Spatial and non-spatial auditory processing of people with and without tinnitus

Abstract

Objectives: To investigate the spatial and non spatial peripheral auditory processing of participants with and without tinnitus, and to explore the predictive factors of the severity of tinnitus. Methods: A total of forty participants were used in this study, twenty one of which had chronic subjective tinnitus. The severity of tinnitus was determined using Tinnitus Sample Case History Questionnaire (TSCHQ) and the Tinnitus Functional Index (TFI). The subjective perception of spatial hearing was measured using the Speech, Spatial and quality of Hearing Scale (SSQ). Spatial and non spatial auditory processing was investigated by analysing the speed of cortical processing during sound detection, sound localisation and frequency discrimination. In addition, the risk factors for the severity of tinnitus were assessed. Results: No significant differences between tinnitus and controls were observed in the spatial tasks. However the tinnitus group showed a marginally significant slower response speed in the pitch discrimination task. Participants with central tinnitus responded significantly more slowly in all experiments compared with those with peripheral tinnitus. The reaction times were significantly correlated with a tinnitus pitch match, type of onset, and auditory thresholds. The severity of tinnitus was significantly correlated with the following variables: type of onset, family history, location of tinnitus, tinnitus pitch match and tinnitus loudness rating. Conclusion: The slower response speed of tinnitus patients in the pitch discrimination task may suggest an impaired ‘what’ pathway of auditory processing. This supports the potential benefits of non-spatial auditory training such as Frequency Discrimination Therapy (FDT) or Auditory Object Identification and Localisation (AOIL) tasks. The discrepancy observed between central and peripheral tinnitus patients supports the presentation of the training stimuli at a location which matches the perceived tinnitus location. In addition, the significantly faster reaction times seen in high frequency tinnitus patients support the habituation theory of tinnitus as well as the recently proposed “noise-cancellation” mechanism of Nucleus Accumbens (NAc).