Toward An Exploration of Habituating to Tinnitus: Perspectives on Sensory Gating.

BACKGROUND: Some tinnitus participants habituate to their tinnitus, but some others do not and complain of its annoyance so much. It has been suggested that tinnitus is a habituation deficit. Habituation and the ability to ignore a sensory input depend on the normal function of filtering mechanism of sensory gating. PURPOSE: The purpose of this study was to compare behavioral aspects of sensory gating in normal and tinnitus participants to search for the reason why some tinnitus participants habituate to their tinnitus but some others do not. RESEARCH DESIGN: This investigation was an observational case-control study. STUDY SAMPLE: There were 60 tinnitus participants who were categorized into two tinnitus groups (30 compensated tinnitus participants and 30 decompensated tinnitus participants) based on the complaint of tinnitus annoyance, visual analog scale (VAS) for tinnitus loudness, annoyance, and awareness, scores on Tinnitus Questionnaire (TQ), and Tinnitus Handicap Inventory (THI). Also, there were 30 normal hearing participants without tinnitus as the normal control group. DATA COLLECTION AND ANALYSIS: Sensory Gating Inventory (SGI), TQ, THI, and VAS was obtained from all participants. THI, TQ, VAS, and SGI total scores and their factors were compared among the groups. Correlations between SGI scores with THI, TQ, and VAS score were calculated. RESULTS: The results showed that SGI total score and the scores of its four factors were significantly higher in decompensated tinnitus participants compared with compensated tinnitus participants and normal controls. Also, there was a positive correlation between SGI perceptual modulation factor and TQ emotional distress factor and with the VAS for loudness in decompensated tinnitus group. CONCLUSIONS: These results suggested that tinnitus associated with behavioral aspects of sensory gating and decompensated tinnitus may be a result of deficient sensory gating.

The potential role of auditory prediction error in decompensated tinnitus: An auditory mismatch negativity study.

INTRODUCTION: Some tinnitus subjects habituate to their tinnitus but some others do not and complain of its annoyance tremendously. Normal sensory memory and change detection processes are needed for detecting the tinnitus signal as a prediction error and habituation to tinnitus. The purpose of this study was to compare auditory mismatch negativity as the index of sensory memory and change detection among the studied groups to search for the factors involving in the perception of tinnitus and preventing habituation in decompensated tinnitus subjects. METHODS: Electroencephalography was recorded from scalp electrodes in compensated tinnitus, decompensated tinnitus, and no tinnitus control subjects. Mismatch negativity was obtained using the oddball paradigm with frequency, duration, and silent gap deviants. Amplitude, latency, and area under the curve of mismatch negativities were compared among the three studied groups. RESULTS: The results showed lower mismatch negativity amplitude and area under the curve for the higher frequency deviant and for the silent gap deviant in decompensated tinnitus group compared to normal control and compensated tinnitus group. CONCLUSIONS: This study revealed a deficit in sensory memory and change detection processing in decompensated tinnitus subjects. This causes persistent prediction errors; tinnitus signal is consistently detected as a new signal and activates the brain salience network and consequently prevents habituation to tinnitus. Mismatch negativity is proposed as an index for monitoring tinnitus rehabilitation.

Developing the Persian Version of Sensory Gating Inventory and Assessing Its Validity and Reliability.

INTRODUCTION: Sensory Gating Inventory (SGI) measures behavioral aspects of Sensory Gating (SG), which filters irrelevant sensory inputs into the higher cortex. It modifies sensitivity to sensory stimuli. Abnormal SG leads to overloading of information in the brain and its subsequent dysfunction. Electrophysiological techniques cannot assess the behavioral aspects of SG. We aimed to design the Persian version of SGI with high validity and reliability. METHODS: After a forward and then backward translation of the original SGI, we assessed the content validity and construct validity of the Persian version. A total of 405 participants filled the Persian version of SGI. To assess test-retest reliability, 100 participants filled the inventory again 7-10 days later. The content validity ratio and index, as well as confirmatory factor analysis, were computed, too. Finally, the Cronbach's alpha, Cohen's kappa, and intraclass correlation coefficients were calculated. RESULTS: The content validity ratios of all items of the inventory were more than 60%, which means that they were necessary according to the experts' opinions. Confirmatory factor analysis confirmed the fitness of the 4-factor structure of the original Inventory. The test-retest reliability using the intraclass correlation coefficient and Cronbach's alpha coefficients were also high for the four subscales. The Cohen's kappa coefficients revealed moderate to substantial level of agreement between the first and second scores for all items. CONCLUSION: The Persian version of SGI has good and acceptable psychometric properties. It can be used as a valid and reliable tool for studying behavioral aspects of SG in Persian speaking population.

Alterations in auditory change detection associated with tinnitus residual inhibition induced by auditory electrical stimulation.

BACKGROUND: Residual inhibition (RI) is a temporary phenomenon that happens following offset of appropriate complete or partial acoustical and electrical masking stimulations in people who experience tinnitus. The biologic mechanisms associated with RI are not yet fully understood. Few studies have been focused on RI. Auditory mismatch negativity (MMN) as a change-detection tool may be an appropriate tool to explore the processing changes because of tinnitus and RI. PURPOSE: The purpose of this study was to investigate alterations in auditory change detection and auditory sensory memory related to RI induced by auditory electrical stimulation (AES) using MMN brain mapping in participants with tinnitus. RESEARCH DESIGN: This investigation was a single-blind randomized controlled clinical trial study. Participants were randomly assigned into two groups: AES and placebo electrical stimulation (PES). STUDY SAMPLE: Twenty-eight participants with chronic subjective tinnitus aged 22- to 45-yr-old participated in the study. INTERVENTION: After randomization, all participants received both AES and PES for 1 min in different sessions. DATA COLLECTION AND ANALYSIS: Brain mapping of multifeature MMN paradigm was recorded from 29 scalp electrodes pre- and post-AES and PES. Following AES, participants were categorized into two groups: RI and nonresidual inhibition (NRI). The grand average MMN waveforms and isopotential topographic maps were obtained in RI, NRI, and PES groups. RESULTS: Three MMN parameters for five deviants of frequency, intensity, duration, location, and silent gap were compared among three groups of RI, NRI, and PES. Statistical analyses revealed significant between-subject effects for AES on MMN amplitude of frequency and duration deviant, MMN area under the curve of frequency, intensity, and duration deviants. CONCLUSIONS: Presence of RI can reestablish change-detection mechanisms in the central auditory pathways. It is suggested that MMN is reliable for assessment of change-detection system in people with tinnitus. It can be a useful technique in monitoring effects of treatments and rehabilitation.

Auditory middle latency responses differ in right- and left-handed subjects: an evaluation through topographic brain mapping.

PURPOSE: To investigate the association of handedness with auditory middle latency responses (AMLRs) using topographic brain mapping by comparing amplitudes and latencies in frontocentral and hemispheric regions of interest (ROIs). METHOD: The study included 44 healthy subjects with normal hearing (22 left handed and 22 right handed). AMLRs were recorded from 29 scalp electrodes in response to binaural 4-kHz tone bursts. RESULTS: Frontocentral ROI comparisons revealed that Pa and Pb amplitudes were significantly larger in the left-handed than the right-handed group. Topographic brain maps showed different distributions in AMLR components between the two groups. In hemispheric comparisons, Pa amplitude differed significantly across groups. A left-hemisphere emphasis of Pa was found in the right-handed group but not in the left-handed group. CONCLUSION: This study provides evidence that handedness is associated with AMLR components in frontocentral and hemispheric ROI. Handedness should be considered an essential factor in the clinical or experimental use of AMLRs.

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.