Session Time: 12:00pm-1:30pm
Location: Exhibit Hall located in Hall B, Level 2
Objective: To demonstrate the functional magnetic resonance imaging response to looming stimuli in the superior colliculus of cervical dystonia patients and their relatives with and without abnormal temporal discrimination thresholds.
Background: Adult onset idiopathic focal dystonia (AOIFD) is the third most common movement disorder and cervical dystonia (CD) is the most common phenotype of AOIFD. Temporal discrimination threshold (TDT) detects the point at which an individual determines two stimuli to be asynchronous (normal = 30 – 50 ms). A majority of patients with CD (97%) and a proportion of their unaffected relatives have abnormal TDT results. We hypothesize that an abnormal TDT and CD are due to a disorder of the mid-brain network for covert attentional orientating caused by reduced GABA inhibition. This inhibition manifests sub clinically as an abnormal TDT due to prolonged firing of the visual sensory neurons in the superficial layer of the superior colliculus and clinically as CD due to excess cephalomotor neuronal activity in the deep layer of the superior colliculus. Looming visual stimuli (as opposed to receding stimuli) activate both superior colliculi. We predict patients with CD and their unaffected relatives with abnormal TDTs will demonstrate reduced activation within the SC during looming stimuli.
Methods: We have examined by 3 tesla fMRI the responses within the SC to looming, receding and random stimuli in participants (16 CD patients, 16 unaffected first degree relatives with abnormal TDTs, 16 healthy first degree relatives with normal TDTs and 16 healthy controls with normal TDTs). All participants were age and sex matched.
Results: Whole brain analysis using a general linear model was performed on all acquired images. Event related analysis of our region of interest, the superior colliculus, will be presented. Participant TDT will be correlated with the BOLD response in the SC during the looming condition to explore the relationship between the TDT and SC.
Conclusions: In this study we aim to demonstrate that an abnormal TDT indicates disordered processing within the SC and thus further our understanding into the pathogenesis of CD.
To cite this abstract in AMA style:E.M. Mc Govern, S. Narasimham, O. Killian, I. Beiser, L. Williams, B. Quinlivan, J.S. Butler, S. O'Riordan, R.B. Reilly, M. Hutchinson. A functional magnetic imaging study of the response in the superior colliculus to looming stimuli in cervical dystonia patients and their relatives [abstract]. Mov Disord. 2016; 31 (suppl 2). https://www.mdsabstracts.org/abstract/a-functional-magnetic-imaging-study-of-the-response-in-the-superior-colliculus-to-looming-stimuli-in-cervical-dystonia-patients-and-their-relatives/. Accessed September 25, 2023.
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