Impairment of visual working memory in patients with Parkinson's disease: a time-frequency analysis

Schmiedt, C.1,2, Meistrowitz, A.1, Basar-Eroglu, C.2, and Herrmann, M.1,3
1Department of Neuropsychology and Behavioral Neurobiology, University of Bremen, Germany; 2Institute of Psychology and Cognitive Research, University of Bremen, Germany; 3Center for Advanced Imaging - Bremen (CAI), Germany

Neural correlates of visual working memory (WM) in non-demented patients with Parkinson’s disease (PD, n=9) and age-matched healthy controls (n=11) were examined using a task involving different delay conditions and requiring a constant monitoring of continuously morphing figures. As stimuli we presented geometrical figures that could not easily be associated to common figures. Electroencephalogram (EEG) was recorded from F3, F4, C3, C4, P3, P4, T5, T6, O1, O2 locations during the task described above. Linked earlobes served as reference. The EEG was analysed and discussed with respect to Fourier estimation of spectral power in selected frequency bands as well as by means of wavelet based time-frequency analysis.

The preliminary analysis of the behavioural data showed slower reaction times only in the shortest delay condition in the group of PD patients compared to the age-matched healthy controls. Furthermore, the PD patients showed significantly more errors mostly marked in the longest delay condition. The lower performance accuracy in the patient group was associated with less complex and apparently less effective memorising strategies. Since this specific visual WM paradigm demands continuous monitoring of stimuli over different delay conditions, these data may be interpreted as resulting from impairments in interference-control or deficits in allocation of attention resources.

Research was supported by DFG (SFB-517) and Center for Advanced Imaging – Bremen (CAI).