A key feature of Parkinson’s disease (PD) is the depletion of striatal dopamine, which is associated with the motor and non-motor symptoms of the disease. In this study, we sought to investigate the role of dopamine in spatial memory in PD patients in a cross-over medication ON/OFF design. We used a virtual reality task to assess striatal- and hippocampal-dependent spatial memory. Results show that PD patients and age-matched controls rely more on striatal cue-based spatial learning than the young adults tested in previous studies. Medication improved striatal-dependent spatial memory. The benefit of medication on hippocampal-dependent spatial memory depended on prior experience with the task. These findings shed new light on dopaminergic modulation of hippocampal-striatal functions in PD.
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Thurm, F., Schuck, N. W., Fauser, M., Doeller, C. F., Stankevich, Y., Evens, R., Riedel, O., Storch, A., Lueken, U., Li, S. C. (2015). Dopamine Modulation of Spatial Navigation Memory in Parkinson’s Disease. Neurobiology of Aging.
Striatal dopamine depletion is a key pathophysiological feature of Parkinson’s disease (PD) causing motor and non-motor symptoms. Research on non-motor symptoms has mainly focused on fronto-striatal functions. However, dopamine pathways ascending from the ventral tegmental area also innervate hippocampal structures and modulate hippocampal-dependent functions, such as spatial memory. Using a virtual spatial navigation task, we investigated dopaminergic modulation of spatial memory in PD patients in a cross-over medication ON/OFF design. We examined medication effects on striatal- and hippocampal-dependent spatial memory by either replacing a location cue in the environment or enlarging its spatial boundary. Key results indicate that in contrast to prior evidence for younger adults, PD patients, like their age-matched controls, rely more on striatal cue-based than hippocampal spatial learning. Medication facilitated navigation in the striatal location cue condition, whereas medication benefit in hippocampal boundary-related spatial memory depended on prior experience with the task. Effects on spatial memory were comparable to and independent of motor effects. These findings shed new light on dopaminergic modulation of hippocampal-striatal functions in PD.