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Guntekin B.,Istanbul Kultur University | Basar E.,Istanbul Kultur University
Neuroscience Letters | Year: 2010

According to previous results, negative emotional facial expressions elicit oscillatory beta responses. The present study analyzes event-related beta oscillations upon presentation of International Affective Picture System (IAPS) and aims to show whether behavior of beta in response to negative IAPS pictures also have similar dynamics. IAPS pictures (unpleasant, pleasant, and neutral) were presented as a block and random passive viewing to 14 healthy subjects (8 male). Only with pictures with similar luminance level were selected as stimuli. Event-Related Potentials (ERPs) were recorded from 30 different scalp locations, and adaptive digital filtering was used for analysis in different frequency windows. The maximum peak-to-peak amplitudes were measured for each subject's averaged beta responses (15-30. Hz) in the 0 and 300. ms time window. Beta responses were significantly higher for unpleasant pictures than for pleasant and neutral pictures (average 50%). Beta responses were significantly higher for unpleasant than for pleasant pictures over frontal, central and parietal electrode sides (p< 0.05). Furthermore, beta responses were significantly higher for unpleasant than for neutral pictures over parietal and occipital electrodes (p< 0.04). In addition, the pleasant pictures elicited higher beta responses than neutral pictures over occipital electrode sites (p< 0.04). The results of the present study indicate that negative emotions are related to increased beta responses in humans, independent of stimulus types (facial expression or IAPS pictures). Accordingly, beta responses to negative emotions are possibly a common phenomenon. The standardization of luminance in pictures may reduce divergences between results from different laboratories. © 2010 Elsevier Ireland Ltd.


Guntekin B.,Istanbul Kultur University | Basar E.,Istanbul Kultur University
Cognitive Neurodynamics | Year: 2010

Previous studies on cognitive dynamics showed that oscillatory responses of P300 are composed of mainly delta and theta responses. In the present study, for the first time, the long-distance intra-hemispheric event related coherence (auditory oddball paradigm) and evoked coherence (simple sound) were compared in order to evaluate the effects of cognitive tasks on the long-distance coherences. Seventeen healthy subjects (8 female, 9 male) were included in the study. The coherence was analyzed for delta (1-3.5 Hz), theta (4-7.5 Hz) and alpha (8-13 Hz) frequency ranges for (F3-P3, F 4-P4, F3-T7, F4-T 8, F3-O1, F4-O2) electrode pairs. The coherence to target responses were higher than the non-target and simple auditory response coherence. This difference is significant for the delta coherence for both hemispheres and for theta coherences over the left hemisphere. The highest coherences were recorded at fronto-temporal locations for all frequency bands (delta, theta, alpha). Furthermore, frontoparietal coherences were higher than the fronto-occipital coherences for all frequency bands (delta, theta, alpha).These results show that the fronto-temporal and fronto-parietal connections are most relevant for the identification of the target signal. This analysis open the way for a new interpretation of dynamic localization results during cognitive tasks. © Springer+Business Media B.V. 2010.


Ayag Z.,Kadir Has University | Gurcan Ozdemir R.,Istanbul Kultur University
International Journal of Production Economics | Year: 2012

The problem of machine tool selection among available alternatives has been critical issue for most companies in fast-growing markets for a long time. In the presence of many alternatives and selection criteria, the problem becomes a multiple-criteria decision making (MCDM) machine tool selection problem. Therefore, most companies have utilized various methods to successfully carry out this difficult and time-consuming process. In this work, both of the most used MCDM methods, the modified TOPSIS and the Analytical Network Process (ANP) are introduced to present a performance analysis on machine tool selection problem. The ANP method is used to determine the relative weights of a set of the evaluation criteria, as the modified TOPSIS method is utilized to rank competing machine tool alternatives in terms of their overall performance. Furthermore, in this paper, we use a fuzzy extension of ANP, a more general form of AHP, which uses uncertain human preferences as input information in the decision-making process, because AHP cannot accommodate the variety of interactions, dependencies and feedback between higher and lower level elements. Instead of using the classical eigenvector prioritization method in AHP, only employed in the prioritization stage of ANP, a fuzzy logic method providing more accuracy on judgments is applied. The resulting fuzzy ANP enhances the potential of the conventional ANP for dealing with imprecise and uncertain human comparison judgments. The proposed approach is also applied for a real-life case in a company. © 2012 Elsevier B.V. All rights reserved.


Basar E.,Istanbul Kultur University
International Journal of Psychophysiology | Year: 2012

Aim of the review: Questions related to the genesis and functional correlates of the brain's alpha oscillations around 10. Hz (Alpha) are one of the fundamental research areas in neuroscience. In recent decades, analysis of this activity has been not only the focus of interest for description of sensory-cognitive processes, but has also led to trials for establishing new hypotheses. The present review and the companion review aim to constitute an ensemble of "reasonings and suggestions" to understand alpha oscillations based on a wide range of accumulated findings rather than a trial to launch a new "alpha theory". Surveyed descriptions related to physiology and brain function: The review starts with descriptions of earlier extracellular recordings, field potentials and also considers earlier alpha hypotheses. Analytical descriptions of evoked and event-related responses, event-related desynchronization, the relationship between spontaneous activity and evoked potentials, aging brain, pathology and alpha response in cognitive impairment are in the content of this review. In essence, the gamut of the survey includes a multiplicity of evidence on functional correlates in sensory processing, cognition, memory and vegetative system, including the spinal cord and heart. © 2012 Elsevier B.V.


Basar E.,Istanbul Kultur University | Duzgun A.,Istanbul Kultur University
International Journal of Psychophysiology | Year: 2016

The aim of this study is threefold: (1) we propose a new framework describing the neurophysiologic functioning and cognitive processing of neural populations, and we extend the neuron doctrine to the physiology of neural assemblies. (2) The extension from neurons to neural populations implies that the brain, with its connectivity, should be considered a working syncytium, which extends Brodmann mapping to the CLAIR model, which includes oscillatory components and their connectivity. (3) In such a working syncytium, a new description of “memory” is needed in the broad time–space continuum, which embraces all memory states. This will be called “hypermemory.” © 2016 The Authors


Basar E.,Istanbul Kultur University | Guntekin B.,Istanbul Kultur University
International Journal of Psychophysiology | Year: 2012

Aim of the report: In the companion report (Başar, this volume), the physiological fundaments of alpha activity in integrative brain function are described. The present report is a review of the significant role of alpha activity in memory and cognitive processes in healthy subjects, and in cognitive impairment. The role of neurotransmitters is also described, briefly, in this context. Towards an understanding of brain alpha: Despite numerous experimental studies, it is indicated that the presented results are only appropriate to establish an ensemble of reasonings and suggestions for analyzing "alphas" in the whole brain. In turn, in the near future, these reasonings and suggestions may serve (or are indispensable to serve) as fundaments of more general and tenable hypotheses on the genesis and function of "alphas". © 2012 Elsevier B.V.


Sarier N.,Istanbul Kultur University | Onder E.,Technical University of Istanbul
Thermochimica Acta | Year: 2012

An organic phase change material (PCM) possesses the ability to absorb and release large quantity of latent heat during a phase change process over a certain temperature range. The use of PCMs in energy storage and thermal insulation has been tested scientifically and industrially in many applications. The broad based research and development studies concentrating on the characteristics of known organic PCMs and new materials as PCM candidates, the storage methods of PCMs, as well as the resolution of specific phase change problems, such as low thermal conductivity and supercooling have been reviewed. The potential industrial applications of PCMs in textiles and clothing systems, the methods of PCM integration into textiles and the methods of evaluating their thermal properties are also presented in this study. © 2012 Elsevier B.V. All rights reserved.


Guntekin B.,Istanbul Kultur University | Basar E.,Istanbul Kultur University
Neuropsychologia | Year: 2014

The differentiation of faces, facial expressions and affective pictures involves processes of higher mental activity that have considerable applications in the psychology of moods and emotions. At present, the search for functional correlates of brain oscillations is an important trend in neuroscience. Furthermore, analyses of oscillatory responses provide key knowledge on the physiology of brain dynamics. Studies analysing oscillatory dynamics in face perception and emotional pictures have increased in recent years; however, the literature lacks a review of the current state of the art. This study provides a comprehensive review of the delta, theta, alpha, beta and gamma oscillatory responses on presentation of faces, facial expressions and affective pictures (International Affective Picture System, IAPS). The reviewed literature revealed that the brain is more sensitive to emotional stimuli than neutral stimuli. A common and reliable finding from all reviewed studies was the increased brain responsiveness towards negative emotional pictures (face expression or IAPS). © 2014 Elsevier Ltd.


Basar E.,Istanbul Kultur University
Dialogues in Clinical Neuroscience | Year: 2013

The term "brain (or neural) oscillations" refers to the rhythmic and/or repetitive electrical activity generated spontaneously and in response to stimuli by neural tissue in the central nervous system. The importance of brain oscillations in sensory-cognitive processes has become increasingly evident. It has also become clear that eventrelated oscillations are modified in many types of neuropathology, in particular in cognitive impairment. This review discusses methods such as evoked/event-related oscillations and spectra, coherence analysis, and phase locking. It gives examples of applications of essential methods and concepts in bipolar disorder that provide a basis for fundamental notions regarding neurophysiologic biomarkers in cognitive impairment. The take-home message is that in the development of diagnostic and pharmacotherapeutic strategies, neurophysiologic data should be analyzed in a framework that uses a multiplicity of methods and frequency bands. © 2013, AICH.


Basar E.,Istanbul Kultur University
International Journal of Psychophysiology | Year: 2013

This review describes a wide range of functional correlates of gamma oscillations in whole-brain work, in neuroethology, sensory-cognitive dynamics, emotion, and cognitive impairment. This survey opens a new window towards understanding the brain's gamma activity.Gamma responses are selectively distributed in the whole brain, and do not reflect only a unique, specific function of the nervous system. Sensory responses from cortex, thalamus, hippocampus, and reticular formations in animal and human brains, and also cognitive responses, were described by several authors.According to reviewed results, it becomes obvious that cognitive disorders, and medication-which influence the transmitter release-change entirely the understanding of the big picture in cognitive processes.Gamma activity is evoked or induced by different sensory stimuli or cognitive tasks. Thus, it is argued that gamma-band synchronization is an elementary and fundamental process in whole-brain operation. In conclusion, reasoning and suggestions for understanding gamma activity are highlighted. © 2013 Elsevier B.V.

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