Support of a patient-specific therapeutical acoustic stimulation in tinnitus by numerical modeling

Abstract

The pathogenesis of tinnitus involves multiple hierarchical levels of auditory processing and appraisal of sensory saliency. Early tinnitus onset is most likely attributed to homeostatic plasticity in the periphery, while the chronification and decompensation are tightly linked to brain areas for the allocation of attentional resources, such as e.g., the thalamocortical feedback loops and the limbic system. Increased spontaneous firing after sensory deafferentation might be sufficient to generate a phantom perception, yet the question why not every peripheral hearing loss automatically elicits a tinnitus sensation is still to be addressed. Utilizing quantitative modeling of multiple hierarchical levels in the auditory pathway, we demonstrate the effects of lateral inhibition on increased spontaneous firing and the resulting elevation of firing regularity and synchronization of neural activity. The presented therapeutical approach is based on the idea of disrupting the heightened regularity of the neural population response in the tinnitus frequency range. This neural activity regularity depends on lateral dispersion of common noise and thus is susceptible for edge effects and might be influenced by a change in neural activity in bordering frequency ranges by fitted acoustical stimulation. We propose the use of patient specifically adapted tailor-made notched acoustic stimulation, utilizing modeling results for the optimal adjustment of the stimulation frequencies to archive a therapeutical edge-effect.

Notched environmental sounds: a new hearing aid‐supported tinnitus treatment evaluated in 20 patients

“…The bandwidth of this notch filter was computed using a specifically designed computational modelling scheme. 6 There was no additional edge amplification. The groups were characterised by their mean PTA (mPTA; PTA derived from 0.5, 1, 2, 4 kHz), mean matched tinnitus frequency (mmtf), mean age and gender proportions: Group 1: mPTA (right) = 29.12 AE 11.06, mPTA (left) = 29.00 AE 14.60, mmtf = 5.8 AE 1.48 kHz, mean age = 53.5 AE 4.8y; 9 m/1f; Group 2: mPTA (right) = 28.38 AE12.22, mPTA (left): 29.25 AE 11.16, mmtf = 4.6 AE 1.51 kHz, mean age: 52.70 AE 5.85y, 8 m/2f; there were no significant (ANOVA, P-level = 0.05) differences between the groups regarding these quantities.…”

“…5 However, apart from possibly limbically trigged reorganisation processes, a key concept of this promising TMNMT might be the suppression of the neural hyperactivity in deprived frequency bands by lateral inhibition using the notch-induced sharp spectral edge. 5,6 In other words, a localised damage in the lower auditory system resultsdue to the tonotopic organisation of hearing pathin the bandspecific neural hyperactivity mentioned before. The tailormade notch is adjusted to the tinnitus frequency and deprived frequency band, respectively, so that the spectral edges of the deprived frequency band are enhanced.…”

“…Up to now, the exact range of the asymmetric lateral inhibition in human is unknown, reducing the theoretical framework of this approach to tonal, small band tinnitus sounds. 6 New approach using hearing aids In this study, we evaluate a new notch-based tinnitus treatment strategy: we use a tailor-made notch, that is a notch that is adjusted to the tinnitus spectra, in hearing aids. This notch induces sharp spectral edges to the environmental sound spectra which might trigger lateral inhibition mechanisms.…”

Suppression of spontaneous activity in a computational tinnitus DCN model depends on notched-stimulation bandwidth

“…This increased downstream neuron activity in the area of a cochlear lesion could be perceived as a pure tone tinnitus [4]. As the following DCN network amplifies pure tones by inhibiting the lateral frequencies, this property should be used to suppress the occurring tinnitus before it is further amplified by hierarchically higher processing stages in the auditory pathway.…”

“…In a computational modeling study we were able to show recently that notched acoustic stimulation is able to reduce increased firing regularity in peripheral auditory neurons [4], which results from elevated spontaneous activity as hypothesized by Schaette et al [5]. An increased spontaneous activity might cause the interconnected neurons to fire more regular and synchronized, providing a sensory stream with a selective advantage in perceptual rivalry [6].…”