The sensory deficits outlined above, and, in particular, previous work demonstrating temporal discrimination deficits, suggest involvement of the superior colliculus in the altered network function in dystonia. The superior colliculus is also believed to be involved in the processing of emotional facial recognition, with recent research examining for potential deficits in social cognition in dystonia [
54]. Social cognition is described as the ability to attribute affect and mental states to others, combining multiple cognitive processes including an ability to recognise emotion and to distinguish between the intentions of others and self. Theory of mind (ToM) is central to social cognition and is defined as an ability to understand and interpret intentions, emotions, and beliefs of others to accurately predict their behaviour and act accordingly. Deficits in social cognition could potentially indicate dysfunction in the collicular-pulvinar-amygdala pathway, which may also account for other NMS observed, including temporal discrimination, anxiety, and depression.
Research in this area has tended to focus on AOIFCD, likely due to its prevalence as well as anecdotal clinical observation that social cognitive deficits may be more evident in adult-onset focal forms of dystonia. However, a single study of Mendelian inherited dystonia (
SGCE, myoclonus dystonia) identified lower emotional recognition scores to a SGCE-negative movement disorder cohort [
55]. A cross-sectional case-controlled study of age-, sex-, education-, and IQ-matched cohorts (
n = 46 in each group) found significantly poorer performance of the AOIFCD cohort in delayed recall (
p < 0.001), recognition (
p = 0.006), and basic social cognition (
p = 0.007) where participants were asked to correctly label affect (happy, sad, fearful, or neutral) for both visual and auditory stimuli [
56]. A second study compared those with AOIFCD and no depressive symptoms (
n = 25) to unaffected controls (
n = 26), finding the AOIFCD cohort to demonstrate significantly reduced ability in inferring both cognitive and affective status, with understanding the intentionality of others being the most prominent area of difference and unrelated to motor symptom severity [
57]. Examination of wider social cognitive abilities, including social perception, ToM, empathy, and social behaviour, alongside anxiety and depression, found 21.74% of the AOIFCD (
n = 46) cohort demonstrated impaired belief reasoning and 5/46 (10.87%) impaired empathy. Interestingly, those with more severe anxiety and depressive symptoms tended to have greater social perception abilities, suggesting some adaptation of social cognitive skills [
36••]. Finally, separation of an AOIFCD cohort into those with (
n = 35) and without (
n = 14) tremor found significantly poorer performance in the affective(
p = 0.009) and cognitive (
p < 0.00001) domains of the ToM tests in the AOIFCD cohort compared to controls, however, with the presence of a tremor only demonstrating an effect in the cognitive domain (
p = 0.03) [
58].