Papers by Akram Pourbakht
Background and Aim: Speech evoked auditory brainstem responses were used in the assessment of sub... more Background and Aim: Speech evoked auditory brainstem responses were used in the assessment of subcortical encoding of the speech stimuli in the English language. These processes are affected by language background and experiences. Considering the language specific acoustic differences, the aims of current study was to establishing the response norms in adult Persian speakers and comparison of the encoding of the speech syllable /da/ between Persian and English languages. Methods: Auditory brainstem responses to speech syllable /da/ in the right ear, gained from 48 normal adults (25 female) with mean age 22.7±2.05 years. After characterizing the onset elements, transition from consonant to vowel, the periodic portion and offset of response, the Persian dataset were compared with 95% confidence interval of USA norms in age range 18-28 years. Results: The response to speech syllable /da/ was successfully recorded in all of the subjects and main features of response were highly overlapped with published English norms.
Background and Aim: The complexities of processing and effects of individual factors on the encod... more Background and Aim: The complexities of processing and effects of individual factors on the encoding of sounds is a feature of brainstem processing. No statistical method, except fuzzy logic modeling, is effective in explaining these complex relationships. The aim of the current study was to explore the behavior of the brainstem in response to complex auditory stimuli using a fuzzy based model. Methods: Auditory brainstem responses to synthetic /da/ stimuli were recorded for 35 normal subjects (17 female) with a mean age of 22.7 years. A fuzzy based model with a Singleton fuzzifier, Mamdani product inference engine, and a center average defuzzifier were used. By providing recorded responses to create a rule base, the behavior of the brainstem was modeled. Results: It appears that, using the training data, the current fuzzy model robustly anticipated and modeled the behavior of speech-evoked responses in the test data set. A mean error of 16.84 % (variance: 1%) was observed for 5 ran...
European archives of oto-rhino-laryngology : official journal of the European Federation of Oto-Rhino-Laryngological Societies (EUFOS) : affiliated with the German Society for Oto-Rhino-Laryngology - Head and Neck Surgery, 2015
The presence of utricular and saccular dysfunction impairs quality of life (QoL) in patients. The... more The presence of utricular and saccular dysfunction impairs quality of life (QoL) in patients. The aims of the present study were to examine the effect of repositioning maneuvers on QoL of patients with idiopathic benign paroxysmal positional vertigo (BPPV) and to describe the effect of cervical vestibular-evoked myogenic potential (cVEMP) or ocular VEMP (oVEMP) abnormalities on patient recovery after rehabilitation. Thirty idiopathic BPPV patients with/without otolith dysfunctions (n = 15, each group) were included in this clinical trial study. Otolith dysfunction was determined using oVEMP and cVEMP abnormalities. EcochG and caloric tests were performed to rule out other causes of secondary BPPV. The QoL in groups of patients with idiopathic BPPV was assessed using a Persian version of the dizziness handicap inventory (DHI-P) before and after treatment with Epley's maneuver. Pre-treatment results showed significant handicaps in both groups. DHI-P scores were higher in BPPV pati...
Journal of research in medical sciences : the official journal of Isfahan University of Medical Sciences, 2014
Dizziness as a common symptom affecting many aspects of the patient's life and it is hard to ... more Dizziness as a common symptom affecting many aspects of the patient's life and it is hard to be fully evaluated. The dizziness handicap inventory (DHI) is a reliable self-perceived questionnaire in the evaluation of dizziness impacts. The purposes of this study are translation of the DHI to Persian language and measuring its psychometric properties, including face, content, discriminate and construct validity, internal consistency and reliability. The English version of the DHI is translated to Persian language based on international quality of life assessment protocol. 97 participants, including 57 patients with mean age of 44.5-year-old and 40 healthy people (mean age of 34.1) participated in this study during the period of November 2012 to June 2013 in audiology clinics of Tehran University of medical sciences. The Persian version of DHI showed good face and content validity. The internal consistency of DHI-P was good, the Cronbach's alpha was 0.79, 0.82, 0.83, and 0.90 f...
Iranian journal of otorhinolaryngology, 2014
Tinnitus is a common otologic symptom that can seriously affect a patient's quality of life. ... more Tinnitus is a common otologic symptom that can seriously affect a patient's quality of life. The purpose of the present study was to translate and validate the Iowa Tinnitus Handicap Questionnaire (THQ) into the Persian language, and to make it applicable as a tool for determining the effects of tinnitus on a patient's life. The main version of the THQ was translated into the Persian language. The agreed Persian version was administered to 150 tinnitus patients. The validity of the Persian THQ was evaluated and internal reliability was confirmed using Cronbach's α-coefficient. Finally, the effect of independent variables such as age, mean patient threshold, gender, and duration of tinnitus were considered in order to determine the psychometric properties of tinnitus. After an exact translation process, the Persian THQ was found to exhibit face validity. In terms of content validity, content validity index in total questionnaire was 0.93. Further, in structural validity m...
Scientifica, 2014
Auditory processing deficits have been hypothesized as an underlying mechanism for stuttering. Pr... more Auditory processing deficits have been hypothesized as an underlying mechanism for stuttering. Previous studies have demonstrated abnormal responses in subjects with persistent developmental stuttering (PDS) at the higher level of the central auditory system using speech stimuli. Recently, the potential usefulness of speech evoked auditory brainstem responses in central auditory processing disorders has been emphasized. The current study used the speech evoked ABR to investigate the hypothesis that subjects with PDS have specific auditory perceptual dysfunction. Objectives. To determine whether brainstem responses to speech stimuli differ between PDS subjects and normal fluent speakers. Methods. Twenty-five subjects with PDS participated in this study. The speech-ABRs were elicited by the 5-formant synthesized syllable/da/, with duration of 40 ms. Results. There were significant group differences for the onset and offset transient peaks. Subjects with PDS had longer latencies for th...
Gathering an insight into brainstem task in generating auditory response to complex stimuli and i... more Gathering an insight into brainstem task in generating auditory response to complex stimuli and its nonlinear behavior can be an important base in auditory system modelling, but no study has been done to demonstrate the nonlinear dynamic behavior of auditory systems considering cABR. This study attends the dynamic modeling of auditory brainstem response to consonant-vowel syllable /da/ using fuzzy logic as nonlinear mapping of the input and output of the system.
Iranian Red Crescent Medical Journal, 2013
Background: Auditory scene analysis (ASA) is the process by which the auditory system separates i... more Background: Auditory scene analysis (ASA) is the process by which the auditory system separates individual sounds in natural-world situations. ASA is a key function of auditory system, and contributes to speech discrimination in noisy backgrounds. It is known that sensorineural hearing loss (SNHL) detrimentally affects auditory function in complex environments, but relatively few studies have focused on the influence of SNHL on higher level processes which are likely involved in auditory perception in different situations.
Auris Nasus Larynx, 2014
Objectives: To investigate the influence of gender on subcortical representation of speech acoust... more Objectives: To investigate the influence of gender on subcortical representation of speech acoustic parameters where simultaneously presented to both ears. Methods: Two-channel speech-evoked auditory brainstem responses were obtained in 25 female and 23 male normal hearing young adults by using binaural presentation of the 40 ms synthetic consonantvowel /da/, and the encoding of the fast and slow elements of speech stimuli at subcortical level were compared in the temporal and spectral domains between the sexes using independent sample, two tailed t-test. Results: Highly detectable responses were established in both groups. Analysis in the time domain revealed earlier and larger Fast-onset-responses in females but there was no gender related difference in sustained segment and offset of the response. Interpeak intervals between Frequency Following Response peaks were also invariant to sex. Based on shorter onset responses in females, composite onset measures were also sex dependent. Analysis in the spectral domain showed more robust and better representation of fundamental frequency as well as the first formant and high frequency components of first formant in females than in males. Conclusions: Anatomical, biological and biochemical distinctions between females and males could alter the neural encoding of the acoustic cues of speech stimuli at subcortical level. Females have an advantage in binaural processing of the slow and fast elements of speech. This could be a physiological evidence for better identification of speaker and emotional tone of voice, as well as better perceiving the phonetic information of speech in women.
Neuroscience Letters, 2005
This investigation tested the hypothesis that a noise-induced temporary threshold shift (TTS) can... more This investigation tested the hypothesis that a noise-induced temporary threshold shift (TTS) can be attenuated by a peroxynitrite scavenger, ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one). Guinea pigs received an oral dose of the vehicle or 10 mg/kg ebselen 1 h before exposure to 115 dB SPL 4-kHz octave band noise for 3 h. In controls, auditory brainstem response (ABR) thresholds increased by 25-45 dB immediately after noise and returned to pre-exposure baseline thresholds 7 days later. Ebselen eliminated this ABR threshold shift following noise exposure. In controls, swelling of the afferent dendrites beneath the inner hair cells was evident immediately after noise, whereas ebselen significantly reduced this pathology. These findings suggest that scavenging peroxynitrite can attenuate noise-induced excitotoxicity and, thereby, TTS.
International Journal of Audiology, 2014
Hearing Research, 2003
Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one), a seleno-organic compound, mimics glutathione ... more Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one), a seleno-organic compound, mimics glutathione peroxidase and reacts with peroxynitrite. It is reported to protect against gentamicin- and cisplatin-induced ototoxicity. We investigated whether it protects the cochlea from acoustic trauma. Male pigmented guinea pigs (250-300 g) with normal auditory brainstem response (ABR) thresholds were exposed for 5 h to 125 dB sound pressure level octave band noise centered at 4 kHz. One hour before and 18 h after exposure, they received orally 0.25 ml chloroform solution containing 0, 10, or 30 mg/kg ebselen (n=6, 5 and 5, respectively). The protective effect of ebselen was evaluated by ABR measurement and quantitative hair cell assessment. Treatment significantly (P<0.01) reduced the extent of permanent threshold shifts and outer hair cell loss. Interestingly, the protective effect of a 30 mg/kg dose was less than that of a 10 mg/kg dose. There were no adverse systemic or auditory function effects in three unexposed control subjects given 30 mg/kg ebselen. These findings indicate that ebselen attenuates noise-induced cochlear damage. The concentration that provides optimal protection against such damage has now to be determined.
Hearing Research, 2003
We compared the extent of permanent threshold shifts (PTS) and cochlear hair cell damage caused b... more We compared the extent of permanent threshold shifts (PTS) and cochlear hair cell damage caused by continuous noise exposure with those caused by intermittent noise exposure. Twenty male pigmented guinea pigs that had been exposed to a one-octave band of noise at 4 kHz for 5 h were placed in four groups: exposure to 115 dB SPL continuous noise (group 1, n=5), 115 dB SPL intermittent noise (group 2, n=5), 125 dB SPL continuous noise (group 3, n=5), and 125 dB SPL intermittent noise (group 4, n=5). PTS at 2, 4, 8, and 16 kHz were assessed by means of auditory brainstem responses measured before noise exposure and 10 days after. The guinea pigs were killed 15 days after noise exposure, and the number of hair cells missing counted in surface preparations of the organs of Corti stained with rhodamine phalloidin. Groups 1 and 3 had significantly greater PTS (P<0.05) at all frequencies than intermittent groups 2 and 4. Group 3 had the greatest PTS at all the frequencies. Intermittent 125 dB noise total energy was greater than that of continuous 115 dB noise, but the latter elicited more PTS than the former. The extent of hair cell damage was comparable to the physiological findings. This indicates that continuous noise causes greater damage to the cochlea than intermittent noise of the same intensity and that, at the intensities tested, damage to the cochlea is not proportional to the total noise energy.
Background and Aim: Neural encoding of sounds starts from the auditory nerve and moves on to the ... more Background and Aim: Neural encoding of sounds starts from the auditory nerve and moves on to the auditory brainstem. What is less defined is how the brainstem responds to complex stimuli. The current study quantified brainstem encoding of fundamental frequencies and first formant amplitude of the spoken syllable /da/ using periodic frequency-following responses. Methods: Auditory brainstem responses to spoken syllables in both ears were monaurally presented under quiet conditions for 48 normal adults (25 female) with a mean age of 2.05 ± 22.7 years. The magnitudes of the sustained periodic frequency-following responses (FFR) were assessed by fundamental frequency, first formant amplitude, and higher frequency harmonics of the first formant. Results: Measures of the FFR components of brainstem response to the spoken syllables were robustly obtained. Responses occurred earlier in right ear presentation than those in left, approaching significance for the FFR second peak (p = 0.004). A...
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Papers by Akram Pourbakht