Social cognition in neurodegenerative diseases: Huntington's disease, Parkinson's disease and multiple sclerosis

Social cognition is impacted in patients with Huntington’s disease (HD), Parkinson’s disease (PD) and multiple sclerosis (MS) as a consequence of neuropathology involving subcortical regions of the brain as well as the neural connections of frontal-striatal networks. A large body of research suggests that difficulties in emotion perception are an important feature of all three disorders. Although this impairment is most documented in facial emotion recognition tasks, impairments have also been identified in other modalities, such as vocal prosody and body language. While the mechanisms of impaired emotion perception in HD, PD and MS remain unclear, a number of possible mechanisms have been the subject of research, including general cognitive decline, face processing abilities, motor impairment and neuropsychiatric syndromes that affect general emotional functioning. Impairments in theory of mind in both the cognitive and affective domains have also been well documented across all three disorders, and cognitive ToM deficits have been frequently linked to impairments in executive function. Importantly, the ecological validity of common measures of emotion perception and ToM have been questioned, and further research is needed to determine the psychosocial outcomes of impaired social cognition in HD, PD and MS.