Objective: Probing the mechanisms underlying disordered sub-cortical processing in the pathogenesis of the non-motor symptoms of cervical dystonia (CD) is of great clinical importance. We are investigating the responsiveness of the amygdala to emotional faces by high-density EEG evoked response potentials (ERP) in CD patients. We postulate a causative association of disrupted salient emotional signalling with abnormalities in mood and social cognition in this cohort.

Background: Cervical dystonia is an autosomal-dominant movement disorder causing abnormal contraction of the muscles of the head, neck and shoulders resulting in irregular movements and postures. An abnormal temporal discrimination threshold (TDT) has been established as a mediational endophenotype in CD and up to 50% of unaffected first-degree relatives, due to disordered sub-cortical inhibition. The sub-cortical collicular-pulvinar-amygdala pathway non-consciously processes emotional stimuli which influence behaviour. Impaired emotional processing has previously been identified in CD, however protocols investigate conscious emotional processing only.

Method: Participants: There will be 20 participants in each of five sub-groups: a) 20 female CD patients with moderate/severe scores (19+) on Beck’s Depression Inventory (BDI- II) and/or Beck’s anxiety Inventory (16+) (BAI). b) 20 female CD patients with normal scores (<10) on BDI- II and BAI. c) 20 unaffected sisters (of patients with CD) with an abnormal TDT. d) 20 unaffected sisters (of patients with CD) with an abnormal TDT. e) 20 healthy control female participants with normal scores (<10) on both BAI and BDI. All groups will be age matched; they will be 45-65 years of age. Methods: We have developed a protocol to probe specific ERP components (N170, P300) in response to faces expressing happiness, disgust or neutrality using an oddball paradigm of facial images from the NimStim database.

Results: We expect patients with CD and their unaffected relatives with abnormal TDT to have impaired recognition of facial emotions compared to other study groups due to abnormalities in the sub-cortical collicular-pulvinar-amygdala pathway.

Conclusion: Impaired recognition of facial emotions is of clinical significance as this may lead to misinterpretation of social cues and predispose individuals to anxiety and depression.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-protocol-to-probe-the-mechanisms-underlying-disordered-sub-cortical-processing-in-cervical-dystonia-using-emotional-faces/