Abstract: Objective To study the feature of theta oscillation during working memory (WM) dysfunction in patients with mild cognitive impairment (MCI). Methods Fifteen MCI patients (MCI group) and 15 healthy subjects for checkup (control group) in Tianjin Medical University General Hospital from January to November 2016 were recruited. The differences of behavioral results in visual WM tasks were compared between the two groups. Thirty four- channel electroencephalogram (EEG) signals were recorded simultaneously. Short- Time Fourier transform was used to calculate spatial and time-frequency distribution of power and spectral coherence of multi-channel EEGs. Results Compared with control group, MCI group showed significantly longer reaction time and lower accuracy in WM tasks (P＜0.01). The analysis of EEGs revealed that the power of Fz channel was the biggest at frontal midline in both groups. And the power density of theta oscillation was lower at frontal electrode sites in MCI group than that of control group ( P＜0.01), and theta coherence was significantly decreased in frontal region and between frontal-posterior regions ( P＜0.05). Conclusion The absence of theta oscillaton in frontal region may be one of the important reasons of working memory dysfunction for MCI.

Key words: mild cognitive impairment, working memory, theta oscillation, multi-channel electroencephalographs