Novelty processing and memory formation in Parkinson׳s disease

• Published in: Neuropsychologia 2014-09, Vol.62, p.124-136
• Main Authors: Schomaker, J., Berendse, H.W., Foncke, E.M.J., van der Werf, Y.D., van den Heuvel, O.A., Theeuwes, J., Meeter, M.
• Format: Article
• Language: English
• Subjects: Dopamine; Learning; Memory; Novelty processing; Parkinson׳s disease; Von Restorff effect
• ISSN: 0028-3932; 1873-3514
• DOI: 10.1016/j.neuropsychologia.2014.07.016

Parkinson׳s disease (PD) is characterized by a degeneration of nigrostriatal dopaminergic cells, resulting in dopamine depletion. This depletion is counteracted through dopamine replacement therapy (DRT). Dopamine has been suggested to affect novelty processing and memory, which suggests that these processes are also implicated in PD and that DRT could affect them. To investigate word learning and novelty processing in patients with PD as indexed by the P2 and P3 event-related potential components, and the role of DRT in these processes. 21 patients with PD and 21 matched healthy controls were included. Patients with PD were tested on and off DRT in two sessions in a counterbalanced design, and healthy controls were tested twice without intervention. Electroencephalogram (EEG) was measured while participants performed a word learning Von Restorff task. Healthy controls showed the typical Von Restorff effect, with better memory for words that were presented in novel fonts, than for words presented in standard font. Surprisingly, this effect was reversed in the patients with PD. In line with the behavioral findings, the P3 was larger for novel than for standard font words in healthy controls, but not in patients with PD. For both groups the P2 and P3 event-related components were larger for recalled versus forgotten words. DRT did not affect these processes. Learning of novel information is compromised in patients with PD. Likewise, the P2 and P3 components that predict successful memory encoding are reduced in PD patients. This was true both on and off DRT, suggesting that these findings reflect abnormalities in learning and memory in PD that are not resolved by dopaminergic medication. •Healthy controls but not Parkinson׳s patients showed a Von Restorff effect•Processing and learning of novel information is compromised in Parkinson׳s patients•The P2 and P3 components reflect novelty and the strength of memory encoding•The P3 for novel font words was reduced in Parkinson׳s patients•Dopamine did not remediate the memory deficit in the Parkinson׳s patients