title: Abnormal cortical functional connections in Alzheimer's disease: analysis of inter- and intra-hemispheric EEG coherence.
abstract: To investigate inter- and intra-hemispheric electroencephalography (EEG) coherence at rest and during photic stimulation of patients with Alzheimer's disease (AD). Thirty-five patients (12 males, 23 females; 52 to approximately 64 y) and 33 sex- and age-matched controls (12 males, 21 females; 56 to approximately 65 y) were recruited in the present study. EEG signals from C3-C4, P3-P4, T5-T6 and O1-O2 electrode pairs resulted from the inter-hemispheric action, and EEG signals from C3-P3, C4-P4, P3-O1, P4-O2, C3-O1, C4-O2, T5-O1 and T6-O2 electrode pairs resulted from the intra-hemispheric action. The influence of inter- and intra-hemispheric coherence on EEG activity with eyes closed was examined, using fast Fourier transformation from the 16 sampled channels. The frequencies of photic stimulation were fixed at 5, 10 and 15 Hz, respectively. The general decrease of AD patients in inter- and intra-hemispheric EEG coherence was more significant than that of the normal controls at the resting EEG, with most striking decrease observed in the alpha-1 (8.0-9.0 Hz) and alpha-2 (9.5-12.5 Hz) bands. During photic stimulation, inter- and intra-hemispheric EEG coherences of the AD patients having lower values in the alpha (9.5-10.5 Hz) band than those of the control group. It suggests that under stimulated and non-stimulated conditions, AD patients had impaired inter- and intra-hemispheric functional connections, indicating failure of brain activation in alpha-related frequency.
authors.affiliation: Department of Psychiatry, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China. Jiang_zju@mail.hz.zj.cn
authors.forename: Zheng-yan
authors.initials: ZY
authors.lastname: Jiang
mesh_terms: D000544:Alzheimer Disease / Q000175:diagnosis / Q000503:physiopathology*; D016022:Case-Control Studies; D002540:Cerebral Cortex / Q000503:physiopathology*; D004566:Electrodes; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged