Ali A. Danesh

The genetic basis of auditory neuropathy spectrum disorder (ANSD).

OBJECTIVEnAuditory neuropathy is a hearing disorder where outer hair cell function within the cochlea is normal, but inner hair cell and/or the auditory nerve function is disrupted. It is a heterogeneous disorder which can have either congenital or acquired causes. Furthermore, the aetiology of auditory neuropathy is vast, which may include prematurity, hyperbilirubinaemia, anoxia, hypoxia, congenital brain anomalies, ototoxic drug exposure, and genetic factors. It is estimated that approximately 40% of cases have an underlying genetic basis, which can be inherited in both syndromic and non syndromic conditions. This review paper provides an overview of the genetic conditions associated with auditory neuropathy spectrum disorders (ANSDs) and highlights some of the defective genes that have been found to be linked to the pathological auditory changes.nnnMETHODnLiterature search was conducted using a number of resources including textbooks, professional journals and the relevant websites.nnnRESULTSnThe largest proportion of auditory neuropathy spectrum disorders (ANSDs) is due to genetic factors which can be syndromic, non-syndromic or mitochondrial related. The inheritance pattern can include all the four main types of inheritances such as autosomal dominant, autosomal recessive, X-linked and mitochondrial.nnnCONCLUSIONnThis paper has provided an overview of mutation with some of the genes and/or loci discovered to be the cause for auditory neuropathy spectrum disorders (ANSDs). It has been noted that different gene mutations may trigger different pathological changes in patients with this disorder. These discoveries have provided us with vital information as to the sites of pathology in auditory neuropathy spectrum disorders (ANSDs), and the results highlight the heterogeneity of the disorder.

DPOAEs and contralateral acoustic stimulation and their link to sound hypersensitivity in children with autism

Abstract Objective: The hypersensitivity of children with autism to sound is a relatively unexplained behavior. The goal of the current study was to investigate the DPOAE characteristics of children with autism compared to a control group. Design: DPOAEs with and without contralateral stimuli were measured in two groups in three different conditions. Study sample: The study employed 14 children with autism and a control group with 28 age-matched participants. Results: In the without-contralateral stimulus condition, the overall S/N of DPOAEs was greater for the control group compared to the autism group (p < 0.0005). For both groups, the DPOAE S/N increased as a function of frequency in both ears. In the with contralateral stimulus condition, group and ear effects were noticed, however, no age, frequency, or contralateral stimulus type (BBN vs. 1000 Hz) effect could be detected. Conclusions: Presence of reduced DPOAEs in the autism group does not support the hypothesis that sound hypersensitivity in children with autism may be related to overactive outer hair cells function; rather it may be due to early cochlear dysfunction. Also, sound hypersensitivity in the autism group may be due to abnormality of the efferent auditory pathway as shown by lack of sufficient contralateral suppression.

Oscillation and its inhibition in a neural oscillator model for tinnitus.

Tinnitus is a symptom of perceiving phantom sounds. As one of its treatment techniques, tinnitus retraining therapy (TRT) has been proposed. It consists of psychotherapy by counseling and physical therapy based on masking theory by external stimuli. Our interest is to explain medical effects of the physical therapy from the viewpoint of engineering. In this paper we proposed a neural oscillator model with plasticity as a model for the tinnitus generation in the auditory central nervous system and its treatment. We investigated not only oscillatory phenomena observed in the model but also inhibition of the oscillation by external stimulus

Central auditory processing during chronic tinnitus as indexed by topographical maps of the mismatch negativity obtained with the multi-feature paradigm.

This study aimed to compare the neural correlates of acoustic stimulus representation in the auditory sensory memory on an automatic basis between tinnitus subjects and normal hearing (NH) controls, using topographical maps of the MMNs obtained with the multi-feature paradigm. A new and faster paradigm was adopted to look for differences between 2 groups of subjects. Twenty-eight subjects with chronic subjective idiopathic tinnitus and 33 matched healthy controls were included in the study. Brain electrical activity mapping of multi-feature MMN paradigm was recorded from 32 surface scalp electrodes. Three MMN parameters for five deviants consisting frequency, intensity, duration, location and silent gap were compared between the two groups. The MMN amplitude, latency and area under the curve over a region of interest comprising: F3, F4, Fz, FC3, FC4, FCz, and Cz were computed to provide better signal to noise ratio. These three measures could differentiate the cognitive processing disturbances in tinnitus sufferers. The MMN topographic maps revealed significant differences in amplitude and area under the curve for frequency, duration and silent gap deviants in tinnitus subjects compared to NH controls. The current study provides electrophysiological evidence supporting the theory that the pre-attentive and automatic central auditory processing is impaired in individuals with chronic tinnitus. Considering the advantages offered by the MMN paradigm used here, these data might be a useful reference point for the assessment of sensory memory in tinnitus patients and it can be applied with reliability and success in treatment monitoring.

Oscillation and its inhibition in a neuronal network model for tinnitus sound therapy

Tinnitus is the perception of phantom sounds in the ears or in the head. Sound therapy techniques for tinnitus treatment have been proposed. In order to investigate mechanisms of tinnitus generation and the clinical effects of sound therapy from the viewpoint of neural engineering, we have proposed a computational model using a neural oscillator. In the present paper, we propose another model that is composed of model neurons described by simplified Hodgkin-Huxley equations. By computer simulation it was detected that this model also has a bistable state, i.e., a stable oscillatory state and a stable equilibrium (non-oscillatory) state coexist at a certain parameter region. It was also noticed that the oscillation can be inhibited by supplying constant or pulse train stimuli, which is hypothesized as an afferent signal that is employed as an acoustical signal for tinnitus treatment. By hypothesizing that the oscillation and the equilibrium correspond to generation and inhibition of tinnitus, respectively, these phenomena could explain the fact that the habituated human auditory system temporarily halts perception of tinnitus following sound therapy.

Distortion-product otoacoustic emissions and contralateral suppression findings in children with Asperger's Syndrome

OBJECTIVESnChildren with Aspergers Syndrome (AS) often demonstrate auditory behaviors such as hypersensitivity to sounds and poor performance in noisy environments. These auditory behaviors may be related to cochlear dysfunction and abnormal medial olivocochlear bundle (MOCB) activity. The objective of this study was to examine the distortion-product otoacoustic emissions (DPOAEs) with and without contralateral white noise to evaluate outer hair cell activity and MOCB activity in children with AS.nnnMETHODSnA case control study where 18 boys with AS and 18 age-matched control subjects participated in the study. For both groups, DPOAEs were recorded at 4031, 2627, 1969, and 1359 Hz f2 frequencies with and without contralateral white noise at 30 dB SL. DPOAE SNRs and difference scores were analyzed for possible differences between both groups and age subgroups (young and old children).nnnRESULTSnIn the quiet condition, there were no significant group or ear differences in DPOAEs SNR. However, DPOAEs SNR were larger at 4031 Hz than at lower frequencies in both groups, mostly due to negative effect of background noise on low frequency response. Contralateral noise resulted in both suppression and enhancement of the DPOAE SNRs in 93% of the control group and 90% of the AS group. However, there were no significant differences in suppression and enhancement between the two groups or age subgroups. The young controls had right ear advantage and significantly larger suppression at all frequencies except 4031 Hz than old controls. The young children with AS had slight left ear advantage and significantly larger suppression only at 2672 Hz compared to the old children with AS.nnnCONCLUSIONSnThe results, indicating minor differences in DPOAEs and contralateral suppression and enhancement of DPOAEs between both control and AS groups and age subgroups, suggest subtle differences in the function of the outer hair cells and the MOCB activity. Therefore, other central auditory processing in the temporal lobe, limbic system and autonomic nervous system may be involved in the generation of hypersensitivity to sounds and difficulty understanding in noisy environments in children with AS.

Dynamical Properties of a Plastic Neural Network Model for Tinnitus Therapy and Inhibition of Oscillation Using Noise Stimulus

Tinnitus is the perception of phantom sounds in the ears or in the head. Sound therapy techniques for tinnitus have been proposed. To account for mechanisms of tinnitus generation and the clinical effects of sound therapies from the viewpoint of neural engineering, we have proposed a plastic neural network model for the human auditory system. We found that this model has a bistable state, i.e., a stable oscillatory state and a stable equilibrium (non-oscillatory) state coexist at a certain parameter region. We also found that the oscillation can be inhibited by supplying sinusoidal stimulus, which is hypothesized as sound for treatment of tinnitus, to the model. By hypothesizing that the oscillation and the equilibrium correspond to generation and inhibition of tinnitus, respectively, we reported that these phenomena could explain the fact that the habituated human auditory system temporarily halts perception of tinnitus following sound therapy. This paper describes dynamical properties of the model and inhibition of the oscillation for two kinds of noise stimuli which correspond to sound for treatment of tinnitus in clinical. Through numerical simulations we found that adequate noise stimulus can inhibits the oscillation.

Auditory temporal processing in patients with temporal lobe epilepsy

OBJECTIVEnAuditory temporal processing is the main feature of speech processing ability. Patients with temporal lobe epilepsy, despite their normal hearing sensitivity, may present speech recognition disorders. The present study was carried out to evaluate the auditory temporal processing in patients with unilateral TLE.nnnMATERIALS AND METHODSnThe present study was carried out on 25 patients with epilepsy: 11 patients with right temporal lobe epilepsy and 14 with left temporal lobe epilepsy with a mean age of 31.1years and 18 control participants with a mean age of 29.4years. The two experimental and control groups were evaluated via gap-in-noise and duration pattern sequence tests. One-way ANOVA was run to analyze the data.nnnRESULTSnThe mean of the threshold of the GIN test in the control group was observed to be better than that in participants with LTLE and RTLE. Also, it was observed that the percentage of correct responses on the DPS test in the control group and in participants with RTLE was better than that in participants with LTLE.nnnCONCLUSIONnPatients with TLE have difficulties in temporal processing. Difficulties are more significant in patients with LTLE, likely because the left temporal lobe is specialized for the processing of temporal information.

Tinnitus and hyperacusis in autism spectrum disorders with emphasis on high functioning individuals diagnosed with Asperger's Syndrome

OBJECTIVESnTo evaluate the prevalence of tinnitus and hyperacusis in individuals with Aspergers Syndrome (AS).nnnMETHODSnA home-developed case-history survey and three item-weighted questionnaires: Tinnitus Reaction Questionnaire (TRQ), Tinnitus Handicap Inventory (THI), and the Hyperacusis Questionnaire (HQ) were employed. These tools categorize the subjective response to tinnitus and hyperacusis. The research tools were mailed to a mailing list of individuals with Aspergers Syndrome.nnnRESULTSnA total of 55 subjects diagnosed with AS were included in the analysis (15.5% response rate). Sixty-nine percent of all respondents (38/55) reported hyperacusis with an average HQ score of 20.7. Furthermore, 35% (19/55) reported perceiving tinnitus with average scores of 27 for the TRQ and 23 for the THI. Thirty-one percent (17/55) reported both hyperacusis and tinnitus. The prevalence of hyperacusis in the AS respondents remained relatively constant across age groups.nnnCONCLUSIONSnHyperacusis and tinnitus are more prevalent in the ASD population subgroup diagnosed with AS under DSM-IV criteria than in the general public. Hyperacusis also appears to be more prevalent in the AS population than in the ASD population at large. Future research is warranted to provide insight into the possible correlation between tinnitus and hyperacusis symptoms and the abnormal social interactions observed in this group.

Inhibition of Oscillation in a Neural Oscillator Model for Sound Therapy of Tinnitus

Abstract Perception of continuous or intermittent sounds ringing in the ears without any external source is referred to as tinnitus. For the management of tinnitus one of the most effective approaches is sound therapy. Previously, we demonstrated a conceptual and computational plastic neural oscillator model for the mechanisms of tinnitus generation and the clinical effects of sound therapy on tinnitus. The proposed model has a stable oscillatory state and a stable equilibrium (non-oscillatory) state. It can be hypothesized that the oscillation state corresponds to the generation of tinnitus and the equilibrium state corresponds to the state in which the tinnitus is inhibited. Through numerical simulations of this model it was found that the oscillation can be inhibited by supplying band-pass noise (BN) stimuli, which clinically has been used as a stimulus for treatment of tinnitus (i.e., sound therapy). The current paper describes the inhibition of the oscillation by yet two different types of noise stimuli: Gaussian white noise (GWN) and additive uniform noise (AUN). This investigation shows that only smaller RMS value of GWN input could inhibit the oscillation. When larger RMS values of GWN were employed the inhibition of oscillation was not frequent. It was observed that AUN can inhibit the oscillation with higher possibility than GWN or BN. It is an interesting result although it does not directly suggest that AUN is better than GWN or BN in clinic.