Journal Article A primary role for nucleus accumbens and related limbic network in vocal tics

William McCairn, Kevin  ,  Nagai, Yuji  ,  Hori, Yukiko  ,  Kikuchi, Erika  ,  Ninomiya, Taihei  ,  Suhara, Tetsuya  ,  Ju-Young, Lee  ,  Iriki, Atsushi  ,  Minamimoto, Takafumi  ,  Takada, Masahiko  ,  Isoda, Masaki  ,  Matsumoto, Masayuki

89 ( 2 )  , pp.300 - 307 , 2016-01 , Elsevier
Inappropriate vocal expressions - e.g., vocal tics in Tourette syndrome - severely impact quality of life. Neural mechanisms underlying vocal tics remain unexplored because of no established animal model representing the condition. We report unilateral disinhibition of the nucleus accumbens (NAc) generates vocal tics in monkeys. Whole-brain PET imaging identified prominent, bilateral limbic corticosubcortical activation. Local field potentials (LFPs) usually developed abnormal spikes in the NAc and the anterior cingulate cortex (ACC). The behavioral manifestation could occur without obvious LFP spikes, however, when phase-phase coupling of alpha oscillations were accentuated between the NAc, ACC, and the primary motor cortex. These findings contrasted with myoclonic motor tics induced by disinhibition of the dorsolateral putamen, where PET activity was confined to the ipsilateral sensorimotor system and LFP spikes always preceded motor tics. We propose that vocal tics emerge as a consequence of dysrhythmic alpha coupling between critical nodes in the limbic and motor networks.

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