REORGANIZATION OF AUDITORY-CORTEX IN TINNITUS

Magnetic source imaging was used to determine whether tonotopy in audi tory cortex of individuals with tinnitus diverges from normative funct ional organization. Ten tinnitus subjects and 15 healthy controls were exposed to four sets of tones while magnetoencephalographic recording s were obtained from the two cortical hemispheres in sequence. A marke d shift of the cortical representation of the tinnitus frequency into an area adjacent to the expected tonotopic location was observed. The Euclidean distance of the tinnitus frequency from the trajectory of th e tonotopic map was 5.3 mm (SD = 3.1) compared with a distance of 2.5 mm (SD = 1.3) of a corresponding frequency in the healthy controls (t = 3.13, P < 0.01). In addition, a strong positive correlation was foun d between the subjective strength of the tinnitus and the amount of co rtical reorganization (r = 0.82, P < 0.01). These results demonstrate that tinnitus is related to plastic alterations in auditory cortex. Si milarities between these data and the previous demonstrations that pha ntom limb pain is highly correlated with cortical reorganization sugge st that tinnitus may be an auditory phantom phenomenon.