title: The somatotopy of tic inhibition: Where and how much?
abstract: BACKGROUND
  Tics are the hallmark feature of Tourette syndrome. The basic phenomenological and neurophysiological characteristics of tics have been widely investigated. Interestingly, the spatial distribution of tics across different body parts has received little attention. No previous study has investigated whether the capacity for voluntary tic inhibition also varies across body parts.
  
  
  METHODS
  We analyzed video sequences of 26 adolescents with Tourette syndrome in a "tic freely" condition, and in a "voluntary tic inhibition" condition, to obtain absolute tic counts for different body parts. Two measures of the spatial distribution of tics were then analyzed. Linear regression analyses were employed to investigate the relation between the contribution of each body part to overall tic behavior and the ability to inhibit tics in that body part, averaged over our patient group.
  
  
  RESULTS
  Tic distribution across patients showed a characteristic somatotopic pattern, with the face most strongly represented. A significant negative relation was found between the ability to inhibit tics and pooled tic frequency across body parts. The body parts that exhibited the fewest tics were the ones for which tic inhibition was most effective.
  
  
  CONCLUSIONS
  Our data are consistent with the idea that tic recruitment order reflects a "tic generator" spreading across a somatotopic map in the brain. Voluntary tic inhibition did not simply cause a proportional reduction of tics in each body part. Rather, the least affected body parts showed most effective voluntary tic inhibition. The results are discussed in terms of signal and noise within cortical-subcortical motor loops.
authors: Institute of Cognitive Neuroscience, University College London, UK.|Department of Neurology, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany.
authors: Christos
authors: C
authors: Ganos
authors: Department of Neurology, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany.
authors: Jens
authors: J
authors: Bongert
authors: Department of Neurology, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany.
authors: Luisa
authors: L
authors: Asmuss
authors: Neurology Department, King's College Hospital NHS Foundation Trust, London.|Queen Elizabeth Hospital, Lewisham & Greenwich NHS Trust, London.
authors: Davide
authors: D
authors: Martino
authors: Institute of Cognitive Neuroscience, University College London, UK.
authors: Patrick
authors: P
authors: Haggard
authors: Department of Paediatric and Adult Movement Disorders and Neuropsychiatry, Institute of Neurogenetics, University of Lübeck, Lübeck, Germany.
authors: Alexander
authors: A
authors: Münchau
mesh_terms: D000293:Adolescent; D002648:Child; D005260:Female; D018594:Human Body; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D012044:Regression Analysis; D012720:Severity of Illness Index; D020323:Tics / Q000503:physiopathology*; D005879:Tourette Syndrome / Q000188:drug therapy / Q000503:physiopathology*; D014741:Video Recording
keywords: Gilles de la Tourette syndrome; tic disorders; tic inhibition; tic suppression; voluntary motor control