Hearing loss and history of otolaryngological conditions in adults with microdeletion 22q11.2.

Previous studies have shown that the 22q11.2 microdeletion, associated with 22q11.2 deletion syndrome (22q11.2DS), conveys an increased risk of chronic otitis media, and hearing loss at young age. This study reports on hearing loss and history of otolaryngological conditions in adults with 22q11.2DS. We conducted a retrospective study of 60 adults with 22q11.2DS (41.7% male) at median age 25 (range 16-74) years who had visited an otolaryngologist and audiologist for routine assessment at a 22q11.2 expert center. Demographic, genetic, audiometric, and otolaryngological data were systematically extracted from the medical files. Regression analysis was used to evaluate the effect of age, sex, full-scale intelligence quotient, and history of chronic otitis media on the severity of hearing loss. Hearing loss, mostly high-frequency sensorineural, was found in 78.3% of adults. Higher age and history of chronic otitis media were associated with more severe hearing loss. Otolaryngological conditions with possible treatment implications included chronic otitis media (56.7%), globus pharyngeus (18.3%), balance problems (16.7%), and obstructive sleep apnea (8.3%). The results suggest that  in 22q11.2DS, high-frequency hearing loss appears to be common from a young adult age, and often unrecognized. Therefore, we recommend periodic audiometric screening in all adults, including high-frequency ranges.

The influence of static eye and head position on the ventriloquist effect.

Orienting responses to audiovisual events have shorter reaction times and better accuracy and precision when images and sounds in the environment are aligned in space and time. How the brain constructs an integrated audiovisual percept is a computational puzzle because the auditory and visual senses are represented in different reference frames: the retina encodes visual locations with respect to the eyes; whereas the sound localisation cues are referenced to the head. In the well-known ventriloquist effect, the auditory spatial percept of the ventriloquist's voice is attracted toward the synchronous visual image of the dummy, but does this visual bias on sound localisation operate in a common reference frame by correctly taking into account eye and head position? Here we studied this question by independently varying initial eye and head orientations, and the amount of audiovisual spatial mismatch. Human subjects pointed head and/or gaze to auditory targets in elevation, and were instructed to ignore co-occurring visual distracters. Results demonstrate that different initial head and eye orientations are accurately and appropriately incorporated into an audiovisual response. Effectively, sounds and images are perceptually fused according to their physical locations in space independent of an observer's point of view. Implications for neurophysiological findings and modelling efforts that aim to reconcile sensory and motor signals for goal-directed behaviour are discussed.

Absence of compensation for vestibular-evoked passive head rotations in human sound localization.

A world-fixed sound presented to a moving head produces changing sound-localization cues, from which the audiomotor system could infer sound movement relative to the head. When appropriately combined with self-motion signals, sound localization remains spatially accurate. Indeed, free-field orienting responses fully incorporate intervening eye-head movements under open-loop localization conditions. Here we investigate the default strategy of the audiomotor system when localizing sounds in the absence of efferent and proprioceptive head-movement signals. Head- and body-restrained listeners made saccades in total darkness toward brief (3, 10 or 100 ms) broadband noise bursts, while being rotated sinusoidally (f=1/9 Hz, V(peak) =112 deg/s) around the vertical body axis. As the loudspeakers were attached to the chair, the 100 ms sounds might be perceived as rotating along with the chair, and localized in head-centred coordinates. During 3 and 10 ms stimuli, however, the amount of chair rotation remained well below the minimum audible movement angle. These brief sounds would therefore be perceived as stationary in space and, as in open-loop gaze orienting, expected to be localized in world-centred coordinates. Analysis of the saccades shows, however, that all stimuli were accurately localized on the basis of imposed acoustic cues, but remained in head-centred coordinates. These results suggest that, in the absence of motor planning, the audio motor system keeps sounds in head-centred coordinates when unsure about sound motion relative to the head. To that end, it ignores vestibular canal signals of passive-induced head rotation, but incorporates intervening eye displacements from vestibular nystagmus during the saccade-reaction time.

Absence of spatial updating when the visuomotor system is unsure about stimulus motion.

How does the visuomotor system decide whether a target is moving or stationary in space or whether it moves relative to the eyes or head? A visual flash during a rapid eye-head gaze shift produces a brief visual streak on the retina that could provide information about target motion, when appropriately combined with eye and head self-motion signals. Indeed, double-step experiments have demonstrated that the visuomotor system incorporates actively generated intervening gaze shifts in the final localization response. Also saccades to brief head-fixed flashes during passive whole-body rotation compensate for vestibular-induced ocular nystagmus. However, both the amount of retinal motion to invoke spatial updating and the default strategy in the absence of detectable retinal motion remain unclear. To study these questions, we determined the contribution of retinal motion and the vestibular canals to spatial updating of visual flashes during passive whole-body rotation. Head- and body-restrained humans made saccades toward very brief (0.5 and 4 ms) and long (100 ms) visual flashes during sinusoidal rotation around the vertical body axis in total darkness. Stimuli were either attached to the chair (head-fixed) or stationary in space and were always well localizable. Surprisingly, spatial updating only occurred when retinal stimulus motion provided sufficient information: long-duration stimuli were always appropriately localized, thus adequately compensating for vestibular nystagmus and the passive head movement during the saccade reaction time. For the shortest stimuli, however, the target was kept in retinocentric coordinates, thus ignoring intervening nystagmus and passive head displacement, regardless of whether the target was moving with the head or not.

The effect of head roll on perceived auditory zenith.

We studied the influence of static head roll on the perceived auditory zenith in head-centred and world-centred coordinates. Subjects sat either upright, or with their head left/right rolled sideways by about 35° relative to gravity, whilst judging whether a broadband sound was heard left or right from the head-centred or world-centred zenith. When upright, these reference frames coincide. Results show that subjects judged the zenith accurately within different planes, although response variability increased for the midsagittal plane. With the head rolled, head-centred auditory zenith shifted by the same amount and was located as accurately as for upright, indicating unaltered localisation cues by head-on-body roll. Interestingly, when judging world-centred zenith subjects made large systematic errors (10-15°) in the direction of head roll, and response variability increased, which resembles the visual Aubert effect. These results demonstrate a significant influence of the vestibular-collic system on auditory spatial awareness, which sheds new light on the mechanisms underlying multisensory integration and spatial updating in sound localisation behaviour.

Eye position determines audiovestibular integration during whole-body rotation.

When a sound is presented in the free field at a location that remains fixed to the head during whole-body rotation in darkness, it is heard displaced in the direction opposing the rotation. This phenomenon is known as the audiogyral illusion. Consequently, the subjective auditory median plane (AMP) (the plane where the binaural difference cues for sound localization are perceived to be zero) shifts in the direction of body rotation. Recent experiments, however, have suggested opposite AMP results when using a fixation light that also moves with the head. Although in this condition the eyes remain stationary in the head, an ocular pursuit signal cancels the vestibulo-ocular reflex, which could induce an additional AMP shift. We tested whether the AMP is influenced by vestibular signals, eye position or eye velocity. We rotated subjects sinusoidally at different velocities, either in darkness or with a head-fixed fixation light, while they judged the laterality (left vs. right with respect to the midsagittal plane of the head) of broadband sounds presented over headphones. Subjects also performed the same task without vestibular stimulation while tracking a sinusoidally moving visual target, which mimicked the average eye-movement patterns of the vestibular experiments in darkness. Results show that whole-body rotation in darkness induces a shift of the AMP in the direction of body rotation. In contrast, we obtained no significant AMP change when a fixation light was used. The pursuit experiments showed a shift of the AMP in the direction of eccentric eye position but not at peak pursuit velocity. We therefore conclude that the vestibular-induced shift in average eye position underlies both the audiogyral illusion and the AMP shift.