Deep brain stimulation in area LC controllably triggers auditory phantom percepts.

BACKGROUND: Tinnitus is predominantly viewed as the consequence of dysfunctional hyperactivity, plastic change, or synchronized oscillations in the central auditory system. An alternative to the current auditory-centric view of auditory phantom perception is the basal ganglia-centric view. Recent electrical stimulation experiments in area LC, a locus of the caudate nucleus positioned at its anterior body, has shown loudness modulation of existing tinnitus percepts.
OBJECTIVE: To demonstrate that auditory phantoms are gated by the dorsal striatum.
METHODS: Electrical stimulation in area LC via a deep brain stimulation lead was performed in 6 interactive adult subjects (3 with and 3 without chronic tinnitus) undergoing surgery to treat movement disorders. Tinnitus loudness was rated on a 0 to 10 scale, sound quality was described, and localization was referenced to 1 or both ears.
RESULTS: Short-term area LC stimulation triggered new phantom tones, clicks, and frequency modulated sounds in 5 subjects and altered sound quality of an existing tinnitus percept in 1 subject. The results of this study indicate that perceptual awareness of auditory phantoms is contingent on satisfying a permission condition controlled by the dorsal striatum. Potential auditory phantoms are not automatically gated to reach perceptual awareness. A phantom percept gate control model is proposed.
CONCLUSION: Neuromodulation of area LC can trigger temporary gate dysfunction and reversibly release new phantoms for conscious awareness. Restoration of restrictive dorsal striatal gate function to treat problematic phantom percepts may be realized by adopting long-term area LC neuromodulation and choosing optimal stimulation parameters.