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    Patients with Mild Cognitive Impairment Display Reduced Auditory Event-Related Delta Oscillatory Responses
    (HINDAWI PUBLISHING CORPORATION, 2014) Kurt, Pinar; Emek-Savas, Derya Durusu; Batum, Kubra; Turp, Bilge; Guntekin, Bahar; Karsidag, Sibel; Yener, Gorsev Gulmen
    Background. Event-related oscillations (ERO) may provide a useful tool for the identification of cognitive deficits in mild cognitive impairment (MCI) and Alzheimer's disease (AD). In the present study, we investigate peak-to-peak amplitude of auditory eventrelated delta oscillations of MCI subjects. Method. The study included twenty-two consecutive patients with MCI recruited in neurology clinic and 21 age-and education-matched normal elderly controls. A classical auditory oddball paradigm was used in the experiments. EEG was recorded from F-3, F-z, F-4, C-3, C-z, C-4, P-3, P-z, P-4, O-1, O-z, and O-2 locations. The maximum peak-to-peak amplitudes for each subject's averaged delta response (0.5-2.2Hz) weremeasured. Results. The amplitudes between groups differed significantly at the frontal and mid-centroparietal locations. ANOVA on delta responses revealed a significant effect for groups (F-(1.41) = 4.84, P = 0.033), indicating a larger delta response for healthy controls thanMCI subjects. Post hoc comparisons revealed that peak-to-peak delta response was significantly larger for healthy controls than for MCI over electrode sites F-3, F-z, F-4, C-z, C-4, and Pz. Discussion. Event-related delta frequency band seems to be the most affected oscillatory response in cognitive impairment due to AD. Therefore, it deserves to be investigated as a candidate electrophysiological biomarker in further studies.
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    What does the broken brain say to the neuroscientist? Oscillations and connectivity in schizophrenia, Alzheimer's disease, and bipolar disorder
    (Elsevier Science BV, 2016) Basar, Erol; Schmiedt-Fehr, Christina; Mathes, Birgit; Femir, Banu; Emek-Savas, Derya Durusu; Tülay, Elif; Tan, Devran; Düzgün, Aysel; Güntekin, Bahar; Özerdem, Ayşegül; Yener, Görsev; Başar-Eroğlu, Canan
    The application of the concept and methods of brain oscillations has been an important research area in neurosciences. In the last decades, besides the application in cognitive processes, the study of changes in brain oscillations in diseases has also become an important focal point of research. In the present paper, some remarkable examples in three different diseases are taken into consideration: 1) schizophrenia (SZ), 2) Alzheimer's disease (AD), 3) bipolar disorders (BD). In the current literature, decreased oscillations in cortical recordings are observed in most of the pathologies. For example, decrease of gamma activity in SZ, decrease of delta activity in almost all diseases, as well as frequency shifts in alpha and the lower frequencies were recorded. However, there are also paradoxical cases in which an increase of oscillatory activities is observed. In BD, whereas alpha activity is greatly decreased, a huge increase of beta activity is observed. Or, in SZ, a paradoxical increase of gamma activity can be observed during cognitive loading. We also observed paradoxical changes in the analysis of connectivity. In AD, we find that alpha, delta, and theta coherences between distant parts of the cortex are greatly decreased, whereas in the gamma band, event-related coherences attain very high values. The comparison of the results and paradoxical changes in diseases may lead to important conclusions related to the web of oscillations and neurotransmitters. In turn, we could gain new insights to approach "brain function", in general. (C) 2016 The Authors. Published by Elsevier B.V.