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Sara Agosta, Raffaella Di Giacopo, Lorella Battelli; Visual extinction in Parkinson patients. Journal of Vision 2014;14(10):1337. doi: 10.1167/14.10.1337.
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Parkison's disease (PD) has been described as a disconnection syndrome. Motor and non-motor symptoms of PD have been explained as a consequence of the disconnection in the cortico-striatal-thalamocortical and cortico-cortical circuitry. The motor onset of PD symptoms, on the right or on the left side of the body, indicate an asymmetrical dysregulation of the dopamine depletion in the substantia nigra and consequently in the striatum and, in turn, dysfunction of basal ganglia and connected cortical areas. For this reason, it is important to determine whether the timecourse of the motor impairment on one side is also correlated with non-motor cognitive impairments more often documented for one specific hemisphere. Interestingly, there is some experimental evidence that left PD patients (LPD, primarily with right hemisphere degeneration) show visuo-spatial deficits similar to patients affected by right parietal lesion (Cronin-Golomb, 2010). We tested a group of PD patients at various stages of the disease on a sustained attention task, namely a multiple object tracking (Battelli et al., 2001). This task is particularly sensitive at revealing signs of left visual extinction in right parietal patients. PD patients were asked to track 4 moving discs amidst moving distracters (8 total discs, four in each hemifield) two in the left and two in the right hemifield. We psychophysically measured left and right visual field tracking speed thresholds at which patients could perform at 80% accuracy. Results showed a double dissociation, LPD patients showed an impaired performance (relative to age-matched controls) in the left hemifield, while right PD patients showed lower thresholds in the right hemifield. This dissociation indicates that PD is a degenerative disease involving motor as well as attentional functions both in the early and late stage of the disease. This results also critically link sustained attention to cortical-basal ganglia connections.
Meeting abstract presented at VSS 2014
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