Effect of perinatal and postnatal thiamine deficiency on auditory pathway of the Wistar-Albino rats

Abstract Objective: In this study, we created an animal model to demonstrate the effects of thiamine on the hearing pathways of new-borns during pregnancy and lactation by inducing a dietary thiamine deficiency in the mother. Methods: The study included 16 female Wistar albino rats. The animals were separated into four groups and provided the appropriate amounts of dietary thiamine according to their groups during pre-pregnancy, pregnancy, and lactation periods. Three pups from each mother were included in the study, and 12 pups were selected from each group. On the fortieth day after birth, the auditory pathways of 48 pups in the 4 groups were examined electro physiologically and ultra-structurally. Results: In Group N-N, morphology of hair cells stereocilia degeneration was not obtained in all turns of cochlea. In Group N-T, Inner Hair Cells (IHCs) and Outher Hair Cells (OHCs) stereocilia didn't show degeneration in all turns of cochlea but had rupture inrows of HCs stereocilia. In group T-N IHCs stereocilia less degeneration was observed in all turns of cochlea. OHC stereocilia partial loss was observed only in basal turn of cochlea. In Group T-T IHCs stereocilia was observed less degeneration and rupture in all turns of cochlea. Conclusion: Thiamine is vital for the development of cochlear hair cells during both prenatal and postnatal periods. Even partial deficiency of thiamine causes significant degeneration to the auditory pathway. Level of evidence: The level of evidence of this article is 5. This article is an experimental animal and laboratory study.

Short Term Test-Retest Reliability of Contralateral Inhibition of Distortion Product Otoacoustic Emissions

BACKGROUND AND OBJECTIVES: Strength of medial olivocochlear reflex can be measured reliably using contralateral inhibition of distortion product otoacoustic emissions (DPOAEs) when its fine structure is considered. However, measurement of fine structure of DPOAE is difficult with clinical equipment. Thus, this study investigated the clinically relevant test-retest reliability of contralateral inhibition of DPOAEs. SUBJECTS AND METHODS: Twenty-six young adults with normal hearing sensitivity participated. DPOAEs were recorded at 27 discrete f2 frequencies between 800 Hz and 8,000 Hz at frequency resolution of 8 points per octave with and without contralateral white noise presented at 50 dB SPL. To check for short term inter-session reliability, contralateral inhibition of DPOAEs were recorded in three sessions, two recording sessions on first day separated by 30 minutes and third time after one week of the first session. Within each session, DPOAEs were recorded twice in single probe-fit condition to test for intra-session reliability. RESULTS: Cronbach’s alpha was calculated having poor reliability (α≤ 0.7) of contralateral inhibition of DPOAEs in both intra-session and inter-session conditions for most of the tested frequencies. 95% confidence intervals of contralateral inhibition magnitude also showed large variability. CONCLUSIONS: The current results showed that though DPOAE amplitudes were highly reliable across sessions, amount of inhibition of DPOAEs was not reliable when DPOAEs were measured at discrete frequencies. These findings are concurrent with the literature.

Psychoacoustic Characteristics of Tinnitus versus Temporal Resolution in Subjects with Normal Hearing Sensitivity

Abstract Introduction Cochlear or neural mechanisms of tinnitus generation may affect auditory temporal resolution in tinnitus patients even with normal audiometry. Thus, studying the correlation between tinnitus characteristics and auditory temporal resolution in subjects with tinnitus may help in proper modification of tinnitus management strategy. Objective This study aims to examine the relationship between the psychoacoustic measures of tinnitus and the auditory temporal resolution in subjects with normal audiometry. Methods Two normal hearing groups with ages ranging from 20 to 45 years were involved: control group of 15 adults (30 ears) without tinnitus and study group of 15 adults (24 ears) with tinnitus. Subjective scaling of annoyance and sleep disturbance caused by tinnitus, basic audiological evaluation, tinnitus psychoacoustic measures and Gaps in Noise test were performed. Data from both groups were compared using independent sample t-test. Psychoacoustic measures of tinnitus and Gaps in Noise test parameters of the tinnitus group were correlated with Pearson's correlation coefficient. Results Significantly higher hearing threshold, higher approximate threshold and lower correct Gaps in Noise scores were observed in tinnitus ears. There was no significant correlation between psychoacoustic measures of tinnitus and Gaps in Noise test parameters of the tinnitus group. Conclusion Auditory temporal resolution impairment was found in tinnitus patients, which could be attributed to cochlear impairment or altered neural firing within the auditory pathway. It is recommended to include temporal resolution testing in the tinnitus evaluation battery to provide a proper management planning.

Diffusion Tensor Imaging Study of Central Auditory Pathway in Patients with Acquired Sensorineural Hearing Loss / 听力学及言语疾病杂志

Objective Magnetic resonance diffusion tensor imaging (DTI) was applied to study the cantral auditong pathway in patients with .Methods A total of 30 cases of acquired hearing loss patients were divided into 2 groups ,group 1 (15 ,sudden deafness) and group 2 (15 ,with duration up to 2 years SNHL group from the time of onset) .A total of 15 cases of normal-hearing patients on MRI examination were selected as the control group for the same period .All subjects received DTI of whole brain .The values of the whole brain DTI were obtained from the inferior colliculus and lateral lemniscus ,consisting of the fractional anisotropy (FA) ,radial diffusion (RD) ,axi‐al dispersion (AD) and mean diffusivity .Results There were significant differences(P0 .05) .Conclusion There was no obviously abnormal change on the central auditory processing in sudden deafness group ,but significant destruction was found on 2 years SNHL group .It indicated that central auditory processing of the history of sensorineural deafness affected the structural changes of the central au‐ditory pathway .

Auditory evoked potentials: predicting speech therapy outcomes in children with phonological disorders

OBJECTIVES: This study investigated whether neurophysiologic responses (auditory evoked potentials) differ between typically developed children and children with phonological disorders and whether these responses are modified in children with phonological disorders after speech therapy. METHODS: The participants included 24 typically developing children (Control Group, mean age: eight years and ten months) and 23 children clinically diagnosed with phonological disorders (Study Group, mean age: eight years and eleven months). Additionally, 12 study group children were enrolled in speech therapy (Study Group 1), and 11 were not enrolled in speech therapy (Study Group 2). The subjects were submitted to the following procedures: conventional audiological, auditory brainstem response, auditory middle-latency response, and P300 assessments. All participants presented with normal hearing thresholds. The study group 1 subjects were reassessed after 12 speech therapy sessions, and the study group 2 subjects were reassessed 3 months after the initial assessment. Electrophysiological results were compared between the groups. RESULTS: Latency differences were observed between the groups (the control and study groups) regarding the auditory brainstem response and the P300 tests. Additionally, the P300 responses improved in the study group 1 children after speech therapy. CONCLUSION: The findings suggest that children with phonological disorders have impaired auditory brainstem and cortical region pathways that may benefit from speech therapy. .

Role of sound stimulation in reprogramming brain connectivity.

Sensory stimulation has a critical role to play in the development of an individual. Environmental factors tend to modify the inputs received by the sensory pathway. The developing brain is most vulnerable to these alterations and interacts with the environment to modify its neural circuitry. In addition to other sensory stimuli, auditory stimulation can also act as external stimuli to provide enrichment during the perinatal period. There is evidence that suggests that enriched environment in the form of auditory stimulation can play a substantial role in modulating plasticity during the prenatal period. This review focuses on the emerging role of prenatal auditory stimulation in the development of higher brain functions such as learning and memory in birds and mammals. The molecular mechanisms of various changes in the hippocampus following sound stimulation to effect neurogenesis, learning and memory are described. Sound stimulation can also modify neural connectivity in the early postnatal life to enhance higher cognitive function or even repair the secondary damages in various neurological and psychiatric disorders. Thus, it becomes imperative to examine in detail the possible ameliorating effects of prenatal sound stimulation in existing animal models of various psychiatric disorders, such as autism.

Diagnosis and management of somatosensory tinnitus: review article

Tinnitus is the perception of sound in the absence of an acoustic external stimulus. It affects 10-17 percent of the world's population and it a complex symptom with multiple causes, which is influenced by pathways other than the auditory one. Recently, it has been observed that tinnitus may be provoked or modulated by stimulation arising from the somatosensorial system, as well as from the somatomotor and visual-motor systems. This specific subgroup -somatosensory tinnitus - is present in 65 percent of cases, even though it tends to be underdiagnosed. As a consequence, it is necessary to establish evaluation protocols and specific treatments focusing on both the auditory pathway and the musculoskeletal system.

Immunoreactivity of Calcium-Binding Proteins in the Central Auditory Nervous System of Aged Rats

OBJECTIVE: While many factors contribute to aging, changes in calcium homeostasis and calcium related neuronal processes are likely to be important. High intracellular calcium is toxic to cells and alterations in calcium homeostasis are associated with changes in calcium-binding proteins, which confine free Ca2+. We therefore assayed the expression of the calcium binding proteins calretinin and calbindin in the central auditory nervous system of rats. METHODS: Using antibodies to calretinin and calbindin, we assayed their expression in the cochlear nucleus, superior olivary nucleus, inferior colliculus, medial geniculate body and auditory cortex of young (4 months old) and aged (24 months old) rats. RESULTS: Calretinin and calbindin staining intensity in neurons of the cochlear nucleus was significantly higher in aged than in young rats (p<0.05) The number and staining intensity of calretinin-positive neurons in the inferior colliculus, and of calbindin-positive neurons in the superior olivary nucleus were greater in aged than in young rats (p<0.05). CONCLUSION: These results suggest that auditory processing is altered during aging, which may be due to increased intracellular Ca2+ concentration, consequently leading to increased immunoreactivity toward calcium-binding proteins.

Neuroimmunological Activation of Afferent Auditory Neural Circuit in LPS-Induced Otitis Media / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES : The goal of this study was to identify the central modulation of the auditory pathway by peripheral inflammation and loud sound exposure, which is associated with proinflammatory cytokines. MATERIALS AND METHOD : Eight male adult Sprague-Dawley rats were exposed to 125-8,000 Hz, 90 dB white noise for three hours. Immediately, 6 hours, 24 hours, and 3 days after the sound stimuli, 2 rats were sacrificed respectively. For the inflammatory stimuli, 10 rats were inoculated with LPS (100 microgram/50 microliter) through ipsilateral tympanic membrane. In 3 hours, 6 hours, 24 hours, 3 days and 7 days, 2 rats were sacrificed respectively. The brains of rats were prepared including the cochlear nucleus and inferior colliculus. The brains were stained for c-fos (proto-oncogene proteins) and IL-1beta. Two normal control rats were sacrificed without treatment. RESULTS : In the noise exposure group, c-fos and IL-1beta were expressed along the previously known auditory neural pathway and some non-hearing-related nuclei. In the LPS injection group, the c-fos and inflammatory cytokine IL-1beta were mainly expressed along the ascending afferent auditory pathway such as cochlear nucleus, trapezoid body, lateral lemniscus, inferior colliculus. IL-1beta expression was also found in the nuclei of non auditory pathway such as locus coeruleus, lateral parabrachial nucleus, and vestibular nucleus. CONCLUSION : These results show that inflammatory reactions of peripheral middle ear cavity and loud sound exposure may induce expression of proinflammatory cytokines along the afferent auditory circuit and the functional auditory pathway. It might be suggested that peripheral changes by inflammation or loud sound could induce functional and physiologic alterations in the auditory system via neuroimmunomodulation.

Computer Generated Three-Dimensional Reconstruction of the Auditory Pathway Structures of Brainstem

OBJECTIVE: The purpose of the study is to draw the three-dimensional reconstructions of nuclei and tracts of the auditory pathway structures of drainstem. METHOD: The drawings of 1 mm sections of the brainstem were scanned with a computer scanner into AUTOCAD program. All lines of structures except for the auditory pathway structures and outlines were removed. Each layer was plotted to a x, y, and z coordinated plotting reference to the corresponding points on the mid-sagittal plane and reconstructed to a three-dimensional drawing. Center point of the auditory pathway structures of all cross section layers were connected with a line in succession and that was thought to be a imaginary pathway of auditory pathway through the brainstem. RESULTS: This auditory pathway has several turning points, at the cochlear nucleus, superior olivary nucleus, and inferior colliculus which correspond with known generation sources of the peak of brainstem evoked potentials. CONCLUSION: This study presents a method for the conversion of the two-dimensional transverse sections into a three-dimensional format, to allow the visualization of the auditory pathway structures from multiple directions.

Pathology in Different Sites of Auditory Pathway had Different Effects on the Central Masking / 听力学及言语疾病杂志

Objective To investigate the appropri ate changes of the central masking effect(CME) when there were pathologies in d ifferent segment of auditory pathway,so as to give some instructions in cli nical masking test. Methods We tested the subjects with one ear normal and th e other ear diseased. The diseased ears included conductive deafness in 30 ca ses?sensory deafness in 27 cases and retrocochlear deafness in 7 cases. Results The pure conductive deafness had very little effect on CME; secretory otistis media and chronic suppurative otistis medi a made CME lower than normal due to the secondary cochlear impairment .When su dden deafness companied with vertigo,CME appeared much higher than the normal and appeared great difference individually;but CME appeared lower than normal at other kinds of cochlear deafness ears.CME appeared differently at retrocochlear deafness ears. Conclusion Audiometry results should be corrected when th e masker higher than 40 dB EM,because the masker can make the CME higher than 5 dB in the conductive impairment ears.In the sudden de afness companied with vertigo ears,CMEs were too high and too individually to fi nd a suitable correction for PTT.Insert earphone should be used in measuring the air-conduction PTT,and bone-conduction PTT test might be given up.

DISTRIBUTION OF SUBSTANCE P-IMMUNOREACTIVE NEURONS IN THE ACCESSORY AUDITORY PATHWAY OF PIGEON / 解剖学报

Objective To observe the distribution of substance P in the accessory auditory pathway of pigeon. Methods Immunocytochemical staining by using specific antibody against substance P was used. Results Intensely stained SP-like immunoreactive (SP-ir) neurons and fibers were mainly observed in the nucleus intercollicularis (ICo), periphery area of nucleus ventralis leminisci lateralis(VLV), shell area of nucleus ovoidalis (Ov), nucleus periventricularis magnocellularis (PVM), nucleus ventromedialis hypothalami(VMN), periphery area of the nucleus taeniae (Tn) of posterior archistriatum, nucleus preopticus anterior(POA), and the tractus septomesencephalicus(TSM).Conclusion There are many SP-ir structures in the accessory auditory pathway and brain regions related to reproductive control of the pigeon. Our results suggest SP may play a functional role in the vocal and endocrine regulation.