Abstract
The pathophysiology underlying tinnitus, a hearing disorder characterized by the chronic perception of phantom sound, has been related to aberrant plastic reorganization of the central auditory system. More specifically, tinnitus is thought to involve changes in the tonotopic representation of sound. In the present study we used high-resolution functional magnetic resonance imaging to determine tonotopic maps in the auditory cortex of 20 patients with tinnitus but otherwise near-normal hearing, and compared these to equivalent outcomes from 20 healthy controls with matched hearing thresholds. Using a dedicated experimental paradigm and data-driven analysis techniques, multiple tonotopic gradients could be robustly distinguished in both hemispheres, arranged in a pattern consistent with previous findings. Yet, maps were not found to significantly differ between the two groups in any way. In particular, we found no evidence for an overrepresentation of high sound frequencies, matching the tinnitus pitch. A significant difference in evoked response magnitude was found near the low-frequency tonotopic endpoint on the lateral extreme of left Heschl’s gyrus. Our results suggest that macroscopic tonotopic reorganization in the auditory cortex is not required for the emergence of tinnitus, and is not typical for tinnitus that accompanies normal hearing to mild hearing loss.
Highlights
Subjective tinnitus is a prevalent and presently incurable hearing disorder that is characterized by the perception of sound in the absence of an identifiable sound source
An important clue lies in the observation that the perceived tinnitus pitch often coincides with frequency regions in which hearing thresholds are found to be elevated
SUBJECTS Twenty healthy controls and 20 chronic subjective tinnitus patients participated in this functional magnetic resonance imaging study on the basis of written informed consent, in approved accordance with the requirements of the medical ethical committee at the University Medical Center Groningen in the Netherlands
Summary
Subjective tinnitus is a prevalent and presently incurable hearing disorder that is characterized by the perception of sound in the absence of an identifiable sound source. An important clue lies in the observation that the perceived tinnitus pitch often coincides with frequency regions in which hearing thresholds are found to be elevated. It is still debated whether tinnitus is most closely associated with the frequency range that covers the hearing loss (Noreña et al, 2002; Roberts et al, 2008) or with the edge-frequency where the audiogram is steepest (König et al, 2006; Moore and Vinay, 2010), but in either case the existence of the association suggests some causal relationship
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