Introduction:The ability to recognize emotional facial expressions relies on brain functional networks, particularly in the right hemisphere, and is impaired in neurodegenerative conditions such as Alzheimer's disease and Parkinson's disease. Given that this ability involves brain networks operating within hundreds of milliseconds, we tested the hypothesis of abnormalities in event-related spectral electroencephalographic coherence, with a focus on the right versus left hemispheres in these patients. Methods:Event-related theta (4-7 Hz) magnitude-squared coherence was calculated for both intra-hemispheric (frontal-temporal, frontal-parietal, central-temporal, and related pairs) and inter-hemispheric homologous electrode pairs (F3-F4, C3-C4, T7-T8, TP7-TP8, P3-P4, O1-O2). We enrolled 25 patients with amnestic mild cognitive impairment, 15 Parkinson's disease patients with mild cognitive impairment, 25 Alzheimer's disease patients with dementia, and 16 Parkinson's disease patients with dementia, along with 25 healthy elderly as controls. Participants were presented with three different facial expressions (angry, happy, and neutral) 60 times each in a pseudo-random order. Results:Theta (4-7 Hz) spectral coherence was higher in the right than the left hemisphere across all groups, with Parkinson's disease patients exhibiting the lowest values. Moreover, interhemispheric theta coherence was lower in Parkinson's disease patients with mild cognitive impairment and dementia compared to the amnestic mild cognitive impairment and healthy elderly groups. Discussion:These findings indicate that cortical functional connectivity related to emotional facial expression processing is more disrupted in Parkinson's disease than in Alzheimer's disease, at both mild cognitive impairment and dementia stages. This disruption affects not only the right hemisphere but also interhemispheric connectivity. Finally, it would occur at theta frequencies.

Children with low birth weight (LBW) often exhibit poorer social and cognitive abilities than their normal birth weight (NBW) peers. These difficulties may persist into young adulthood and are accompanied by altered resting-state electroneurophysiological patterns. Considering the results of these studies, understanding the neural substrates of birth weight becomes more important. Here, we used EEG event-related oscillations to unravel differences between children born with low and normal birth weights during a visual memory encoding to explore further the birth weight effect on the brain oscillatory responses of 6-to-7-year-old children. This study used an observational, cross-sectional, between-group design comparing LBW/preterm (N = 15) and NBW (N = 17) children. EEGs of the children were recorded during the encoding phase of visual memory task. Additionally, all children were administered two subtests from the WISC-IV IQ assessment: working memory (WM) and processing speed (PS). We employed time-frequency analysis to investigate event-related brain oscillatory pattern to distinguish differentiation between LBW/preterm and NBW. Consistent with previous studies, our behavioral results demonstrated that LBW/preterm group scored worse on WM and PS than their NBW peers. EEG results highlighted a topological differentiation between LBW/preterm and NBW groups, with greater posterior event-related alpha and especially beta responses in the LBW/preterm group during item encoding. Importantly, posterior beta oscillatory responses negatively correlated with the PS score in NBW children. Based on our results, the differences in cognitive abilities in the LBW/ preterm group may be associated with posterior overactivity, characterized by increased eventrelated alpha and beta responses. This overactivity may reflect a greater reliance on perceptual processing strategies during memory encoding in early school-aged children born with low birth

OBJECTIVE:Temporale lobe and occipito-temporal cortical areas play an important role in facial emotion perception (FEP). FEP might be represented by event-related brain oscillations. In patients with temporal lobe epilepsy (TLE), impairment of FEP was shown with behavioral and functional neuroimaging (FMRI, PET, MEG) but not event-related oscillations, which is a well known method for cognitive research studies. The present study aims to explore FEP by analyzing EEG event-related theta oscillations in patients with TLE. METHODS:21 patients with TLE and 19 healthy volunteers were included. During EEG recording, 15 photographs from Ekman and Friesen's photo series showing five different facial expressions (angry, happy, neutral, fearful, sad) were used. Event-related theta (3-8 Hz) power spectrum and phase locking were analyzed by wavelet transform method using the Brain Vision Analyzer program. RESULTS:The difference between TLE patients and healthy volunteers was found to be significant for theta power (P < 0,05), but there was no significant difference between right and left TLE patients (P > 0,05). Lower theta power was observed against all faces in the patient group, especially in temporo-parietal and parietal areas, compared to healthy volunteers (P < 0,05). Patients with left TLE were significantly impaired in happy facial expressions, patients with right TLE were significantly impaired in fearful facial expressions. CONCLUSIONS:Impaired FEP in patients with TLE is characterized by decreased event-related theta responses, particularly in temporo-parietal and parietal areas. The present study presents the electrophysiological indicators of impaired FEP in TLE patients for the first time in the literature. The current study could be a guide for future research related to neural networks in cognitive tasks and epilepsy.

IntroductionInhibitory 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.MethodsTwenty 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.ResultsThe 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.DiscussionThe 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.

Parkinson's disease (PD) is a multifaceted neurodegenerative disorder accompanied by mild cognitive impairment (MCI) as a crucial nonmotor manifestation. Event-related oscillations (EROs) are suggested to reflect cognitive status associated with subcortical structures in neurodegenerative conditions. In this study, 36 individuals with PD-MCI and 32 PD-CN were compared with 60 healthy control (HC) participants using visual EROs by measures of event-related spectral perturbation and inter-trial coherence, along with subcortical gray matter volumes based on the FIRST algorithm. Cross-correlations among electrophysiological, neuropsychological, and structural parameters were investigated exploratively. Both PD-MCI and PD-CN patients had diminished delta and alpha phase-locking than HC, however, electrophysiological abnormalities were more pronounced in PD-MCI over frontal, central, parietal, and temporal locations in almost all frequency bands, accompanied by bilateral thalamus, hippocampus, and right putamen atrophy. PD-CN had lower hippocampal volumes than HC, without exhibiting any subcortical differences from PD-MCI. Lastly, EROs showed low-to-high correlations with structural and neuropsychological measures. These findings may highlight the complex interplay between electrophysiological, neuropsychological, and structural parameters in detected abnormalities of PD-CN and PD-MCI.

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 reveal the brain dynamics during successful facial expression recognition. Furthermore, the impairment of facial recognition in Alzheimer's disease patients were represented with abnormal EROs (Güntekin et al., 2019). The present study aims to compare the impaired facial expression recognition between different types of dementia by analysis of event‐related delta responses. The role of delta responses in facial expression and emotional paradigms was reported previously by several researchers (Güntekin and Başar, 2014).

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 types of dementia patients, functional connectivity changes in patients with mild cognitive impairment, and patients with dementia were investigated by event‐related EEG‐coherence.

AbstractBackgroundSeveral researchers have reported the impairment of recognition of facial expressions in Alzheimer’s disease (AD) patients. AD had reduced theta and alpha responses compared to healthy controls during the recognition of facial expressions (Güntekin et al. 2019). Gamma responses also have a crucial role in the recognition of facial expression in healthy young adults (Güntekin and Başar 2014). AD had increased late gamma responses compared to healthy controls during working memory paradigms (Başar et al. 2017). The present study aims to analyze the gamma responses during the recognition of facial expressions in AD and healthy controls. We hypothesized that if the increase of late gamma responses is a general phenomenon in AD patients independent of the stimulation type, we expect to find increase gamma responses in AD patients in comparison to healthy controls.MethodEEGs of 40 healthy controls (HCs) and 41 AD patients were recorded during their perception of three different facial expressions (angry, happy, neutral). Event‐related power spectrum and phase locking were analyzed for three different gamma bands (30‐35 Hz, 35‐ 40Hz, 40‐48 Hz) in two different time windows (0‐200 ms, 200‐400 ms).ResultThe group difference between AD patients and HCs was not significant for the phase‐locking values. AD patients had higher gamma power responses compared to healthy controls in 200‐400 ms time window for 30‐35 Hz(p=0.016), 35‐40 Hz(p=0.018) and 40‐48 Hz (p=0.039). The only significant group difference for the early time window (0‐200 ms) was found for 35‐40 Hz (p=0.046). The figure shows topographical plots of gamma (35‐40 Hz) power for 200‐400 ms time window in patients (upper part) and healthy controls (lower part) for angry, happy and neutral facial expressions.ConclusionThe present study showed that the increase of late (200‐400 ms) gamma were independent of stimulus type in AD patients. The increase of gamma power in a 200‐400 ms time window was found in AD patients compared to healthy controls for all three facial expressions. The facial expression recognition in AD patients was differentiated from healthy controls by increased gamma power. Acknowledgments: This work (grant number 218S314) was supported by TUBITAK.

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.