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A tug of war: antagonistic effective connectivity patterns over the motor cortex and the severity of motor symptoms in Gilles de la Tourette syndrome
Author(s) -
Zapparoli Laura,
Tettamanti Marco,
Porta Mauro,
Zerbi Alberto,
Servello Domenico,
Banfi Giuseppe,
Paulesu Eraldo
Publication year - 2017
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/ejn.13658
Subject(s) - supplementary motor area , tourette syndrome , neuroscience , premotor cortex , motor cortex , psychology , sma* , putamen , primary motor cortex , basal ganglia , functional connectivity , correlation , functional magnetic resonance imaging , medicine , central nervous system , anatomy , psychiatry , geometry , mathematics , dorsum , combinatorics , stimulation
We tested the hypothesis that Gilles de la Tourette syndrome ( GTS ) is characterized by perturbed connectivity within cortico–subcortical motor networks. To this end, we performed a dynamic causal modelling ( DCM ) analysis of fMRI data collected during a finger opposition task in 24 normal controls and 24 GTS patients. The DCM analysis allowed us to assess whether any GTS ‐specific patterns of brain activity were related to intrinsic and/or to task‐dependent connectivity. While no abnormalities were found for task‐dependent connectivity, intrinsic connectivity was abnormally increased in the premotor network, with stronger connections from the supplementary motor area ( SMA ), from the dorsolateral premotor cortex and from the putamen to the right superior frontal gyrus, an area where GTS showed over‐activation in a previous univariate analysis. We also found a positive correlation between the connectivity strength from the right basal ganglia to the right primary motor cortex (M1) and disease severity measured by the Yale Global Tic Severity Scale ( YGTSS ). This pattern was mirrored by a negative correlation between the connection strength from the right SMA to the right area M1 and the YGTSS score. These two reverse correlation effects showed a specific relationship with individual disease severity: the greater the imbalance between subcortical and premotor connectivity towards area M1, the higher the YGTSS score. These results reveal the existence of perturbed intrinsic connectivity patterns in the motor networks of GTS patients with two competing forces operating in a tug of war‐like mechanism: aberrant subcortical afferents to M1, compensated for by inputs from the premotor cortex.