Recent studies have shown that when phonating subjects hear their voice pitch feedback shift upward or downward, they respond with a change in voice fundamental frequency (F0) output. Three experiments were performed to improve our understanding of this response and to explore the effects of different stimulus variables on voice F0 responses to pitch-shift stimuli. In experiment 1, it was found that neither the absolute level of feedback intensity nor the presence of pink masking noise significantly affect magnitude or latency of the voice F0 response. In experiment 2, changes in stimulus magnitude led to no systematic differences in response magnitudes or latencies. However, as stimulus magnitude was increased from 25 to 300 cents, the proportion of responses that changed in the direction opposite that of the stimulus ("opposing" response) decreased. A corresponding increase was observed in the proportion of same direction responses ("following" response). In experiment 3, increases in pitch-shift stimulus durations from 20 to 100 ms led to no differences in the F0 response. Durations between 100 and 500 ms led to longer duration voice F0 responses with greater response magnitude, and suggested the existence of a second F0 response with a longer latency than the first.

AAN ϭ American Academy of Neurology; BPPV ϭ benign paroxysmal positional vertigo; CONSORT ϭ Consolidated Standards of Reporting Trials; CRP ϭ canalith repositioning procedure; NNT ϭ number needed to treat.

Previous findings have shown that subjects respond to an alteration, or shift, of auditory feedback pitch with a change in voice fundamental frequency (F0). When pitch shifts exceeding 500 ms in duration were presented, subjects' averaged responses appeared to consist of both an early and a late component. The latency of the second response was long enough to be produced voluntarily. To test the hypothesis that there are two responses to pitch-shift stimuli and to clarify the role of intention, subjects were instructed to change their voice F0 in the opposite direction of the pitch-shift stimulus, in the same direction, or not to respond at all. In a second group, subjects were tested under the above conditions as well as under instructions to raise voice F0 or to lower F0 as rapidly as possible upon hearing a pitch shift. Results showed that, when given instructions to produce a voluntary response, subjects made both an early vocal response (VR1) and a later vocal response (VR2). The second response, VR2, was almost always made in the instructed direction, whereas VR1 was often made incorrectly. The latency of VR1 was reduced under instructions to respond to feedback pitch shifts by changing voice F0 in the opposite direction, compared with that when told to ignore the pitch shifts. Latency and amplitude measures of VR2 differed under the various experimental conditions. These results demonstrate that there are two responses to pitch-shift stimuli. The first is relatively automatic but may be modulated by instructions to the participant. The second response is probably a voluntary one.

The present study tested whether subjects respond to unanticipated short perturbations in voice loudness feedback with compensatory responses in voice amplitude. The role of stimulus magnitude (±1,3 vs 6 dB SPL), stimulus direction (up vs down), and the ongoing voice amplitude level (normal vs soft) were compared across compensations. Subjects responded to perturbations in voice loudness feedback with a compensatory change in voice amplitude 76% of the time. Mean latency of amplitude compensation was 157 ms. Mean response magnitudes were smallest for 1-dB stimulus perturbations (0.75 dB) and greatest for 6-dB conditions (0.98 dB). However, expressed as gain, responses for 1-dB perturbations were largest and almost approached 1.0. Response magnitudes were larger for the soft voice amplitude condition compared to the normal voice amplitude condition. A mathematical model of the audio-vocal system captured the main features of the compensations. Previous research has demonstrated that subjects can respond to an unanticipated perturbation in voice pitch feedback with an automatic compensatory response in voice fundamental frequency. Data from the present study suggest that voice loudness feedback can be used in a similar manner to monitor and stabilize voice amplitude around a desired loudness level.

Overview. Neurologists are frequently called upon to evaluate patients with vertigo and dizziness and, in some cases, to make sense of abnormal vestibular tests. Consequently, it is useful to have some familiarity with the methods used to test vestibular function.The vestibulo-ocular reflex (VOR) is a reflex that acts at short latency to generate eye movements that compensate for head rotations in order to preserve clear vision during locomotion. The VOR is the most accessible gauge of vestibular function. Evaluating the VOR requires application of a vestibular stimulus and measurement of the resulting eye movements.This report reviews the advantages and limitations of the methods of stimulating the vestibular system: caloric irrigation, rotational chair testing, and auto-rotational testing. Vestibular testing in children is given additional consideration because of the paucity of recent reviews on the topic. This report will not address eye movement recording techniques, the neurophysiology of the VOR, which is reviewed elsewhere, 1,2 or interpretation of nystagmus.Literature review. This evidence-based assessment was developed from a review of published articles obtained through the MEDLINE database of the National Library of Medicine. Relevant publications were rated by the strength of evidence according to a scheme approved by the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology (see Appendix 2).

Previous studies have shown that voice fundamental frequency (F0) is modified by changes in the pitch of vocal feedback and have demonstrated that the audio-vocal control system has both open- and closed-loop control properties. However, the extent to which this system operates in closed-loop fashion may have been underestimated in previous work. Because the step-type stimuli used were very rapid, and people are physically unable to change their voice F0 as rapidly as the stimuli, feedback responses might have been reduced or suppressed. In the present study, pitch-shift stimuli, consisting of a disparity between voice F0 and feedback pitch of varying ramp onset velocities, were presented to subjects vocalizing a steady /ah/ sound to examine the effect of stimulus onset on voice F0 responses. Results showed that response velocity covaried with stimulus velocity. Response latency and time of the peak response decreased with increases in stimulus velocity, while response magnitude decreased. A simple feedback model reproduced most features of these responses. These results strongly support previous suggestions that the audio-vocal system monitors auditory feedback and, through closed-loop negative feedback, adjusts voice F0 so as to cancel low-level fluctuations in F0.

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This article describes the clinical features of anterior semicircular canal benign paroxysmal positional vertigo (AC-BPPV) and a new therapeutic maneuver for its management. Our study was a retrospective review of cases from an ambulatory tertiary referral center. Thirteen patients afflicted with positional paroxysmal vertigo exhibiting brief positional down-beating nystagmus in positional tests (Dix-Hallpike and head-hanging position) were treated with a maneuver comprised of the following movements: Sequential head positioning beginning supine with head hanging 30 degrees dependent with respect to the body, then supine with head inclined 30 degrees forward, and ending sitting with head 30 degrees forward. All cases showed excellent therapeutic response to our repositioning procedure, i.e. relief of vertigo and elimination of nystagmus. The maneuver described is an option for AC-BPPV treatment.