Search

Semantic priming in Turkish was examined in 36 right-handed healthy participants in a delayed lexical decision task via taxonomic relations using EEG. Prime-target relations included related- unrelated- and pseudo-words. Taxonomically related words at long stimulus onset asynchrony (SOA) were shown to modulate N400 and late positive component (LPC) amplitudes. N400 semantic priming effect in the time window of 300-500 ms was the largest for pseudo-words, intermediate for semantically-unrelated targets, and smallest for semantically-related targets as a reflection of lexical-semantic retrieval. This finding contributes to the ERP literature showing how remarkably universal the N400 brain potential is, with similar effects across languages and orthography. The ERP data also revealed different influences of related, unrelated, and pseudo-word conditions on the amplitude of the LPC. Attention scores and mean LPC amplitudes of related words in parietal region showed a moderate correlation, indicating LPC may be related to "relationship-detection process".

Brain-predicted age difference scores are calculated by subtracting chronological age from ‘brain’ age. Positive scores reflect accelerated ageing and are associated with increased mortality risk and poorer physical function. To date, however, the relationship between brain-predicted age difference scores and specific cognitive functions has not been systematically examined. First, applying machine learning to 1,359 T1-weighted MRI scans, we predicted the relationship between chronological age and voxel-wise grey matter data. This model was then applied to MRI data from three independent datasets, significantly predicting chronological age: Dokuz Eylul University (n=175), the Cognitive Reserve/Reference Ability Neural Network study (n=380), and The Irish Longitudinal Study on Ageing (n=487). Each independent dataset had rich neuropsychological data. Brain-predicted age difference scores were significantly negatively correlated with general cognitive status (two datasets); processing speed, visual attention, cognitive flexibility (three datasets); visual attention and cognitive flexibility (two datasets); and semantic verbal fluency (two datasets). They were not significantly correlated with processing speed, cognitive flexibility, response inhibition and selective attention, sustained attention, verbal episodic memory or working memory in any dataset. As such, there is firm evidence of correlations between increased brain-predicted age differences and reduced cognitive function only in some domains that are implicated in cognitive ageing.

Objective The Stroop test Capa version does not have normative data, despite its extensive use in clinical and research settings to assess executive functions. The aim of the present study was to test the validity and reliability of the Stroop test Capa version and to establish stratified normative data in individuals aged between 18-83 years. Method The norm determination phase of the study included 541 healthy participants, stratified by age, education, and gender. The relative contributions of the demographic variables on the completion times of Stroop subtests were assessed with multiple linear regression analysis. The main effects of age, education and gender variables and of interactions between these on the completion times of subtests were investigated with 6x3x2 ANOVA design. In addition, the concurrent validity, test-retest reliability and internal consistency of the test were examined. Results Multiple linear regression models that included age and education accounted for 23-42% of the completion time variances of all subtests. In the factorial ANOVA, main effects, as well as interaction effects of age and education were found on all subtests. For all Stroop subtests, the completion times were the shortest for the individuals in the 18-29 age group with the highest education level and longest for the individuals in the 70-83 age group with the lowest education level. The test demonstrated acceptable internal consistency and high test-retest reliability. Conclusion Normative data of the Stroop Test Capa Version were provided for the assessment of executive functions in young and middleaged adults and elderly population.

Objective: The clock drawing test (CDT) version with the pre-drawn circle has been widely used in research and clinical practice without standardized Turkish norms. The present study aimed to standardize CDT scores according to the most frequently used scoring methods in the literature (Manos-Wu and Shulman) and to estimate the validity and reliability of both methods. Materials and Methods: The norm determination phase of the study was performed with 244 healthy individuals in the age range of 50-92 years. The effects of age, education, and sex on the CDT scores were examined and normative data stratified by age and education were derived. Test-retest reliability, inter-rater reliability, and concurrent validity and criterion validity of the two scoring methods were tested. Criterion validity was assessed using the ROC analysis to examine the extent to which the CDT scores could distinguish among healthy individuals, patients with mild cognitive impairment (MCI), and patients with Alzheimer’s disease (AD). Results: In the Manos-Wu method, age and education had significant effects on CDT scores of healthy individuals; however, in the Shulman method, only an education effect was found. Both methods had high test-retest reliability (Manos-Wu, 0.81; Shulman, 0.72) and inter-rater reliability (Manos-Wu, 0.98; Shulman, 0.96) and showed high correlations with each other and with other cognitive screening tests. The area under the ROC curve had high values only in discriminating between healthy individuals and AD, and healthy individuals and MCI. Conclusion: In the present study, detailed normative data for individuals aged 50 and older were established. Age and education levels should be taken into account when interpreting CDT scores. Both scoring methods provided similar results in terms of high test-retest and inter-rater reliability, as well as high concurrent and criterion validity.

Extending Basar's theory of event-related EEG oscillations, here we hypothesize that even in quiet wakefulness, transient increases in delta rhythms 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).Clinical and EEG datasets in 100 ADD and 100 Nold individuals matched as demography, education, and gender were taken from an international archive. Standard delta (< 4 Hz) and alpha1 (8-10.5 Hz) bands were used for the main analysis, while alpha2 (10.5-13 Hz), theta (4-8 Hz), beta1 (13-20 Hz), beta2 (20-35 Hz), and gamma (35-40 Hz) served as controls. In the interpretation, the higher the alpha1 power (density), the lower that arousal. As expected, when compared to the Nold group, the ADD group showed higher global (scalp) power density at the delta-theta band and lower global power density at the alpha-beta bands. As novel findings, we observed that: (1) in the Nold group, the global delta and alpha1-2 power were negatively and linearly correlated; (2) in the ADD group, this correlation was just marginal; and (3) in both Nold and AD groups, the EEG epochs with the highest delta power (median value for stratification) were associated with the lowest global alpha1 power. This effect was related to eLORETA freeware solutions showing maximum alpha1 source activations in posterior cortical regions.These results suggest that even in quiet wakefulness, delta and alpha rhythms are related to each other, and ADD partially affects this cross-band neurophysiological mechanism. Ministry of Health, Italy ; Ministry of Health Italy - Ricerca Corrente (MOH-RC) ; H2020 Marie S. Curie ITN-ETN project with the short title "BBDiag" ; H2020-TWINN-2015 project with the short title "SynaNet"

Objective: Here we tested if cortical sources of resting state electroencephalographic (rsEEG) rhythms may differ in sub-groups of patients with prodromal and overt dementia with Lewy bodies (DLB) as a function of relevant clinical symptoms.Methods: We extracted clinical, demographic and rsEEG datasets in matched DLB patients (N = 60) and control Alzheimer's disease (AD, N = 60) and healthy elderly (Nold, N = 60) seniors from our international database. The eLORETA freeware was used to estimate cortical rsEEG sources.Results: As compared to the Nold group, the DLB and AD groups generally exhibited greater spatially distributed delta source activities (DLB > AD) and lower alpha source activities posteriorly (AD > DLB). As compared to the DLB ``controls", the DLB patients with (1) rapid eye movement (REM) sleep behavior disorders showed lower central alpha source activities (p < 0.005); (2) greater cognitive deficits exhibited higher parietal and central theta source activities as well as higher central, parietal, and occipital alpha source activities (p < 0.01); (3) visual hallucinations pointed to greater parietal delta source activities (p < 0.005).Conclusions: Relevant clinical features were associated with abnormalities in spatial and frequency features of rsEEG source activities in DLB patients.Significance: Those features may be used as neurophysiological surrogate endpoints of clinical symptoms in DLB patients in future cross-validation prospective studies. Ministry of Health, Italy; H2020 Marie S. Curie ITN-ETN project; H2020-TWINN-2015 project

Compared with Alzheimer's disease (AD), Parkinson's disease (PD) shows peculiar clinical manifestations related to vigilance (i.e., executive cognitive deficits and visual hallucinations) that may be reflected in resting-state electroencephalographic rhythms. To test this hypothesis, clinical and resting-state electroencephalographic rhythms in age-, sex-, and education-matched PD patients (N = 136) and Alzheimer's disease patients (AD, N = 85), and healthy older participants (Nold, N = 65), were available from an international archive. Electroencephalographic sources were estimated by eLORETA software. The results are as follows: (1) compared to the Nold participants, the AD and PD patients showed higher widespread delta source activities (PD > AD) and lower posterior alpha source activities (AD > PD); (2) the PD patients with the most pronounced motor deficits exhibited very low alpha source activities in widespread cortical regions; (3) the PD patients with the strongest cognitive deficits showed higher alpha source activities in widespread cortical regions; and (4) compared to the PD patients without visual hallucinations, those with visual hallucinations were characterized by higher posterior alpha sources activities. These results suggest that in PD patients resting in quiet wakefulness, abnormalities in cortical neural synchronization at alpha frequencies are differently related to cognitive, motor, and visual hallucinations. Interestingly, parallel PD neuropathological processes may have opposite effects on cortical neural synchronization mechanisms generating cortical alpha rhythms in quiet wakefulness. (C) 2020 Elsevier Inc. All rights reserved.

Behavioral studies have shown that the recognition of facial expressions may be impaired in patients with Alzheimer's disease (AD). The identification and recognition of a facial expression might be represented by event-related brain oscillations. The present study aims to analyze EEG event-related oscillations and determine the electrophysiological indicators of impaired facial expression recognition in AD patients. EEGs of 30 healthy controls and 30 AD patients were recorded during their perception of three different facial expressions (angry, happy, neutral). Event-related power spectrum and phase locking were analyzed in the theta (4-7) and alpha (8-13 Hz) frequency bands with the EEGLAB open toolbox. There was a significant facial Expression × Group interaction (p < 0.05) for the theta power spectrum; the healthy control group had higher theta power than the AD group during the perception of angry facial expressions (p < 0.05). There was a significant hemisphere difference between the two groups (p < 0.05). There was a right hemisphere alpha power dominance in healthy subjects. However, AD patients did not have this alpha power asymmetry. The present study, for the first time in the literature, presents the electrophysiological indicators of impaired recognition of facial expression in AD patients. The current study could be a basis for future studies that will analyze emotional processing in different kinds of dementia patients, and this study may have provided indicators of electrophysiological correlates of behavioral problems observed in clinical practice.

Background 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: 25–30 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., Highlights • Treated and untreated Alzheimer's disease (AD) patients and controls were examined. • Visual sensory-evoked and event-related gamma coherences were investigated. • Long-distance intrahemispheric pairs for three sub-gamma bands were calculated. • Gamma coherences were significantly higher in AD patients than healthy controls.

Amnesic mild cognitive impairment (MCI) represents a risk of developing Alzheimer's disease (AD), but not all MCI subjects progress to dementia of AD type. Magnetic resonance imaging (MRI) of cortical and hippocampal atrophy supports early diagnosis of AD in MCI subjects, while frontal event-related oscillations (EROS) at delta frequencies (

Objective Functional and structural brain alterations of cognitively normal Parkinson’s disease (PD-CN) and Parkinson’s disease mild cognitive impairment (PD-MCI) patients were investigated using event-related potentials (ERP) P300 and volumetric magnetic resonance imaging (MRI) parameters. Methods Twenty three patients with PD-CN, 21 with PD-MCI, and 23 demographically-matched healthy controls were included. EEGs were recorded using a visual oddball task and mean amplitude and peak latency values of P300 were measured. Gray matter volumes (GMV) of thalamus, caudate, putamen, globus pallidus, hippocampus, amygdala and nucleus accumbens were obtained using FMRIB Integrated Registration and Segmentation Tool. Correlations among P300, subcortical GMV and cognitive performances were assessed. Results PD-CN patients demonstrated reduced P300 amplitudes compared to healthy controls. PD-MCI patients had lower P300 amplitudes than both PD-CN patients and controls and reduced volumes of the putamen compared to controls. Both putamen volumes and P300 amplitudes showed moderate associations with executive functions. Conclusions Our findings support that P300 amplitude may be a useful marker for the detection of preclinical changes before the appearance of cognitive and structural deterioration in PD, as shown by decreased frontal P300 amplitudes in PD-CN. The reduction further spread to centro-parietal areas in PD-MCI patients, which was accompanied by lower putamen volumes. Significance This study is the first to report on changes in ERP P300 amplitude and subcortical volume in well-matched samples of PD-CN, PD-MCI and healthy controls.

Orjinal Makale: Functional cortical source connectivity of resting state electroencephalographic alpha rhythms shows similar abnormalities in patients with mild cognitive impairment due to Alzheimer's and Parkinson's diseases. 129(4), 766-782. https://doi.org/10.1016/j.clinph.2018.01.009

WOS: 000465302200012 PubMed ID: 30797169 Previous evidence has shown different resting-state eyes-closed electroencephalographic delta (

WOS: 000450412900002 PubMed ID: 30312790 We hypothesized that dopamine neuromodulation might affect cortical excitability in Parkinson's disease (PD) patients set in quiet wakefulness, as revealed by resting state eyes-closed electroencephalographic (rsEEG) rhythms at alpha frequencies (8-12 Hz). Clinical and rsEEG rhythms in PD with dementia (N = 35), PD with mild cognitive impairment (N = 50), PD with normal cognition (N = 35), and normal (N = 50) older adults were available from an international archive. Cortical rsEEG sources were estimated by exact low-resolution brain electromagnetic tomography. Compared with the normal older group, the PD groups showed reduced occipital alpha sources and increased widespread delta (

Objectives: The present study aims to evaluate the amplitude and latency of event-related potentials (ERPs) P100, N170, VPP and N230 in individuals with Alzheimer's disease (AD) compared to healthy elderly controls, using a passive viewing task of emotional facial expressions. Methods: Twenty-four individuals with mild to moderate AD and 23 demographically matched healthy elderly controls were included in the study. ERP P100, N170, VPP and N230 amplitude and latency values were compared between groups. Results: The categorization of emotional facial expressions was intact; yet, increased P100 amplitude and latency, decreased N170 amplitude, and increased VPP amplitude were observed in AD compared to controls. Increased N230 amplitude and latency were observed in response to angry expressions, while neutral expressions elicited decreased amplitude and latency. Conclusions: Increased P100 amplitude and latency may reflect reduced amygdala volume and disruptions in the visual system, while decreased N170 and increased VPP amplitudes may reflect impaired perceptual processing, mitigated by a greater involvement of prefrontal areas for task performance in AD. Significance: This study is the first to report a complex pattern of ERPs to emotional facial expressions in individuals with AD. (C) 2019 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

WOS: 000466619600006 PubMed ID: 30851280 Event-related oscillatory responses reflect the cognitive status in many neuropsychiatric conditions including mild cognitive impairment (MCI). In this study, a total of 30 patients with amnestic MCI (aMCI) and 25 patients with MCI of Parkinson's disease (PD-MCI) were compared with 28 aged-, gender-, education-matched healthy control (HC) participants using visual event-related delta, theta, alpha oscillatory responses by methods of event related spectral perturbation and inter-trial coherence. PD-MCI and aMCI groups commonly share a decreased theta power, but all electrophysiological deviations from the controls were more prominent in PD-MCI than aMCI in all frequency bands. Additionally, decreased phase-locking in all studied frequency bands was encountered only in PD-MCI group, but it was preserved in aMCI. These findings indicate that visual networks in PD-MCI are more severely affected than aMCI. Reduced phase-locking in PD-MCI may possibly relate to dysfunctioning subcortical modulating centers that take a role in the generation of event-related responses. Scientific and Technological Research Council of Turkey-TUBITAK [112S459] This study was supported by the Scientific and Technological Research Council of Turkey-TUBITAK (Project number: 112S459).

WOS: 000424245200019 PubMed ID: 29439335 The present study tested the hypothesis that cortical sources of resting state eyes-closed electroencephalographic (rsEEG) rhythms reveal different abnormalities in cortical neural synchronization in groups of patients with mild cognitive impairment due to Alzheimer's disease (ADMCI) and dementia with Lewy bodies (DLBMCI) as compared to cognitively normal elderly (Nold) subjects. Clinical and rsEEG data in 30 ADMCI, 23 DLBMCI, and 30 Nold subjects were available in an international archive. Age, gender, and education were carefully matched in the three groups. The Mini-Mental State Evaluation (MMSE) score was matched between the ADMCI and DLBMCI groups. Individual alpha frequency peak (IAF) was used to determine the delta, theta, alpha1, alpha2, and alpha3 frequency band ranges. Fixed beta1, beta2, and gamma bands were also considered. eLORETA estimated the rsEEG cortical sources. Receiver operating characteristic curve (ROCC) classified these sources across individuals. Compared to Nold, IAF showed marked slowing in DLBMCI and moderate in ADMCI. Furthermore, the posterior alpha 2 and alpha 3 source activities were more abnormal in the ADMCI than the DLBMCI group, while widespread delta source activities were more abnormal in the DLBMCI than the ADMCI group. The posterior delta and alpha sources correlated with the MMSE score and correctly classified the Nold and MCI individuals (area under the ROCC > 0.85). In conclusion, the ADMCI and DLBMCI patients showed different features of cortical neural synchronization at delta and alpha frequencies underpinning brain arousal and vigilance in the quiet wakefulness. Future prospective cross-validation studies will have to test the clinical validity of these rsEEG markers. H2020 Marie S. Curie ITN-ETN project The present study was developed based on the data of the informal European Consortium PDWAVES and European Consortium of Dementia with Lewy Bodies. The members and institutional affiliations of the Consortia are reported in the cover page of this manuscript. The research activities of the Unit of University of Rome "La Sapienza" were partially supported by the H2020 Marie S. Curie ITN-ETN project with the short title "BBDiag" (http://bbdiag-itn-etn.eu). We thank Mrs. Jessica Janson and Mrs. Marina Selivanova for their support to those activities in the framework of the BBDiag project.

WOS: 000428233700003 PubMed ID: 29407464 Previous evidence showed abnormal posterior sources of resting-state delta (< 4 Hz) and alpha (8-12 Hz) rhythms in patients with Alzheimer's disease with dementia (ADD), Parkinson's disease with dementia (PDD), and Lewy body dementia (DLB), as cortical neural synchronization markers in quiet wakefulness. Here, we tested the hypothesis of additional abnormalities in functional cortical connectivity computed in those sources, in ADD, considered as a "disconnection cortical syndrome", in comparison with PDD and DLB. Resting-state eyes-closed electroencephalographic (rsEEG) rhythms had been collected in 42 ADD, 42 PDD, 34 DLB, and 40 normal healthy older (Hold) participants. Exact low-resolution brain electromagnetic tomography (eLORETA) freeware estimated the functional lagged linear connectivity (LLC) from rsEEG cortical sources in delta, theta, alpha, beta, and gamma bands. The area under receiver operating characteristic (AUROC) curve indexed the classification accuracy between Nold and diseased individuals (only values > 0.7 were considered). Interhemispheric and intrahemispheric LLCs in widespread delta sources were abnormally higher in the ADD group and, unexpectedly, normal in DLB and PDD groups. Intrahemispheric LLC was reduced in widespread alpha sources dramatically in ADD, markedly in DLB, and moderately in PDD group. Furthermore, the interhemispheric LLC in widespread alpha sources showed lower values in ADD and DLB than PDD groups. At the individual level, AUROC curves of LLC in alpha sources exhibited better classification accuracies for the discrimination of ADD versus Nold individuals (0.84) than for DLB versus Nold participants (0.78) and PDD versus Nold participants (0.75). Functional cortical connectivity markers in delta and alpha sources suggest a more compromised neurophysiological reserve in ADD than DLB, at both group and individual levels. (C) 2017 Elsevier Inc. All rights reserved. H2020 Marie S. Curie ITN-ETN project The present study was developed based on the data of the informal European Consortium PDWAVES and European Consortium of Dementia with Lewy Body. The members and institutional affiliations of the consortia are reported in the cover page of this manuscript. The research activities of the Unit of University of Rome "La Sapienza" were partially supported by the H2020 Marie S. Curie ITN-ETN project with the short title "BBDiag" (http://bddiag-itn-etn.eu). We thank Mrs. Jessica Janson and Mrs. Marina Selivanova for their support to those activities in the framework of the BBDiag project.

WOS: 000427485900009 PubMed ID: 29448151 Objective: This study tested the hypothesis that markers of functional cortical source connectivity of resting state eyes-closed electroencephalographic (rsEEG) rhythms may be abnormal in subjects with mild cognitive impairment due to Alzheimer's (ADMCI) and Parkinson's (PDMCI) diseases compared to healthy elderly subjects (Nold). Methods: rsEEG data had been collected in ADMCI, PDMCI, and Nold subjects (N = 75 for any group). eLORETA freeware estimated functional lagged linear connectivity (LLC) from rsEEG cortical sources. Area under receiver operating characteristic (AUROC) curve indexed the accuracy in the classification of Nold and MCI individuals. Results: Posterior interhemispheric and widespread intrahemispheric alpha LLC solutions were abnormally lower in both MCI groups compared to the Nold group. At the individual level, AUROC curves of LLC solutions in posterior alpha sources exhibited moderate accuracies (0.70-0.72) in the discrimination of Nold vs. ADMCI-PDMCI individuals. No differences in the LLC solutions were found between the two MCI groups. Conclusions: These findings unveil similar abnormalities in functional cortical connectivity estimated in widespread alpha sources in ADMCI and PDMCI. This was true at both group and individual levels. Significance: The similar abnormality of alpha source connectivity in ADMCI and PDMCI subjects might reflect common cholinergic impairment. (C) 2018 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved. H Marie S. Curie ITN-ETN project The present study was developed based on the data of the informal European Consortium PDWAVES and European Consortium of Dementia with Lewy Body. The members and institutional affiliations of the Consortia are reported in the cover page of this manuscript. Dr. Erol Basar passed away due to health problems on October 28th (November 18th 1938-October 28th 2017) in Istanbul, during the editorial processing of this manuscript. Until the end of his life, he had been working to the development of EEG science and its application in Clinical Neurophysiology. He leaves to all us an invaluable scientific legacy in the Science of Brain Rhythms and Human Cognition. He also leaves a permanent reminder of scientific passion, academic soul, and social responsibility to all fortunate people who met and knew him during his intense life. The research activities of the Unit of University of Rome "La Sapienza" were partially supported by the H2020 Marie S. Curie ITN-ETN project with the short title "BBDiag" (http://bbdiag-ITNetn.eu). We thank Mrs. Jessica Janson and Mrs. Marina Selivanova for their support to those activities in the framework of the BBDiag project.

Obstructive sleep apnea syndrome (OSAS) is a sleep disorder characterized with upper airway obstructions. Some studies showed cognitive and electrophysiological changes in patients with OSAS; however, contradictory results were also reported. The purpose of the present study was twofold: (1) to investigate cognitive changes in severe OSAS patients by using neuropsychological tests and electrophysiological methods together, (2) to investigate influence of hypoxemia levels on cognition. Fifty-four severe OSAS patients and 34 age-, gender- and education matched healthy subjects were participated. OSAS patients were further divided into two subgroups according to minimum oxygen saturation levels. All participants underwent a detailed neuropsychological test battery. A classical visual oddball task was used to elicit ERP P300 and mean P300 amplitudes were measured from F(z), C(z) and P(z) electrode sites. OSAS patients showed reduced mean P300 amplitudes up to 43–51% on all electrode sites compared to healthy controls. Subgroup analysis revealed significant differences in neuropsychological test scores between healthy controls and high hypoxemia OSAS group, as well as between low and high hypoxemia groups. Moreover, both low and high hypoxemia OSAS groups had lower P300 amplitudes compared with healthy controls. P300 amplitudes showed a gradual decline in parallel with increasing hypoxemia severity; however, the difference between high and low hypoxemia OSAS groups did not reach significance. Moderate correlations were found between sleep parameters, neuropsychological test scores and P300 amplitudes. These results suggest that electrophysiological measures could be better indicators of cognitive changes than neuropsychological tests in OSAS, particularly in mildly affected patients.

WOS: 000405068100016 PubMed ID: 28454845 The aim of this retrospective exploratory study was that resting state eyes-closed electroencephalographic (rsEEG) rhythms might reflect brain arousal in patients with dementia due to Alzheimer's disease dementia (ADD), Parkinson's disease dementia (PDD), and dementia with Lewy body (DLB). Clinical and rsEEG data of 42 ADD, 42 PDD, 34 DLB, and 40 healthy elderly (Nold) subjects were available in an international archive. Demography, education, and Mini-Mental State Evaluation score were not different between the patient groups. Individual alpha frequency peak (IAF) determined the delta, theta, alpha 1, alpha 2, and alpha 3 frequency bands. Fixed beta 1, beta 2, and gamma bands were also considered. rsEEG cortical sources were estimated by means of the exact low-resolution brain electromagnetic source tomography and were then classified across individuals, on the basis of the receiver operating characteristic curves. Compared to Nold, IAF showed marked slowing in PDD and DLB and moderate slowing in ADD. Furthermore, all patient groups showed lower posterior alpha 2 source activities. This effect was dramatic in ADD, marked in DLB, and moderate in PDD. These groups also showed higher occipital delta source activities, but this effect was dramatic in PDD, marked in DLB, and moderate in ADD. The posterior delta and alpha sources allowed good classification accuracy (approximately 0.85-0.90) between the Nold subjects and patients, and between ADD and PDD patients. In quiet wakefulness, delta and alpha sources unveiled different spatial and frequency features of the cortical neural synchronization underpinning brain arousal in ADD, PDD, and DLB patients. Future prospective cross-validation studies should test these rsEEG markers for clinical applications and drug discovery. project "GRIDCORE" (Italian Ministry of Health, Finalized Research program) [RF-2010-2319113] The present study was developed based on the data of the informal European Consortium PDWAVES. The members and institutional affiliations of the Consortium are reported in the cover page of this manuscript. The activities for this study of Dr. Claudio Babiloni, Claudio Del Percio, and Roberta Lizio performed in the framework of the project "GRIDCORE" (Italian Ministry of Health, Finalized Research program, prot. RF-2010-2319113).

WOS: 000404876400029 PubMed ID: 28621693 The aim of this retrospective and exploratory study was that the cortical sources of resting state eyes-closed electroencephalographic (rsEEG) rhythms might reveal different abnormalities in cortical neural synchronization in groups of patients with mild cognitive impairment due to Alzheimer's disease (ADMCI) and Parkinson's disease (PDMCI) as compared to healthy subjects. Clinical and rsEEG data of 75 ADMCI, 75 PDMCI, and 75 cognitively normal elderly (Nold) subjects were available in an international archive. Age, gender, and education were carefully matched in the three groups. The Mini-Mental State Evaluation (MMSE) was matched between the ADMCI and PDMCI groups. Individual alpha frequency peak (IAF) was used to determine the delta, theta, alpha1, alpha2, and alpha3 frequency band ranges. Fixed beta1, beta2, and gamma bands were also considered. eLORETA estimated the rsEEG cortical sources. Receiver operating characteristic curve (ROC) classified these sources across individuals. Results showed that compared to the Nold group, the posterior alpha2 and alpha3 source activities were more abnormal in the ADMCI than the PDMCI group, while the parietal delta source activities were more abnormal in the PDMCI than the ADMCI group. The parietal delta and alpha sources correlated with MMSE score and correctly classified the Nold and diseased individuals (area under the ROC=0.77-0.79). In conclusion, the PDMCI and ADMCI patients showed different features of cortical neural synchronization at delta and alpha frequencies underpinning brain arousal and vigilance in the quiet wakefulness. Future prospective cross-validation studies will have to test these rsEEG markers for clinical applications and drug discovery. Italian Ministry of Health [RF-2010-2319113] The present study was developed based on the data of the informal European Consortium PDWAVES. The members and institutional affiliations of the Consortium are reported in the cover page of this manuscript. The activities for this study of Dr. Claudio Babiloni, Claudio Del Percio, and Roberta Lizio were performed in the framework of the project "GRIDCORE" (Italian Ministry of Health, Finalized Research program, prot. RF-2010-2319113).

WOS: 000407132800007 PubMed ID: 27582502 Parkinson's disease (PD) is a common progressive neurodegenerative disorder. This study aims to compare sensory-evoked oscillations (SEOs) and event-related oscillations (EROs) of visual modality in cognitively normal PD patients and healthy controls. Sixteen PD and 16 age-, gender-, and education-matched healthy controls participated in the study. A simple flashlight was used for SEO and a classical visual oddball paradigm was used for target ERO. Oscillatory responses in the delta frequency range (0.5-3.5 Hz) were examined. Significantly lower delta ERO and SEO responses were found in PD patients than healthy controls. Delta ERO responses were decreased at all frontal, central and parietal locations, whereas delta SEO responses were decreased over mid and right central locations in PD. According to the notion that SEO reflects the activity of sensory networks and ERO reflects cognitive networks, these findings indicate that PD patients have impairments in both cognitive and sensory networks of visual modality. Decreased delta ERO responses indicate that the subliminal cognitive changes in PD can be detected by electrophysiological methods. These results demonstrate that brain oscillatory responses have the potential to be studied as a biomarker for visual cognitive and sensory networks in PD.

Cerebrospinal fluid (CSF) biomarkers may support the diagnosis of Alzheimer's disease (AD). We studied if the diagnostic power of AD CSF biomarker concentrations, i.e., Aβ42, total tau (t-tau), and phosphorylated tau (p-tau), is affected by differences in lateral ventricular volume (VV), using CSF biomarker data and magnetic resonance imaging (MRI) scans of 730 subjects, from 13 European Memory Clinics. We developed a Matlab-algorithm for standardized automated segmentation analysis of T1 weighted MRI scans in SPM8 for determining VV, and computed its ratio with total intracranial volume (TIV) as proxy for total CSF volume. The diagnostic power of CSF biomarkers (and their combination), either corrected for VV/TIV ratio or not, was determined by ROC analysis. CSF Aβ42 levels inversely correlated to VV/TIV in the whole study population (Aβ42: r=-0.28; p42 alone (AUC: 0.75 versus 0.81) or in combination with t-tau (AUC: 0.81 versus 0.91). In conclusion, differences in VV may be an important confounder in interpreting CSF Aβ42 levels.

Background: The purpose of this study was to investigate changes in delta event-related oscillations (EROs) in younger and older healthy elderly subjects. We hypothesized that delta EROs were affected by age-related changes, which could be reflected in a visual oddball paradigm. Method: The study included two groups of subjects, 17 younger healthy elderly (mean age: 63.1 +/- 2.8 years) and 17 gender- and education-matched older healthy elderly (mean age: 79.6 +/- 5.2 years), who performed a visual oddball paradigm. EEG was recorded from F-3, F-z, F-4, C-3, C-z, C-4, P-3, P-z, P-4, O-1, O-z and O-2 locations. Peak-to-peak amplitudes of delta (0.5-3 Hz) target ERO responses during the post-stimulus 0-800 ms time window were measured. Repeated measures of ANOVA was used to analyze four locations (frontal, central, parietal, occipital), at three sagittal (left, midline, right) sites. Independent t-tests were applied for post-hoc analyses. Results: The older healthy elderly group had 16-25% lower values for the maximum peak-to-peak amplitudes of delta ERO compared with the younger healthy elderly group over frontal (p < 0.003), central (p < 0.0001) and parietal (p < 0.007) locations [F-3.95 = 4396, p = 0.015] Furthermore, there was a moderate negative correlation between age and C-z peak-to-peak amplitude of target delta responses [r = -0.401, p < 0.02], indicating the notion that peak-to-peak amplitude of C-z decreases as age increases. Conclusion: In the present study younger healthy elderly showed significantly higher event-related delta responses than older healthy elderly at frontal, central and parietal locations. Moreover, delta ERO responses decreased in accordance with age. (C) 2015 Elsevier B.V. All rights reserved.

Event-related oscillations (EROs) reflect cognitive brain dynamics, while sensory-evoked oscillations (SEOs) reflect sensory activities. Previous reports from our lab have shown that those with Alzheimer's disease (AD) or mild cognitive impairment (MCI) have decreased activity and/or coherence in delta, theta, alpha and beta cognitive responses. In the current study, we investigated gamma responses in visual SEO and ERO in 15 patients with AD and in 15 age-, gender- and education-matched healthy controls. The following parameters were analyzed over the parietal-occipital regions in both groups: (i) latency of the maximum gamma response over a 0–800 ms time window; (ii) the maximum peak-to-peak amplitudes for each participant's averaged SEO and ERO gamma responses in 3 frequency ranges (25–30, 30–35, 40–48 Hz); and (iii) the maximum peak-to-peak amplitudes for each participant's averaged SEO and ERO gamma responses over a 0–800 ms time block containing four divided time windows (0–200, 200–400, 400–600, and 600–800 ms). There were main group effects in terms of both latency and peak-to-peak amplitudes of gamma ERO. However, peak-to-peak gamma ERO amplitude differences became noticeable only when the time block was divided into four time windows. SEO amplitudes in the 25–30 Hz frequency range of the 0–200 ms time window over the left hemisphere were greater in the healthy controls than in those with AD. Gamma target ERO latency was delayed up to 138 ms in AD patients when compared to healthy controls. This finding may be an effect of lagged neural signaling in cognitive circuits, which is reflected by the delayed gamma responses in those with AD. Based on the results of this study, we propose that gamma responses should be examined in a more detailed fashion using multiple frequency and time windows., Highlights • Gamma responses elicited by sensory or cognitive stimulation were investigated. • Three frequency bands and four time windows were analyzed. • Alzheimer's disease (AD) patients and healthy controls were included in the study. • AD patients showed delayed cognitive gamma responses. • This delay was possibly due to lagged neural signals in cognitive circuits.

Introduction Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. Cognitive changes in PD are less observable than motor symptoms; thus, research on cognitive processes, which are known to be impaired from the early stages of PD, is minimal. The purpose of this study is to research the brain dynamics of cognitively normal PD patients and healthy elderly controls using event-related potentials (ERPs) and to evaluate their relationships with neuropsychological tests. Methods Eighteen cognitively normal PD patients and 18 age-, gender-, and education-matched healthy controls were included in the study. Detailed neuropsychological tests were applied to all participants. Electroencephalography (EEG) was performed according to the international 10-20 system, and a classical visual oddball paradigm was used in the experiments. ERP responses in the 0.5 to 25 Hz frequency range were examined. P300 amplitude and latency values were measured from the F3, Fz, F4, C3, Cz, C4, P3, Pz, P4, O1, Oz, and O2 electrode sites. In addition, the correlations between P300 responses and neuropsychological test scores were analyzed. Results Significant differences were found between the P300 amplitudes of cognitively normal PD patients and healthy elderly controls [F(1,31)=9.265; p=0.005]. P300 amplitudes were significantly lower for PD patients at the F3, FZ, Cz, C4, Pz, and P4 electrode sites than for healthy elderly controls. Moderate correlations were found between Stroop test score and P4 amplitude, digit span forward and C3 and Pz amplitude, and digit span backward and O1 amplitude. Conclusion The major finding of this study was the detection of cognitive changes by electrophysiological methods in PD patients who were indicated to be cognitively normal by neuropsychological tests. These finding suggests that cognitive changes in PD patients, which are not yet reflected in neuropsychological tests, may be detected by electrophysiological methods in earlier stages.

Occipital sources of resting-state electroencephalographic (EEG) alpha rhythms are abnormal, at the group level, in patients with amnesic mild cognitive impairment (MCI) and Alzheimer's disease (AD). Here, we evaluated the hypothesis that amplitude of these occipital sources is related to neuro-degeneration in occipital lobe as measured by magnetic resonance imaging. Resting-state eyes-closed EEG rhythms were recorded in 45 healthy elderly (Nold), 100 MCI, and 90 AD subjects. Neuro-degeneration of occipital lobe was indexed by weighted averages of gray matter density, estimated from structural MRIs. EEG rhythms of interest were alpha 1 (8-10.5 Hz) and alpha 2 (10.5-13 Hz). EEG cortical sources were estimated by low-resolution brain electromagnetic tomography. Results showed a positive correlation between occipital gray matter density and amplitude of occipital alpha 1 sources in Nold, MCI, and AD subjects as a whole group (r = 0.3, p = 0.000004, N = 235). Furthermore, there was a positive correlation between the amplitude of occipital alpha 1 sources and cognitive status as revealed by Mini Mental State Examination score across all subjects (r = 0.38, p = 0.000001, N = 235). Finally, amplitude of occipital alpha 1 sources allowed a moderate classification of individual Nold and AD subjects (sensitivity: 87.8%; specificity: 66.7%; area under the receiver operating characteristic curve: 0.81). These results suggest that the amplitude of occipital sources of resting- state alpha rhythms is related to AD neurodegeneration in occipital lobe along pathologic aging. (C) 2015 Elsevier Inc. All rights reserved.

Mild Cognitive Impairment (MCI) is considered in many as prodromal stage of Alzheimer's disease (AD). Event-related oscillations (ERO) reflect cognitive responses of brain whereas sensory-evoked oscillations (SE) inform about sensory responses. For this study, we compared visual SEO and ERO responses in MCI to explore brain dynamics (Background). Forty-three patients with MCI (mean age=74.0 year) and 41 age- and education-matched healthy-elderly controls (HC) (mean age=71.1 year) participated in the study. The maximum peak-to-peak amplitudes for each subject's averaged delta response (0.5-3.0 Hz) were measured from two conditions (simple visual stimulation and classical visual oddball paradigm target stimulation) (Method). Overall, amplitudes of target ERO responses were higher than SEO amplitudes. The preferential location for maximum amplitude values was frontal lobe for ERO and occipital lobe for SEO. The ANOVA for delta responses showed significant results for the group Xparadigm. Post-hoc tests indicated that (1) the difference between groups were significant for target delta responses, but not for SEO, (2) ERO elicited higher responses for HC than MCI patients, and (3) females had higher target ERO than males and this difference was pronounced in the control group (Results). Overall, cognitive responses display almost double the amplitudes of sensory responses over frontal regions. The topography of oscillatory responses differs depending on stimuli: visualsensory responses are highest over occipitals and -cognitive responses over frontal regions. A group effect is observed in MCI indicating that visual sensory and cognitive circuits behave differently indicating preserved visual sensory responses, but decreased cognitive responses (Conclusion). (C) 2014 Elsevier B.V. All rights reserved.

WOS: 000333848200001, PubMed ID: 24825953, Background. Event-related oscillations (ERO) may provide a useful tool for the identification of cognitive deficits in mild cognitive impairment (MCI) and Alzheimer's disease (AD). In the present study, we investigate peak-to-peak amplitude of auditory eventrelated delta oscillations of MCI subjects. Method. The study included twenty-two consecutive patients with MCI recruited in neurology clinic and 21 age-and education-matched normal elderly controls. A classical auditory oddball paradigm was used in the experiments. EEG was recorded from F-3, F-z, F-4, C-3, C-z, C-4, P-3, P-z, P-4, O-1, O-z, and O-2 locations. The maximum peak-to-peak amplitudes for each subject's averaged delta response (0.5-2.2Hz) weremeasured. Results. The amplitudes between groups differed significantly at the frontal and mid-centroparietal locations. ANOVA on delta responses revealed a significant effect for groups (F-(1.41) = 4.84, P = 0.033), indicating a larger delta response for healthy controls thanMCI subjects. Post hoc comparisons revealed that peak-to-peak delta response was significantly larger for healthy controls than for MCI over electrode sites F-3, F-z, F-4, C-z, C-4, and Pz. Discussion. Event-related delta frequency band seems to be the most affected oscillatory response in cognitive impairment due to AD. Therefore, it deserves to be investigated as a candidate electrophysiological biomarker in further studies., Scientific and Technological Research Council of Turkey [112S459], This study has been founded by the Scientific and Technological Research Council of Turkey (Project no. 112S459).

Kurt, Pınar (Arel Author) --- #nofulltext#, Mild 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.

Objective Decreased delta event-related oscillations (ERO) have been reported in prior studies of Alzheimer’s disease (AD) and mild cognitive impairment (MCI); however no study has examined its utility in predicting disease progression. In this study, we examined the longitudinal changes in brain dynamics of MCI by using delta ERO and volumetric MRI (vMRI). Methods Twenty-two MCI and 23 matched control subjects were included. Peak-to-peak amplitudes of delta (0.5–3.5 Hz) auditory target ERO and vMRI were measured at baseline and a year later. The ERO and vMRI of stable and progressive MCI were compared. Results Decreased amplitudes of delta ERO were found in MCI for baseline and follow-up [F1.43 = 11.394, p = 0.002]. Progressive MCI had lower delta ERO than stable MCI at F3 electrode site at baseline. vMRI revealed that MCI had lower volumes at baseline in whole brain and left hippocampus, and at follow-up in whole brain, right and left hippocampi. Moreover, a moderate correlation was found between left hippocampus volumes and delta ERO at C4 electrode site. Conclusions These findings indicate that delta ERO may detect early changes in MCI and can be a useful tool to predict disease progression. Brain oscillatory responses have the potential to be used as biomarker in MCI.

Objective Parkinson’s disease (PD) is the second most common progressive neurodegenerative disorder which affects both motor and cognitive functioning. This study aims to investigate the sensory evoked oscillations (SEO) and event-related oscillations (ERO) of visual modality in cognitively normal PD patients and healthy controls. Methods Sixteen PD and 16 matched control subjects were participated to the study. Simple flashlight was used for SEO and a classical visual oddball paradigm was used for target ERO. Oscillatory responses in delta frequency range (0.5–3.0 Hz) were examined. Results Significant differences were found between groups on the maximum peak-to-peak amplitudes of both delta ERO and SEO responses [ F 1.27 = 8.573, p = 0.007; F 1.27 = 6.306, p = 0.018, respectively], indicating significantly lower delta responses in PD than healthy controls. Delta ERO responses were decreased in PD in frontal, central and parietal locations ( p Conclusions In this study, both target delta ERO and SEO responses were decreased in PD. According to the notion that the activity of sensory networks are reflected by SEO and cognitive networks by ERO, these findings indicate that PD patients have impairments in both networks of visual modality. Brain oscillatory responses have a potential to be searched as a biomarker for visual cognitive and sensory status of PD.

Kurt, Pınar (Arel Author), The aim of the present study was to investigate the role of beta oscillatory responses upon cognitive load in healthy subjects and in subjects with mild cognitive impairment (MCI). The role of beta oscillations upon cognitive stimulation is least studied in comparison to other frequency bands. The study included 17 consecutive patients with MCI (mean age = 70.8 ± 5.6 years) according to Petersen's criteria, and 17 age- and education-matched normal elderly controls (mean age = 68.5 ± 5.5 years). The experiments used a visual oddball paradigm. EEG was recorded at 30 cortical locations. EEG-evoked power, inter-trial phase synchronization, and event-related beta responses filtered in 15–20 Hz were obtained in response to target and non-target stimuli for both groups of subjects. In healthy subjects, EEG-evoked beta power, inter-trial phase synchronization of beta responses and event-related filtered beta responses were significantly higher in responses to target than non-target stimuli (p b 0.05). In MCI patients, there were no differences in evoked beta power between target and non-target stimuli. Furthermore, upon presentation of visual oddball paradigm, occipital electrodes depict higher beta response in comparison to other electrode sites. The increased beta response upon presentation of target stimuli in healthy subjects implies that beta oscillations could shift the system to an attention state, and had important function in cognitive activity. This may, in future, open the way to consider beta activity as an important operator in brain cognitive processes.