Picture ordering task EEG

Daily activities like preparing a meal rely on the ability to arrange thoughts and actions in the right order. Patients with Parkinson’s disease (PD) have difficulties in sequencing tasks. Their deficits in sequential working memory have been associated with basal ganglia dysfunction. Here we demonstrate that altered parietal alpha-theta oscillations correlate with sequential working memory in PD. We included 15 PD patients (6 women, mean age 66.0 years), 24 healthy young (HY, 14 women, mean age 24.1 years), and 16 older participants (HO, 7 women, mean age 68.6 years). Participants completed a picture ordering task with scalp EEG recording, where they arranged five pictures in a specific order and memorized them over a delay. During encoding and the delay, the baseline alpha peak frequency for ordered trials was 10.0 Hz in HY, 10.1 Hz in HO, and 8.9 Hz in PD. PD showed a lower baseline alpha peak frequency with higher alpha power than HY and HO. PD with a higher baseline alpha power tended to respond more slowly. In response to sequence manipulation, the frequency of maximal power change between random and ordered trials (Fmax) was 10.0 Hz in HY, 11.3 Hz in HO, and 7.7 Hz in PD. PD showed a lower Fmax than HY and HO, whereas HO showed a higher Fmax than HY. Compared to PD with Fmax in the alpha band (8-15 Hz, n=11), PD with Fmax in the theta band (4-7 Hz, n=4) tended to show a higher ordering-related accuracy cost in the picture ordering task and lower accuracy and slower responses in an independent working memory task. In conclusion, altered baseline alpha oscillations and task-dependent modulation of alpha-theta oscillations may be a neural marker of poor sequential working memory in PD.