A team of international researchers, led by Dr. Kevin W. McCairn, Ph.D. announced today the discovery of a system in the brain that may underlie the development of involuntary vocalizations (commonly called vocal tics) that often occur in people with Tourette syndrome. The study is published in the January 2016 issue of the journal Neuron and was supported by the Tourette Syndrome Association of America. “The findings from this group of researchers will help to explain how vocals tics develop which can be a significant problem for individuals with TS and related disorders,” said Kevin McNaught, Ph.D., Executive Vice President, Research and Medical Programs, Tourette Association of America.
Tourette syndrome (TS) and other tic disorders are neurodevelopmental conditions that affect 1 in 100 school-aged children, as well as a significant number of adults in the United States. These disorders are defined by complex patterns of involuntary movements and sounds called tics. The latter can range from simple sounds to complex vocalizations, such as coprolalia, which is the utterance of words and phrases that can be obscene and socially unacceptable. These symptoms are difficult to manage due to a lack of effective treatments and represent a significant source of challenge for people with TS.
Dr. McCairn and his team at the Korea Brain Research Institute – Korea, in collaboration with researchers at the National Institute of Radiological Science – Japan, Primate Research Institute – Kyoto University, RIKEN, Kansai and Tsukuba University, used PET imaging experiments to monitor metabolic activity in the brain of non-human primates as different regions were stimulated to induce vocal tics. It was found that a network called the limbic system, a region of the brain that is involved in emotional processing, exhibited very high activity suggesting that it plays a role in vocal tic generation. These findings are in line with previous findings from Tourette Association of America funded research on motor tics, conducted by Dr. McCairn and Dr. Bar-Gad at Bar Ilan University, Israel.
Dr. Kevin W. McCairn and colleagues describe their latest findings on how various regions of the brain (basal ganglia and cortex) interact to produce different subtypes of tics (motor vs. vocal). They demonstrate that vocal tics are a consequence of abnormalities in the limbic system and emerge as a consequence of increased alpha (7–12 Hz) phase coupling between nucleus accumbens and anterior cingulate cortex.
Dr. McCairn said “Identification of the brain regions and mechanisms that control the abnormal vocalizations associated with TS has been a goal of researchers and clinicians since the initial description of the disorder by Gilles de La Tourette in the 19th century. A reproducible model of these behaviors now provides an opportunity to more fully understand how the disease affects the brain and provides a platform on which to test new treatments.”
This NeuroscienceNews.com article was submitted by Dr. Kevin W. McCairn, Ph.D.. We would like to thank Dr. McCairn for submitting this post to us.
Source: Dr. Kevin W. McCairn, Ph.D. – Kyoto University/Tourette Association of America
Image Source: The image is credited to the researchers
Video Source: The video is available at the Cellvideoabstracts YouTube page
Original Research: Abstract for “A Primary Role for Nucleus Accumbens and Related Limbic Network in Vocal Tics” by Kevin W. McCairn, Yuji Nagai, Yukiko Hori, Taihei Ninomiya, Erika Kikuchi, Ju-Young Lee, Tetsuya Suhara, Atsushi Iriki, Takafumi Minamimoto, Masahiko Takada, Masaki Isoda, and Masayuki Matsumoto in Neuron. Published online January 20 2016 doi:10.1016/j.neuron.2015.12.025
A Primary Role for Nucleus Accumbens and Related Limbic Network in Vocal Tics
•First demonstration of modeled TS symptoms utilizing PET in monkeys
•Vocal tics correlated with widespread increases in blood flow in the limbic network
•Direct comparison of vocal tics with established motor tic model
•Cross-domain electrophysiological recording (motor versus limbic) during tic expression
Inappropriate vocal expressions, e.g., vocal tics in Tourette syndrome, severely impact quality of life. Neural mechanisms underlying vocal tics remain unexplored because no established animal model representing the condition exists. We report that unilateral disinhibition of the nucleus accumbens (NAc) generates vocal tics in monkeys. Whole-brain PET imaging identified prominent, bilateral limbic cortico-subcortical activation. Local field potentials (LFPs) developed abnormal spikes in the NAc and the anterior cingulate cortex (ACC). Vocalization 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.
“A Primary Role for Nucleus Accumbens and Related Limbic Network in Vocal Tics” by Kevin W. McCairn, Yuji Nagai, Yukiko Hori, Taihei Ninomiya, Erika Kikuchi, Ju-Young Lee, Tetsuya Suhara, Atsushi Iriki, Takafumi Minamimoto, Masahiko Takada, Masaki Isoda, and Masayuki Matsumoto in Neuron. Published online January 20 2016 doi:10.1016/j.neuron.2015.12.025