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PubMed2006

Rehabilitation plasticity: influence of hearing aid fitting on frequency discrimination performance near the hearing-loss cut-off.

Several studies have already demonstrated that patients with steeply sloping hearing loss of cochlear origin exhibit an improvement in frequency discrimination performance at or around the cut-off frequency. This enhancement cannot be explained in terms of peripheral mechanisms and should rather be interpreted in terms of central reorganization: i.e., injury-induced cortical plasticity. However, the reversibility and time course of such reorganization has not yet been described. The main goal of the present study was therefore to investigate the occurrence of rehabilitation plasticity associated with hearing-aid fitting in human subjects. Nine subjects with steeply sloping hearing loss and who were candidates for auditory rehabilitation were tested. Discrimination-limen-for-frequency (DLF) enhancement was investigated at the frequency with the best DLF (bDLF) for each individual subject before and during auditory rehabilitation (at 1 month, 3 months and 6 months). From 1 month on, frequency discrimination performance decreased significantly at the bDLF frequency, while remaining stable at other frequencies. This normalization may reflect a new central reorganization reversing the initial injury-induced changes in the cortical map. A correlation between subject's age and alteration in DLF at 1 month was also found, suggesting that plasticity operates faster in younger patients.

Adult↗
PubMed2006

Effects of sound level on fMRI activation in human brainstem, thalamic and cortical centers.

The dependence of fMRI activation on sound level was examined throughout the auditory pathway of normal human listeners using continuous broadband noise, a stimulus widely used in neuroscientific investigations of auditory processing, but largely neglected in neuro-imaging. Several specialized techniques were combined here for the first time to enhance detection of brainstem activation, mitigate scanner noise, and recover temporal resolution lost by the mitigation technique. The main finding was increased activation with increasing level in cochlear nucleus, superior olive, inferior colliculus, medial geniculate body and auditory cortical areas. We suggest that these increases reflect monotonically increasing activity in a preponderance of individual auditory neurons responsive to broadband noise. While the time-course of activation changed with level, the change was subtle and only significant in a part of the cortex. To our knowledge, these are the first fMRI data showing the effects of sound level in subcortical centers or for a non-tonal, non-speech stimulus at any stage of the pathway. The present results add to the body of parametric data in normal human listeners and are fundamental to the design of any fMRI experiment employing continuous noise.

Acoustic Stimulation↗
PubMed2006

Effects of pulse rate on thresholds and loudness of biphasic and alternating monophasic pulse trains in electrical hearing.

Detection thresholds and most comfortable loudnesses (MCLs) were determined as a function of pulse rate for standard biphasic pulse trains (BP) and for anodic and cathodic monophasic phases alternating at fixed intervals (ALT-m). Three different phase durations were examined. With a 100-micros phase duration, thresholds for the ALT-m stimulus were substantially (up to 12 dB) lower than for the BP stimuli at relatively low rates (200 pps), but were similar to the BP thresholds at high rates (1000 pps). Thresholds for BP pulse trains decreased monotonically with increasing rate, whereas the function for ALT-m waveforms was non-monotonic with a maximum between 400 and 1000 pps. These trends occurred for three different cochlear implant devices, different electrode configurations, and, generally, for different phase durations (10.8, 25, and 100 micros/phase). However, at the shorter phase durations, thresholds remained lower for the ALT-m stimulus, even at 5000 pps, the highest rate studied. Dynamic ranges of the BP pulse trains increased with increasing rate, irrespective of the phase duration under test, but for the ALT-m stimuli this was only true at the shorter phase durations tested. At a 100-mus phase duration, dynamic ranges for the ALT-m waveforms did not differ significantly as a function of rate. The results confirm previous reports that delaying charge recovery, in this case by switching from a BP to an ALT-m wave shape, can substantially reduce thresholds [Van Wieringen, A., Carlyon, R.P., Laneau, J., Wouters, J., 2005. Effects of waveform shape on human sensitivity to electrical stimulation of the inner ear. Hear. Res. 200, 73-86; Carlyon, R.P., van Wieringen, A., Deeks, J.M., Long, C.J., Lyzenga, J, Wouters, J., 2005. Effect of inter-phase gap on the sensitivity of cochlear implant users to electrical stimulation. Hear. Res. 205, 210-224]. However, at high pulse rates, this advantage only occurs at short phase durations. In addition, we show that the complex interaction between the effects of pulse shape, rate, and phase duration on thresholds can be captured by the simple linear model described by Carlyon et al.

Adult↗
PubMed2006

Dead regions in the cochlea and enhancement of frequency discrimination: Effects of audiogram slope, unilateral versus bilateral loss, and hearing-aid use.

Following a restricted lesion of the cochlea, which produces a "dead region" (DR), animal experiments have revealed an increase in the cortical representation of frequencies just below the edge frequency (f(e)) of the DR. This may result in improved difference limens for frequency (DLFs) just below f(e). In previous studies to assess this, the value of f(e) was not determined precisely. We measured DLFs using human subjects with DRs for whom the values of f(e) had been determined precisely using psychophysical tuning curves. To prevent use of loudness cues, stimuli for the measurement of DLFs had a mean level falling along an equal-loudness contour and levels were roved over a 12-dB range. DLFs were measured for thirteen subjects with a DR in at least one ear. Almost all subjects with bilateral hearing loss exhibited enhanced DLFs near f(e), consistent with cortical reorganisation. This occurred for subjects whose audiograms had both steep and shallow slopes, regardless of hearing aid use, and for two subjects with low-frequency DRs. One subject with a high-frequency DR in one ear and good hearing in the other ear showed an enhanced DLF in her better ear.

Acoustic Stimulation↗
PubMed2007

An electrophysiological endophenotype of hypomanic and hyperthymic personality.

BACKGROUND: Hyperthymic Temperament (HYT) and a closely related trait, Hypomanic Personality (HYP), have both been related to bipolar affective disorder (BAD). Intensity dependence of auditory evoked potentials (IAEP) is a suggested inverse indicator of serotonergic neurotransmission and has been found to be elevated in BAD. Therefore the present study explored for the first time whether subclinical variance of HYT/HYP is also associated with IAEP in a healthy sample. As several traits from biological personality research are correlated with HYT/HYP and also with BAD, the specificity of results against these traits was further analyzed by calculating multiple regression analyses. METHODS: Evoked potentials were recorded from a sample (N=87) homogenous for confounding variables influencing IAEP. For this reason, only 19 to 27-year-old non-smoker psychiatrically healthy male students were included. RESULTS: Significant correlations were found between IAEP and both HYP and HYT. Including Sensation or Novelty Seeking and Extraversion in Regression Analyses did not weaken the associations of HYP with IAEP much, but did affect those of HYT. However, these competing biological personality traits were hardly able to predict IAEP themselves. Impulsivity, though, was able to reduce the predictive power of HYP and HYT and to explain unique IAEP-variance. This was even more the case for Behavioral-Activation-System-Sensitivity (BAS) subscale Fun Seeking clearly dominating all regression analyses. LIMITATIONS: Homogeneity of sample. CONCLUSIONS: The impact of BAS is in agreement with the assumption that heightened BAS-sensitivity is an underlying biological cause for HYP/HYT and for BAD. Future studies on BAD should include BAS and Impulsivity besides HYP/HYT to further explore uniqueness of the latter and to develop questionnaires based on those items of a hyperthymic-hypomanic-impulsive-funseeking item pool, which possess the most external validity.

Adult↗
PubMed2005

Relationship between masking levels and phonatory stability in normal-speaking women.

Disruption of auditory feedback such as masking has been shown to influence vocal production. A reliable finding is an increase in intensity level; an increase in fundamental frequency (F0) is a less robust finding. Research is lacking concerning the effects of auditory masking on measures of phonatory stability such as jitter and harmonics-to-noise ratio (HNR). This study investigated changes in intensity, F0, jitter, and HNR in 22 normally speaking college aged women. Subjects produced the vowel /a/ under three conditions: no masking level (0-dB ML), 50-dB ML, and 80-dB ML. Significant differences between conditions emerged for intensity; means for the other measures were not significantly different. Intraindividual differences between conditions for each variable are discussed in the framework of auditory versus kinesthetic feedback.

Adult↗
PubMed2003

Musical structure is processed in "language" areas of the brain: a possible role for Brodmann Area 47 in temporal coherence.

The neuroanatomical correlates of musical structure were investigated using functional magnetic neuroimaging (fMRI) and a unique stimulus manipulation involving scrambled music. The experiment compared brain responses while participants listened to classical music and scrambled versions of that same music. Specifically, the scrambled versions disrupted musical structure while holding low-level musical attributes constant, including the psychoacoustic features of the music such as pitch, loudness, and timbre. Comparing music to its scrambled counterpart, we found focal activation in the pars orbitalis region (Brodmann Area 47) of the left inferior frontal cortex, a region that has been previously closely associated with the processing of linguistic structure in spoken and signed language, and its right hemisphere homologue. We speculate that this particular region of inferior frontal cortex may be more generally responsible for processing fine-structured stimuli that evolve over time, not merely those that are linguistic.

Acoustic Stimulation↗
PubMed2004

Systematic latency variation of the auditory evoked M100: from average to single-trial data.

Standard analyses of neurophysiologically evoked response data rely on signal averaging across many epochs associated with specific events. The amplitudes and latencies of these averaged events are subsequently interpreted in the context of the given perceptual, motor, or cognitive tasks. Can such critical timing properties of event-related responses be recovered from single-trial data? Here, we make use of the M100 latency paradigm used in previous magnetoencephalography (MEG) research to evaluate a novel single-trial analysis approach. Specifically, the latency of the auditory evoked M100 varies systematically with stimulus frequency over a well-defined time range (lower frequencies, e.g., 125 Hz, yield up to 25 ms longer latencies than higher frequencies, e.g., 1000 Hz). Here, we show that the complex filtering approach to single-trial analysis recovers this key characteristic of the M100 response, as well as some other important response properties relating to lateralization. The results illustrate (i) the utility of the complex filtering method and (ii) the potential of the M100 latency to be used for stimulus encoding, since the relevant variation can be observed in single trials.

Acoustic Stimulation↗
PubMed2004

Sound frequency representation in cat auditory cortex.

Using the intrinsic signal optical recording technique, we reconstructed the two-dimensional pattern of stimulus-evoked neuronal activities in the auditory cortex of anesthetized and paralyzed cats. The average magnitude of intrinsic signal in response to a pure tone stimulus increased steadily as the sound pressure level increased. A detailed analysis demonstrated that the evoked signals at early frames were scaled by the sound pressure level, which in turn indicated the presence of a minimum level of sound pressure beyond which stimulus-related intrinsic signal can be generated. Intrinsic signals evoked significantly by pure tone stimuli of different frequencies were localized and arranged in an orderly manner in the middle ectosylvian gyrus, which indicates that the primary auditory field (AI) is tonotopically organized. The arrangement of optimal frequencies obtained from optical recordings of the same auditory cortex, which were conducted on different days, was highly reproducible. Furthermore, other auditory fields surrounding AI in the recorded area were allocated based on the observed tonotopicity. We also conducted unit recordings on the cats used for optical recording with the same set of acoustic stimuli. The gross feature of the arrangement of optimal frequencies determined by unit recordings agreed with the tonotopic arrangement determined by the optical recording, although the precise agreement was not obtained.

Acoustic Stimulation↗
PubMed2006

Gamma-band activity dissociates between matching and nonmatching stimulus pairs in an auditory delayed matching-to-sample task.

Electro- and magnetoencephalography studies have suggested that increased gamma-band activity (GBA) is a correlate of activated neural stimulus representations. In this study, a delayed matching-to-sample paradigm for auditory spatial information was employed to investigate the role of magnetoencephalographic gamma-band activity in the differentiation between matching and nonmatching stimulus pairs. Twelve subjects made same-different judgments about the lateralization angle of pairs of filtered noise stimuli (S1 and S2) presented with 0.8-s delays. One half of the subjects had to respond to matching stimulus pairs, the other half to nonmatching stimulus pairs. Cortical oscillatory activity in the memory task was compared to a control task requiring the detection of background noise intensity changes. Memory-related GBA increases were revealed over midline parietal areas in the middle of the delay phase and during the presentation of S2 and over frontocentral areas at the end of the delay phase. This replicated previous findings. In addition, nonmatching trials were associated with increased GBA over right parietal areas in response to S2. The midline parietal GBA increase during S2 in the memory condition may have reflected the representation of S1 needed for a comparison between S1 and S2. When S1 and S2 were identical, no further representation was required. In contrast, for nonmatching pairs, a second representation was activated over right parietal areas.

Adult↗
PubMed2006

Increased event-related theta activity as a psychophysiological marker of comorbidity in children with tics and attention-deficit/hyperactivity disorders.

OBJECTIVE: The question as to whether coexisting tic disorder (TD) and attention-deficit/hyperactivity disorder (ADHD) in children represent a combination of two independent pathologies, a separate nosologic entity manifested by both tics and hyperactivity or a phenotype subgroup of one of the two major clinical forms has received increasing attention. The aim of the present study was to classify the TD+ADHD comorbidity in the neurocognitive domain and to elucidate the neurophysiological background of TD+ADHD coexistence by analyzing event-related electroencephalographic (EEG) oscillations in the theta (3-7.5 Hz) frequency band. METHODS: Event-related potentials were recorded at 10 electrodes in 53 children (9-13 years old) from four groups (healthy controls, TD-only, ADHD-only, and combined TD+ADHD patients), while they performed an auditory selective attention task requiring a button press to a predefined target. Event-related theta oscillations were analyzed by means of time-frequency decomposition (wavelet analysis) in two latency ranges-early (0-200 ms) and late (200-450 ms). The effects of psychopathology factors (TD and ADHD) and task variables (attended channel and stimulus task relevance) on early (ETR) and late (LTR) theta responses were evaluated statistically. Theta response measures were further correlated with psychopathology scores and spontaneous theta EEG activity. RESULTS: (1) The ETR was enhanced only in comorbid children and did not differ between the control, TD-only, and ADHD-only groups. (2) The LTR was larger in children with ADHD (ADHD-only and comorbid), but this effect was mediated by the spontaneous theta EEG activity. (3) The ETR was larger to attended stimuli at frontal-central electrodes contralateral to the side of attention, to the target stimulus type at frontal locations, and at the hemisphere contralateral to the side of the response. The functional reactivity and scalp distribution of ETRs were modulated by psychopathological factors. CONCLUSIONS: In the neurocognitive domain, the TD+ADHD comorbidity can be identified as a unique nosologic entity. Both the spontaneous theta activity and late event-related theta oscillations appear as neurophysiological markers of the ADHD condition. In children, the early event-related theta oscillations may be associated with representations of relevant target features in working memory. SIGNIFICANCE: (1) A new model is proposed according to which TD+ADHD comorbidity can be classified at different levels (from neurobiological to cognitive). (2) The functional significance of stimulus-synchronized theta oscillations in children is described for the first time.

Adolescent↗
PubMed2006

Frequency organization of the 40-Hz auditory steady-state response in normal hearing and in tinnitus.

We used the 40-Hz auditory steady-state response (SSR) to compare for the first time tonotopic frequency representations in the region of primary auditory cortex (PAC) between subjects with chronic tinnitus and hearing impairment and normal hearing controls. Frequency representations were measured in normal hearing (n=17) and tinnitus (n=28) subjects using eight carrier frequencies between 384 and 6561 Hz, each amplitude modulated (AM) at 40-Hz on trials of 3 min duration under passive attention. In normal hearing subjects, frequency gradients were observed in the medial-lateral, anterior-posterior, and inferior-superior axes, which were consistent with the orientation of Heschl's gyrus and with functional organization revealed by fMRI investigations. The frequency representation in the right hemisphere was approximately 5 mm anterior and approximately 7 mm lateral to that in the left hemisphere, corroborating with MEG measurements hemispheric asymmetries reported by cytoarchitectonic studies of the PAC and by MRI morphometry. In the left hemisphere, frequency gradients were inflected near 2 kHz in normal hearing subjects. These SSR frequency gradients were attenuated in both hemispheres in tinnitus subjects. Dipole power was also elevated in tinnitus, suggesting that more neurons were entrained synchronously by the AM envelope. These findings are consistent with animal experiments reporting altered tonotopy and changes in the response properties of auditory cortical neurons after hearing loss induced by noise exposure. Degraded frequency representations in tinnitus may reflect a loss of intracortical inhibition in deafferented frequency regions of the PAC after hearing injury.

Acoustic Stimulation↗
PubMed2006

Nonmonotonic synaptic excitation and imbalanced inhibition underlying cortical intensity tuning.

Intensity-tuned neurons, characterized by their nonmonotonic response-level function, may play important roles in the encoding of sound intensity-related information. The synaptic mechanisms underlying intensity tuning remain unclear. Here, in vivo whole-cell recordings in rat auditory cortex revealed that intensity-tuned neurons, mostly clustered in a posterior zone, receive imbalanced tone-evoked excitatory and inhibitory synaptic inputs. Excitatory inputs exhibit nonmonotonic intensity tuning, whereas with tone intensity increments, the temporally delayed inhibitory inputs increase monotonically in strength. In addition, this delay reduces with the increase of intensity, resulting in an enhanced suppression of excitation at high intensities and a significant sharpening of intensity tuning. In contrast, non-intensity-tuned neurons exhibit covaried excitatory and inhibitory inputs, and the relative time interval between them is stable with intensity increments, resulting in monotonic response-level function. Thus, cortical intensity tuning is primarily determined by excitatory inputs and shaped by cortical inhibition through a dynamic control of excitatory and inhibitory timing.

Acoustic Stimulation↗
PubMed2004

Misoprostol in the treatment of tinnitus: a double-blind study.

OBJECTIVE: To test the efficacy of misoprostol as a treatment for tinnitus. DESIGN: A prospective, placebo-controlled, double-blind study. SETTING: Başkent University Otolaryngology Clinic. PATIENTS: Forty adult patients who had had tinnitus for a minimum of 6 months and were free of systemic or otolaryngologic disease. Twenty-eight patients were randomly assigned to the experimental group (group I) and 12 to the control group (group II). INTERVENTION: The respective groups received active drug and placebo in increasing doses for 4 months. The effect of medications on tinnitus were evaluated by determining improvement rates in tinnitus loudness and subjective tinnitus scoring. RESULTS: In the experimental group, 18 of 28 patients showed improvement in tinnitus loudness, representing an improvement rate of 64%. The improvement rate based on subjective tinnitus scoring was 36% (10 of 28 patients). In the control group, the improvement rate for tinnitus loudness was 33% (n = 4), and the rate for subjective tinnitus scoring was 17% (n = 2). The difference between improvement rate for tinnitus loudness of the experimental group and control group was found to be statistically significant (P = 0.039), but difference between improvement rate based on subjective tinnitus scoring was insignificant (P = 0.119). When results in the experimental group were analyzed according to etiological factors, the improvement rate was highest in the sudden-onset subgroup (77%). CONCLUSIONS: Misoprostol provided therapeutic relief for some patients with tinnitus we studied, but further investigation of larger groups is needed.

Adult↗
PubMed2005

DPOAE-grams in patients with acute tonal tinnitus.

OBJECTIVE: To investigate cochlear outer hair cell function in patients with acute tonal tinnitus and normal or near-normal hearing threshold. STUDY DESIGN AND SETTING: Prospective controlled study in an academic tertiary health center. Distortion products of otoacoustic emissions (DPOAE)-grams of 32 ears with acute tonal tinnitus and normal hearing or minimal hearing loss were compared with those of 17 healthy nontinnitus ears. RESULTS: Tinnitus ears exhibited relatively increased amplitudes of DPOAE at high frequencies (4-6.3 kHz) when compared with the group of healthy ears and relatively decreased DPOAE amplitudes at middle frequencies (1650-2400 Hz). Statistically significant ( P < 0.01) increased mean values of DPOAE amplitudes were observed only at a frequency of f2 equal to 4.9 kHz. CONCLUSIONS AND SIGNIFICANCE: These findings suggest an altered functional state of the outer hair cells at a selected high-frequency region of the cochlea in ears with acute tonal tinnitus and normal or near-normal hearing threshold.

Acoustic Stimulation↗
PubMed2006

Perceptual voice characteristics in pediatric unilateral vocal fold paralysis.

OBJECTIVE: To describe the voice characteristics of pediatric unilateral vocal fold paralysis (UVFP). STUDY DESIGN AND SETTING: Retrospective series from a children's hospital, 1996 to present. RESULTS: Forty-two patients with a mean age of 7.1 years were diagnosed with UVFP in our voice clinic (prevalence = 5.4%). Paralysis was left sided in 88%, and was most commonly seen after cardiac surgery (28.5%) and prolonged intubation/prematurity (16.7%). Voice analysis showed a moderate degree of breathiness, mild-to-moderate hoarseness and straining, mild muscle tension, and soft loudness. Twenty-six percent of patients required surgical intervention, including injection into the paralyzed fold (7 patients) and medialization thyroplasty (4 patients). Pre-operatively, breathiness was worse (P < .05) in patients undergoing surgical intervention. CONCLUSIONS: Voice characteristics of pediatric UVFP include increased breathiness, hoarseness, straining, muscle tension, and soft loudness. One-fourth of patients underwent surgical intervention; breathiness was the predominant abnormal voice characteristic in the operative cohort. SIGNIFICANCE: The voice characteristics of pediatric patients with UVFP are described. EBM RATING: C-4.

Adolescent↗
PubMed2006

Acoustical analysis of snoring: can the probability of success be predicted?

PURPOSE: Palatal flutter snoring is the most common form of snoring. However, other types of snoring do exist. Does identifying palatal snoring beforehand translate into improved subjective treatment success with palatal stiffening procedures? METHODS: Fifty-three patients presenting with snoring were evaluated with a commercially available device. The proportion (%) and magnitude of palatal flutter (dB) were quantified. Patients then underwent a palatal stiffening procedure and subjective success/failure was assessed. RESULTS: Overall subjective treatment success was 85% (45 of 53). The percent palatal flutter was the most predictive of success (area under ROC = 0.8556, 95% CI = .7428-.9683). Patients exceeding 68% palatal flutter had a 95% (39 of 41) success rate (P = 0.001, Fisher's exact) and an adjusted odds ratio of treatment success of 25.2 (95% CI = 3.22-196, P = 0.002). CONCLUSION: Palatal stiffening treatments are successful in the majority of patients. However, identifying patients with predominant palatal flutter snoring significantly increases the probability of subjective treatment success. EBM RATING: B-2b.

Acoustics↗
PubMed1997

The audiogenic startle reflex in Tourette's syndrome.

The motor response pattern of the audiogenic startle reflex was studied in 15 Tourette's syndrome (TS) patients and 15 normal, age-matched control subjects, using auditory stimuli at 88 and 114 dB. The louder stimuli readily elicited responses in the orbicularis oculi (in all subjects), masseter, sternomastoid, trapezius, deltoid, and biceps (in most subjects) muscles, with a few subjects having responses in the forearm flexors and quadriceps. The TS subjects did not differ from controls in the onset latency, amplitude, and first peak latency of the reflex response in any of the muscles. Rates of habituation in the orbicularis oculi muscle were widely variable across the subjects, and the two groups did not differ overall in the habituation rates. Our study does not support the reports of an abnormal audiogenic startle reflex in TS.

Acoustic Stimulation↗