LAUSR

The thalamic medial geniculate body (MGB) is uniquely positioned within the neural tinnitus networks. Deep brain stimulation (DBS) of the MGB has been proposed as a possible novel treatment for tinnitus, yet mechanisms remain elusive. The aim of this study was to characterize neurophysiologic hallmarks in the MGB after noise-exposure and to assess the neurophysiological effects of electrical stimulation of the MGB. Fourteen male Sprague Dawley rats were included. Nine subjects were unilaterally exposed to a 16 kHz octave-band noise at 115 dB for 90 minutes, five received sham exposure. Single units were recorded from the contralateral MGB where spontaneous firing, coefficient of variation, response type, rate-level functions and thresholds were determined. Local field potentials and electroencephalographical (EEG) recordings were performed before and after high frequency DBS of the MGB. Thalamocortical synchronization and power were analyzed. In total, 214 single units were identified (n = 145 in noise-exposed group, n = 69 in control group). After noise-exposure, fast-responding neurons become less- or non-responsive without change to their spontaneous rate, while sustained and suppressed type neurons exhibit enhanced spontaneous activity without change to their stimulus driven activity. MGB DBS suppressed thalamocortical synchronization in the beta and gamma bands, supporting suppression of thalamocortical synchronization as an underlying mechanism of tinnitus suppression by high frequency DBS. These findings contribute to our understanding of the neurophysiologic consequences of noise-exposure and the mechanism of potential DBS therapy for tinnitus.