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"Hearing - physiology"
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Assistive listening devices drive neuroplasticity in children with dyslexia
Children with dyslexia often exhibit increased variability in sensory and cognitive aspects of hearing relative to typically developing peers. Assistive listening devices (classroom FM systems) may reduce auditory processing variability by enhancing acoustic clarity and attention. We assessed the impact of classroom FM system use for 1 year on auditory neurophysiology and reading skills in children with dyslexia. FM system use reduced the variability of subcortical responses to sound, and this improvement was linked to concomitant increases in reading and phonological awareness. Moreover, response consistency before FM system use predicted gains in phonological awareness. A matched control group of children with dyslexia attending the same schools who did not use the FM system did not show these effects. Assistive listening devices can improve the neural representation of speech and impact reading-related skills by enhancing acoustic clarity and attention, reducing variability in auditory processing.
Journal Article
Enhancement of Visual Motion Detection Thresholds in Early Deaf People
In deaf people, the auditory cortex can reorganize to support visual motion processing. Although this cross-modal reorganization has long been thought to subserve enhanced visual abilities, previous research has been unsuccessful at identifying behavioural enhancements specific to motion processing. Recently, research with congenitally deaf cats has uncovered an enhancement for visual motion detection. Our goal was to test for a similar difference between deaf and hearing people. We tested 16 early and profoundly deaf participants and 20 hearing controls. Participants completed a visual motion detection task, in which they were asked to determine which of two sinusoidal gratings was moving. The speed of the moving grating varied according to an adaptive staircase procedure, allowing us to determine the lowest speed necessary for participants to detect motion. Consistent with previous research in deaf cats, the deaf group had lower motion detection thresholds than the hearing. This finding supports the proposal that cross-modal reorganization after sensory deprivation will occur for supramodal sensory features and preserve the output functions.
Journal Article
Identification of the Spectrotemporal Modulations That Support Speech Intelligibility in Hearing-Impaired and Normal-Hearing Listeners
Purpose: Age-related sensorineural hearing loss can dramatically affect speech recognition performance due to reduced audibility and suprathreshold distortion of spectrotemporal information. Normal aging produces changes within the central auditory system that impose further distortions. The goal of this study was to characterize the effects of aging and hearing loss on perceptual representations of speech. Method: We asked whether speech intelligibility is supported by different patterns of spectrotemporal modulations (STMs) in older listeners compared to young normal-hearing listeners. We recruited 3 groups of participants: 20 older hearing-impaired (OHI) listeners, 19 age-matched normal-hearing listeners, and 10 young normal-hearing (YNH) listeners. Listeners performed a speech recognition task in which randomly selected regions of the speech STM spectrum were revealed from trial to trial. The overall amount of STM information was varied using an up-down staircase to hold performance at 50% correct. Ordinal regression was used to estimate weights showing which regions of the STM spectrum were associated with good performance (a \"classification image\" or CImg). Results: The results indicated that (a) large-scale CImg patterns did not differ between the 3 groups; (b) weights in a small region of the CImg decreased systematically as hearing loss increased; (c) CImgs were also nonsystematically distorted in OHI listeners, and the magnitude of this distortion predicted speech recognition performance even after accounting for audibility; and (d) YNH listeners performed better overall than the older groups. Conclusion: We conclude that OHI/older normal-hearing listeners rely on the same speech STMs as YNH listeners but encode this information less efficiently.
Journal Article
A Melodic Contour Repeatedly Experienced by Human Near-Term Fetuses Elicits a Profound Cardiac Reaction One Month after Birth
Human hearing develops progressively during the last trimester of gestation. Near-term fetuses can discriminate acoustic features, such as frequencies and spectra, and process complex auditory streams. Fetal and neonatal studies show that they can remember frequently recurring sounds. However, existing data can only show retention intervals up to several days after birth.
Here we show that auditory memories can last at least six weeks. Experimental fetuses were given precisely controlled exposure to a descending piano melody twice daily during the 35(th), 36(th), and 37(th) weeks of gestation. Six weeks later we assessed the cardiac responses of 25 exposed infants and 25 naive control infants, while in quiet sleep, to the descending melody and to an ascending control piano melody. The melodies had precisely inverse contours, but similar spectra, identical duration, tempo and rhythm, thus, almost identical amplitude envelopes. All infants displayed a significant heart rate change. In exposed infants, the descending melody evoked a cardiac deceleration that was twice larger than the decelerations elicited by the ascending melody and by both melodies in control infants.
Thus, 3-weeks of prenatal exposure to a specific melodic contour affects infants 'auditory processing' or perception, i.e., impacts the autonomic nervous system at least six weeks later, when infants are 1-month old. Our results extend the retention interval over which a prenatally acquired memory of a specific sound stream can be observed from 3-4 days to six weeks. The long-term memory for the descending melody is interpreted in terms of enduring neurophysiological tuning and its significance for the developmental psychobiology of attention and perception, including early speech perception, is discussed.
Journal Article
Auditory Resting-State Network Connectivity in Tinnitus: A Functional MRI Study
The underlying functional neuroanatomy of tinnitus remains poorly understood. Few studies have focused on functional cerebral connectivity changes in tinnitus patients. The aim of this study was to test if functional MRI \"resting-state\" connectivity patterns in auditory network differ between tinnitus patients and normal controls. Thirteen chronic tinnitus subjects and fifteen age-matched healthy controls were studied on a 3 tesla MRI. Connectivity was investigated using independent component analysis and an automated component selection approach taking into account the spatial and temporal properties of each component. Connectivity in extra-auditory regions such as brainstem, basal ganglia/NAc, cerebellum, parahippocampal, right prefrontal, parietal, and sensorimotor areas was found to be increased in tinnitus subjects. The right primary auditory cortex, left prefrontal, left fusiform gyrus, and bilateral occipital regions showed a decreased connectivity in tinnitus. These results show that there is a modification of cortical and subcortical functional connectivity in tinnitus encompassing attentional, mnemonic, and emotional networks. Our data corroborate the hypothesized implication of non-auditory regions in tinnitus physiopathology and suggest that various regions of the brain seem involved in the persistent awareness of the phenomenon as well as in the development of the associated distress leading to disabling chronic tinnitus.
Journal Article
Onset Asynchrony: Cue to Aid Dichotic Vowel Segregation in Listeners With Normal Hearing and Hearing Loss
Purpose: The effect of onset asynchrony on dichotic vowel segregation and identification in normal-hearing (NH) and hearing-impaired (HI) listeners was examined. We hypothesized that fusion would decrease and identification performance would improve with increasing onset asynchrony. Additionally, we hypothesized that HI listeners would gain more benefit from onset asynchrony. Method: A total of 18 adult subjects (nine NH, nine HI) participated. Testing included dichotic presentation of synthetic vowels, /i/, /u/, /a/, and /ae/. Vowel pairs were presented with the same or different fundamental frequency (f[subscript o]; f[subscript o] = 106.9,151.2, or 201.8 Hz) across the two ears and one onset asynchrony of 0, 1, 2, 4,10, or 20 ms throughout a block (one block = 80 runs). Subjects identified the one or two vowels that they perceived on a touchscreen. Subjects were not informed that two vowels were always presented or that there was onset asynchrony. Results: The effect of onset asynchrony on fusion and vowel identification was greatest in both groups when [delta]f[subscript o] = 0 Hz. Mean fusion scores across increasing onset asynchronies differed significantly between the two groups with HI listeners exhibiting less fusion across pooled [delta]f[subscript o]. There was no significant difference with identification performance. Conclusions: As onset asynchrony increased, dichotic vowel fusion decreased and identification performance improved. Onset asynchrony exerted a greater effect on fusion and identification of vowels when [delta]f[subscript o] = 0, especially in HI listeners. Therefore, the temporal cue promotes segregation in both groups of listeners, especially in HI listeners when the f[subscript o] cue was unavailable.
Journal Article
Nicotine enhances auditory processing in healthy and normal-hearing young adult nonsmokers
RationaleElectrophysiological studies show that systemic nicotine narrows frequency receptive fields and increases gain in neural responses to characteristic frequency stimuli. We postulated that nicotine enhances related auditory processing in humans.ObjectivesThe main hypothesis was that nicotine improves auditory performance. A secondary hypothesis was that the degree of nicotine-induced improvement depends on the individual’s baseline performance.MethodsYoung (18–27 years old), normal-hearing nonsmokers received nicotine (Nicorette gum, 6mg) or placebo gum in a single-blind, randomized, crossover design. Subjects performed four experiments involving tone-in-noise detection, temporal gap detection, spectral ripple discrimination, and selective auditory attention before and after treatment. The perceptual differences between posttreatment nicotine and placebo conditions were measured and analyzed as a function of the pre-treatment baseline performance.ResultsNicotine significantly improved performance in the more difficult tasks of tone-in-noise detection and selective attention (effect size = − 0.3) but had no effect on relatively easier tasks of temporal gap detection and spectral ripple discrimination. The two tasks showing significant nicotine effects further showed no baseline-dependent improvement.ConclusionsNicotine improves auditory performance in difficult listening situations. The present results support future investigation of nicotine effects in clinical populations with auditory processing deficits or reduced cholinergic activation.
Journal Article
Spectral content (colour) of noise exposure affects work efficiency
Introduction: As part of an effort to enhance the efficiency of workers, experiments relating to three types of noise exposure were conducted. Previous studies have proved that pink noise can cause a brain wave to reach a lower potential. In this study, we utilized physical methods, in cognitive experiments, to understand the impacts that three colour noises have on working efficiency. Subjects and Methods: All 22 participants were exposed to a sound environment of quiet, red, pink and white noises respectively. After a laboratory experiment, details of psychomotor speed, continuous performance, executive function and working memory were recorded. Results: Red, pink and white noises were significantly positive in comparison with the quiet environment of the psychomotor speed test. As for the continuous performance test, pink noise gave the only significantly positive result. Red, pink and white noise resulted in a better executive function test. Red and pink noise showed significantly positive improvement, while white noise was significantly positive in comparison with the quiet environment of the working memory test. In addition, the results from the comfort questionnaires showed that red and pink noise increase the possibility of better judgment, implementation, and overall environment. Conclusion: At present time, it is considered that noise has negative effects on hearing and health. However, experimental results show that certain noise can enhance environmental comfort. It is feasible, in the future, to use knowledge of colour noises to improve productivity in a workplace with a healthy environment.
Journal Article