Subcallosal brain structure: Correlation with hearing threshold at supra-clinical frequencies (> 8 kHz), but not with tinnitus

Dept. of Otology and Laryngology, Harvard Medical School, Boston MA, USA
Hearing research (Impact Factor: 2.97). 04/2012; 295. DOI: 10.1016/j.heares.2012.03.013
Source: PubMed


This study tested for differences in brain structure between tinnitus and control subjects, focusing on a subcallosal brain region where striking differences have been inconsistently found previously. Voxel-based morphometry (VBM) was used to compare structural MRIs of tinnitus subjects and non-tinnitus controls. Audiograms of all subjects were normal or near-normal at standard clinical frequencies (≤8 kHz). Mean threshold through 14 kHz, age, sex and handedness were matched between groups. There were no definitive differences between tinnitus and control groups in modulated or unmodulated maps of gray matter (GM) probability (i.e., GM volume and concentration, respectively). However, when the image data were tested for correlations with parameters that were either not measured or not matched between the tinnitus and control groups of previous studies, a notable correlation was found: Threshold at supra-clinical frequencies (above 8 kHz) was negatively correlated with modulated GM probability in ventral posterior cingulate cortex, dorsomedial prefrontal cortex, and a subcallosal region that included ventromedial prefrontal cortex and coincided with previously-reported differences between tinnitus and control subjects. The results suggest an explanation for the discrepant findings in subcallosal brain: threshold at supra-clinical frequencies may have differed systematically between tinnitus and control groups in some studies but not others. The observed correlation between (1) brain structure in regions engaged in cognitive and attentional processes and (2) hearing sensitivity at frequencies generally considered unnecessary for normal human auditory behavior is surprising and worthy of follow up.

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    • "Most such studies investigated sound-evoked activity. Interpretation of these data is difficult as associated comorbidities such as hearing loss and hyperacusis have to be considered (Gu et al., 2010; Melcher et al., 2013; Schecklmann et al., 2013). If a tinnitus-like sound is used for stimulation it is a challenge to exactly measure the pitch and volume of the tinnitus (Hoare et al., 2014). "
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    ABSTRACT: Chronic tinnitus is associated with neuroplastic changes in auditory and non-auditory cortical areas. About 10 years ago, repetitive transcranial magnetic stimulation (rTMS) of auditory and prefrontal cortex was introduced as potential treatment for tinnitus. The resulting changes in tinnitus loudness are interpreted in the context of rTMS induced activity changes (neuroplasticity). Here, we investigate the effect of single rTMS sessions on oscillatory power to probe the capacity of rTMS to interfere with tinnitus-specific cortical plasticity. We measured 20 patients with bilateral chronic tinnitus and 20 healthy controls comparable for age, sex, handedness, and hearing level with a 63-channel electroencephalography (EEG) system. Educational level, intelligence, depressivity and hyperacusis were controlled for by analysis of covariance. Different rTMS protocols were tested: Left and right temporal and left and right prefrontal cortices were each stimulated with 200 pulses at 1 Hz and with an intensity of 60% stimulator output. Stimulation of central parietal cortex with 6-fold reduced intensity (inverted passive-cooled coil) served as sham condition. Before and after each rTMS protocol 5 min of resting state EEG were recorded. The order of rTMS protocols was randomized over two sessions with 1 week interval in between. Analyses on electrode level showed that people with and without tinnitus differed in their response to left temporal and right frontal stimulation. In tinnitus patients left temporal rTMS decreased frontal theta and delta and increased beta2 power, whereas right frontal rTMS decreased right temporal beta3 and gamma power. No changes or increases were observed in the control group. Only non-systematic changes in tinnitus loudness were induced by single sessions of rTMS. This is the first study to show tinnitus-related alterations of neuroplasticity that were specific to stimulation site and oscillatory frequency. The observed effects can be interpreted within the thalamocortical dysrhythmia model assuming that slow waves represent processes of deafferentiation and that high frequencies might be indicators for tinnitus loudness. Moreover our findings confirm the role of the left temporal and the right frontal areas as relevant hubs in tinnitus related neuronal network. Our results underscore the value of combined TMS-EEG measurements for investigating disease related changes in neuroplasticity.
    Frontiers in Cellular Neuroscience 11/2015; 9:421. DOI:10.3389/fncel.2015.00421 · 4.29 Impact Factor
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    • "Hearing loss is typically comorbid with tinnitus suggesting the tinnitus percept is a direct consequence of maladaptive neuroplastic responses to hearing loss [3]. Current models of tinnitus generation therefore focus on the potential consequences of hearing loss on neuronal activity within the central auditory system [4]–[12], although neuronal structures or networks responsible for tinnitus that are independent of those for hearing loss are yet to be convincingly determined [13]–[16]. "
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    ABSTRACT: BackgroundPrevious studies of frequency discrimination training (FDT) for tinnitus used repetitive task-based training programmes relying on extrinsic factors to motivate participation. Studies reported limited improvement in tinnitus symptoms.PurposeTo evaluate FDT exploiting intrinsic motivations by integrating training with computer-gameplay.MethodsSixty participants were randomly assigned to train on either a conventional task-based training, or one of two interactive game-based training platforms over six weeks. Outcomes included assessment of motivation, tinnitus handicap, and performance on tests of attention.ResultsParticipants reported greater intrinsic motivation to train on the interactive game-based platforms, yet compliance of all three groups was similar (∼70%) and changes in self-reported tinnitus severity were not significant. There was no difference between groups in terms of change in tinnitus severity or performance on measures of attention.ConclusionFDT can be integrated within an intrinsically motivating game. Whilst this may improve participant experience, in this instance it did not translate to additional compliance or therapeutic benefit.Trial NCT02095262
    PLoS ONE 09/2014; 9(9):e107430. DOI:10.1371/journal.pone.0107430 · 3.23 Impact Factor
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    • "Although hearing loss is not supposed to be a predictor for response to rTMS treatment [24], previous studies have shown that hearing loss is an important confounder concerning GM changes in tinnitus patients [14, 60, 61]. To be able to thoroughly interpret research results, future work should try to include pure tone audiogram including high frequency audiogram [14, 60, 61] for all patients. Second, the lacking correlation between treatment outcome and GM changes might have been due to the small treatment effects. "
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    ABSTRACT: Repetitive transcranial magnetic stimulation (rTMS) of the temporal cortex has been used to treat patients with subjective tinnitus. While rTMS is known to induce morphological changes in healthy subjects, no study has investigated yet whether rTMS treatment induces grey matter (GM) changes in tinnitus patients as well, whether these changes are correlated with treatment success, and whether GM at baseline is a useful predictor for treatment outcome. Therefore, we examined magnetic resonance images of 77 tinnitus patients who were treated with rTMS of the left temporal cortex (10 days, 2000 stimuli/day, 1 Hz). At baseline and after the last treatment session high-resolution structural images of the brain were acquired and tinnitus severity was assessed. For a subgroup of 41 patients, additional brain scans were done after a follow-up period of 90 days. GM changes were analysed by means of voxel based morphometry. Transient GM decreases were detectable in several brain regions, especially in the insula and the inferior frontal cortex. These changes were not related to treatment outcome though. Baseline images correlated with change in tinnitus severity in the frontal cortex and the lingual gyrus, suggesting that GM at baseline might hold potential as a possible predictor for treatment outcome.
    Neural Plasticity 06/2014; 2014:132058. DOI:10.1155/2014/132058 · 3.58 Impact Factor
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