HP03: Abnormal Dynamic Neuronal Connectivity in children with dystonia

Abstract

Dystonia is a network disorder resulting from dysfunction of, or abnormal connectivity within, the cortico-basal ganglia-cerebellar network. Despite the dynamic nature of the disorder, stimulus-related changes in connectivity have not been studied. We investigate modulation of neuronal connectivity by a proprioceptive stimulus in dystonia. Methods: Sixteen young people with dystonia and eight controls participated (age 6-20years, mean 12.5). A robotic wrist interface delivered passive wrist extension movements, producing a brief stretch of the right wrist flexors. Scalp EEG (10-20 system) was sampled at 2500Hz. Wrist position was monitored and movement onset synchronised with EEG. Data were segmented into epochs (1 second pre- and 3.5 seconds post-stimulus). Up to 160 epochs were averaged per subject to produce a Stretch Evoked Potential (StretchEP). Event-related network dynamics were estimated using the imaginary part of Wavelet Transform Coherency, excluding volume conduction, with bootstrapping to test for significance against random coupling between brain areas. The overall engagement of cortical areas into short-lived stimulus-related networks (global microscale nodal strength - GMNS) was estimated for each subject. Results: Clear StretchEPs were evoked over contralateral sensorimotor cortex. Individual dynamic connectivity maps revealed particularly strong event-related connectivity in the theta (4-8Hz) band in dystonia. At group level, theta band GMNS was significantly higher in dystonia than controls (p=0.045). The spatial extent of the networks was also stronger in dystonia than controls (non-significant trend). Conclusion: Young people with dystonia show an exaggerated dynamic network response to proprioceptive stimuli, displaying excessive, widespread theta-band synchronisation and over-recruitment across the sensorimotor network.