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Different cortex activation between young and middle-aged people during different type problem-solving: an EEG&fNIRS study
(2025) Sarıcaoğlu, Mevhibe; Yücel, Meryem Ayşe; Budak, Miray; Omurtag, Ahmet; Hanoğlu, Lütfü
Problem-solving strategies vary depending on the type of problem and aging. This study investigated the hemodynamic response measured by the changes in the oxyhemoglobin concentration (HbO), alpha frequency power, and their interrelation during problem-solving in healthy young and middle-aged individuals, employing combined electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) recordings. The study included 39 young and 30 middle-aged subjects. The brain activation that occurred while answering different questions was recorded using combined EEG and fNIRS. During the EEG & fNIRS recording, four questions (arithmetic, general knowledge, insight, and basic operation) were used for problem-solving. Alpha power (8–13 Hz) and HbO changes were analyzed. The behavioral results indicated significant differences between age groups in various question types. While the middle-aged group performed better on the general knowledge questions, the older group performed better on the insight and four-process questions. The fNIRS results reveal significant differences in brain activation during problem-solving tasks, particularly in regions like DLPFC/TA, STG, pSSC/Wernicke, and STG/angular gyrus Wernicke's area. The young group with the highest HbO was recorded during arithmetic questions, general knowledge questions, and basic operation questions. In contrast, there was no significant highest HbO during insight questions. Similar findings were observed in the middle-aged group, with the highest HbO recorded during general knowledge questions. However, there was no significant HbO in other channels during the solving of other question types in this group. The alpha power varied across different electrodes for various question types in both young and middle-aged groups. The highest alpha frequency band power for different electrodes was recorded while solving general knowledge questions in the young group and insight questions in the middle-aged group. Finally, the EEG and fNIRS correlation results showed positive correlations between HbO and alpha frequency band power in specific brain regions while solving general knowledge questions, particularly in the middle-aged group. The study reveals age-related differences in behavioral performance, brain activation patterns, and neural correlates during various cognitive tasks, showcasing distinct strengths between middle-aged and young individuals in specific question types.
Electrophysiological and cognitive changes in hard coal miners associated with working underground
(2024) Çelik, Samet; Yıldırım, Ebru; Güntekin, Bahar
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 electroencephalogram (EEG). Twenty underground miners and control groups, equal to each other in age, education level, and working duration, participated in this study. Neuropsychological tests were applied to all participants to examine their cognitive characteristics. Then, 20-channel EEG was recorded for electrophysiological changes during visual oddball paradigm. Event-related power spectrum and phase locking were analyzed in delta (0.5-3.5), theta (4-7), and alpha (8-13?Hz) frequency bands. It was determined that the delta responses that emerged during the target stimulus differed between the two groups in terms of phase locking (p < 0.05). Considering event-related alpha responses, a statistical difference was found regarding power spectrum and phase locking (p < 0.05). Moreover, the alpha power spectrum in the miners was found to be negatively statistically correlated with working duration (p < 0.05). This study determined that the event-related electrophysiological responses of the miners were negatively affected depending on the working conditions. In addition, neuropsychological assessment determined miners had deficiencies in learning and memory skills and many other cognitive functions such as attention, behavioral inhibition, and visual perception.
Reconstructing brain functional networks through identifiability and deep learning
(MIT Press Journals, 2024) Zanin, Massimiliano; Aktürk, Tuba; Yıldırım, Ebru; Yerlikaya, Deniz; Yener, Görsev; Güntekin, Bahar
We propose a novel approach for the reconstruction of functional networks representing brain dynamics based on the idea that the coparticipation 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 deep learning models in supervised classification tasks and therefore requires no a priori assumptions about the nature of such coparticipation. The method is tested on EEG recordings obtained from Alzheimer’s and Parkinson’s disease patients, and matched healthy volunteers, for eyes-open and eyes-closed resting–state conditions, and the resulting functional networks are analysed through standard topological metrics. Both groups of patients are characterised by a reduction in the identifiability of the corresponding EEG signals, and by differences in the patterns that support such identifiability. Resulting functional networks are similar, but not identical to those reconstructed by using a correlation metric. Differences between control subjects and patients can be observed in network metrics like the clustering coefficient and the assortativity in different frequency bands. Differences are also observed between eyes open and closed conditions, especially for Parkinson’s disease patients.
Lower oddball event-related EEG delta and theta responses in patients with dementia due to Parkinson's and Lewy body than Alzheimer's disease
(Elsevier Inc., 2024) Yıldırım, Ebru; Aktürk, Tuba; Hanoğlu, Lütfü; Yener, Görsev; Babiloni, Claudio; Güntekin, Bahar
Oddball task-related EEG delta and theta responses are associated with frontal executive functions, which are significantly impaired in patients with dementia due to Parkinson's disease (PDD) and Lewy bodies (DLB). The present study investigated the oddball task-related EEG delta and theta responses in patients with PDD, DLB, and Alzheimer's disease dementia (ADD). During visual and auditory oddball paradigms, EEG activity was recorded in 20 ADD, 17 DLB, 20 PDD, and 20 healthy (HC) older adults. Event-related EEG power spectrum and phase-locking analysis were performed at the delta (1–4 Hz) and theta (4–7 Hz) frequency bands for target and nontarget stimuli. Compared to the HC persons, dementia groups showed lower frontal and central delta and theta power and phase-locking associated with task performance and neuropsychological test scores. Notably, this effect was more significant in the PDD and DLB than in the ADD. In conclusion, oddball task-related frontal and central EEG delta and theta responses may reflect frontal supramodal executive dysfunctions in PDD and DLB patients.
Low frequency oscillations during hand laterality judgment task with and without personal perspectives: a preliminary study
(Springer, 2023) Dilek, Burcu; Yıldırım, Ebru; Hanoğlu, Lütfü
Sense of personal perspective is crucial for understanding in attentional mechanisms of the perception in "self" or "other's" body. In a hand laterality judgment (HLJ) task, perception of perspective can be assessed by arranging angular orientations and depths of images. A total of 11 healthy, right-handed participants (8 females, mean age: 38.36 years, education: 14 years) were included in the study. The purpose of this study was to investigate behavioural and cortical responses in low-frequency cortical rhythms during a HLJ task. A total of 80-visual hand stimuli were presented through the experiment. Hand visuals were categorized in the way of side (right vs. left) and perspective (1st vs. 3rd personal perspective). Both behavioural outcomes and brain oscillatory characteristics (i.e., frequency and amplitude) of the Electroencephalography were analysed. All reaction time and incorrect answers for 3rd person perspective were higher than the ones for 1st person perspective. Location effect was statistically significant in event-related theta responses confirming the dominant activity of theta frequency in spatial memory tasks on parietal and occipital areas. In addition, we found there were increasing in delta power and phase in hand visuals with 1st person perspective and increasing theta phase in hand visuals with 3rd person perspective (p < 0.05). Accordingly, a clear dissociation in the perception of perspectives in low-frequency bands was revealed. These different cortical strategy in the perception of hand visual with and without perspectives may be interpreted as delta activity may be related in self-body perception, whereas theta activity may be related in allocentric perception.
Functional neural networks stratify Parkinson's disease patients across the spectrum of cognitive impairment
(Wiley, 2024) Hajebrahimi, Farzin; Budak, Miray; Sarıcaoğlu, Mevhibe; Temel, Zeynep; Kahraman Demir, Tuğçe; Hanoğlu, Lütfü; Yıldırım, Süleyman; Bayraktaroğlu, Zübeyir
Introduction Cognitive impairment (CI) is a significant non-motor symptoms in Parkinson's disease (PD) that often precedes the emergence of motor symptoms by several years. Patients with PD hypothetically progress from stages without CI (PD-normal cognition [NC]) to stages with Mild CI (PD-MCI) and PD dementia (PDD). CI symptoms in PD are linked to different brain regions and neural pathways, in addition to being the result of dysfunctional subcortical regions. However, it is still unknown how functional dysregulation correlates to progression during the CI. Neuroimaging techniques hold promise in discriminating CI stages of PD and further contribute to the biomarker formation of CI in PD. In this study, we explore disparities in the clinical assessments and resting-state functional connectivity (FC) among three CI stages of PD.Methods We enrolled 88 patients with PD and 26 healthy controls (HC) for a cross sectional clinical study and performed intra- and inter-network FC analysis in conjunction with comprehensive clinical cognitive assessment.Results Our findings underscore the significance of several neural networks, namely, the default mode network (DMN), frontoparietal network (FPN), dorsal attention network, and visual network (VN) and their inter-intra-network FC in differentiating between PD-MCI and PDD. Additionally, our results showed the importance of sensory motor network, VN, DMN, and salience network (SN) in the discriminating PD-NC from PDD. Finally, in comparison to HC, we found DMN, FPN, VN, and SN as pivotal networks for further differential diagnosis of CI stages of PD.Conclusion We propose that resting-state networks (RSN) can be a discriminating factor in distinguishing the CI stages of PD and progressing from PD-NC to MCI or PDD. The integration of clinical and neuroimaging data may enhance the early detection of PD in clinical settings and potentially prevent the disease from advancing to more severe stages.
Relationship between default mode network and resting-state electroencephalographic alpha rhythms in cognitively unimpaired seniors and patients with dementia due to alzheimer’s disease
(Oxford University Press, 2023) Babiloni, Claudio; Lopez, Susanna; Noce, Giuseppe; Ferri, Raffaele; Panerai, Simonetta; Catania, Valentina; Carducci, Filippo
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 PDWAVES Consortium (www.pdwaves.eu). Individual rsEEG delta, theta, alpha, and fixed beta and gamma bands were considered. Freeware platforms served to derive (1) the (gray matter) volume of the DMN, dorsal attention (DAN), and sensorimotor (SMN) cortical networks and (2) the rsEEG cortical eLORETA source activities. We found a significant positive association between the DMN gray matter volume, the rsEEG alpha source activity estimated in the posterior DMN nodes (parietal and posterior cingulate cortex), and the global cognitive status in the Nold and ADD participants. Compared with the Nold, the ADD group showed lower DMN gray matter, lower rsEEG alpha source activity in those nodes, and lower global cognitive status. This effect was not observed in the DAN and SMN. These results suggest that the DMN structural integrity and the rsEEG alpha source activities in the DMN posterior hubs may be related and predict the global cognitive status in ADD and Nold persons.
Factors affecting static and dynamic balance in individuals with pes planus: A 45 case clinical study
(Yüzüncü Yıl University Faculty of Medicine, 2023) Tan, Mehmet Salih; Yıldırım, Ebru
Pes planus is one of the most common biomechanical disorders of the lower extremities caused by different intrinsic and extrinsic factors and negatively affects activities of daily living from mild to severe. Balance-based domestic or international studies give limited data on the diagnosis of flatfoot. For this reason, we aimed to give the view of the static and dynamic balance states of individuals with pes planus in our clinic. Twenty-two patients diagnosed with pes planus of deformity grade 2 and above according to the Feiss line and 23 volunteers without pes planus were included in the study. All participants were evaluated for static (30TST and single leg stance tests) and dynamic [Berg balance scale (BBS), Tinetti balance & gait test and timed up & go (TUG) tests] balance. The distribution among the groups evaluated with nonparametric tests was significant in terms of both static {[?group*t andem(1)=17.107, p=0.000], [?(1)group*single_leg=13.442, p=0.000]} and dynamic [(Ugroup*berg=60, p=0.000), (Ugroup*t inett i=30, p=0.000), (Ugroup*t imed_up&go=7.5, p=0.000)] tests. In all static balance and dynamic tests, the time to stay in balance was found to be lower in the pes planus group, as expected. Apart from this, when the relationship between demographic and clinical data, balance tests and groups was evaluated, no statistically significant relationship was found (p>0.05). Accordingly, static and dynamic balance tests were effective in evaluating flat feet, while factors such as obesity and gender did not affect the degree of disease.
Event-related delta and theta responses may reflect the valence discrimination in the emotional oddball task
(Springer Science and Business Media Deutschland GmbH, 2023) Bölükbaş, Burcu; Aktürk, Tuba; Ardalı, Hilal; Dündar, Yasemin; Güngör, Ceren; Kahveci, Şaika; Güntekin, Bahar
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 included in the study. They completed two tasks, namely: the positive emotional oddball task and the negative emotional oddball task. Each task included the target, non-target, and distractor stimuli. Positive and negative pictures were the target stimuli in the positive and negative emotional oddball task. We asked participants to determine the number of target stimuli in each task. During sessions, EEGs were recorded with 32 electrodes. We found that (negative) target stimuli elicit higher delta (1–3.5 Hz) and theta (4–7 Hz) power responses but not the phase-locking responses compared to (positive) distractor stimuli during the negative oddball task. On the other hand, the same effect was not seen during the positive emotional oddball task. Here, we showed that the valence dimension interacted with the target status. Finally, we summarized our results that the presence of negative distractors attenuated the target effect of the positive stimuli due to the negative bias.
Immature event-related alpha dynamics in children compared with the young adults during inhibition shown by day-night stroop task
(Frontiers Media SA, 2023) Güntekin, Bahar; Alptekin, Simay; Yıldırım, Ebru; Aktürk, Tuba; Uzunlar, Hakan; Çalışoğlu, Pervin; Eroğlu Ada, Figen; Atay, Enver; Ceran, Ömer
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 differences in brain responses between children and young adults when confronted with a stimulus that should be inhibited. Because, unlike event-related designs, task-related designs involve continuous tasks over a certain period, which precludes the possibility of making such a comparison. Accordingly, by employing event-related design, the present study first time in the literature, aimed to analyze the event-related alpha phase locking and event-related alpha synchronization/ desynchronization to differentiate the inhibitory processes in children compared to young adults. Methods: Twenty children between the ages of 6 to 7 years and 20 healthy young adult subjects between the ages of 18 to 30 years were included in the study. Day-night Stroop task was applied to all subjects during 18-channel EEG recordings. Event-related time-frequency analysis was performed with the complex Morlet Wavelet Transform for the alpha frequency band (8–13 Hz). Event related spectral perturbation (ERSP) in three different time windows (0–200 ms, 200–400 ms, 400–600 ms) and Event-related phase locking in the early time window (0–400 ms) was calculated. Results: The children had increased alpha power in early and late time windows but decreased alpha phase locking in the early time windows compared to young adults. There were also topological differences between groups; while young adults had increased alpha phase-locking in frontal and parietal electrode sites, children had increased occipital alpha power and phase locking. Discussion: The shift in event-related alpha power observed from posterior to anterior regions with age may suggest a progressive maturation of the frontal areas involved in inhibitory processes from childhood to adulthood. The results of the present study showed that children and young adults had different EEG oscillatory dynamics during inhibitory processes at alpha frequency range.
Resting state alpha electroencephalographic rhythms are affected by sex in cognitively unimpaired seniors and patients with alzheimer's disease and amnesic mild cognitive impairment: A retrospective and exploratory study
(Oxford University Press Inc, 2022) Babiloni, Claudio; Noce, Giuseppe; Ferri, Raffaele; Lizio, Roberta; Lopez, Susanna; Lorenzo, Ivan; Tucci, Federico; Soricelli, Andrea; Zurrón, Montserrat; Díaz, Fernando; Nobili, Flavio; Arnaldi, Dario; Famà, Francesco; Buttinelli, Carla; Giubilei, Franco; Cipollini, Virginia; Marizzoni, Moira; Güntekin, Bahar; Yıldırım, Ebru; Hanoğlu, Lütfü; Yener, Görsev; Hünerli Gündüz, Duygu; Onorati, Paolo; Stocchi, Fabrizio; Vacca, Laura; Maestú, Fernando; Frisoni, Giovanni B.; del Percio, Claudio
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 were taken from an international archive. The rsEEG rhythms were investigated at individual delta, theta, and alpha frequency bands and fixed beta (14-30 Hz) and gamma (30-40 Hz) bands. Each group was stratified into matched females and males. The sex factor affected the magnitude of rsEEG source activities in the Nold seniors. Compared with the males, the females were characterized by greater alpha source activities in all cortical regions. Similarly, the parietal, temporal, and occipital alpha source activities were greater in the ADMCI-females than the males. Notably, the present sex effects did not depend on core genetic (APOE4), neuropathological (A beta 42/phospho-tau ratio in the cerebrospinal fluid), structural neurodegenerative and cerebrovascular (MRI) variables characterizing sporadic AD-related processes in ADMCI seniors. These results suggest the sex factor may significantly affect neurophysiological brain neural oscillatory synchronization mechanisms underpinning the generation of dominant rsEEG alpha rhythms to regulate cortical arousal during quiet vigilance.
Are there consistent abnormalities in event-related EEG oscillations in patients with Alzheimer's disease compared to other diseases belonging to dementia?
(John Wiley and Sons Inc, 2022) Güntekin, Bahar; Aktürk, Tuba; Arakaki, Xianghong; Bonanni, Laura; Del Percio, Claudio; Edelmayer, Rebecca; Farina, Francesca; Ferri, Raffaele; Hanoğlu, Lütfü; Kumar, Sanjeev; Lizio, Roberta; Lopez, Susanna; Murphy, Brian; Noce, Giuseppe; Randall, Fiona; Sack, Alexander T.; Stocchi, Fabrizio; Yener, Görsev; Yıldırım, Ebru; Babiloni, Claudio
Cerebrospinal and structural-molecular neuroimaging in-vivo biomarkers are recommended for diagnostic purposes in Alzheimer’s disease (AD) and other dementias; however, they do not explain the effects of AD neuropathology on neurophysiological mechanisms underpinning cognitive processes. Here, an Expert Panel from the Electrophysiology Professional Interest Area of the Alzheimer’s Association reviewed the field literature and reached consensus on the event-related electroencephalographic oscillations (EROs) that show consistent abnormalities in patients with significant cognitive deficits due to Alzheimer’s, Parkinson’s (PD), Lewy body (LBD), and cerebrovascular diseases. Converging evidence from oddball paradigms showed that, as compared to cognitively unimpaired (CU) older adults, AD patients had lower amplitude in widespread delta (>4 Hz) and theta (4–7 Hz) phase-locked EROs as a function of disease severity. Similar effects were also observed in PD, LBD, and/or cerebrovascular cognitive impairment patients. Non-phase-locked alpha (8–12 Hz) and beta (13–30 Hz) oscillations were abnormally reduced (event-related desynchronization, ERD) in AD patients relative to CU. However, studies on patients with other dementias remain lacking. Delta and theta phase-locked EROs during oddball tasks may be useful neurophysiological biomarkers of cognitive systems at work in heuristic and intervention clinical trials performed in AD patients, but more research is needed regarding their potential role for other dementias.
Oscillatory delta and theta frequencies differentially support multiple items encoding to optimize memory performance during the digit span task
(Academic Press Inc., 2022) Aktürk, Tuba; de Graaf, Tom A.; Erdal, Furkan; Sack, Alexander T.; Güntekin, Bahar
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 chunking where particular items are ‘grouped’ to reduce the number of items to store artificially. Additionally, related to the position of an item within a series, there is a tendency to remember the first and last items on the list better than the middle ones, which calls the “serial position effect”. Although relatively well-established in behavioral research, the neuronal mechanisms underlying such encoding strategies and memory effects remain poorly understood. Here, we used event-related EEG oscillation analyses to unravel the neuronal substrates of serial encoding strategies and effects during the behaviorally controlled execution of the digit span task. We recorded EEG in forty-four healthy young-adult participants during a backward digit span (ds) task with two difficulty levels (i.e., 3-ds and 5-ds). Participants were asked to recall the digits in reverse order after the presentation of each set. We analyzed the pattern of event-related delta and theta oscillatory power in the time-frequency domain over fronto-central and parieto-occipital areas during the item (digit) list encoding, focusing on how these oscillatory responses changed with each subsequent digit being encoded in the series. Results showed that the development of event-related delta power evoked by digits in each series matched the ‘serial position curve’, with higher delta power being present during the first, and especially last, digits as compared to digits presented in the middle of a set, for both difficulty levels. Event-related theta power, in contrast, rather resembled a neural correlate of a chunking pattern where, during the 5-ds encoding, a clear change in event-related theta occurred around the third/fourth positions, with decreasing power values for later digits. This suggests that different oscillatory mechanisms linked to different frequency bands may code for the different encoding strategies and effects in serial item presentation. Furthermore, recall-EEG correlations suggested that participants with higher fronto-central delta responses during digit encoding showed also higher recall scores. The here presented findings contribute to our understanding of the neural oscillatory mechanisms underlying multiple item encoding, directly informing recent efforts towards memory enhancement through targeted oscillation-based neuromodulation.
Treatment effects on event-related EEG potentials and oscillations in Alzheimer's disease
(Elsevier B.V., 2022) Yener, Görsev; Hünerli Gündüz, Duygu; Yıldırım, Ebru; Aktürk, Tuba; Başar Eroğlu, Canan; Bonanni, Laura; Del Percio, Claudio; Farina, Francesca; Ferri, Raffaele; Güntekin, Bahar; Hajós, Mihály; Ibáñez, Agustín; Jiang, Yang; Lizio, Roberta; Lopez, Susanna; Noce, Giuseppe; Parra, Mario A.; Randall, Fiona; Stocchi, Fabrizio; Babiloni, Claudio
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., Aducanumab). Therefore, there is a need to identify and use biomarkers probing the neurophysiological underpinnings of human cognitive functions to test the clinical efficacy of that drug. In this regard, event-related electroencephalographic potentials (ERPs) and oscillations (EROs) are promising candidates. Here, an Expert Panel from the Electrophysiology Professional Interest Area of the Alzheimer's Association and Global Brain Consortium reviewed the field literature on the effects of the most used symptomatic drug against ADD (i.e., Acetylcholinesterase inhibitors) on ERPs and EROs in ADD patients with MCI and dementia at the group level. The most convincing results were found in ADD patients. In those patients, Acetylcholinesterase inhibitors partially normalized ERP P300 peak latency and amplitude in oddball paradigms using visual stimuli. In these same paradigms, those drugs partially normalize ERO phase-locking at the theta band (4–7 Hz) and spectral coherence between electrode pairs at the gamma (around 40 Hz) band. These results are of great interest and may motivate multicentric, double-blind, randomized, and placebo-controlled clinical trials in MCI and ADD patients for final cross-validation.
Telling functional networks apart using ranked network features stability
(NLM (Medline), 2022) Zanin, Massimiliano; Güntekin, Bahar; Aktürk, Tuba; Yıldırım, Ebru; Yener, Görsev; Kıyı, İlayda; Hünerli Gündüz, Duygu; Sequeira, Henrique; Papo, David
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 but, more basically, to discriminate between experimental conditions or populations, thus to find a way to compute differences between them. This in turn involves two important aspects: defining discriminative features and quantifying differences between them. Here we show that the ranked dynamical stability of network features, from links or nodes to higher-level network properties, discriminates well between healthy brain activity and various pathological conditions. These easily computable properties, which constitute local but topographically aspecific aspects of brain activity, greatly simplify inter-network comparisons and spare the need for network pruning. Our results are discussed in terms of microstate stability. Some implications for functional brain activity are discussed.
The correlation of non-motor symptoms and sleep on balance in Parkinson's disease patients with normal cognition and mild cognitive impairment
(Springer London Ltd, 2021) Sarıcaoğlu, Mevhibe; Helvacı Yılmaz, Nesrin; Özer, Fahriye Feriha; Hanoğlu, Lütfü
Background Parkinson's disease (PD) is characterized by non-motor symptoms (NMS) as well as by motor symptoms. Together with the impairment of cognitive functions, NMS and sleep also affect motor symptoms negatively. The aim of our study is to examine the correlation of NMS and sleep on balance in PD patients with normal cognition (PD-NC) and with mild cognitive impairment (PD-MCI). Methods A total of 69 patients were included in our study. Using the Standardized Mini-Mental State Examination, participants were divided into 2 groups, PD-NC and PD-MCI. Patients were assessed with the Unified Parkinson's Disease Rating Scale (UPDRS), the Berg Balance Scale (BBS), the Tinetti Balance Assessment Tool (TBAT), the Non-Motor Symptoms Questionnaire (NMSQ), and the Parkinson's Disease Questionnaire (PDQ-39). Results PD-MCI patients had statistically significant worse motor symptoms and more balance disorder compared to PD-NC (UPDRS: p = 0.009; BBS: p = 0.010; TBAT: p = 0.004). PD-MCI patients had greater severity of non-motor symptoms and worse sleep quality than the PD-NC group (NMSQ-total: p = 0.02; NMSQ-sleep total: p = 0.01). The evaluation has shown that with a diagnosis of MCI, NMS, and sleeping problems were correlated, and the correlation was associated with impairment of the balance function. While being more pronounced in the PD-MCI group, quality of life was affected in both groups (p < 0.05). Conclusion Our data demonstrate a negative effect on the balance function in patients with cognitive impairment suffering increased NMS and sleeping disorders. Treatment of these patients needs to concentrate on NMS and cognitive functions as much as on motor symptoms.
Event-related EEG oscillatory responses elicited by dynamic facial expression
(BMC, 2021) Aktürk, Tuba; de Graaf, Tom A.; Abra, Yasemin; Şahoğlu Göktaş, Sevilay; Özkan, Dilek; Kula, Aysun; Güntekin, Bahar
Background Recognition of facial expressions (FEs) plays a crucial role in social interactions. Most studies on FE recognition use static (image) stimuli, even though real-life FEs are dynamic. FE processing is complex and multifaceted, and its neural correlates remain unclear. Transitioning from static to dynamic FE stimuli might help disentangle the neural oscillatory mechanisms underlying face processing and recognition of emotion expression. To our knowledge, we here present the first time-frequency exploration of oscillatory brain mechanisms underlying the processing of dynamic FEs. Results Videos of joyful, fearful, and neutral dynamic facial expressions were presented to 18 included healthy young adults. We analyzed event-related activity in electroencephalography (EEG) data, focusing on the delta, theta, and alpha-band oscillations. Since the videos involved a transition from neutral to emotional expressions (onset around 500 ms), we identified time windows that might correspond to face perception initially (time window 1; first TW), and emotion expression recognition subsequently (around 1000 ms; second TW). First TW showed increased power and phase-locking values for all frequency bands. In the first TW, power and phase-locking values were higher in the delta and theta bands for emotional FEs as compared to neutral FEs, thus potentially serving as a marker for emotion recognition in dynamic face processing. Conclusions Our time-frequency exploration revealed consistent oscillatory responses to complex, dynamic, ecologically meaningful FE stimuli. We conclude that while dynamic FE processing involves complex network dynamics, dynamic FEs were successfully used to reveal temporally separate oscillation responses related to face processing and subsequently emotion expression recognition.
Theta and alpha oscillatory responses differentiate between six-to seven-year-old children and adults during successful visual and auditory memory encoding
(Elsevier, 2020) Güntekin, Bahar; Uzunlar, Hakan; Çalışoğlu, Pervin; Eroğlu-Ada, Figen; Yıldırım, Ebru; Aktürk, Tuba; Atay, Enver; Ceran, Ömer
The healthy maturation of the brain is one of the intriguing topics that need to be investigated to understand human brain and child development. The present study aimed to investigate the development of memory processes both for auditory and visual memory using electroencephalography (EEG)-Brain Dynamics methodologies.Sixteen healthy children between the ages of 6 and 7 years and eighteen healthy young adults (age: 21.32 +/- 3.28 years) were included in the study. EEG was recorded from 18 channels during the visual and auditory memory paradigms. Two different subtests of the WISC-IV IQ test were applied to all children. Eventrelated theta (4-7 Hz), alpha (8-13 Hz) power and phase-locking were analyzed.The young adults had higher memory performance than the children for both auditory and visual paradigms. The children had increased theta phase-locking and left alpha power in response to the remembered objects in comparison to the forgotten objects. The young adults had higher theta and alpha phase-locking than the children over the frontal and central locations (p < 0.05), and the children had higher parietal-occipital alpha phase-locking than the young adults. There was an increase in alpha power in children, whereas young adults had decreased post-stimulus alpha power in response to memory paradigms.The present study showed that frontocentral theta and alpha phase-locking had an essential role in brain maturation and successful memory performance. Event-related theta and alpha responses could be one of the important indicators of the mature and healthy brain, and these responses could change depending on the maturation state and age.
Rehabilitation of cognitive disorder after temporal lobe epilepsy surgery: Proposal for a protocol
(Kare Publishing, 2020) Sarıcaoğlu, Mevhibe; Oğul, Özden Erkan; Özkara, Çiğdem; Hanoğlu, Lütfü
Objectives: Surgical intervention is a crucial and effective treatment option for patients with temporal lobe epilepsy whose seizures are not under con-trol. However, there is a possibility that surgical intervention may have a negative effect on cognitive functions. Cognitive rehabilitation is a treatment option that has been recently investigated for various neurocognitive problems. This study proposes a protocol for the rehabilitation of the cognitive dysfunctions after temporal lobe epilepsy surgery. Methods: To overcome the cognitive deficits that occurred after surgery, a six-step program was developed, which included the compensatory and adaptation strategies and memory and executive functions. This program was performed after epilepsy surgery in two patients who were evaluated with neuropsychometric test battery. Results: Cognitive rehabilitation program had a significant and positive effect on the neuropsychometric test results in two epilepsy patients who had postoperative attention, memory and executive function problems. Discussion: In the postoperative period, patients with temporal lobe epilepsy may be able to recover from cognitive disorders with an effective CR program. Although our results were obtained only with two patients, they suggest that cognitive rehabilitation had a significant and positive effect on epilepsy patients with postoperative attention, memory and executive function problems. However, the onset of the rehabilitation before or after surgery, the duration and the content of the rehabilitation are controversial issues. Conclusion: Future studies should show evidence basis of the standardized rehabilitation program for patients after epilepsy surgery, and the short and long-term effects of the rehabilitation with larger participants.
Abnormalities in auditory and visual cognitive processes are differentiated with theta responses in patients with Parkinson's disease with and without dementia
(Elsevier, 2020) Güntekin, Bahar; Aktürk, Tuba; Yıldırım, Ebru; Helvacı Yılmaz, Nesrin; Hanoğlu, Lütfü; Yener, Görsev
The research on the abnormalities of event-related oscillations in Parkinson's disease (PD) was mostly studied with cognitively normal patients. The present study aims to show the adverse effects of cognitive decline in PD patients via the EEG-Brain Oscillations approach by comparing the electrophysiological responses in two modalities, i.e. auditory, and visual in which PD group show deficit. We conducted a study in which we analyzed event-related theta power and phase-locking during auditory and visual oddball paradigm. Cognitively normal PD (PDCN) patients (N = 15), PD with mild cognitive impairment (PDMCI) patients (N = 22), PD dementia (PDD) patients (N = 11) and healthy controls (HC) (N = 17) were included in the study. Neuropsychological assessments were applied to all participants. There was a gradual decrease in scores of neuropsychological tests (HC, PDCN, PDMCI, PDD, respectively). Most of the neuropsychological test scores of the participants were highly correlated with the theta power and theta phase locking values, especially over frontal-central areas. HC had higher theta phase-locking and power in comparison to PDMCI and PDD. The differentiation between HC and PDCN was specific to frontal-central areas. Theta power and theta phase-locking were decreased overall locations in PDMCI and PDD both during visual and auditory oddball paradigms compared with PDCN. The results indicate that theta responses in PD patients decreased gradually as the cognitive decline increased. We can conclude that complex abnormalities in their neurotransmitter and neuronal signal systems that occur with the progression of the disease could be responsible for these results.

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