title: Delay of cognitive gamma responses in Alzheimer's disease.
abstract: Event-related oscillations (EROs) reflect cognitive brain dynamics, while sensory-evoked oscillations (SEOs) reflect sensory activities. Previous reports from our lab have shown that those with Alzheimer's disease (AD) or mild cognitive impairment (MCI) have decreased activity and/or coherence in delta, theta, alpha and beta cognitive responses. In the current study, we investigated gamma responses in visual SEO and ERO in 15 patients with AD and in 15 age-, gender- and education-matched healthy controls. The following parameters were analyzed over the parietal-occipital regions in both groups: (i) latency of the maximum gamma response over a 0-800 ms time window; (ii) the maximum peak-to-peak amplitudes for each participant's averaged SEO and ERO gamma responses in 3 frequency ranges (25-30, 30-35, 40-48 Hz); and (iii) the maximum peak-to-peak amplitudes for each participant's averaged SEO and ERO gamma responses over a 0-800 ms time block containing four divided time windows (0-200, 200-400, 400-600, and 600-800 ms). There were main group effects in terms of both latency and peak-to-peak amplitudes of gamma ERO. However, peak-to-peak gamma ERO amplitude differences became noticeable only when the time block was divided into four time windows. SEO amplitudes in the 25-30 Hz frequency range of the 0-200 ms time window over the left hemisphere were greater in the healthy controls than in those with AD. Gamma target ERO latency was delayed up to 138 ms in AD patients when compared to healthy controls. This finding may be an effect of lagged neural signaling in cognitive circuits, which is reflected by the delayed gamma responses in those with AD. Based on the results of this study, we propose that gamma responses should be examined in a more detailed fashion using multiple frequency and time windows.
authors.affiliation: Brain Dynamics, Cognition and Complex Systems Research Center, Istanbul Kultur University, Istanbul 34156, Turkey. Electronic address: e.basar@iku.edu.tr.
authors.forename: Erol
authors.initials: E
authors.lastname: Başar
authors.affiliation: Brain Dynamics, Cognition and Complex Systems Research Center, Istanbul Kultur University, Istanbul 34156, Turkey; Department of Psychology, Dokuz Eylül University, Izmir 35160, Turkey; Department of Neurosciences, Dokuz Eylül University, Izmir 35340, Turkey.
authors.forename: Derya Durusu
authors.initials: DD
authors.lastname: Emek-Savaş
authors.affiliation: Brain Dynamics, Cognition and Complex Systems Research Center, Istanbul Kultur University, Istanbul 34156, Turkey.
authors.forename: Bahar
authors.initials: B
authors.lastname: Güntekin
authors.affiliation: Brain Dynamics, Cognition and Complex Systems Research Center, Istanbul Kultur University, Istanbul 34156, Turkey; Department of Neurosciences, Dokuz Eylül University, Izmir 35340, Turkey; Brain Dynamics Multidisciplinary Research Center, Dokuz Eylül University, Izmir 35340, Turkey; Department of Neurology, Dokuz Eylül University Medical School, Izmir 35340, Turkey.
authors.forename: Görsev G
authors.initials: GG
authors.lastname: Yener
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D058256:Brain Waves / Q000502:physiology*; D003071:Cognition / Q000502:physiology*; D060825:Cognitive Dysfunction / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D004569:Electroencephalography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation / Q000379:methods; D055815:Young Adult
keywords: Alzheimer's disease; EEG; Event-related; Gamma; Oscillation; P300; Sensory-evoked