Person: BAŞAR, EROL
Loading...
Email Address
Birth Date
Research Projects
Organizational Units
Job Title
Prof.Dr.
Last Name
BAŞAR
First Name
EROL
Name
130 results
Search Results
Now showing 1 - 10 of 130
Publication Multiple gamma oscillations in the brain: A new strategy to differentiate functional correlates and P300 dynamics(Elsevıer Science Bv, Po Box 211, 1000 Ae Amsterdam, Netherlandi, 2015-03) Tülay, Elif; Güntekin, Bahar; BAŞAR, EROL; 142226; 204666Brain oscillations in the gamma frequency band, - i.e. oscillations greater than 25 Hz - have attracted increasing attention over the last few decades in the research of sensory-cognitive processes. In the neuroscience research literature, a great number of reports aim to describe the functional correlates of oscillatory responses in the gamma frequency window. However, analysis using a broadband frequency window often leads to divergent functional interpretations and controversies. In order to provide a more exact approach, we have used a strategy by defining multiple frequency and multiple time windows according to the combined analysis of conventional power spectral windows, frequency adaptive multiple filters, and inter-trial coherence. The analysis in frequency windows of 25-30 Hz, 30-35 Hz, and 4048 Hz enables the investigator to provide a distinction of cognitive and/or sensory responses. Moreover, according to topological differentiation and the consideration of neuroanatomic pathways, more reliable interpretations of gamma responses are reached. (C) 2015 The Authors. Published by Elsevier B.V.Publication Increased long distance event-related gamma band connectivity in Alzheimer's disease(Elsevier Sci Ltd, The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1Gb, Oxon, England, 2017) Femir, Banu; Emek Savaş, Derya Durusu; Güntekin, Bahar; Yener, Görsev G.; BAŞAR, EROL; 142226; 227002; 204666; 143760Background: Brain oscillatory responses can be used for non-invasive analyses of cortico-cortical connectivity, local neuronal synchronization, and coherence of oscillations in many neuropsychiatric conditions including Alzheimer's disease (AD). In the present paper, we examine sensory-evoked and event-related gamma coherences elicited by visual stimuli in three sub-gamma bands in two sub-groups of patients with AD (i.e., acetylcholinesterase-inhibitor treated and untreated) and healthy controls. Methods: We studied a total of 39 patients with probable mild AD (according to NINCDS-ADRDA criteria) who had been sub-divided into untreated (n = 21) and treated (n = 18) (patients either on cholinergic monotherapy or combined therapy with memantine) AD groups, and 21 age-, gender-, and education-matched healthy elderly controls. A simple flash visual paradigm was applied for the acquisition of sensory-evoked coherences. Event-related coherences were elicited using a classical visual oddball paradigm. Both sensory-evoked and event-related gamma coherences were calculated for long-distance intrahemispheric pairs for three frequency ranges: 2530 Hz, 30-35 Hz, and 40-48 Hz in post-stimulus 0-800 ms duration. The long-distance intrahemispheric pairs from both sides were fronto-parietal, fronto-temporal, fronto-temporoparietal, fronto-occipital, centro-occipital and parieto-occipital. Results: The sensory-evoked or event-related gamma coherences revealed that both treated and untreated AD patients had significantly increased values compared to healthy controls in all three sub-gamma bands. Moreover, the treated AD patients demonstrated significantly higher fronto-parietal gamma coherences during both sensory stimulation and oddball paradigm and lower occipito-parietal coherences during oddball paradigm in comparison to untreated AD patients. Conclusion: The present study demonstrated that an increase of gamma coherences was present in response to both visual sensory and cognitive stimulation in AD patients in all gamma sub-bands. Therefore, gamma oscillatory activity seems to be fundamental in brain functions at both the sensory and cognitive levels. The increase of gamma coherence values was not due to cholinergic treatment to any significant extent, as both treated and untreated AD patients had increased gamma coherence values compared to healthy controls. The use of coherence values reflecting brain connectivity holds potential for neuroimaging of AD and understanding brain dynamics related to the effects of medication. (C) 2017 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Publication Resting state Rolandic mu rhythms are related to activity of sympathetic component of autonomic nervous system in healthy humans(Elsevier Science Bv, Po Box 211, 1000 AE Amsterdam, Netherlands, 2016-05) Triggiani, Antonio Ivano; Valenzano, Anna; Del Percio, Claudio; Marzano, Nicola; Soricelli, Andrea; Petito, Annamaria; Bellomo, Antonello; Mundi, Ciro; Cibelli, Giuseppe; Babiloni, Claudio; BAŞAR, EROL; 142226We tested the hypothesis of a relationship between heart rate variability (HRV) and Rolandic mu rhythms in relaxed condition of resting state. Resting state eyes-closed electroencephalographic (EEG) and electrocardiographic (ECG) data were recorded (10-20 System) in 42 healthy adults. EEG rhythms of interest were high frequency alpha (10.5-13 Hz) and low-frequency beta (13-20 Hz), which are supposed to form Rolandic mu rhythms. Rolandic and occipital (control) EEG sources were estimated by LORETA software. Results showed a statistically significant (p < 0.05, corrected) negative correlation across all subjects between Rolandic cortical sources of low-frequency beta rhythms and the low-frequency band power (LF, 0.04-0.15 Hz) of tachogram spectrum as an index of HRV. The lower the amplitude of Rolandic sources of low-frequency beta rhythms (as a putative sign of activity of somatomotor cortex), the higher the LF band power of tachogram spectrum (as a putative sign of sympathetic activity). This effect was specific as there was neither a similar correlation between these EEG rhythms and high-frequency band power of tachogram spectrum (as a putative sign of parasympathetic vagal activity) neither between occipital sources of low-frequency beta rhythms (as a putative sign of activity of visual cortex) and LF band power of tachogram spectrum. These results suggest that Rolandic low frequency beta rhythms are related to sympathetic activity regulating heart rate, as a dynamic neurophysiologic oscillatory mechanism sub-serving the interaction between brain neural populations involved in somatomotor control and brain neural populations regulating ANS signals to heart for on-going homeostatic adaptations. (C) 2015 Elsevier B.V. All rights reserved.Publication Brain-Body-Mind in the nebulous cartesian system: A holistic approach by oscillations(SPRINGER, 233 SPRING STREET, NEW YORK, NY 10013, UNITED STATES, 2011) BAŞAR, EROLPublication Views of hayek, hebb, and heiisenberg:Toward an approach to brain functioning(2011) BAŞAR, EROLPurpose - The conceptual ideas of Hebb, Heisenberg, and Feynman are embedded in the framework Hayek's so-called New Psychology. The present survey tries to bridge these concepts. Methodology - A theoretical and empirical informed approach. Findings - The theory of D. O. Hebb opened the way to "Neurobiology of Learning" in the past century. The S-Matrix theory of Werner Heisenberg and the so-called Feynman Diagrams that consider everything in the path-history of particles opened up new avenues to predict production of elementary particles. This as Hayek proposed or assumed in his theoretical monograph The Sensory Order. Originality/value of paper - Besides Fuster and Edelman few (if any) currently practicing neuroscientists have any knowledge of or appreciation of Hayek's philosophical psychology.Publication Reduced Visual Event-Related Delta Oscillatory Responses in Amnestic Mild Cognitive Impairment(Ios Press, Nieuwe Hemweg 6B, 1013 Bg Amsterdam, Netherlands, 2013) Yener, Görsev; Kurt, Pınar; Emek Savaş, Derya Durusu; Güntekin, Bahar; BAŞAR, EROL; 143760; 24351; 227002; 204666; 142226Mild 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.Publication Selective Gamma Activation in Alzheimer, Bipolar Disease and Schizophrenia(Elsevier Science Inc, 360 Park Ave South, New York, Ny 10010-1710 Usa, 2011-05-01) Başar Eroğlu, Canan; Güntekin, Bahar; Özerdem, Ayşegül; Yener, Görsev; BAŞAR, EROL; 142226; 274866; 204666; 140995; 143760Publication 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 Cognitive Impairment in Parkinson's Disease Is Reflected with Gradual Decrease of EEG Delta Responses during Auditory Discrimination(Frontiers Media Sa, Avenue Du Tribunal Federal 34, Lausanne, Ch-1015, Switzerland, 2018-02-21) Güntekin, Bahar; Hanoğlu, Lütfü; Güner, Dilan; Helvacı Yılmaz, Nesrin; Çadırcı, Fadime; Mantar, Nagihan; Aktürk, Tuba; Emek Savaş, Derya Durusu; Özer, Fahriye Feriha; Yener, Görsev G.; BAŞAR, EROL; 204666; 171122; 194489; 259227; 259226; 275116; 227002; 38782; 143760; 142226Parkinson's disease (PD) is a neurodegenerative disease that is characterized by loss of dopaminergic neurons in the substantia nigra. Mild Cognitive impairment (MCI) and dementia may come along with the disease. New indicators are necessary for detecting patients that are likely to develop dementia. Electroencephalogram (EEG) Delta responses are one of the essential electrophysiological indicators that could show the cognitive decline. Many research in literature showed an increase of delta responses with the increased cognitive load. Furthermore, delta responses were decreased in MCI and Alzheimer disease in comparison to healthy controls during cognitive paradigms. There was no previous study that analyzed the delta responses in PD patients with cognitive deficits. The present study aims to fulfill this important gap. 32 patients with Parkinson's disease (12 of them were without any cognitive deficits, 10 of them were PD with MCI, and 10 of them were PD with dementia) and 16 healthy subjects were included in the study. Auditory simple stimuli and Auditory Oddball Paradigms were applied. The maximum amplitudes of each subject's delta response (0.5-3.5 Hz) in 0-600 ms were measured for each electrode and for each stimulation. There was a significant stimulation x group effect [F(df = 6; 88 = 3,21; p < 0.015; eta(2)(p) = 0.180], which showed that the difference between groups was specific to the stimulation. Patients with Parkinson's disease (including PD without cognitive deficit, PD with MCI, and PD with dementia) had reduced delta responses than healthy controls upon presentation of target stimulation (p < 0.05, for all comparisons). On the other hand, this was not the case for non-target and simple auditory stimulation. Furthermore, delta responses gradually decrease according to the cognitive impairment in patients with PD. Conclusion: The results of the present study showed that cognitive decline in PD could be represented with decreased event related delta responses during cognitive stimulations. Furthermore, the present study once more strengthens the hypothesis that decrease of delta oscillatory responses could be the candidate of a general electrophysiological indicator for cognitive impairment.Publication 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.