The neurobiology of cognition in progressive supranuclear palsy

Social cognition has not been studied in PSP, despite its clinical importance with regard to patients’ progressive decline in independence and communication. This thesis focuses on the extent and neural basis of social cognition in PSP. Cognitive function was assessed in multiple domains including social cognition, executive function and perception, at baseline and after one year. At baseline, subjects underwent structural magnetic resonance imaging and saccadometry. Patients were poor at both emotion recognition and theory of mind tasks in visual and auditory modalities, compared with matched controls. Social cognition correlated with global cognitive decline but was not attributable to perceptual disturbance and was independent if executive function. The latency of visually evoked saccades correlated with global and social cognitive performance. Regression analysis revealed latency as the best predictor of cognitive function, above disease duration and motor function. Voxel based morphometry of grey and white matter confirms that areas previously implicated in social cognition were atrophic in PSP. Moreover, this atrophy correlated with social cognition dysfunction, implying a functional association. In summary, social cognition is an integral part of the cognitive syndrome of PSP, and is associated with focal atrophy of regions associated with normal social cognition.