Deafness alters the spatial mapping of touch.

Auditory input plays an important role in the development of body-related processes. The absence of auditory input in deafness is understood to have a significant, and even irreversible, impact on these processes. The ability to map touch on the body is an important element of body-related processing. In this research, the crossed-arm temporal order judgment (TOJ) task was used to evaluate the spatial mapping of touch. This task elicits a conflict between visual and somatosensory body-related information through a change in posture. We used the crossed-arm TOJ task to evaluate the spatial mapping of touch in deaf participants. Results suggested that a change in posture had a greater impact on congenitally deaf participant TOJ than for hearing participants. This provides the first evidence for the role of early auditory exposure on spatial mapping of touch. More importantly, most deaf participants had auditory prosthetics which provided auditory input. This suggests an important, and possibly irreversible, impact of early auditory deprivation on this body-related process.

Long-Term Musical Training Alters Tactile Temporal-Order Judgment.

Long-term musical training is an enriched multisensory training environment that can alter uni- and multisensory substrates and abilities. Amongst these altered abilities are faster reaction times for simple and complex sensory tasks. The crossed arm temporal-order judgement (TOJ) task is a complex tactile task in which TOJ error rate increases when arms are crossed. Reaction times (RTs) for this task are typically proportionate to the difficulty of the stimulus onset asynchrony (SOA) and increase more when the arms are crossed than when uncrossed. The objective of this study was to study the impact of musical training on RTs and accuracy for the crossed arm TOJ task. Seventeen musicians and 20 controls were tested. Musicians had significantly faster RTs for all crossed arm conditions and half of the uncrossed conditions. However, musicians had significantly more TOJ errors for the crossed posture. We speculate that faster musician TOJ RTs leave little time to consolidate conflicting internal and external task-related information when crossing the arms, leading to increased incorrect responses. These results provide novel insights on the potential mechanisms underlying the increased TOJ error rates when arms are crossed. Moreover, they add to the growing literature of altered sensory ability in musicians and propose an unexpected consequence of faster reaction times.

The effects of brief swaying on postural control.

Postural control can be improved with balance training. However, the nature and duration of the training required to enhance posture remains unclear. We studied the effects of 5 min of a self-initiated balance exercise along a single axis on postural control in healthy individuals. Postural control was measured before and after a 5-min period where members of the experimental group were asked to lean their entire body forward and backward and members of the control group were asked to remain seated. A significant improvement for sway velocity, a postural control variable significantly associated with an increased risk of falls, was found in the experimental group following the body sway exercise. These data suggest that a basic exercise can rapidly improve postural control and reduce the risk of falls.

Dichotic Listening Deficit Associated With Solvent Exposure.

HYPOTHESIS: A significant left ear deficit can be observed in solvent-exposed individuals using the dichotic digit test. BACKGROUND: Solvents are ubiquitous in global industrial processes. Due to their lipophilic nature, solvents can adversely affect large white matter tracks such as the corpus callosum. Previous investigations reveal that long-term workplace exposure to solvents is also deleterious to various auditory processes. Investigations in exposed populations suggest a decreased performance for dichotic listening. METHODS: In this present study, we examined the lateralization of a dichotic digit test score for 49 solvent-exposed individuals along with 49 age- and sex-matched controls. We evaluated group differences between test scores and the right ear advantage using a laterality index (LI). RESULTS: Individual ear results suggest that long-term workplace solvent exposure is associated with a significantly lower dichotic listening score for the left ear. A binaural compound score analysis using a laterality index supports this left-ear deficit. CONCLUSION: These results provide an insight on the effects of solvent exposure on dichotic listening abilities. Further research should investigate the importance of using dichotic listening tasks to screen for solvent-induced auditory dysfunction in exposed individuals.

Sensory reweighting after loss of auditory cues in healthy adults.

We maintain our balance using information provided by the visual, somatosensory, and vestibular systems on the position of our body in space. Recent evidence has suggested that auditory input also plays a significant role for postural control, yet further investigations are required to better understand the contributions of audition to this process in healthy adults. To date, the process of sensory reweighting when auditory cues are disturbed during postural control has been overlooked. The aim of this study is to determine the impact of hearing protection on sensory reweighting for postural control in healthy adults. For this, we studied 14 healthy adults on a force platform using four different postural conditions either with or without attenuation of auditory cues. Our results suggest that disturbing auditory cues increases the reliance on visual cues for postural control. This is the first study to demonstrate such a sensory reweighting occurs in the event of a sudden disturbance of auditory cues in healthy adults.

Ear Fullness as a Symptom of Endolymphatic Hydrops in non-Ménière's Patient.

OBJECTIVE: 1) To determine if unexplained ear fullness might be a symptom of endolymphatic hydrops (EH) by using Electrocochleography (ECochG) SP/AP area and amplitude ratios. 2) To assess if individuals with unexplained ear fullness without vertigo differ significantly from individuals with ear fullness due to Ménière's disease (MD). MATERIALS AND METHODS: In a case-control study in our tertiary care center, we evaluated 62 ears across 49 patients, including 18 normal healthy ears across 12 control patients, 26 ears with unexplained ear fullness across 20 patients (6 had bilateral symptoms of ear fullness), and 18 ears with definite MD across 17 patients (1 bilateral disease). Outcome measures were SP/AP amplitude and area ratio, hearing threshold, and air-bone gap. RESULTS: The analysis of auditory thresholds revealed a significant group effect for air conduction [F(2,50)=49.627; p<0.001] and for bone conduction [F(2,50)=45.625; p<0.001]. We observed significant differences between MD (36.36±4.87) and control patients (19.85±2.55) (p=0.015) for amplitude ratio. Moreover, significant differences were noted between MD (5.32±1.06) and controls (1.36±0.07) (p=0.035) and between ear fullness (5.16±1.17) and controls (p=0.026) for the area ratio parameter. No significant correlation was observed between SP/AP area or amplitude ratios and air-bone gap at any of the tested frequencies. The amplitude ratio was not significantly different between the ear fullness and control groups (p=0.406). The area and amplitude ratios did not reveal significant differences between MD and ear fullness (p=1.00). CONCLUSION: EH can be present even in the absence of vertigo and when patients report unexplained ear fullness. This study, to our knowledge, is the first to possibly allow early identification of cochlear EH in patients suffering from ear fullness without vertigo.

Musicians react faster and are better multisensory integrators.

The results from numerous investigations suggest that musical training might enhance how senses interact. Despite repeated confirmation of anatomical and structural changes in visual, tactile, and auditory regions, significant changes have only been reported in the audiovisual domain and for the detection of audio-tactile incongruencies. In the present study, we aim at testing whether long-term musical training might also enhance other multisensory processes at a behavioural level. An audio-tactile reaction time task was administrated to a group of musicians and non-musicians. We found significantly faster reaction times with musicians for auditory, tactile, and audio-tactile stimulations. Statistical analyses between the combined uni- and multisensory reaction times revealed that musicians possess a statistical advantage when responding to multisensory stimuli compared to non-musicians. These results suggest for the first time that long-term musical training reduces simple non-musical auditory, tactile, and multisensory reaction times. Taken together with the previous results from other sensory modalities, these results strongly point towards musicians being better at integrating the inputs from various senses.

Temporal and spectral audiotactile interactions in musicians.

Previous investigations have revealed that the complex sensory exposure of musical training alters audiovisual interactions. As of yet, there has been little evidence on the effects of musical training on audiotactile interactions at a behavioural level. Here, we tested audiotactile interaction in musicians using the audiotactile illusory flash and the parchment-skin illusion. Significant differences were only found between musicians and non-musicians for the audiotactile illusory flash. Both groups had similar task-relevant unisensory abilities, but unlike non-musicians, the number of auditory stimulations did not have a statistically important influence on the number of perceived tactile stimulations for musicians. Musicians and non-musicians similarly perceived the parchment-skin illusion. Spectral alterations of self-generated palmar sounds similarly altered the perception of wetness and dryness for both groups. These results suggest that musical training does not seem to alter multisensory interactions at large. The specificity of the sensory enhancement suggests that musical training specifically alters processes underlying the interaction of temporal audiotactile stimuli and not the global interaction between these modalities. These results are consistent with previous unisensory and multisensory investigations on sensory abilities related to audiotactile processing in musicians.

Short-term visual deprivation can enhance spatial release from masking.

This research aims to study the effect of short-term visual deprivation on spatial release from masking, a major component of the cocktail party effect that allows people to detect an auditory target in noise. The Masking Level Difference (MLD) test was administered on healthy individuals over three sessions: before (I) and after 90min of visual deprivation (II), and after 90min of re-exposure to light (III). A non-deprived control group performed the same tests, but remained sighted between sessions I and II. The non-deprived control group displayed constant results across sessions. However, performance in the MLD test was improved following short-term visual deprivation and performance returned to pre-deprivation values after light re-exposure. This study finds that short-term visual deprivation transiently enhances the spatial release from masking. These data suggest the significant potential for enhancing a process involved in the cocktail party effect in normally developing individuals and adds to an emerging literature on the potential to enhance auditory ability after only a brief period of visual deprivation.

The Effects of Aging on Clinical Vestibular Evaluations.

Balance disorders are common issues for aging populations due to the effects of normal aging on peripheral vestibular structures. These changes affect the results of vestibular function evaluations and make the interpretation of these results more difficult. The objective of this article is to review the current state of knowledge of clinically relevant vestibular measures. We will first focus on otolith function assessment methods cervical-VEMP (cVEMP) and ocular-VEMP (oVEMP), then the caloric and video-head impulse test (vHIT) methods for semicircular canals assessment. cVEMP and oVEMP are useful methods, though research on the effects of age for some parameters are still inconclusive. vHIT results are largely independent of age as compared to caloric stimulation and should therefore be preferred for the evaluation of the semicircular canals function.

Auditory imagery forces motor action.

A large number of neuroimaging studies have investigated imagined sensory processing and motor behaviours. These studies have reported neural activation patterns for imagined processes that resemble those of real sensory and motor events. The widespread use of such methods has raised questions about the extent to which imagined sensorimotor events mimic their overt counterparts, including their ability to elicit sensorimotor interactions. Direct behavioural evidence of imagery-induced multisensory interactions has been found recently in tasks involving auditory and visual processing. An influence of sensory imagery on the control of motor action, however, has not been investigated previously. Here, we show that both real and imagined moving sounds induce involuntary ocular movement in a nonvisual tracking task. The present data build on the results of previous studies of sensory imagery by showing that such conditions activate sensory neural areas. Moreover, we show an engagement of functional sensorimotor networks for imagined stimuli in a manner similar to the processing of real auditory stimuli.

Audiotactile interaction can change over time in cochlear implant users.

Recent results suggest that audiotactile interactions are disturbed in cochlear implant (CI) users. However, further exploration regarding the factors responsible for such abnormal sensory processing is still required. Considering the temporal nature of a previously used multisensory task, it remains unclear whether any aberrant results were caused by the specificity of the interaction studied or rather if it reflects an overall abnormal interaction. Moreover, although duration of experience with a CI has often been linked with the recovery of auditory functions, its impact on multisensory performance remains uncertain. In the present study, we used the parchment-skin illusion, a robust illustration of sound-biased perception of touch based on changes in auditory frequencies, to investigate the specificities of audiotactile interactions in CI users. Whereas individuals with relatively little experience with the CI performed similarly to the control group, experienced CI users showed a significantly greater illusory percept. The overall results suggest that despite being able to ignore auditory distractors in a temporal audiotactile task, CI users develop to become greatly influenced by auditory input in a spectral audiotactile task. When considered with the existing body of research, these results confirm that normal sensory interaction processing can be compromised in CI users.

Short-term visual deprivation improves the perception of harmonicity.

Neuroimaging studies have shown that the perception of auditory stimuli involves occipital cortical regions traditionally associated with visual processing, even in the absence of any overt visual component to the task. Analogous behavioral evidence of an interaction between visual and auditory processing during purely auditory tasks comes from studies of short-term visual deprivation on the perception of auditory cues, however, the results of such studies remain equivocal. Although some data have suggested that visual deprivation significantly increases loudness and pitch discrimination and reduces spatial localization inaccuracies, it is still unclear whether such improvement extends to the perception of spectrally complex cues, such as those involved in speech and music perception. We present data demonstrating that a 90-min period of visual deprivation causes a transient improvement in the perception of harmonicity: a spectrally complex cue that plays a key role in music and speech perception. The results provide clear behavioral evidence supporting a role for the visual system in the processing of complex auditory stimuli, even in the absence of any visual component to the task.

Temporary deafness can impair multisensory integration: a study of cochlear-implant users.

Previous investigations suggest that temporary deafness can have a dramatic impact on audiovisual speech processing. The aim of this study was to test whether temporary deafness disturbs other multisensory processes in adults. A nonspeech task involving an audiotactile illusion was administered to a group of normally hearing individuals and a group of individuals who had been temporarily auditorily deprived. Members of this latter group had their auditory detection thresholds restored to normal levels through the use of a cochlear implant. Control conditions revealed that auditory and tactile discrimination capabilities were identical in the two groups. However, whereas normally hearing individuals integrated auditory and tactile information, so that they experienced the audiotactile illusion, individuals who had been temporarily deprived did not. Given the basic nature of the task, failure to integrate multisensory information could not be explained by the use of the cochlear implant. Thus, the results suggest that normally anticipated audiotactile interactions are disturbed following temporary deafness.