RESUMEN
OBJECTIVE: Theory of mind (ToM) and empathy are severely impaired in the behavioural variant of frontotemporal dementia (bvFTD) and more mildly in Alzheimer's (AD) and Parkinson's diseases (PD). Such impairments are associated with behavioural disorders. Modification of visual scanning strategies of complex visual scenes is also found in these pathologies. We hypothesised that these patients applied atypical gaze strategies when observing social events, which does not allow them to properly process social cues and results in the production of erroneous inferences and lack of empathy towards others. METHODS: Fifty-five participants were divided into four groups: five bvFTD subjects, 19 AD subjects, 17 PD subjects and 14 matched control subjects. ToM and empathy were assessed by eye movement recording (eye-tracking) and by a questionnaire during a painting observation. Scores obtained were compared between each group and to social cognition reference tests and correlated to the NeuroPsychiatric Inventory. RESULTS: Our paradigm was suitable for assessing cognitive ToM while it lacked sensitivity for empathy assessment. Severe ToM impairment was highlighted in bvFTD, while milder difficulties were observed in AD and for PD. Subjects with bvFTD and AD produced erroneous inferences from cognitive mental states. ToM performances were linked to visual exploration strategies of the painting. Atypical visual observation was highlighted in the bvFTD and AD groups causing a time delay in taking the perspective of the other person. Finally, we highlighted that social cognition performances, gaze strategies and behavioural disorders were correlated. CONCLUSION: Observing a painting in association with eye-tracking technology can be a good support for social cognition assessment. We highlighted a link between atypical visual scanning strategies, ToM impairment and behavioural disorders in these pathologies. ToM skills could be improved by training in the search for visual social cues. Therefore, this kind of remediation could have positive effects on behavioural disorders.