N400 and Emotional Word Processing in Parkinson’s Disease
Objective: Emotional and cognitive disturbances are common complications in Parkinson’s disease (PD). N400 is an event related potential (ERP) strongly linked to lexical-semantic processing and has demonstrated alterations in amplitude and latency when PD patients performed semantic priming tasks. The present study investigated the role of N400 in an automatic affective priming paradigm in PD. Other ERP components relevant to emotion processing were also examined. Method: Twenty-two PD patients and 17 healthy adults performed an automatic affective priming task while ERPs were recorded using 128 channels. Prime–target word pairs of negative or neutral valence were presented at a stimulus onset asynchrony of 250 ms. Participants were asked to evaluate the valence of the target word by button press. Results: A larger N400 amplitude for incongruent compared with congruent neutral targets was observed at right central and parietal regions and did not differ between PD and controls. PD and controls also displayed larger P300 and late positive potential (LPP) amplitudes for negative compared with neutral targets at central parietal and right frontal regions. In contrast, whereas controls showed a larger slow negative wave (SNW) for negative targets compared with neutral targets at left frontal and left central regions, PD group demonstrated a significant reduction in SNW amplitude difference at the left central region. Conclusion: N400 is intact in PD when processing evaluative judgments of emotional words. P300 and LPP were also intact in PD. The altered left central SNW in PD suggests an ERP marker for emotional dysfunction in PD.