Psychometrics of inertial heading perception

Abstract

Background: Inertial self-motion perception is thought to depend primarily on otolith cues. Recent evidence demonstrated that vestibular perceptual thresholds (including inertial heading) are adaptable, suggesting novel clinical approaches for treating perceptual impairments resulting from vestibular disease.

Objective: Little is known about the psychometric properties of perceptual estimates of inertial heading like test-retest reliability. Here we investigate the psychometric properties of a passive inertial heading perceptual test.

Methods: Forty-seven healthy subjects participated across two visits, performing in an inertial heading discrimination task. The point of subjective equality (PSE) and thresholds for heading discrimination were identified for the same day and across day tests. Paired t-tests determined if the PSE or thresholds significantly changed and a mixed interclass correlation coefficient (ICC) model examined test-retest reliability. Minimum detectable change (MDC) was calculated for PSE and threshold for heading discrimination.

Results: Within a testing session, the heading discrimination PSE score test-retest reliability was good (ICC = 0. 80) and did not change (t(1,36) = -1.23, p = 0.23). Heading discrimination thresholds were moderately reliable (ICC = 0.67) and also stable (t(1,36) = 0.10, p = 0.92). Across testing sessions, heading direction PSE scores were moderately correlated (ICC = 0.59) and stable (t(1,46) = -0.44, p = 0.66). Heading direction thresholds had poor reliability (ICC = 0.03) and were significantly smaller at the second visit (t(1,46) = 2.8, p = 0.008). MDC for heading direction PSE ranged from 6-9 degrees across tests.

Conclusion: The current results indicate moderate reliability for heading perception PSE and provide clinical context for interpreting change in inertial vestibular self-motion perception over time or after an intervention.

Keywords: Heading; inertia; perception; psychometrics; vestibular.

Figure 1

Diagram representing the experimental flow across visits. Subjects were randomized to participate in a single inertial heading perceptual test or two inertial heading perceptual tests on their first visit. They participated in the other test on the second visit. 9 subjects declined a second test on their initial visit and are not represented in the same-day test-retest analysis.

Figure 2

Study design representation. A) Experimental set-up, subjects sat in a chair on the Moog that translated linearly from the origin in the horizontal plane to either the left (black arrow) or right (white arrow) of center (gray arrow). B) Exemplar motion profiles showing sinusoidal acceleration, velocity, and displacement corresponding to a 2 second motion stimulus. C) Subjects always responded either left (black circle) or right (gray circle) to each motion. D) Example data from a representative subject showing fitting binary data using logistic regression to determine PSE and Threshold. Filled gray circles indicate average subject responses (either 0 or 1) and size of the circle corresponds to the number of presentations at that heading angle. The dashed black line represents the fit function. PSE is the x-coordinate value at the y-value = 0.5, threshold is the width of the fitted function.

Figure 3

Average (gray bar graphs) and individual (open circles) data representing PSE and threshold values for same day test-retest (A and B respectively) and across visit test-retest (C and D respectively). Black lines connect circles to highlight changes within an individual between respective tests.