Reduced visual event-related δ oscillatory responses in amnestic mild cognitive impairment.
Mild cognitive impairment (MCI) is considered as a prodromal stage for Alzheimer's disease (AD) in the majority of cases. Event-related oscillations might be used for detection of cognitive deficits. Our group's earlier results showed diminished delta visual and auditory target oscillatory responses in AD, and we investigated whether this prevails for MCI. Eighteen MCI subjects and 18 age-matched healthy elderly controls were investigated. The maximum peak-to-peak amplitudes of oscillatory responses for each subject's averaged oscillatory target responses in delta, theta, and alpha frequency bands upon application of visual oddball paradigm were measured. Repeated measures of ANOVA was used to analyze four locations (frontal, central, parietal, occipital), at three coronal (left, midline, right) sites. Independent t tests were applied for post-hoc analyses. The oddball target delta response (0.5-3.0 Hz) was 26-32% lower in MCI than healthy controls over fronto-central-parietal regions [F(1.34) = 4.562, p = 0.04]. Without a group effect, theta oscillatory responses (4-7 Hz) showed significant differences in coronal electrodes indicating highest values over mid-electrode sites, and a anteriorposterior x coronal effect, being maximum at mid-central. Alpha frequency band analyses indicated no statistical differences. Peak-to-peak amplitudes of visual target delta oscillatory responses were lower in fronto-central-parietal regions in MCI than in healthy controls. This supports our earlier findings in AD, showing hypoactive delta fronto-central-parietal regions during cognitive tasks. These results indicate that event-related oscillations may detect early changes of brain dynamics in MCI, and deserves to be investigated as a candidate biomarker in further studies using multimodal techniques.
Brain Dynamics Multidisciplinary Research Center, Dokuz Eylül University, Izmir, Turkey Department of Neurosciences, Dokuz Eylül University, Izmir, Turkey Department of Neurology, Dokuz Eylül University Medical School, Izmir, Turkey Brain Dynamics, Cognition and Complex Systems Research Center, Istanbul Kültür University, Istanbul, Turkey.
Görsev G
GG
Yener
Pınar
P
Kurt
Derya Durusu
DD
Emek-Savaş
Bahar
B
Güntekin
Erol
E
Başar
D000368:Aged; D000647:Amnesia / Q000175:diagnosis / Q000503:physiopathology*; D060825:Cognitive Dysfunction / Q000175:diagnosis* / Q000503:physiopathology*; D003700:Delta Rhythm / Q000502:physiology*; D015536:Down-Regulation / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods*; D011446:Prospective Studies; D014793:Visual Cortex / Q000502:physiology*
Biomarker; early diagnosis of Alzheimer's disease; electroencephalographic rhythms; event-related potentials; mild cognitive impairment; oscillations