Bahar Güntekin

Istanbul Medipol University · School of Medicine

Method and concepts of brain oscillations pervade the neuroscience literature, especially in cognitive processes. Electrophysiological changes in patients with cognitive impairment will provide fundamental knowledge, not only for clinical studies but also, in turn, for understanding cognitive processes in healthy subjects. This review includes desc...

The 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 cha...

The differentiation of "facial expressions" is a process of higher mental activity, which has considerable applications in "psychology of moods and emotions". We applied the approach of event-related oscillations (EROs) to investigate the modulation of electrical manifestations related to emotional expression in EEG recordings of 20 healthy subject...

In the last decade, the brain's oscillatory responses have invaded the literature. The studies on delta (0.5-3.5Hz) oscillatory responses in humans upon application of cognitive paradigms showed that delta oscillations are related to cognitive processes, mainly in decision making and attentional processes. The present manuscript comprehensively rev...

Functional networks representing human brain dynamics have become a standard tool in neuroscience, providing an accessible way of depicting the computation performed by the brain in healthy and pathological conditions. Yet, these networks share multiple characteristics with those representing other natural and man-made complex systems, leading to t...

Underground mine workers face many risk factors at work sites that are known to affect the neural system. Observational studies report that these risk factors precede neuromuscular and neurodegenerative disorders, especially in old-age miners. Neurodegenerative disorders have electrophysiological, anatomical, and functional changes long before symp...

Background Biomarkers of Alzheimer’s disease (AD) and mild cognitive impairment (MCI, or prodromal AD) are highly significant for early diagnosis, clinical trials and treatment outcome evaluations. Electroencephalography (EEG), being noninvasive and easily accessible, has recently been the center of focus. However, a comprehensive understanding of...

Background Structural income inequality – the uneven income distribution across regions or countries – could affect brain structure and function, beyond individual differences. However, the impact of structural income inequality on the brain dynamics and the roles of demographics and cognition in these associations remains unexplored. Methods Here...

Many coronavirus disease 2019 (COVID‐19) positive individuals exhibit abnormal electroencephalographic (EEG) activity reflecting “brain fog” and mild cognitive impairments even months after the acute phase of infection. Resting‐state EEG abnormalities include EEG slowing (reduced alpha rhythm; increased slow waves) and epileptiform activity. An exp...

Brain clocks, which quantify discrepancies between brain age and chronological age, hold promise for understanding brain health and disease. However, the impact of diversity (including geographical, socioeconomic, sociodemographic, sex and neurodegeneration) on the brain-age gap is unknown. We analyzed datasets from 5,306 participants across 15 cou...

Neurodegenerative diseases such as Parkinson's (PD) and Alzheimer's (AD) exhibit considerable heterogeneity of functional brain features within patient populations, complicating diagnosis, treatment, prognosis, and drug discovery. Here, we use electroencephalography (EEG) and normative modeling to investigate neurophysiological oscillatory mechanis...

Alongside rapid population ageing, we are experiencing increasing numbers of people with cognitive impairment and dementia. There is great scientific effort being committed to understanding cognitive and brain functioning, with the aim of helping to promote healthy ageing and independence, and improve quality of life. This Cognitive Ageing Collecti...

The present exploratory study tested the hypothesis that computerized cognitive training (CCT) in home telemonitoring may beneficially affect eyes-closed resting-state electroencephalographic (rsEEG) rhythms in Parkinson's disease patients with cognitive deficits (PDCD). A Eurasian database provided clinical-demographic-rsEEG datasets in 40 PDCD pa...

Brain clocks, which quantify discrepancies between brain age and chronological age, hold promise for understanding brain health and disease. However, the impact of multimodal diversity (geographical, socioeconomic, sociodemographic, sex, neurodegeneration) on the brain age gap (BAG) is unknown. Here, we analyzed datasets from 5,306 participants acr...

Miners working underground face some risk factors that affect the nervous system—such as high noise, dark environment, chronic stress, and exposure to toxic gases. However, it is not known whether these risk factors affect the cognition of miners. In this study, the cognitive changes of miners were examined through event-related oscillations via el...

Background Repetitive transcranial magnetic stimulation (rTMS) has emerged as a promising alternative therapy for Alzheimer's disease (AD) due to its ability to modulate neural networks and enhance cognitive function. This treatment offers the unique advantage of enabling real‐time monitoring of immediate cognitive effects and dynamic brain changes...

Background Previous studies have shown that patients with Mild Cognitive Impairment due to Alzheimer’s disease (ADMCI) were characterized by reduced posterior rsEEG alpha rhythms after a 12‐month follow‐up (Babiloni et al., 2013). However, none of them have found an alpha deterioration considering a shorter follow‐up. A promising neurophysiological...

Background Abnormalities in cortical sources of resting‐state eyes closed electroencephalographic (rsEEG) rhythms recorded by hospital settings (10‐20 montage) with 19 scalp electrodes characterized Alzheimer’s disease (AD) from preclinical to dementia stages. An intriguing rsEEG application is the monitoring and evaluating of AD progression in lar...

Background Although recent studies showed that gamma frequency entrainment might have therapeutic effects on Alzheimer’s Disease (AD) (Iaccarino et al. 2016), the gamma band abnormalities in AD patients are still poorly understood, while some studies presented increased gamma responses in AD, others showed reduced gamma responses (Güntekin et al.,...

Background Patients with dementia due to Alzheimer’s disease (ADD) and Parkinson’s disease (PDD) suffer from vigilance dysregulation. We hypothesized that such dysregulation may be reflected by altered reactivity of posterior resting‐state electroencephalographic (rsEEG) alpha rhythms during the vigilance transition from eyes‐closed to ‐open condit...

We propose a novel approach for the reconstruction of functional networks representing brain dynamics based on the idea that the co-participation of two brain regions in a common cognitive task should result in a drop in their identifiability, or in the uniqueness of their dynamics. This identifiability is estimated through the score obtained by De...

Here, we discuss relevant literature findings on abnormal resting-state scalp-recorded electroencephalographic (rsEEG) rhythms in old patients with severe cognitive deficits and disabilities in activities of daily living (i.e., dementia) due to Alzheimer’s (ADD), Parkinson’s (PDD), and Lewy body (DLB) neurodegenerative diseases. Furthermore, we des...

Introduction Inhibitory control develops gradually from infancy to childhood and improves further during adolescence as the brain matures. Related previous studies showed the indispensable role of task-related alpha power during inhibition both in children and young adults. Nonetheless, none of the studies have been able to investigate the direct d...

How emotion and cognition interact is still a matter of debate. Investigation of this interaction in terms of the brain oscillatory dynamics appears to be an essential approach. To investigate this topic, we designed two separate three-stimulus oddball tasks, including emotional stimuli with different valences. Twenty healthy young subjects were in...

Here we tested the hypothesis of a relationship between the cortical default mode network (DMN) structural integrity and the resting-state electroencephalographic (rsEEG) rhythms in patients with Alzheimer’s disease with dementia (ADD). Clinical and instrumental datasets in 45 ADD patients and 40 normal elderly (Nold) persons originated from the PD...

Background Abnormalities in the neurophysiological oscillatory mechanisms generating dominant resting‐state eyes closed electroencephalographic (rsEEG) rhythms portray the Alzheimer’s disease (AD) continuum, from the preclinical to the dementia stage. Here, we tested whether these abnormalities may be reproducible by analyzing the rsEEG signals acq...

Background The resting state eyes‐closed electroencephalographic (rsEEG) alpha (8‐12 Hz) rhythms reflect cortical neural synchronization mechanisms underpinning the inhibition of sensory, cognitive, and motor areas in parietal, temporal, and occipital cortex during a condition of low vigilance. Here we tested the hypothesis that age may diversely a...

Background Graph theory models a network by its nodes and connections. “Degree” hubs reflect node centrality, while “connector” hubs are those linked to several clusters of nodes. Here we compared hubs modelled from measures of interdependencies of between‐electrode resting‐state eyes‐closed electroencephalography (rsEEG) rhythms in normal old (Nol...

Objective: In the last decades, machine learning (ML) approaches have been widely used to distinguish Parkinson's disease (PD) and many other neuropsychiatric diseases. They also speed up the clinicians and facilitate decision-making for several conditions with similar clinical symptoms. The current study attempts to detect PD with dementia (PDD) b...

Introduction: Graph theory models a network by its nodes (the fundamental unit by which graphs are formed) and connections. 'Degree' hubs reflect node centrality (the connection rate), while 'connector' hubs are those linked to several clusters of nodes (mainly long-range connections). Methods: Here, we compared hubs modeled from measures of int...

Successful use of sensory 40 Hz‐gamma entrainment has been shown in Alzheimer’s Disease animal models. Few studies had used 40 Hz‐gamma sensory gamma entrainment on human subjects and there are contradictory results on these studies. We think there could be different frequency dynamics in animals and in humans. To answer this question, we aimed to...

Objectives Working memory performances are based on brain functional connectivity, so that connectivity may be deranged in individuals with mild cognitive impairment (MCI) and patients with dementia due to Alzheimer’s disease (ADD). Here we tested the hypothesis of abnormal functional connectivity as revealed by the imaginary part of coherency (ICo...

Abnormalities in cortical sources of resting-state eyes closed electroencephalographic (rsEEG) rhythms recorded by hospital settings (10-20 montage) with 19 scalp electrodes characterized Alzheimer's disease (AD) from preclinical to dementia stages. An intriguing rsEEG application is the monitoring and evaluation of AD progression in large populati...

Parkinson's disease (PD) is a multifaceted neurodegenerative disorder accompanied by mild cognitive impairment (MCI) as a crucial non-motor manifestation. Event-related oscillations (EROs) are suggested to reflect cognitive status associated with subcortical structures in neurodegenerative conditions. In this study, thirty-six individuals with PD-M...

Abnormalities in cortical sources of resting-state eyes-closed electroencephalographic (rsEEG) rhythms recorded by hospital settings (10–20 electrode montage) with 19 scalp electrodes provide useful markers of neurophysiological dysfunctions in the vigilance regulation in patients with Alzheimer's disease dementia (ADD). Here we tested whether thes...

Unlabelled: Alzheimer's disease (AD) is an important brain disease associated with aging. It involves various functional and structural changes which alter the EEG characteristics. Although numerous studies have found changes in delta, theta, alpha, and beta power, fewer studies have looked at the changes in the resting state EEG gamma activity ch...

Parkinson's disease (PD) is a movement disorder caused by degeneration in dopaminergic neurons. During the disease course, most of PD patients develop mild cognitive impairment (PDMCI) and dementia, especially affecting frontal executive functions. In this study, we tested the hypothesis that PDMCI patients may be characterized by abnormal neurophy...

The human brain has limited storage capacity often challenging the encoding and recall of a long series of multiple items. Different encoding strategies are therefore employed to optimize performance in memory processes such as the strategy for the overall number of items to be stored (chunking). Additionally, related to the position of an item wit...

The coupling of gamma oscillation (~ 40+ Hz) amplitude to the phase of ongoing theta (~ 6 Hz) oscillations has been proposed to be directly relevant for memory performance. Current theories suggest that memory capacity scales with number of gamma cycles that can be fitted into the preferred phase of a theta cycle. Following this logic, transcranial...

Alzheimer's disease dementia (ADD) is the most diffuse neurodegenerative disorder belonging to mild cognitive impairment (MCI) and dementia in old persons. This disease is provoked by an abnormal accumulation of amyloid-beta and tauopathy proteins in the brain. Very recently, the first disease-modifying drug has been licensed with reserve (i.e., Ad...

Introduction: This report examines the effects of a multimodal rehabilitation program which includes cognitive, physical, and somatosensory rehabilitation after right temporo-parietal tumor resection on cognitive, motor, somatosensory, and electrophysiological parameters. Case description: A 22-year-old patient presented with sensory loss in the...

Here we tested if the reactivity of posterior resting-state electroencephalographic (rsEEG) alpha rhythms from the eye-closed to eyes-open condition may differ in patients with dementia due to Lewy Bodies (DLB) and Alzheimer's disease (ADD), as a functional probe of the dominant cortical neural synchronization mechanisms regulating the vigilance in...

Over the past few years, it has become standard to describe brain anatomical and functional organisation in terms of complex networks, wherein single brain regions or modules and their connections are respectively identified with network nodes and the links connecting them. Often, the goal of a given study is not that of modelling brain activity bu...

Background: Corticobasal degeneration (CBD) is a rare neurological disease caused by the pathological accumulation of tau protein. The primary pathological features of CBD include progressive neurodegenerative processes resulting in remarkable frontoparietal and basal ganglia atrophy. Objective: Like in many other neurodegenerative disorders, th...

Background Parkinson's disease with dementia (PDD) and dementia with Lewy bodies (DLB) are characterized by intracellular Lewy bodies in the brain neurons and clinical symptoms including cognitive impairment and flucations, motor symptoms, and hallucinations with some differences, namely non‐motor symptoms appear earlier in DLB over PDD patients (M...

Background Impairment of facial expression recognition in dementia is one of the cognitive deficits that could affect the social life of dementia patients. The severity of the facial expression recognition in different types of dementia has not been fully addressed. Previous studies showed that EEG event‐related oscillation (ERO) studies could reve...

Background The neurophysiological differences between Parkinson’s disease mild cognitive impairment (PD‐MCI) and cognitively normal Parkinson’s disease (PD‐CN) have been poorly understood, covering limited electrophysiological interpretation. Delta event‐related oscillations (ERO) are recognized as a useful electrophysiological indicator of cogniti...

Background Here we tested the hypothesis that gender may diversely affect resting state eyes‐closed electroencephalographic (rsEEG) alpha (8‐12 Hz) rhythms recorded in normal elderly (Nold) seniors and patients with Alzheimer’s disease and mild cognitive impairment (ADMCI). Method Clinical and rsEEG datasets in 69 ADMCI and 57 Nold individuals ‐ m...

Background Keeping in mind Başar’s theory of event‐related EEG oscillations, here we hypothesize that transient increases in delta rhythms in quiet wakefulness may enhance global cortical arousal as revealed by the desynchronization of alpha rhythms in normal (Nold) seniors with some derangement in Alzheimer’s disease dementia (ADD). Method Clinic...

Background Alzheimer's disease dementia (ADD) and Parkinson's disease dementia (PDD) are the most common types of dementia. ADD and PDD have different pathophysiology and clinical profile. It is important to understand mechanisms underlying pathophysiology, clinical symptoms, and the electrophysiological differences between these two types of demen...

Background The performance of facial expression recognition is affected both in neurocognitive disorders and in healthy elderly. Emotional content processing is expected to be adversely affected in dementia and as well in Parkinson's disease patients. The present study aims to compare the impaired facial expression recognition between different typ...

Background The rsEEG alpha rhythms reflect cortical neural synchronization mechanisms underpinning the inhibition of sensory, cognitive, and motor areas in parietal, temporal, and occipital cortex during a condition of low vigilance. Here we tested the hypothesis that age may diversely affect rsEEG alpha (8‐12 Hz) rhythms recorded in normal elderly...

Background In normal old (Nold) and Alzheimer’s disease (AD) persons, a high cognitive reserve makes them more resistant and resilient to brain neuropathology and neurodegeneration. Here we tested whether these effects may affect neurophysiological oscillatory mechanisms generating dominant resting state electroencephalographic (rsEEG) alpha rhythm...

Background Early differentiation between Alzheimer’s disease (AD) and Dementia with Lewy Bodies (DLB) is important for accurate prognosis, as DLB patients typically show faster disease progression. Cortical neural networks, necessary for human cognitive function, may be disrupted differently in DLB and AD patients, allowing diagnostic differentiati...

In the present retrospective and exploratory study, we tested the hypothesis that sex may affect cortical sources of resting state eyes-closed electroencephalographic (rsEEG) rhythms recorded in normal elderly (Nold) seniors and patients with Alzheimer's disease and mild cognitive impairment (ADMCI). Datasets in 69 ADMCI and 57 Nold individuals wer...