Person: BAŞAR, EROL
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BAŞAR
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EROL
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Publication Metadata only Disturbance In Long Distance Gamma Coherence In Bipolar Disorder(Pergamon-Elsevier Science Ltd, The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1Gb, England, 2010-08-16) Özerdem, Ayşegül; Güntekin, Bahar; Saatçı, Ertuğrul; Tunca, Zeliha; BAŞAR, EROL; TR140995; TR204666; TR10488; TR142226The aim of this study was to investigate long distance event-related gamma (28-48 Hz) coherence in mania before and after valproate monotherapy. Gamma coherence in response to visual oddball paradigm in ten medication-free, manic patients was studied before and after six weeks of valproate monotherapy in comparison to ten controls. Inter-hemispheric F(3)-F(4), C(3)-C(4), T(3)-T(4), T(5)-T(6), P(3)-P(4), O(1)-O(2) and intra-hemispheric F(3)-P(3), F(4)-P(4), F(3)-T(5), F(4)-T(6), F(3)-O(1), F(4)-O(2), C(3)-O(1), C(2)-O(4) electrode pairs were included in the analysis. Repeated measures ANOVA revealed a significant difference between groups with regard to pre-treatment coherence values (p: 0.018). The coherence to the target stimuli at the right fronto-temporal location was significantly reduced by 35.41% in the patients compared to controls (p: 0.003). Patients showed significantly lower pretreatment coherence values in response to non-target stimuli compared to controls at the right frontotemporal (28.51%, p: 0.004), right fronto-occipital (23.71%, p: 0.024), and right centro-occipital (25.69%, p: 0.029) locations. After six weeks of valproate monotherapy, manic symptoms improved significantly. Post-treatment change in target and non-target coherence values was statistically non-significant. EEG coherence is a measure of functional connectivity in the brain. Event-related gamma oscillations are essential for brain electrical activity. The results show that acute mania presents right sided long distance connectivity disturbance, thus pointing to the potential importance of measuring oscillatory responses in the search for consistent neurobiological markers in such a complicated condition as bipolar disorder. (C) 2010 Elsevier Inc. All rights reserved.Publication Metadata only Brain oscillations are highly influenced by gender differences(ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS, 2007-09) Güntekin, Bahar; BAŞAR, EROL; TR204666; TR142226There are few studies describing gender differences in event related oscillations (EROS). In the present report we demonstrate that gender differences are apparent in EROS even during simple visual stimulation, possibly activating very basic sensory networks. The data of 32 (16 males) healthy subjects were recorded from thirteen different scalp locations (F-3, F-4, C-z, C-3, C-4, T-3, T-4, T-5, T-6, P-3, P-4, O-1, O-2). Analysis was performed in the delta (0.5-3.5 Hz), theta (5-8.5 Hz), alpha (9-13 Hz), beta (15-24 Hz), and gamma (28-48 Hz) frequency ranges. The results showed that the maximum peak-to-peak delta response amplitudes for women were significantly higher than for men over occipital, parietal, central and temporal electrode locations. There were also differentiations in the beta and gamma oscillatory responses. These gender differences were most pronounced over the electrode Site O-2, that is, over primary visual areas. It is suggested that this study might serve as a standard to investigate gender differences in electrophysiology. (c) 2007 Elsevier B.V All rights reserved.Publication Open Access Beta Oscillatory Responses in Healthy Subjects and Subjects with Mild Cognitive Impairment Upon Application of Stimuli with Cognitive Load(Elsevier Science Inc, 360 Park Ave South, New York, Ny 10010-1710 USA, 2013-05-01) Güntekin, Bahar; Emek, Derya Durusu; Yener, Görsev; Kurt, Pınar; BAŞAR, EROL; 142226; 204666; 227002; 143760; 24351The aim of the present study was to investigate the role of beta oscillatory responses upon cognitive load in healthy subjects and in subjects with mild cognitive impairment (MCI). The role of beta oscillations upon cognitive stimulation is least studied in comparison to other frequency bands. The study included 17 consecutive patients with MCI (mean age = 70.8 ± 5.6 years) according to Petersen's criteria, and 17 age- and education-matched normal elderly controls (mean age = 68.5 ± 5.5 years). The experiments used a visual oddball paradigm. EEG was recorded at 30 cortical locations. EEG-evoked power, inter-trial phase synchronization, and event-related beta responses filtered in 15–20 Hz were obtained in response to target and non-target stimuli for both groups of subjects. In healthy subjects, EEG-evoked beta power, inter-trial phase synchronization of beta responses and event-related filtered beta responses were significantly higher in responses to target than non-target stimuli (p < 0.05). In MCI patients, there were no differences in evoked beta power between target and non-target stimuli. Furthermore, upon presentation of visual oddball paradigm, occipital electrodes depict higher beta response in comparison to other electrode sites. The increased beta response upon presentation of target stimuli in healthy subjects implies that beta oscillations could shift the system to an attention state, and had important function in cognitive activity. This may, in future, open the way to consider beta activity as an important operator in brain cognitive processes.Publication Metadata only Brain oscillations in bipolar disorder as emerging biomakers(Wiley-Blackwell, Commerce Place, 350 Main St, Malden 02148, Ma Usa, 2012-03) Güntekin, Bahar; Özerdem, Ayşegül; BAŞAR, EROL; 204666; 140995; 142226Publication Open Access Beyin-Beden-Zihin Etkileşiminde "Nebulöz Kartezyen Sistem"(İstanbul Kültür Üniversitesi Yayınları, 2006-12) Güntekin, Bahar; BAŞAR, EROL; TR142226; TR204666Rene Descartes 'in gelistirdigi Kartezyen Sistem "Newton 'un Dinamik Kurallari" ile ilintili ve iç içe geçmis olan temel bir kavramsal ve analitik sistemdir. Rönesans'tan itibaren modem bilimin youlunu açmistir. 20 inci yüzyil'in baslarinda Kuantum süreçlerini analiz etmek amaciyla, fizikçiler nedensellik ilkesinin olasiliksal ilkeye dönüstügü bir Probabilistik (olasiliksal) Kartezyen Sisteme yönelmislerdir. Bu da (kuantum kurallarina itaat eden) elementar parçaciklarin yörüngelerinin sadece bulutlu dalga paketleriyle açiklanabilecegi anlamina gelmektedir. Beyin-beden-zihin sorununa yönelik bir yaklasim modern fizik ve kuantum dinamigindeki çabalardan daha fazlasini gerektirmektedir. Beyin-beden-zihin yapisinin analizine belirsiz nedensizlikleri ve dolayisiyla da "çoklu belirsiz nedensellikleri" dahil etmemiz gerekir. Bu çoklu nedensellikler (I) vejetatif sistemin nonlineer özelliklerinden (biyokimyasal transmitörlerdeki düzensizlikler, kardiak çiktisi, vasküler sistemdeki turbülanslar, respiratuar apne, peristalsisdeki nonlineer salinimsal etkilesimler); (2) nöronal elektirisitenin nonlineer davranisi (örnegin EEG'nin kaotik yapisi) ve (3) genetik modülasyonlardan kaynaklanabilir, ayrica, (4) bu fizyolojik olgular yaninda vücuttaki fiziksel süreçlerin nonlineer özelliklerini de hesaba katmamiz gerekmektedir. Beyin; yaklasik D2=6'lik, düz kaslar da D2=3'lük korelasyon boyutu olan deterministik kaos gösterir. Bu gerçekler isiginda, beyin-beden sistemindeki süreçleri tanimlamada ve analiz etmede hiperprobabilistik bir yaklasimla veya bir Hiper-Olasiliksal Kartezyen Sistemi'yle karsilasiriz. Eger bu yapiya veya zaten hiper-probabilistik olan bu yapiya "hislerimizi", duygularimizi ve yaraticiligi eklersek bu "Yeni Kartezyen Sistem" hiper-probabilistik olmanin ötesine geçerek bir Nebü[öz Sisteme dönüsür, gelecege iliskin olarak, sadece nebülöz tahminler yürütebiliriz; tüm bunlara ragmen bu mantik zincirine• bagli kalarak beyin-beden-zihin ortakliklarindan yola çikarak tahminlerde bulunabiliriz. Kesinliginden emin olma.sak da, beyin-beden-zihin ortakligina ait mekanizmalarinin "bulutlu veya sisli bir günde yürünecek yolu bulmak" metaforuyla benzer bir sekilde analiz ve tahmin edilebilecegini varsaymaktayiz. "Nebülöz Kartezyen Sistem" de (NKS) iste budur. Rene Descartes, yasadigi çagda dahice girisiminde bulunurken bugünkü modem fizyoloji ve modern fizigin bilgi birikimine sahip degildi. Biz Yeni KartezyenSistem üzerine düsünmenin vaktinin geldigini düsünüyoruz. Bunu basarmak için Heisenberg S-Matrisinin ve "Feynman Beyin Semalari" adini verdigimiz modifiye Feynman semalarinin kullanilmasini önermekteyiz. NKS'ya dair salinimsal yaklasimin içindeele alinmasi gereken bir diger metafor ise "sicim kurami" (string theory) dir. Ayrica beyin-beden-zihin ortakliginin kendi dinamik çerçevesini olusturmak için temel adimlar atilmasi gerektigini de israrla öne sürmekteyiz, fizik ve matematige ait önermeler ve metaforlar faydalidir ancakbeyne özgü dile ait gramerin biyolojik temellere dayali, uyarlanir-olasiliksal bir Kartezyen Sistemle çözülmelidir. Bu yeni Kartezyen Sistem mutasyonlar geçirecek ve Beyin-bedenzihin sorununa yaklasimda yeni kapilar açmak için Charles Darwin'in evrim teorisiyle paralellik içinde Henri Bergson'un felsefesine uzanacaktir..Publication Open Access Auditory Delta Event-related Oscillatory Responses are Decreased in Alzheimer's Disease(Ios Press, Nieuwe Hemweg 6B, 1013 Bg Amsterdam, Netherlands, 2012) Yener, Görsev; Güntekin, Bahar; Necioğlu Örken, Dilek; Forta, H.; BAŞAR, EROL; 142226; 143760; 204666Background: Visual delta event-related (ERO) and evoked oscillations (EO) of Alzheimer patients (AD) are different than healthy. In the present study, the analysis is extented to include auditory ERO and EO in AD. The rationale is to reveal whether the auditory ERO delta responses are also reduced, and whether this is a general phenomenon in Alzheimer patients upon applying stimuli with cognitive load. Methods.: Thirty-four mild AD subjects 117 de-novo and 17 medicated (cholinergic)l and seventeen healthy controls were included. Auditory oddball paradigm and sensory auditory stimuli were applied to the subjects. Oscillatory responses were analyzed by measuring maximum amplitudes in delta frequency range (0.5-3.5 Hz). Results: Auditory delta ERO (0.5-3.5 Hz) responses of healthy controls were higher than either de-novo AD or medicated AD group, without a difference between two AD subgroups. Furthermore, the auditory EO after presentation of tone bursts yielded no group difference. Conclusion: Our findings imply that delta ERO is highly unstable in AD patients in comparison to age-matched healthy controls only during the cognitive paradigm. Our results favor the hypothesis that neural delta networks are activated during cognitive tasks and that the reduced delta response is a general phenomenon in AD, due to cognitive impairment.Publication Metadata only Increased Beta Frequency (15-30 Hz) Oscillatory Responses in Euthymic Bipolar Patients Under Lithium Monotherapy(Sage Publications Inc, 2455 Teller Rd, Thousand Oaks, Ca 91320 USA, 2016-04) Tan, Devran; Özerdem, Ayşegül; Güntekin, Bahar; Atagün, Murat İlhan; Tülay, Elif; Karadağ, Figen; BAŞAR, EROL; 103606; 140995; 204666; 25145; 111061; 142226The effect of lithium on neurocognition is not still fully explored. Brain oscillatory activity is altered in bipolar disorder. We aimed to assess the oscillatory responses of euthymic bipolar patients and how they are affected by lithium monotherapy. Event-related oscillations in response to visual target stimulus during an oddball paradigm in 16 euthymic drug-free and 13 euthymic lithium-treated bipolar patients were compared with 16 healthy controls. The maximum peak-to-peak amplitudes were measured for each subject's averaged beta (15-30 Hz) responses in the 0- to 300-ms time window over frontal (F3, Fz, F4), central (C3, Cz, C4), temporal (T7, T8), temporo-parietal (TP7, TP8), parietal (P3, Pz, P4), and occipital (O1, Oz, O2) areas. Patients under lithium monotherapy had significantly higher beta responses to visual target stimuli than healthy controls (P = .017) and drug-free patients (P = .015). The increase in beta response was observed at all electrode locations, however, the difference was statistically significant for the left (T7; P = .016) and right (T8; P = .031) temporal beta responses. Increased beta responses in drug-free patients and further significant increase in lithium-treated patients may be indicative of a core pathophysiological process of bipolar disorder and how it is affected by lithium. Whether the finding corresponds to lithium's corrective effect on the underlying pathology or to its neurocognitive side effect remains to be further explored. In either case, the finding is a sign that the oscillatory activity may be useful in tracking medication effect in bipolar disorder.Publication Metadata only A review of brain oscillations in cognitive disorders and the role of neurotransmitters(ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS, 2008-10-15) Güntekin, Bahar; BAŞAR, EROL; TR142226; TR204666The analysis of the functional correlates of "brain oscillations" has become an important branch of neuroscience. Although research on the functional correlates of brain oscillation has progressed to a high level, studies on cognitive disorders are rare and mainly limited to schizophrenia patients. The present review includes the results of the changes in brain oscillations in patients with Alzheimer's, schizophrenia, bipolar disorders, mild cognitive impairment, attention-deficit hyperactivity disorder (ADHD), alcoholism and those with genetic disorders. Furthermore, the effects of pharmaca and the influence of neurotransmitters in patients with cognitive disorders are also reviewed. Following the review, a short synopsis is given related to the analysis of brain oscillations. (c) 2008 Elsevier B.V. All rights reserved.Publication Metadata only Event-related delta oscillatory responses of Alzheimer patients(WILEY-BLACKWELL, COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA, 2008-06) Yener, Görsev; Güntekin, Bahar; BAŞAR, EROL; TR142226; TR143760; TR204666Background and purpose: Alzheimer type of dementia (AD) is the most common neuropsychiatric morbidity in elderly individuals. Event-related oscillations (ERO) provide an useful tool for detecting subtle abnormalities of cognitive processes with high temporal resolution. Methods: In the present report, event-related oscillations of patients with AD were analyzed by using a visual oddball paradigm. A total of 22 mild probable AD subjects according to NINCDS-ADRDA criteria and 20 age-, gender-, and education-matched healthy control subjects were compared. AD group consisted from 11 untreated patients and 11 patients treated with cholinesterase inhibitor. Oscillatory responses were recorded from 13 scalp electrodes. Results: Significant differences in delta frequency range were seen between the groups by using repeated measures of ANOVA analysis [F(9.120) = 2.228; P = 0.022]. Post-hoc analyses using Wilcoxon test showed that at mid- and left central regions, (Cz, C3) peak amplitudes of delta responses of healthy subjects were significantly higher than either group. Also cholinesterase inhibitors did not have effect on delta oscillatory responses. Conclusions: Our findings imply that the delta oscillatory responses at central locations are highly instable in mild probable AD patients regardless of treatment when compared to the healthy aged controls. This study supports the importance of oscillatory event-related potentials for investigating AD brain dynamics.