) between the visuospatial biases measured using each hand in the haptic task (Pearson’s correlation: r2 = 0.38, p < 0.001).
- Figure 5.
Mean spatial bias measured with each head tilt separated by hand use in right-handers and left-handers. Error bars show the SEM.
Tables
- Table 1
SHV and SVV Results with negative values as leftward bias and positive values as rightward bias
Head Hand used SHV ± SEM (°) SVV ± SEM (°) Task
bias ± SEM (°)SHV spatial
bias ± SEM (°)SVV spatial
bias ± SEM (°)Left tilt Left hand −0.2 ± 1.1 3.9 ± 1.1 4.4 ± 0.7 −4.2 ± 1.5 3.9 ± 0.7 4.3 ± 1.0 4.9 ± 0.7 Right hand 11.8 ± 0.9 4.9 ± 1.0 6.9 ± 1.3 4.4 ± 0.7 5.4 ± 0.9 Upright Left hand −4.2 ± 1.1 −0.4 ± 0.4 −0.5 ± 0.3 −3.7 ± 1.1 Right hand 7.4 ± 1.0 −0.5 ± 0.4 7.9 ± 1.0 Right tilt Left hand −8.8 ± 0.9 −6.0 ± 1.3 −5.2 ± 0.9 −2.8 ± 1.5 −4.6 ± 0.9 −5.6 ± 1.4 −4.7 ± 1.0 Right hand 2.8 ± 1.0 −4.3 ± 1.3 7.2 ± 1.5 −4.6 ± 0.8 −3.8 ± 1.3 The task bias was calculated as the difference between the SHV task and the SVV task for each subject. The spatial bias was calculated as the difference between SHV or SVV task values with the head tilted and upright.
Head SHV ± SEM (°) Left handed Right handed Left tilt Left hand 0.2 ± 1.6 −0.7 ± 1.4 Right hand 11.2 ± 1.2 12.5 ± 1.3 Upright Left hand −3.7 ± 1.7 −4.6 ± 1.4 Right hand 6.7 ± 1.4 8.1 ± 1.3 Right tilt Left hand −9.2 ± 1.4 −8.3 ± 1.3 Right hand 2.6 ± 1.3 3.1 ± 1.5 Head SHV ± SEM (°) SVV ± SEM (°) Left tilt 3.8 ± 0.2 Left hand 3.7 ± 0.3 3.6 ± 0.4 (left handed) 2.1 ± 0.1 3.7 ± 0.5 (right handed) Right hand 3.9 ± 0.3 3.8 ± 0.4 (left handed) 3.9 ± 0.5 (right handed) Upright 3.6 ± 0.2 Left hand 3.7 ± 0.3 3.4 ± 0.3 (left handed) 1.1 ± 0.1 4.0 ± 0.6 (right handed) Right hand 3.5 ± 0.2 3.2 ± 0.3 (left handed) 3.8 ± 0.4 (right handed) Right tilt 3.7 ± 0.2 Left hand 3.7 ± 0.3 3.6 ± 0.3 (left handed) 2.1 ± 0.1 3.9 ± 0.4 (right handed) Right hand 3.8 ± 0.3 3.2 ± 0.3 (left handed) 4.4 ± 0.5 (right handed)
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