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GABA involvement was studied in 23 TS children, aged 8-12, and 67 controls using a battery of vibrotactile tasks with a subset of the children (i.e., 19 with TS, 25 controls) also undergoing GABA-edited magnetic resonance spectroscopy (MRS) \citep{26041822}. Lower GABA concentration in the right sensorimotor cortex was associated with greater motor tic severity (r=-0.55). There were no significant differences between groups on reaction time and baseline amplitude discrimination threshold. However, TS children showed impaired tactile adaptation. The authors suggest that MRS GABA and tactile measures might useful as biomarkers of treatment response.  A detailed review discusses focuses on  histaminergic modulation of striatal function by the tuberomamillary nucleus of the hypothalamus \citep{26275849}. Histamine suppresses both the thalamic and cortical drive to medium-spiny projection neurons (MSNs), modulates thalamostriatal synapses resulting its possible role  in a facilitation of thalamic input, and suppresses lateral feedback inhibition. TS \citep{26275849}.  The authors suggest that, during wakefulness and increased attention, histaminergic neurons will be more active with the result that  the striatum will be more responsive to thalamostriatal input and consequently and  feed-forward inhibition will predominate. The dominate. Several lines of evidence related to the  role of histamine in TS was discussed in terms of were discussed. A family linkage study identified  a rare mutationinvolving histamine synthesizing enzyme, histidine decarboxylase,  in one TS human adult, the gene encoding histidine decarboxylase. HDC transgenic mice exhibit  decreased pre-pulse inhibition of startle responses, responses  andin a rodent model  an increase in a variety of amphetamine-induced stereotypies which decreased in response to that were prevented by pretreatment with  histamine infusion or use of haloperidol. These effects were thought Reduced histamine production was suggested  to occur as a result of the histaminergic control produce dopaminergic disregulation  of the lateral GABAergic inhibitory connections between MSNs. The authors also discussed ongoing research on histaminergic treatments for basal ganglia and sympotoms similar to those seen in  TS. ### Clinical and neuropsychological studies