Papers by Derya Durusu Emek-Savaş
Alzheimer's & Dementia, 2014
Noro Psikiyatri Arsivi, 2016
NeuroImage: Clinical, 2016
Brain Research, 2014
Mild Cognitive Impairment (MCI) is considered in many as prodromal stage of Alzheimer&amp... more 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 (SEO) 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).
Alzheimer's & Dementia, 2014
Background: Mild cognitive impairment (MCI) patients with different biomarker profiles might be c... more Background: Mild cognitive impairment (MCI) patients with different biomarker profiles might be characterized by different patterns of cortical thinning and subcortical atrophy. Methods: 53 MCI patients (mean age 71, female 49%) were enrolled from 2 Italian Memory Clinics. Abeta42 and Tau CSF levels, temporo parietal hypometabolism and hippocampal volumes were measured. According to their biormarker profiles, patients were divided in two groups: (i) suspected n on-amyloid pathology (SNAP, N¼21) and (ii) patients with amyloid plus neurodegeneration (A+N, N¼32). Cortical thickness and sucortical volumes were quantified using the freesurfer pipeline. Comparisons were made at group level with 15 subjective memory complainers (SMC), considered as the control group. Results: SMC were cognitively intact, younger than SNAP and A+N patients (p<.006). Relative to SMC group, A+N showed cortical thinning in the left/right parietal inferior and superior regions (p<.028), temporal middle and superior temporo-lateral gyri (p¼.05), left inferior frontal gyrus (p¼.009), right lateral fusyform gyrus (p<.002), insula and precentral sulcus (p¼.01). SNAP patients compared to SMC exhibited cortical thinning in the left central sulcus (p¼.025), right superior and inferior tempro-lateral (p<.002) and parietal gyri (p¼.04), and precentral sulcus (p¼.011). The direct comparison between A+N and SNAP showed significant cortical thinning only in the A+N group in the right and left lateral fusyform gyrus (p<.039), left occipital middle and lingual gyri (p¼.020 and p¼.007), parietal regions (p<.049) and orbito-lateral sulcus (p¼.041). Both SNAP and A+N groups compared to SMC showed substantial subcortical volume reductions bilaterally in the hippocampus (p<.05), the nucleus accumbens (p<.046), the right pallidum (p<.0401), the left amygdala (p<.005). The direct comparisons between the two patient groups revealed a significant right amygdala atrophy in A+N patients. Conclusions: Our results support the hypothesis that SNAP patients are characterized by a different cortical and subcortical involvement relative to A+N due to different underlying pathologic changes.
Alzheimer's & Dementia, 2014
International Journal of Psychophysiology, 2012
International Journal of Psychophysiology, 2012
Neurobiology of Aging, 2015
Occipital sources of resting-state electroencephalographic (EEG) alpha rhythms are abnormal, at t... more 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 (8e10.5 Hz) and alpha 2 (10.5e13 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 ¼ 0.3, p ¼ 0.000004, N ¼ 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 ¼ 0.38, p ¼ 0.000001, N ¼ 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: Neurobiology of Aging xxx (2014) 1e15 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.
Behavioural Neurology, 2014
Background. Event-related oscillations (ERO) may provide a useful tool for the identification of ... more 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 locations. The maximum peak-to-peak amplitudes for each subject's averaged delta response (0.5-2.2 Hz) were measured. 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, = 0.033), indicating a larger delta response for healthy controls than MCI 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 P z . 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.
NeuroImage: Clinical, 2013
The aim of the present study was to investigate the role of beta oscillatory responses upon cogni... more 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&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;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 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 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.
Mild cognitive impairment (MCI) is considered as a prodromal stage for Alzheimer's disease (AD) i... more 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 midcentral. 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.
International Journal of Psychophysiology, 2014
International Journal of Psychophysiology, 2014
a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: P300 Event-related oscillat... more a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: P300 Event-related oscillations Delta Aging Healthy elderly
International Journal of Psychophysiology, 2015
a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Event-related Oscillations ... more a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Event-related Oscillations EEG MRI Frontal Volumetry Delta MCI Alzheimer Dementia
Alzheimer's & Dementia, 2014
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Papers by Derya Durusu Emek-Savaş