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. 2016 Sep 1;116(3):1275-85.
doi: 10.1152/jn.00322.2016. Epub 2016 Jun 22.

Perception of Combined Translation and Rotation in the Horizontal Plane in Humans

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Free PMC article

Perception of Combined Translation and Rotation in the Horizontal Plane in Humans

Benjamin T Crane. J Neurophysiol. .
Free PMC article

Abstract

Thresholds and biases of human motion perception were determined for yaw rotation and sway (left-right) and surge (fore-aft) translation, independently and in combination. Stimuli were 1 Hz sinusoid in acceleration with a peak velocity of 14°/s or cm/s. Test stimuli were adjusted based on prior responses, whereas the distracting stimulus was constant. Seventeen human subjects between the ages of 20 and 83 completed the experiments and were divided into 2 groups: younger and older than 50. Both sway and surge translation thresholds significantly increased when combined with yaw rotation. Rotation thresholds were not significantly increased by the presence of translation. The presence of a yaw distractor significantly biased perception of sway translation, such that during 14°/s leftward rotation, the point of subjective equality (PSE) occurred with sway of 3.2 ± 0.7 (mean ± SE) cm/s to the right. Likewise, during 14°/s rightward motion, the PSE was with sway of 2.9 ± 0.7 cm/s to the left. A sway distractor did not bias rotation perception. When subjects were asked to report the direction of translation while varying the axis of yaw rotation, the PSE at which translation was equally likely to be perceived in either direction was 29 ± 11 cm anterior to the midline. These results demonstrated that rotation biased translation perception, such that it is minimized when rotating about an axis anterior to the head. Since the combination of translation and rotation during ambulation is consistent with an axis anterior to the head, this may reflect a mechanism by which movements outside the pattern that occurs during ambulation are perceived.

Keywords: human; multisensor; otolith; rotation; semicircular canal; translation; vestibular.

Figures

Fig. 1.
Fig. 1.
Trial blocks, including combined rotation and translation. Each condition included both rotation and translation with subjects asked to judge left-right sway (top), forward-back surge (middle), or left-right rotation (bottom).
Fig. 2.
Fig. 2.
Sample date from an individual subject (#5, a 23-yr-old woman) for the sway-yaw condition. During the stimulus presentations, there was a 7° (14°/s peak velocity) leftward rotation (A and B) and similar rightward rotation (C and D). The subject was asked to report the amount of left-right sway translation. A and C: the circles represent this subject's responses and are drawn in proportion to the number of stimuli presented for a given combination. The smaller circles represent a single stimulus presentation, whereas the larger circles represent 4 stimuli. The solid lines represent the best fit of a cumulative Gaussian function to the responses. The values in parentheses represent the 95% confidence interval (CI). The same data are shown in the time domain (B and D). Four randomly interleaved staircases are shown. Each panel includes 2 staircases: 1 that began with a 14-cm/s translation (light) and another that began with a −14 cm/s translation (dark). The direction of each response is shown by the orientation of the triangles.
Fig. 3.
Fig. 3.
Translation thresholds. Thresholds, as determined from the width (sigma) of the psychometric function, are shown for 17 subjects. The control condition in which only translation was presented (no yaw rotation) is shown with circles. Conditions in which there was a simultaneous distracting yaw motion are shown with triangles. Data for individual subjects (–17) are in order of age; error bars represent the 95% CI. The CI tended to be larger with higher thresholds due to the fixed number of stimulus presentations in each trial block. Average data from subjects under age 50 (–12) are shown in the column labeled Y (younger). Average data from the subjects 50 and over (–17) are shown in the column labeled O (older). For the grouped data, error bars represent SD. A: surge (for-aft) translation. B: sway (lateral) translation.
Fig. 4.
Fig. 4.
Yaw rotation threshold. The control condition in which only rotation occurred (no translation) is represented by circles. Conditions in which there was a simultaneous distracting translation are shown with triangles. Data for individual subjects (–17) are in order of age; error bars represent the 95% CI. The CI tended to be larger with higher thresholds due to the fixed number of stimulus presentations in each trial block. Average data from subjects under age 50 (–12) are shown in the column labeled Y (younger). Average data from the subjects 50 and over (13–17) are shown in the column labeled O (older). For the grouped data, error bars represent SD. A: distracting stimulus was surge (for-aft) translation. B: distracting stimulus was sway (lateral) translation.
Fig. 5.
Fig. 5.
Translation bias. The bias or mean of the psychometric function is the PSE, at which reporting of left or right motion was equally likely. The control condition (only translation without rotation) is represented by circles. Conditions in which there was a simultaneous distracting yaw motion are shown with triangles. Data for individual subjects (–17) are in order of age; error bars represent the 95% CI. Average data from subjects under age 50 (–12) are shown in the column labeled Y (younger). Average data from the subjects 50 and over (13–17) are shown in the column labeled O (older). For the grouped data, error bars represent SD. A: for-aft direction of surge was reported during yaw rotation. Although some individual subjects had some biases during this condition, the average bias was close to 0. B: the left-right direction of sway was reported during yaw rotation. Most subjects had a bias, such as with leftward yaw, as they were more likely also to report leftward translation.
Fig. 6.
Fig. 6.
Yaw rotation bias. The control condition in which only rotation occurred (no translation) is represented by circles. Conditions in which there was a simultaneous distracting translation are shown with triangles. Data for individual subjects (–17) are in order of age; error bars represent the 95% CI. Average data from subjects under age 50 (–12) are shown in the column labeled Y (younger). Average data from the subjects 50 and over (–17) are shown in the column labeled O (older). For the grouped data, error bars represent SD. A: distracting stimulus was surge (for-aft) translation. B: distracting stimulus was sway (lateral) translation. Although some subjects did demonstrate biases, they were not in a consistent direction, and the average bias was near 0.
Fig. 7.
Fig. 7.
Position of the rotation axis at which subjects were equally likely to report translation in either direction. The rotation direction (left vs. right) is represented using triangles. Data for individual subjects (–17) are in order of age; error bars represent the 95% CI. Average data from subjects under age 50 (–12) are shown in the column labeled Y (younger). Average data from the subjects 50 and over (13–17) are shown in the column labeled O (older). For the grouped data, the error bars represent SD. A: the rotation axis was translated laterally, and the subjects reported fore-aft displacement. The axis at which the PSE occurred was located near the midline. B: the rotation axis was translated fore-aft, and the subjects reported the direction of lateral displacement. The axis at which the PSE occurred was anterior to the head (negative) in most subjects but was posterior in 2 young subjects. The eldest subject (#17) had an axis displaced >1 m anterior, which skewed the results for the older group.
Fig. 8.
Fig. 8.
Summary of threshold by age and test condition. Each symbol represents the average data for each age group. Data are grouped by the test stimulus with the distractor in parentheses. Control data are represented as a circle; conditions in which there was a distractor present are represented with a triangle. Error bars represent ± 1 SD.
Fig. 9.
Fig. 9.
Summary of bias (i.e., PSE) by age and test condition. Each symbol represents the average data for each age group. Data are grouped by the test stimulus with the distractor in parentheses. Control data are represented as circles; conditions in which there was a distractor present are represented with triangles. Error bars represent SD. A: combined translation and rotation. Biases were largest when subjects reported the direction of sway in the presence of a yaw distractor. B: location of rotation axis at which the PSE of translation direction occurs. Yaw rotation to the left and right is shown using triangles.

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