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.
The present study aims to analyze the impaired recognition of facial expression in Alzheimer's disease (AD) patients by the analysis of event related theta and alpha responses. The Alzheimer's disease patients had lower theta power during the recognition of “angry” facial expressions; this result supports the behavioral studies indicating that impairment in AD patients exists in the recognition of negative emotions. Healthy controls had higher right alpha power, AD patients did not have this alpha power asymmetry. The present study presents, for the first time in the literature, the electrophysiological indicators of impaired recognition of facial expression in AD patients.
The Stroop test Çapa 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 Çapa version and to establish stratified normative data in individuals aged between 18-83 years.
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.
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.
Normative data of the Stroop Test Çapa Version were provided for the assessment of executive functions in young and middleaged adults and elderly population.
Background
Amnestic mild cognitive impairment (aMCI) is a transitional state between normal aging and dementia, and identifying early biomarkers is crucial for disease detection and intervention. ...Functional magnetic resonance imaging (fMRI) has the potential to identify changes in neural activity in MCI.
Methods
We investigated neural activity changes in the visual network of the aMCI patients (n:20) and healthy persons (n:17) using resting‐state fMRI and visual oddball task fMRI. We used independent component analysis to identify regions of interest and compared the activity between groups using a false discovery rate correction.
Results
Resting‐state fMRI revealed increased activity in the areas that have functional connectivity with the visual network, including the right superior and inferior lateral occipital cortex, the right angular gyrus and the temporo‐occipital part of the right middle temporal gyrus (p‐FDR = 0.008) and decreased activity in the bilateral thalamus and caudate nuclei, which are part of the frontoparietal network in the aMCI group (p‐FDR = 0.002). In the visual oddball task fMRI, decreased activity was found in the right frontal pole, the right frontal orbital cortex, the left superior parietal lobule, the right postcentral gyrus, the right posterior part of the supramarginal gyrus, the right superior part of the lateral occipital cortex, and the right angular gyrus in the aMCI group.
Conclusion
Our results suggest the alterations in the visual network are present in aMCI patients, both during resting‐state and task‐based fMRI. These changes may represent early biomarkers of aMCI and highlight the importance of assessing visual processing in cognitive impairment. However, future studies with larger sample sizes and longitudinal designs are needed to confirm these findings.
Our study investigated neural activity changes in the visual network of mild cognitive impairment (MCI) patients using resting‐state and task‐based fMRI. We found that alterations in the visual network may represent early biomarkers of MCI and highlight the importance of assessing visual processing in cognitive impairment.
•Reduced frontal P300 may precede cognitive and structural changes in cognitively normal Parkinson's disease (PD).•The reduction in P300 amplitude further spreads to centro-parietal areas in PD with ...mild cognitive impairment (PD-MCI).•PD-MCI demonstrated reduced putamen volume, which was associated with impaired executive function.
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.
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.
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.
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.
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.
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.
•In Parkinson's disease patients, resting-state delta and alpha electroencephalographic source activities were abnormal.•Those abnormalities were differently related to cognitive, motor, and perceptual deficits.•Those source activities may reflect the effect of Parkinson's disease on cognitive, motor, and perceptual systems.
Objective
The objective of this study was to investigate the functional changes associated with mild cognitive impairment (MCI) using independent component analysis (ICA) with the word generation ...task functional magnetic resonance imaging (fMRI) and resting‐state fMRI.
Methods
In this study 17 patients with MCI and age and education‐matched 17 healthy individuals as control group are investigated. All participants underwent resting‐state fMRI and task‐based fMRI while performing the word generation task. ICA was used to identify the appropriate independent components (ICs) and their associated networks. The Dice Coefficient method was used to determine the relevance of the ICs to the networks of interest.
Results
IC‐14 was found relevant to language network in both resting‐state and task‐based fMRI, IC‐4 to visual, and IC‐28 to dorsal attention network (DAN) in word generation task‐based fMRI by Sorento‐Dice Coefficient. ICA showed increased activation in language network, which had a larger voxel size in resting‐state functional MRI than word generation task‐based fMRI in the bilateral lingual gyrus. Right temporo‐occipital fusiform cortex, right hippocampus, and right thalamus were also activated in the task‐based fMRI. Decreased activation was found in DAN and visual network MCI patients in word generation task‐based fMRI.
Conclusion
Task‐based fMRI and ICA are more sophisticated and reliable tools in evaluation cognitive impairments in language processing. Our findings support the neural mechanisms of the cognitive impairments in MCI.
•ERPs can be used as a valuable tool to investigate emotional face processing in AD.•The categorization of emotional facial expressions was intact in individuals with AD.•P100, N170, and VPP to ...emotional expressions were altered in AD compared to controls.
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.
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.
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.
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.
This study is the first to report a complex pattern of ERPs to emotional facial expressions in individuals with AD.
Abstract 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 neurodegeneration 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. Neurodegeneration 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.
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.
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.
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.
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.
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.
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