Visual search in progressive supranuclear palsy and Parkinson's disease 2016-2019

This project investigated the effect of paralysis of the eyes on visuospatial cognition. Specifically, we explored whether the vertical gaze palsy associated with a rare neurodegenerative disease called Progressive Supranuclear Palsy (PSP) led to problems with visuospatial attention and spatial short-term memory (STM). It was predicted that neuropsychological patients with PSP would also present with deficits of attention and short term memory that corresponded to their oculomotor dysfunction. To test this hypothesis we examined spatial attention and memory in Fifteen people with PSP (8 female, Mage 69.5, age range: 53–80 years, Mdisease duration 35 months), 16 with Parkinson’s Disease (Mage 68.2, age range 58–78, Mdisease duration 62 months) and 15 Age Matched Controls (Mage 69.7, age range 58–80). We used 2 computerized visual search tasks to measure how quickly participants were able to detect a target item among varying numbers of distractors to measure attention. In one task we the target was defined by a single feature (orientation) and in the other it was defined by a unique conjunction of features (colour and orientation). We also measured the accuracy of their responses. As predicted, feature and conjunction search were significantly slower in the PSP group compared to the other groups, and this deficit was significantly worse for feature compared to conjunction search. The PD group did not differ from AMC on feature search but were significantly impaired on the conjunction search. The PSP group also had a pronounced vertical sSTM impairment that was not present in PD or AMC groups. The data suggest that PSP is associated with specific impairment of visuospatial cognition which is caused by degeneration of the oculomotor structures that support exogenous spatial attention, consistent with the prediction of the Motor Bias Theory of Attention.