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Signal detection theory and vestibular perception: II. Fitting perceptual thresholds as a function of frequency.

ABSTRACT: Vestibular perceptual thresholds are defined by a dynamic sensory system. To capture these dynamics, thresholds were previously fit as a function of frequency. In this paper, we compare fits using two published models with two new models. Furthermore, a new fitting method that utilizes vestibular perceptual dynamics is developed to improve fit quality and overcome problems associated with the conventional approach. Combinations of the four models and two fitting methods are tested using both simulated data and previously published experimental data. Simulations reveal that the conventional approach underestimates thresholds when the number of trials at each frequency is limited (circa 50); this underestimation is reduced fivefold by the new fitting method that simultaneously utilizes data across frequencies. The new fitting method also scored best for goodness of fit for both the simulations and experimental data. In fact, the new approach of fitting simultaneously across frequencies proved more accurate, more precise, more robust, and more efficient than the conventional approach of fitting the responses at each frequency individually and then fitting these threshold data across frequency. The revised fit of published yaw rotation threshold data shows that these are best fit by a first-order high-pass filter having a plateau of 0.5°/s (roughly a factor of 4 higher than the motion platform vibration) at frequencies above the cutoff frequency of 0.26 Hz, which is well above the cutoff frequency of the semicircular canals (circa 0.03 Hz). This dynamic analysis suggests the contributions of a velocity leakage mechanism to human yaw rotation thresholds.

SUBMITTER: Lim K

PROVIDER: S-EPMC4105942 | biostudies-literature | 2012 Oct

REPOSITORIES: biostudies-literature

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Signal detection theory and vestibular perception: II. Fitting perceptual thresholds as a function of frequency.

Lim Koeun K Merfeld Daniel M DM

Experimental brain research 20120826 3

Vestibular perceptual thresholds are defined by a dynamic sensory system. To capture these dynamics, thresholds were previously fit as a function of frequency. In this paper, we compare fits using two published models with two new models. Furthermore, a new fitting method that utilizes vestibular perceptual dynamics is developed to improve fit quality and overcome problems associated with the conventional approach. Combinations of the four models and two fitting methods are tested using both sim ...[more]

PMID: 22923225

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Project description:Little is known about the vestibulo-perceptual (VP) system, particularly after a unilateral vestibular lesion. We investigated vestibulo-ocular (VO) and VP function in 25 patients with vestibular neuritis (VN) acutely (2 days after onset) and after compensation (recovery phase, 10 weeks). Since the effect of VN on reflex and perceptual function may differ at threshold and supra-threshold acceleration levels, we used two stimulus intensities, acceleration steps of 0.5°/s(2) and velocity steps of 90°/s (acceleration 180°/s(2)). We hypothesised that the vestibular lesion or the compensatory processes could dissociate VO and VP function, particularly if the acute vertiginous sensation interferes with the perceptual tasks. Both in acute and recovery phases, VO and VP thresholds increased, particularly during ipsilesional rotations. In signal detection theory this indicates that signals from the healthy and affected side are still fused, but result in asymmetric thresholds due to a lesion-induced bias. The normal pattern whereby VP thresholds are higher than VO thresholds was preserved, indicating that any 'perceptual noise' added by the vertigo does not disrupt the cognitive decision-making processes inherent to the perceptual task. Overall, the parallel findings in VO and VP thresholds imply little or no additional cortical processing and suggest that vestibular thresholds essentially reflect the sensitivity of the fused peripheral receptors. In contrast, a significant VO-VP dissociation for supra-threshold stimuli was found. Acutely, time constants and duration of the VO and VP responses were reduced - asymmetrically for VO, as expected, but surprisingly symmetrical for perception. At recovery, VP responses normalised but VO responses remained shortened and asymmetric. Thus, unlike threshold data, supra-threshold responses show considerable VO-VP dissociation indicative of additional, higher-order processing of vestibular signals. We provide evidence of perceptual processes (ultimately cortical) participating in vestibular compensation, suppressing asymmetry acutely in unilateral vestibular lesions.

Project description:OBJECTIVES:Pediatric vestibular evaluations incorporate cervical and ocular vestibular evoked myogenic potential (c- and oVEMP, respectively) testing; however, in children, c- and oVEMP thresholds have been minimally investigated and frequency tuning is unknown. Children are also at risk for unsafe sound exposure secondary to VEMP. While it is unknown if VEMP threshold testing leads to cochlear changes, it is possible that this risk increases due to the increased number of trials needed to obtain a threshold. Obtaining VEMP thresholds at various frequencies in children provides further information for pediatric normative VEMP data. Assessing for cochlear changes after VEMP threshold testing would provide information on the safety of threshold VEMP testing in children. The objectives of this study were to (1) characterize c- and oVEMP thresholds in children, adolescents, and young adults with normal hearing using 500 and 750 Hz tone burst (TB) stimuli, (2) compare frequency tuning of 500 and 750 Hz TB, and (3) assess whether cochlear changes exist after VEMP threshold testing. It is hypothesized that children, adolescents, and young adults would not show age-related changes to the vestibular system. Therefore, reliable VEMP thresholds would be seen below maximum acoustical stimulation levels (e.g., <125 dB SPL) and frequency tuning will be similar for 500 and 750 Hz TB stimuli. DESIGN:Ten children (age 4-9), 10 adolescents (age 10-19), and 10 young adults (age 20-29) with normal hearing and tympanometry participated. All subjects received c- and oVEMP testing at maximum stimulation and threshold. To address frequency tuning, but not exceed recommended sound exposure allowance, subjects received a 500 Hz TB stimulus in one ear and a 750 Hz TB stimulus in the other ear. Subjects completed tympanometry pre-VEMP, and audiometric threshold testing, distortion product otoacoustic emission testing, and subjective questionnaire pre- and post-VEMP to study the effect of VEMP exposure on cochlear function for each stimulus frequency. RESULTS:(1) cVEMP thresholds were determined for both stimulus frequencies for children (500 Hz = 106 dB SPL; 750 Hz = 106 dB SPL), adolescents (500 Hz = 107.5 dB SPL; 750 Hz = 109.5 dB SPL), and young adults (500 Hz = 111.5 dB SPL; 750 Hz = 112 dB SPL). oVEMP thresholds were also obtained in response to both stimulus frequencies for children (500 Hz = 111.1 dB SPL; 750 Hz = 112.2 dB SPL), adolescents (500 Hz = 112.5 dB SPL; 750 Hz = 114.5 dB SPL), and young adults (500 Hz = 116 dB SPL; 750 Hz = 117 dB SPL). Similar thresholds were found between groups except for children who had significantly lower thresholds compared with adults for cVEMP (500 Hz: p = 0.002; 750 Hz: p = 0.004) and oVEMP (500 Hz: p = 0.01; 750 Hz: p = 0.02). In addition, equivalent ear-canal volume and VEMP thresholds were linearly correlated. (2) There was no significant effect of stimulus frequency on VEMP response rates, latencies, peak to peak amplitudes, or thresholds, suggesting similar frequency tuning for 500 and 750 Hz. (3) There were no significant effects of VEMP threshold testing on cochlear function for either stimulus frequency. CONCLUSIONS:Children, adolescents, and young adults show VEMP thresholds below high stimulation levels and had similar frequency tuning between 500 and 750 Hz. Use of 750 Hz could be regarded as the safer stimuli due to its shorter duration and thus reduced sound exposure. Children with smaller ear-canal volume had present responses at maximum stimulation and lower thresholds, suggesting that VEMP testing could be initiated at lower acoustic levels to minimize sound exposure and optimize testing.

Dataset Information

Signal detection theory and vestibular perception: II. Fitting perceptual thresholds as a function of frequency.

Publications

Signal detection theory and vestibular perception: II. Fitting perceptual thresholds as a function of frequency.

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