A Study of the Midbrain Network for Covert Attentional Orienting in Cervical Dystonia Patients using Dynamic Causal Modelling.

Understanding the neuronal network dynamics underlying the third most common movement disorder, cervical dystonia, can be achieved using dynamic causal modelling. Current literature establishes structures of the midbrain network for covert attentional orienting as dysfunctional in patients with cervical dystonia. One of these structures is the superior colliculus, for which it is hypothesised that deficient GABAergic activity therein causes cervical dystonia. To understand the role that this node plays in cervical dystonia, various connectivity models of the midbrain network were compared under the influence of a loom-recede visual stimulus fMRI paradigm. These models included the thalamus and striatum, crucial nodes in the direct/indirect pathways for motor movement and inhibition. The parametric empirical Bayes approach was used to quantify the difference in connection strengths across the winning models between patients and controls. Our findings demonstrated greater modulation by a looming stimulus event on the strength of connection from the striatum to the superior colliculus in patients. These results offer new means to understanding the pathophysiology of cervical dystonia.