Active Head Rotation Research Articles

The precision of signals encoding active self-movement.

Everyday actions like moving the head, walking around, and grasping objects are typically self-controlled. This presents a problem when studying the signals encoding such actions because active self-movement is difficult to control experimentally. Available techniques demand repeatable trials, but each action is unique, making it difficult to measure fundamental properties like psychophysical thresholds. We present a novel paradigm that recovers both precision and bias of self-movement signals with minimal constraint on the participant. The paradigm relies on linking image motion to previous self-movement, and two experimental phases to extract the signal encoding the latter. The paradigm takes care of a hidden source of external noise not previously accounted for in techniques that link display motion to self-movement in real time (e.g., virtual reality). We use head rotations as an example of self-movement, and show that the precision of the signals encoding head movement depends on whether they are being used to judge visual motion or auditory motion. We find that perceived motion is slowed during head movement in both cases. The "nonimage" signals encoding active head rotation (motor commands, proprioception, and vestibular cues) are therefore biased toward lower speeds and/or displacements. In a second experiment, we trained participants to rotate their heads at different rates and found that the imprecision of the head rotation signal rises proportionally with head speed (Weber's law). We discuss the findings in terms of the different motion cues used by vision and hearing, and the implications they have for Bayesian models of motion perception.NEW & NOTEWORTHY We present a psychophysical technique for measuring the precision of signals encoding active self-movements. Using head movements, we show that 1) precision is greater when active head rotation is performed using visual comparison stimuli versus auditory; 2) precision decreases with head speed (Weber's law); 3) perceived speed is lower during head rotation. The findings may reflect the steps needed to convert different cues into common units, and challenge standard Bayesian models of motion perception.

Incongruent active head rotations increase visual motion detection thresholds.

Attributing a visual motion signal to its correct source-be that external object motion, self-motion, or some combination of both-seems effortless, and yet often involves disentangling a complex web of motion signals. Existing literature focuses on either translational motion (heading) or eye movements, leaving much to be learnt about the influence of a wider range of self-motions, such as active head rotations, on visual motion perception. This study investigated how active head rotations affect visual motion detection thresholds, comparing conditions where visual motion and head-turn direction were either congruent or incongruent. Participants judged the direction of a visual motion stimulus while rotating their head or remaining stationary, using a fixation-locked Virtual Reality display with integrated head-movement recordings. Thresholds to perceive visual motion were higher in both active-head rotation conditions compared to stationary, though no differences were found between congruent or incongruent conditions. Participants also showed a significant bias to report seeing visual motion travelling in the same direction as the head rotation. Together, these results demonstrate active head rotations increase visual motion perceptual thresholds, particularly in cases of incongruent visual and active vestibular stimulation.

Short-term learning of the vestibulo-ocular reflex induced by a custom interactive computer game.

Retinal image slip during head rotation drives motor learning in the rotational vestibulo-ocular reflex (VOR) and forms the basis of gaze-stability exercises that treat vestibular dysfunction. Clinical exercises, however, are unengaging, cannot easily be titrated to the level of impairment, and provide neither direct feedback nor tracking of the patient's adherence, performance, and progress. To address this, we have developed a custom application for VOR training based on an interactive computer game. In this study, we tested the ability of this game to induce VOR learning in individuals with normal vestibular function, and we compared the efficacy of single-step and incremental learning protocols. Eighteen participants played the game twice on different days. All participants tolerated the game and were able to complete both sessions. The game scenario incorporated a series of brief head rotations, similar to active head impulses, that were paired with a dynamic acuity task and with a visual-vestibular mismatch (VVM) intended to increase VOR gain (single-step: 300 successful trials at ×1.5 viewing; incremental: 100 trials each of ×1.13, ×1.33, and ×1.5 viewing). Overall, VOR gain increased by 15 ± 4.7% (mean ± 95% CI, P < 0.001). Gains increased similarly for active and passive head rotations, and, contrary to our hypothesis, there was little effect of the learning strategy. This study shows that an interactive computer game provides robust VOR training and has the potential to deliver effective, engaging, and trackable gaze-stability exercises to patients with a range of vestibular dysfunctions.NEW & NOTEWORTHY This study demonstrates the feasibility and efficacy of a customized computer game to induce motor learning in the high-frequency rotational vestibulo-ocular reflex. It provides a physiological basis for the deployment of this technology to clinical vestibular rehabilitation.

Does somatosensory feedback from the plantar foot sole contribute to verticality perception?

Aim of the study In upright standing, the human foot sole is the only point of contact with the ground conveying information about the pressure distribution under the feet. We examined how the altered somatosensory input from the plantar foot receptors, when standing on a soft surface, affects the subjective estimation of the earth vertical in different sensory contexts. Materials and methods Twelve (12) healthy young females (mean age: 21.8 ± 2.4 years) adjusted the orientation of a visual line (35 × 1.5 cm) representing the roll orientation of a hand-held (attached on a 24.9 × 4 cm cylinder) or head-attached electromagnetic tracking sensor (Nest of Birds, Ascension Technologies Inc., VT. USA, 60 Hz) under two visual conditions (eyes open, eyes closed) while standing on a soft or firm surface. The mean absolute (accuracy) and variable (precision) error in the verticality estimate was depicted in the sensor’s roll deviation from the gravitational vertical. Results The accuracy and the precision of the estimate decreased in the absence of vision, while standing on the soft surface and when the estimate was provided by an active hand rather than head rotation. The surface effect was significant only in the absence of vision and when the estimate was provided by the hand. Conclusions The contribution of the plantar foot mechanoreceptors to gravity perception is sensory context dependent. Perception of the earth vertical is more accurate when estimated by active head rotation due to the integration of the vestibular and neck proprioceptive afferents.

Gaze shift dynamic visual acuity: A functional test of gaze stability that distinguishes unilateral vestibular hypofunction.

BACKGROUND:Embedded within most rapid head rotations are gaze shifts, which is an initial eye rotation to a target of interest, followed by a head rotation towards the same target. Gaze shifts are used to acquire an image that initially is outside of the participant’s current field of vision. Currently, there are no tools available that evaluate the functional relevance of a gaze shift.OBJECTIVE:The purpose of our study was to measure dynamic visual acuity (DVA) while performing a gaze shift.METHODS:Seventy-one healthy participants (42.79±16.89 years) and 34 participants with unilateral vestibular hypofunction (UVH) (54.59±20.14 years) were tested while wearing an inertial measurement unit (IMU) sensor on the head and walking on a treadmill surrounded by three monitors. We measured visual acuity during three subcomponent tests: standing (static visual acuity), while performing an active head rotation gaze shift, and an active head rotation gaze shift while walking (gsDVAw).RESULTS:While doing gsDVAw, patients with Left UVH (n = 21) had scores worse (p = 0.023) for leftward (0.0446±0.0943 LogMAR) head rotation compared with the healthy controls (–0.0075±0.0410 LogMAR). Similarly, patients with right UVH (N = 13) had worse (p = 0.025) gsDVAw for rightward head motion (0.0307±0.0481 LogMAR) compared with healthy controls (–0.0047±0.0433 LogMAR). As a whole, gsDVAw scores were worse in UVH compared to the healthy controls when we included the ipsilesional head rotation on both sides gsDVAw (0.0061±0.0421 LogMAR healthy vs. 0.03926±0.0822 LogMAR UVH, p = 0.003). Controlling for age had no effect, the gsDVAw scores of the patients were always worse (p < 0.01).CONCLUSION:The gaze shift DVA test can distinguish gaze stability in patients with UVH from healthy controls. This test may be a useful measure of compensation for patients undergoing various therapies for their vestibular hypofunction.

Improvement After Vestibular Rehabilitation Not Explained by Improved Passive VOR Gain.

Gaze stability exercises are a critical component of vestibular rehabilitation for individuals with vestibular hypofunction and many studies reveal the rehabilitation improves functional performance. However, few studies have examined the vestibular physiologic mechanisms (semicircular canal; otolith) responsible for such recovery after patients with vestibular hypofunction complete gaze and gait stability exercises. The purpose of this study was to compare behavioral outcome measures (i.e., visual acuity during head rotation) with physiological measures (i.e., gain of the vestibulo-ocular reflex) of gaze stability following a progressive vestibular rehabilitation program in patients following unilateral vestibular deafferentation surgery (UVD). We recruited n = 43 patients (n = 18 female, mean 52 ± 13 years, range 23–80 years) after unilateral deafferentation from vestibular schwannoma; n = 38 (25 female, mean 46.9 ± 15.9 years, range 22–77 years) age-matched healthy controls for dynamic visual acuity testing, and another n = 28 (14 female, age 45 ± 17, range 20–77 years) healthy controls for video head impulse testing. Data presented is from n = 19 patients (14 female, mean 48.9 ± 14.7 years) with UVD who completed a baseline assessment ~6 weeks after surgery, 5 weeks of vestibular physical therapy and a final measurement. As a group, subjective and fall risk measures improved with a meaningful clinical relevance. Dynamic visual acuity (DVA) during active head rotation improved [mean ipsilesional 38.57% ± 26.32 (n = 15/19)]; mean contralesional 39.96% ± 22.62 (n = 12/19), though not uniformly. However, as a group passive yaw VOR gain (mean ipsilesional pre 0.44 ± 0.18 vs. post 0.44 ± 0.15; mean contralesional pre 0.81 ± 0.19 vs. post 0.85 ± 0.09) did not show any change (p ≥ 0.4) after rehabilitation. The velocity of the overt compensatory saccades during ipsilesional head impulses were reduced after rehabilitation; no other metric of oculomotor function changed (p ≥ 0.4). Preserved utricular function was correlated with improved yaw DVA and preserved saccular function was correlated with improved pitch DVA. Our results suggest that 5 weeks of vestibular rehabilitation using gaze and gait stability exercises improves both subjective and behavioral performance despite absent change in VOR gain in a majority of patients, and that residual otolith function appears correlated with such change.

Human vestibulo-ocular reflex adaptation is frequency selective

The vestibulo-ocular reflex (VOR) is the only system that maintains stable vision during rapid head rotations. The VOR gain (eye/head velocity) can be trained to increase using a vestibular-visual mismatch stimulus. We sought to determine whether low-frequency (sinusoidal) head rotation during training leads to changes in the VOR during high-frequency head rotation testing, where the VOR is more physiologically relevant. We tested eight normal subjects over three sessions. For training protocol 1, subjects performed active sinusoidal head rotations at 1.3 Hz while tracking a laser target, whose velocity incrementally increased relative to head velocity so that the VOR gain required to stabilize the target went from 1.1 to 2 over 15 min. Protocol 2 was the same as protocol 1, except that head rotations were at 0.5 Hz. For protocol 3, head rotation frequency incrementally increased from 0.5 to 2 Hz over 15 min, while the VOR gain required to stabilize the target was kept at 2. We measured the active and passive, sinusoidal (1.3Hz) and head impulse VOR gains before and after each protocol. Sinusoidal and head impulse VOR gains increased in protocols 1 and 3; however, although the sinusoidal VOR gain increase was ~20%, the related head impulse gain increase was only ~10%. Protocol 2 resulted in no-gain adaptation. These data show human VOR adaptation is frequency selective, suggesting that if one seeks to increase the higher-frequency VOR response, i.e., where it is physiologically most relevant, then higher-frequency head movements are required during training, e.g., head impulses.NEW & NOTEWORTHY This study shows that human vestibulo-ocular reflex adaptation is frequency selective at frequencies >0.3 Hz. The VOR in response to mid- (1.3 Hz) and high-frequency (impulse) head rotations were measured before and after mid-frequency sinusoidal VOR adaptation training, revealing that the mid-frequency gain change was higher than high-frequency gain change. Thus, if one seeks to increase the higher-frequency VOR response, where it is physiologically most relevant, then higher-frequency head movements are required during training.

New advances regarding adaptation of the vestibulo-ocular reflex.

This is a review summarizing the development of vestibulo-ocular reflex (VOR) adaptation behavior with relevance to rehabilitation over the last 10 years and examines VOR adaptation using head-on-body rotations, specifically the influence of training target contrast, position and velocity error signal, active vs. passive head rotations, and sinusoidal vs. head impulse rotations. This review discusses optimization of the single VOR adaptation training session, consolidation between repeated training sessions, and dynamic incremental VOR adaptation. Also considered are the effects of aging and the roles of the efferent vestibular system, cerebellum, and otoliths on angular VOR adaptation. Finally, this review examines VOR adaptation findings in studies using whole body rotations.

Functional Head Impulse Testing Might Be Useful for Assessing Vestibular Compensation After Unilateral Vestibular Loss.

Background: Loss of the vestibulo-ocular reflex (VOR) affects visual acuity during head movements. Previous studies have shown that compensatory eye-saccades improve visual acuity and that the timing of the saccade is important. Most of the tests involved in testing VOR are made with passive head movement, that do not necessarily reflect the activities of daily living and thus not being proportionate to symptoms and distresses of the patients.Objective: To examine differences between active (self-generated) or passive (imposed by the examiner) head rotations while trying to maintain visual focus on a target.Method: Nine subjects with unilateral total vestibular loss were recruited (4 men and 5 women, mean age 47) and tested with video Head Impulse Test (vHIT) and Head Impulse Testing Device-Functional Test (HITD-FT) during passive and active movements while looking at a target. VOR gain, latencies of covert saccades, frequency of covert saccades and visual acuity were measured and analyzed.Results: Active head-impulses toward the lesioned side resulted in better visual acuity (p = 0.002) compared to conventional passive head-impulses and generated eye-saccades with significantly shorter latencies (p = 0.004). Active movements to the lesioned side generated dynamic visual acuities that were as good as when testing the intact side.Conclusion: Actively generated head impulses resulted in normal dynamic visual acuity, even when performed toward the side of total vestibular loss. This might be attributed to the appearance of short-latency covert saccades. The results show a strong relationship between self-generated movements, latencies of covert saccades and outcome in HITD-FT, i.e., a better dynamic visual function with less retinal slip which is the main function of the VOR. The method of active HITD-FT might be valuable in assessing vestibular compensation and monitoring ongoing vestibular rehabilitation.

Developmental Changes in the Effect of Active Left and Right Head Rotation on Random Number Generation.

Numbers are thought to be spatially organized along a left-to-right horizontal axis with small/large numbers on its left/right respectively. Behavioral evidence for this mental number line (MNL) comes from studies showing that the reallocation of spatial attention by active left/right head rotation facilitated the generation of small/large numbers respectively. While spatial biases in random number generation (RNG) during active movement are well established in adults, comparable evidence in children is lacking and it remains unclear whether and how children’s access to the MNL is affected by active head rotation. To get a better understanding of the development of embodied number processing, we investigated the effect of active head rotation on the mean of generated numbers as well as the mean difference between each number and its immediately preceding response (the first order difference; FOD) not only in adults (n = 24), but also in 7- to 11-year-old elementary school children (n = 70). Since the sign and absolute value of FODs carry distinct information regarding spatial attention shifts along the MNL, namely their direction (left/right) and size (narrow/wide) respectively, we additionally assessed the influence of rotation on the total of negative and positive FODs regardless of their numerical values as well as on their absolute values. In line with previous studies, adults produced on average smaller numbers and generated smaller mean FODs during left than right rotation. More concretely, they produced more negative/positive FODs during left/right rotation respectively and the size of negative FODs was larger (in terms of absolute value) during left than right rotation. Importantly, as opposed to adults, no significant differences in RNG between left and right head rotations were observed in children. Potential explanations for such age-related changes in the effect of active head rotation on RNG are discussed. Altogether, the present study confirms that numerical processing is spatially grounded in adults and suggests that its embodied aspect undergoes significant developmental changes.

A unified internal model theory to resolve the paradox of active versus passive self-motion sensation.

Brainstem and cerebellar neurons implement an internal model to accurately estimate self-motion during externally generated ('passive') movements. However, these neurons show reduced responses during self-generated ('active') movements, indicating that predicted sensory consequences of motor commands cancel sensory signals. Remarkably, the computational processes underlying sensory prediction during active motion and their relationship to internal model computations during passive movements remain unknown. We construct a Kalman filter that incorporates motor commands into a previously established model of optimal passive self-motion estimation. The simulated sensory error and feedback signals match experimentally measured neuronal responses during active and passive head and trunk rotations and translations. We conclude that a single sensory internal model can combine motor commands with vestibular and proprioceptive signals optimally. Thus, although neurons carrying sensory prediction error or feedback signals show attenuated modulation, the sensory cues and internal model are both engaged and critically important for accurate self-motion estimation during active head movements.

Alteration of neck proprioceptive capacity in women with fibromyalgia

Fibromyalgia (FM) is a syndrome whose primary symptoms include chronic widespread muscle pain and fatigue. Muscles of neck and shoulder are often painful and fatigable. According to the literature, pain and fatigue of the muscles of the neck can induce proprioceptive troubles. The aim of this study was to determine if patients with FM have more often a reduction of neck proprioceptive capacity. We compared individuals affected by fibromyalgia to healthy individuals without any cervical problems. Cervicocephalic Relocation Test was used to determine deficit of proprioception. Head repositioning absolute value of the global error (AE) was calculated after 20 active head rotations (10 right, 10 left). According to Revel (1991), the cut-off of 4.5° error has been chosen. After calculation of the necessary sample size (power 80%), an overall of 20 subjects were included in the study (10 in each group), they were from 27 to 68 years old. The 10 healthy subjects showed normal AE. Their AE was 2.5 ± 1.0° (m ± SD). Five of the 10 FM patients showed deficit ( P < 0.01) with AE > 4.5°. Mean AE of FM patients was 4.5 ± 1.3° (median = 4.7°). Fibromyalgia Impact Questionnaire score was 47.5 ± 17.6. It would be interesting to pursue the study to seek a global proprioception alteration within subjects who suffer from fibromyalgia. Postural deficit described in literature could be occurred by proprioceptive deficit. Moreover, it would be also interesting to see the effects of a rehabilitation targeted on proprioception, pain and tiredness.

Perception of active head rotation in patients with severe left unilateral spatial neglect

Unilateral spatial neglect is a common neurological syndrome following predominantly right hemisphere damage, and is characterized by a failure to perceive and report stimuli in the contralesional side of space. To test the reference shift hypothesis that contralesional spatial neglect in right-brain-damaged patients is attributed to a rightward deviation of the egocentric reference frame, we measured the final angular position to which controls and left-side neglect patients actively turned their head toward the left in response to a verbal instruction given from each of three locations—right, left, and front—in two conditions, with and without visual feedback. When neglect patients were asked to “look straight ahead”, they deviated about 30° toward the right in the eyes-open condition. However, the rightward deviation was markedly reduced in the eyes-closed condition. Regardless of visual feedback, there was no significant difference between controls and neglect patients in the final angular position of active head rotation when the verbal instruction came from the subject’s left or front side; however, the final angular position was significantly smaller in the neglect patients than in the controls when the verbal instruction was given from the right. These results support the contention that cervico-vestibular stimulation during active head rotation restores spatial remapping and sensori-motor correlations and so improves neglect without affecting the position of the egocentric reference; however, once left-side neglect patients respond to verbal instruction from the right side, they are unable to disengage attention from the hemispace, and the performance of head rotation is disturbed.

A 1-Diopter Vertical Prism Induces a Decrease of Head Rotation: A Pilot Investigation.

Clinical studies in non-specific chronic arthralgia and back pain seem to indicate an association between vertical heterophoria (VH – latent vertical retinal misalignment) and asymmetrical head rotation. Such clinical observations suggest a link between VH and head rotation, but this was never tested. The purpose of this study was to simulate a VH in healthy subjects and examine its influence on the amplitude of active head rotation during 3D motion capture in upright stance. Subjects were asked to rotate their head three times from the straight ahead position and then to the right, back to straight ahead, to the left, and back to the straight ahead again. Three randomized conditions were run: normal viewing, with a 1-diopter prism base down on the dominant eye, or the non-dominant eye. The most important finding is that the experimental VH whichever the eye with the prism induces a significant decrease in the mean angle of head rotation compared to the normal viewing condition. This decrease was significant for rotation to the left. We suggest that the prism-induced VH modifies the reference posture and thereby affects head rotation; further studies are needed to confirm this effect and to extend to other types of dynamic activities.

Visual afference mediates head and trunk stability in vestibular hypofunction

Humans must maintain head and trunk stability while walking. The purpose of this study was to compare the kinematics of healthy controls and patients with vestibular hypofunction (VH) when walking and making head rotations of different frequencies in both light and dark conditions. We recruited eight individuals with VH and nine healthy control subjects to perform four tasks at their preferred gait speed, being normal walk, walking and making yaw head rotations at 1.5Hz and 2Hz, and walking in the dark and making yaw head rotations at 1.5Hz. Linear kinematics as well as head, trunk, and pelvis angular velocities were captured using the Vicon motion analysis system (Vicon Motion Systems, Oxford, UK). We found no difference in walking velocities for any of the four walking conditions across groups. The lateral displacement of the center of mass was increased in VH patients. In the dark, patients had more head instability in pitch (larger amplitudes and velocities) even though they were walking and making active yaw head rotations. Patients also had a smaller relative phase angle (mean 3.50±standard deviation 2.13°) than controls (mean 10.31±standard deviation 2.70°) (p<0.01). Our data suggest that patients with VH have difficulty walking with a straight trajectory when turning their head. Additionally, patients with VH have an abnormal excursion of spontaneous pitch head rotation while walking and making active yaw head turns, which is dependent on vision. Rehabilitation for these patients should consider applying unique head rotation frequencies when training gait with head turns as well as alternating their exposure to light.

Utilization of oculomotor therapies in the treatment of vertigo originating from mild traumatic brain injury

Event Abstract Back to Event Utilization of oculomotor therapies in the treatment of vertigo originating from mild traumatic brain injury Beau Arrieta1 and Susan E. Esposito1* 1 Life University, United States Background: A 25-year-old caucasian female chiropractor presented with mild traumatic brain injury following an automobile accident. Subsequent to being struck, her vehicle was thrown into a right multi-rotational spin. The patient complained of extreme vertigo, fatigue, and difficulty falling asleep which collectively precluded her ability to work. Magnetic resonance imaging and computerized tomography scans were unremarkable. Methods: A neurological exam revealed a right accommodation spasm that inhibited normal ocular divergence. It was ascertained that she was able to generate appropriate reflexive responses to optokinetic stimuli up to a maximum distance of 2.5 feet. Notably, optokinetic stimulation at a distance beyond 2.5 feet, administered in any direction, elicited a vertiginous response. Optokinetic stimulation at a distance exceeding 2.5 feet produced a reduction in both fast- and slow-phase eye movements with a positive correlation between distance-to-stimulus and level of diminution. Treatment consisted of weekly 2-hour sessions, for 4 weeks. Numerous oculomotor therapies were utilized including: (1) passively activated times-one viewing vertical gaze stability exercises tracking a distancing target; (2) horizontal pursuits tracking a distancing sinusoidal target; and (3) rightward optokinetic stimulation with an in-phase target coupled with active head rotation in-phase with the optokinetic target. Results: Post-treatment evaluation revealed restoration of normal ocular divergence and reinstatement of appropriate optokinetic reflexes at all distances. Optokinetic stimulation no longer induced vertiginous responses at any distance or in any direction. Additionally, the patient reported that her fatigue and sleeping complications had subsided, and she was able to return to work. Conclusion: The positive outcome of this case demonstrates that the utilization of oculomotor therapies can be efficacious in the treatment of vertigo due to mild traumatic brain injury. We recommend further investigation into the use of oculomotor therapies in the treatment of vertigo originating from mild traumatic brain injury. Keywords: Traumatic Brain Injury, Chiropractic, oculomotor therapy, Vertigo, Fatigue Conference: International Symposium on Clinical Neuroscience: Clinical Neuroscience for Optimization of Human Function, Orlando, United States, 7 Oct - 9 Oct, 2016. Presentation Type: Poster Presentation Topic: Abstracts ISCN 2016 Citation: Arrieta B and Esposito SE (2016). Utilization of oculomotor therapies in the treatment of vertigo originating from mild traumatic brain injury. Front. Neurol. Conference Abstract: International Symposium on Clinical Neuroscience: Clinical Neuroscience for Optimization of Human Function. doi: 10.3389/conf.fneur.2016.59.00005 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 28 Aug 2016; Published Online: 07 Sep 2016. * Correspondence: Dr. Susan E Esposito, Life University, Marietta, Ga, 30144, United States, susanesposito@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Beau Arrieta Susan E Esposito Google Beau Arrieta Susan E Esposito Google Scholar Beau Arrieta Susan E Esposito PubMed Beau Arrieta Susan E Esposito Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Updating and orientation in auditory space

For stable sound localization in space, a listener has to account for self-motion. This requires a head-to-world coordinate transformation by combining proprioceptive and vestibular inputs with the binaural cues for sound localization. Proprioceptive and vestibular information influence the evaluation of spatial auditory cues as indicated by the numerous proprioceptive and vestibular neural inputs into the auditory brainstem. First, we evaluate the relative influence of vestibular and proprioceptive cues on updating the world-centered position of auditory targets during active and passive head and/or body rotations in azimuth. Our results show that both vestibular and proprioceptive signals are used to update the spatial representations of auditory targets, but that vestibular inputs contribute more than proprioceptive inputs. Second, we explore the interplay of spatial audition and self-motion in subjects for which auditory space evaluation is of utmost importance, namely, for blind humans relying on ech...

The Oculus Rift: a cost-effective tool for studying visual-vestibular interactions in self-motion perception.

For years now, virtual reality devices have been applied in the field of vision science in an attempt to improve our understanding of perceptual principles underlying the experience of self-motion. Some of this research has been concerned with exploring factors involved in the visually-induced illusory perception of self-motion, known as vection. We examined the usefulness of the cost-effective Oculus Rift in generating vection in seated observers. This device has the capacity to display optic flow in world coordinates by compensating for tracked changes in 3D head orientation. We measured vection strength in three conditions of visual compensation for head movement: compensated, uncompensated, and inversely compensated. During presentation of optic flow, the observer was instructed to make periodic head oscillations (±22° horizontal excursions at approximately 0.53 Hz). We found that vection was best in the compensated condition, and was weakest in the inversely compensated condition. Surprisingly, vection was always better in passive viewing conditions, compared with conditions where active head rotations were performed. These findings suggest that vection is highly dependent on interactions between visual, vestibular and proprioceptive information, and may be highly sensitive to limitations of temporal lag in visual-vestibular coupling using this system.

The Control of Postural Stability during Standing is Decreased in Stroke Patients during Active Head Rotation.

[Purpose] The aim of this study was to evaluate the effect of active head rotation on postural control in stroke patients during standing as compared with age-matched healthy subjects. [Subjects and Methods] In total, 46 stroke patients and 37 age-matched healthy subjects were recruited for the study. A stabilometer was used to assess postural stability in participants during standing, with or without active head rotation, and with their eyes open or closed. Subjects were asked to stand on a force plate while rotating their head in the yaw plane at a frequency of 1.0 Hz. A metronome was used to maintain the head rotation frequency, and the head rotation range was maintained at a total of 70° during the postural stability examinations. [Results] The control of postural stability during standing with active head rotation was significantly decreased in the stroke group as compared with the healthy group with both the eyes open and closed. No significant differences in relation to standing without head motion were observed between groups. [Conclusion] The findings suggest that postural instability is increased in stroke patients during active head rotation, and therefore, vestibular function in relation to head rotation might be reduced in stroke patients.

Minimum audible angle at the subjective front during listener’s active and passive head rotation

Listener’s head movement, particularly horizontal rotation, effectively improves sound localization acuity (Wallach, 1939; Thurlow, 1967; Kawaura, 1989). However, few findings have been obtained concerning sound localization during head rotation. In the present study, we directly investigated the minimum audible angle (MAA) at the front during horizontal rotation. A sound stimulus (30-ms noise burst) was presented from a loudspeaker of a circular array (r = 1.1 m), with a loudspeaker separation of 2.5 degrees. The listener, sitting at the center of the circle, was asked to answer whether the sound stimulus was presented from the left or right of the subjective front (2AFC). We designed three listening conditions, static, active rotation and passive rotation. In the static condition, listeners were asked to keep their heads still. For the active rotation condition, listeners were asked to rotate their heads. Meanwhile, for the passive rotation condition, listeners sitting on a revolving chair were rotated by an experimenter. In the latter two conditions, the test stimulus was triggered during head movement. Results showed the MAA to deteriorate significantly in the two rotation conditions. This implies that the improvements in sound localization due to head motion could be explained by the multiple-look model (Viemeister, 1991).