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Thread: Scientists Find Key Brain Chemical to Control Tics

  1. #1
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    Post Scientists Find Key Brain Chemical to Control Tics

    Tourette's Treatment: Scientists Find Key Brain Chemical to Control Tics

    International Business Times
    September 25, 2014

    A chemical in the brain that plays a vital role in controlling the involuntary tics associated with Tourette's Syndrome has been discovered by scientists.

    Tourette's is a neuropsychiatric disorder characterised by a combination of involuntary sounds and movements called tics. It normally starts in childhood and continues into adulthood. While there is not a cure, people can learn to control the symptoms.

    Researchers at the University of Nottingham have now identified a brain chemical that could be a potential new target for more effective treatments for the disorder.

    Published in the journal Current Biology, researchers discovered that people with Tourette's had an unusual increase in a neurotransmitter called Gamma-Aminobutyric Acid, (GABA), in the supplementary motor area (SMA), which is involved in the control of movement.

    The increase in GABA is strange because this chemical is involved in the dampening down brain activity.

    The team also found that people with the highest levels of GABA had the most connecting fibres in the brain, suggesting that the more connecting fibres people have, the more excitatory signals are being produced. This, in turn, leads to the need for even more GABA to calm excessive hyperactivity.

    Study leader Amelia Draper said: "This result is significant because new brain stimulation techniques can be used to increase or decrease GABA in targeted areas of the cortex. It may be possible that such techniques to adjust the levels of GABA in the SMA could help young people with Tourette's gain greater control over their tics."

    Most people with Tourette's eventually learn to control their tics until they only have mild symptoms in adulthood. However, this can be too late for some people, with the condition disrupting their education and social life.

    Researchers say their findings may lead to more targeted approaches to controlling tics, such as low-level neurostimulation that could be used to increase or decrease GABA in targeted areas.

    Study supervisor Stephen Jackson said: "In Tourette syndrome, as in many other disorders, the brain may adapt and reorganise the way it works so as to reduce or compensate for the effects of the disorder.

    "In this case, the effects of excitatory signals that give rise to cortical hyperexcitability and unwanted movements may be compensated for by increased levels of GABA which act to 'damp-down' or reduce excitability within a localised brain area."

    "[We] will now explore whether this increased 'tonic' inhibition mechanism can be seen in other brain areas in Tourette syndrome, and also in other hyperactive disorders, such as obsessive compulsive disorder and autism, which are highly similar to Tourette syndrome and are often co-occurring."

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    Default Re: Scientists Find Key Brain Chemical to Control Tics

    Increased GABA Contributes to Enhanced Control over Motor Excitability in Tourette Syndrome
    Current Biology
    September 2014
    Amelia Draper, Mary C. Stephenson, Georgina M. Jackson, Sophia Pépés, Paul S. Morgan, Peter G. Morris, Stephen R. Jackson

    Highlights
    •We report a 7 T 1H MRS investigation of GABA in Tourette syndrome (TS)
    •GABA levels within the SMA are significantly elevated in TS
    •SMA GABA is negatively correlated with SMA BOLD and cortical excitability
    •SMA GABA is predicted by motor tic severity and corpus callosum FA values

    Summary
    Tourette syndrome (TS) is a developmental neurological disorder characterized by vocal and motor tics [ 1 ] and associated with cortical-striatal-thalamic-cortical circuit dysfunction [ 2, 3 ], hyperexcitability within cortical motor areas [ 4 ], and altered intracortical inhibition [ 4–7 ].

    TS often follows a developmental time course in which tics become increasingly more controlled during adolescence in many individuals [ 1 ], who exhibit enhanced control over their volitional movements [ 8–11 ]. Importantly, control over motor outputs appears to be brought about by a reduction in the gain of motor excitability [ 6, 7, 12, 13 ]. Here we present a neurochemical basis for a localized gain control mechanism.

    We used ultra-high-field (7 T) magnetic resonance spectroscopy to investigate in vivo concentrations of γ-aminobutyric acid (GABA) within primary and secondary motor areas of individuals with TS. We demonstrate that GABA concentrations within the supplementary motor area (SMA)—a region strongly associated with the genesis of motor tics in TS [ 14 ]—are paradoxically elevated in individuals with TS and inversely related to fMRI blood oxygen level-dependent activation.

    By contrast, GABA concentrations in control sites do not differ from those of a matched control group. Importantly, we also show that GABA concentrations within the SMA are inversely correlated with cortical excitability in primary motor cortex and are predicted by motor tic severity and white-matter microstructure (FA) within a region of the corpus callosum that projects to the SMA within each hemisphere. Based upon these findings, we propose that extrasynaptic GABA contributes to a form of control, based upon localized tonic inhibition within the SMA, that may lead to the suppression of tics.



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    Default Re: Scientists Find Key Brain Chemical to Control Tics

    How the brain gains control over Tourette syndrome
    Science Codex
    September 25, 2014

    Tourette syndrome is a developmental disorder characterized by involuntary, repetitive, and stereotyped movements or utterances. Now researchers reporting in the Cell Press journal Current Biology on September 25 have new evidence to explain how those with Tourette syndrome in childhood often manage to gain control over those tics. In individuals with the condition, a portion of the brain involved in planning and executing movements shows an unusual increase compared to the average brain in the production of a primary inhibitory neurotransmitter known as GABA.

    The paradoxical findings—that the brains of people with Tourette syndrome produce more GABA than usual, not less—suggest that non-drug treatments that serve to increase the nerve messenger, such as brain stimulation, may speed the slow process whereby people with Tourettes naturally gain control over their disease symptoms. A major advantage of such an approach, the researchers say, is that, unlike the effect of drugs, such therapies might be targeted at the specific region where change is needed rather than the whole brain.

    "In Tourette syndrome, as in many other disorders, the brain may adapt and reorganize the way it works so as to reduce or compensate for the effects of the disorder," says Stephen Jackson of the University of Nottingham. "In this case, the effects of excitatory signals that give rise to cortical hyperexcitability and unwanted movements may be compensated for by increased levels of GABA which act to 'damp-down' or reduce excitability within a localized brain area."

    Jackson and his colleagues used a technique called magnetic resonance spectroscopy (MRS) to safely and noninvasively investigate levels of brain chemicals in individuals with Tourette syndrome. They were particularly interested in the amounts of GABA because of its status as the primary inhibitory neurotransmitter in the brain. They measured GABA in three brain regions—the primary motor cortex, the supplementary motor area (SMA), and a "control area" involved in visual processing—to find that people with Tourette syndrome had elevated concentrations of GABA only within the SMA.

    The findings may have implications for the understanding and treatment of other neurodevelopmental conditions as well, Jackson notes, many of which are characterized by imbalances of excitatory and inhibitory influences in particular brain regions. Jackson says his team "will now explore whether this increased 'tonic' inhibition mechanism can be seen in other brain areas in Tourette syndrome, and also in other hyperactive disorders, such as obsessive compulsive disorder and autism, which are highly similar to Tourette syndrome and are often co-occurring."

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    Default Re: Scientists Find Key Brain Chemical to Control Tics

    Wow - how cool

    Quote Originally Posted by Steve View Post
    Tourette's Treatment: Scientists Find Key Brain Chemical to Control Tics

    International Business Times
    September 25, 2014

    A chemical in the brain that plays a vital role in controlling the involuntary tics associated with Tourette's Syndrome has been discovered by scientists.

    "

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    Default Re: Scientists Find Key Brain Chemical to Control Tics


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