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Search Results: 1 - 10 of 149583 matches for " H;Anghinah "
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The effects of automated artifact removal algorithms on electroencephalography-based Alzheimer's disease diagnosis
Raymundo Cassani,Tiago H. Falk,Francisco J. Fraga,Renato Anghinah
Frontiers in Aging Neuroscience , 2014, DOI: 10.3389/fnagi.2014.00055
Abstract: Over the last decade, electroencephalography (EEG) has emerged as a reliable tool for the diagnosis of cortical disorders such as Alzheimer's disease (AD). EEG signals, however, are susceptible to several artifacts, such as ocular, muscular, movement, and environmental. To overcome this limitation, existing diagnostic systems commonly depend on experienced clinicians to manually select artifact-free epochs from the collected multi-channel EEG data. Manual selection, however, is a tedious and time-consuming process, rendering the diagnostic system “semi-automated.” Notwithstanding, a number of EEG artifact removal algorithms have been proposed in the literature. The (dis)advantages of using such algorithms in automated AD diagnostic systems, however, have not been documented; this paper aims to fill this gap. Here, we investigate the effects of three state-of-the-art automated artifact removal (AAR) algorithms (both alone and in combination with each other) on AD diagnostic systems based on four different classes of EEG features, namely, spectral, amplitude modulation rate of change, coherence, and phase. The three AAR algorithms tested are statistical artifact rejection (SAR), blind source separation based on second order blind identification and canonical correlation analysis (BSS-SOBI-CCA), and wavelet enhanced independent component analysis (wICA). Experimental results based on 20-channel resting-awake EEG data collected from 59 participants (20 patients with mild AD, 15 with moderate-to-severe AD, and 24 age-matched healthy controls) showed the wICA algorithm alone outperforming other enhancement algorithm combinations across three tasks: diagnosis (control vs. mild vs. moderate), early detection (control vs. mild), and disease progression (mild vs. moderate), thus opening the doors for fully-automated systems that can assist clinicians with early detection of AD, as well as disease severity progression assessment.
Study of normal standard of adult population through quantitative electroencephalography
Arquivos de Neuro-Psiquiatria , 1999,
Characterizing Alzheimer’s Disease Severity via Resting-Awake EEG Amplitude Modulation Analysis
Francisco J. Fraga, Tiago H. Falk, Paulo A. M. Kanda, Renato Anghinah
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0072240
Abstract: Changes in electroencephalography (EEG) amplitude modulations have recently been linked with early-stage Alzheimer’s disease (AD). Existing tools available to perform such analysis (e.g., detrended fluctuation analysis), however, provide limited gains in discriminability power over traditional spectral based EEG analysis. In this paper, we explore the use of an innovative EEG amplitude modulation analysis technique based on spectro-temporal signal processing. More specifically, full-band EEG signals are first decomposed into the five well-known frequency bands and the envelopes are then extracted via a Hilbert transform. Each of the five envelopes are further decomposed into four so-called modulation bands, which were chosen to coincide with the delta, theta, alpha and beta frequency bands. Experiments on a resting-awake EEG dataset collected from 76 participants (27 healthy controls, 27 diagnosed with mild-AD, and 22 with moderate-AD) showed significant differences in amplitude modulations between the three groups. Most notably, i) delta modulation of the beta frequency band disappeared with an increase in disease severity (from mild to moderate AD), ii) delta modulation of the theta band appeared with an increase in severity, and iii) delta modulation of the beta frequency band showed to be a reliable discriminant feature between healthy controls and mild-AD patients. Taken together, it is hoped that the developed tool can be used to assist clinicians not only with early detection of Alzheimer’s disease, but also to monitor its progression.
Gamma band oscillations in parietooccipital areas during performance of a sensorimotor integration task: a qEEG coherence study
Teixeira, S;Velasques, B;Machado, S;Paes, F;Cunha, M;Budde, H;Anghinah, R;Basile, L F H;Cagy, M;Piedade, R;Ribeiro, P;
Arquivos de Neuro-Psiquiatria , 2011, DOI: 10.1590/S0004-282X2011000300007
Abstract: this study aimed to elucidate cortical mechanisms involved in anticipatory actions when 23 healthy right-handed subjects had to catch a free falling object through quantitative electroencephalogram (qeeg). for this reason, we used coherence that represents a measurement of linear covariation between two signals in the frequency domain. in addition, we investigated gamma-band (30-100 hz) activity that is related to cognitive and somatosensory processes. we hypothesized that gamma coherence will be increase in both parietal and occipital areas during moment after ball drop, due to their involvement in manipulation of objects, visuospatial processing, visual perception, stimuli identification and attention processes. we confirmed our hypothesis, an increase in gamma coherence on p3-p4 (t= -2.15; p=0.033) and pz-oz (t= -2.16; p=0.034) electrode pairs was verified for a paired t-test. we conclude that to execute tasks involving anticipatory movements (feedforward mechanisms), like our own task, probably, there is no need of a strong participation of visual areas in the process of information organization to manipulate objects and to process visuospatial information regarding the contact hand-object.
Index of Alpha/Theta Ratio of the Electroencephalogram: A New Marker for Alzheimer’s Disease
Magali T. Schmidt,Luis F. H. Basile,Helder Frederico da Silva Lopes,Regina Baratho,Antonio E. Nardi,Jéssica N. Ianof,Renato Anghinah
Frontiers in Aging Neuroscience , 2013, DOI: 10.3389/fnagi.2013.00060
Abstract: Objective: We evaluated quantitative EEG measures to determine a screening index to discriminate Alzheimer’s disease (AD) patients from normal individuals.
Minor and Unsystematic Cortical Topographic Changes of Attention Correlates between Modalities
Luis F. H. Basile,Mirna D. Lozano,Milkes Y. Alvarenga,José F. Pereira Jr.,Sérgio Machado,Bruna Velasques,Pedro Ribeiro,Roberto Piedade,Renato Anghinah,Gennady Knyazev,Renato T. Ramos
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0015022
Abstract: In this study we analyzed the topography of induced cortical oscillations in 20 healthy individuals performing simple attention tasks. We were interested in qualitatively replicating our recent findings on the localization of attention-induced beta bands during a visual task [1], and verifying whether significant topographic changes would follow the change of attention to the auditory modality. We computed corrected latency averaging of each induced frequency bands, and modeled their generators by current density reconstruction with Lp-norm minimization. We quantified topographic similarity between conditions by an analysis of correlations, whereas the inter-modality significant differences in attention correlates were illustrated in each individual case. We replicated the qualitative result of highly idiosyncratic topography of attention-related activity to individuals, manifested both in the beta bands, and previously studied slow potential distributions [2]. Visual inspection of both scalp potentials and distribution of cortical currents showed minor changes in attention-related bands with respect to modality, as compared to the theta and delta bands, known to be major contributors to the sensory-related potentials. Quantitative results agreed with visual inspection, supporting to the conclusion that attention-related activity does not change much between modalities, and whatever individual changes do occur, they are not systematic in cortical localization across subjects. We discuss our results, combined with results from other studies that present individual data, with respect to the function of cortical association areas.
Lack of Systematic Topographic Difference between Attention and Reasoning Beta Correlates
Luis F. H. Basile, Jo?o R. Sato, Milkes Y. Alvarenga, Nelson Henrique, Henrique A. Pasquini, William Alfenas, Sérgio Machado, Bruna Velasques, Pedro Ribeiro, Roberto Piedade, Renato Anghinah, Renato T. Ramos
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0059595
Abstract: Based on previous evidence for individual-specific sets of cortical areas active during simple attention tasks, in this work we intended to perform within individual comparisons of task-induced beta oscillations between visual attention and a reasoning task. Since beta induced oscillations are not time-locked to task events and were first observed by Fourier transforms, in order to analyze the cortical topography of attention induced beta activity, we have previously computed corrected-latency averages based on spontaneous peaks of band-pass filtered epochs. We then used Independent Component Analysis (ICA) only to single out the significant portion of averaged data, above noise levels. In the present work ICA served as the main, exhaustive means for decomposing beta activity in both tasks, using 128-channel EEG data from 24 subjects. Given the previous observed similarity between tasks by visual inspection and by simple descriptive statistics, we now intended another approach: to quantify how much each ICA component obtained in one task could be explained by a linear combination of the topographic patterns from the other task in each individual. Our hypothesis was that the major psychological difference between tasks would not be reflected as important topographic differences within individuals. Results confirmed the high topographic similarity between attention and reasoning beta correlates in that few components in each individual were not satisfactorily explained by the complementary task, and if those could be considered “task-specific”, their scalp distribution and estimated cortical sources were not common across subjects. These findings, along with those from fMRI studies preserving individual data and conventional neuropsychological and neurosurgical observations, are discussed in support of a new functional localization hypothesis: individuals use largely different sets of cortical association areas to perform a given task, but those individual sets do not change importantly across tasks that differ in major psychological processes.
Prevalence of potentially reversible dementias in a dementia outpatient clinic of a tertiary university-affiliated hospital in Brazil
Takada Leonel Tadao,Caramelli Paulo,Radanovic Marcia,Anghinah Renato
Arquivos de Neuro-Psiquiatria , 2003,
Abstract: The importance of investigating the etiology for dementia lies in the possibility of treating potentially reversible dementias. The aims of this retrospective study are to determine the prevalence of potentially reversible dementias among 454 outpatients seen at the Cognitive and Behavioral Neurology Unit, Hospital das Clínicas, S o Paulo University School of Medicine - Brazil, between the years of 1991 and 2001, and observe their evolution in follow-up. Among the initial 454 patients, 275 fulfilled the DSM-IV criteria for dementia. Alzheimer's disease was the most frequent diagnosis (164 cases; 59.6%). Twenty-two cases (8.0%) of potentially reversible dementia were observed, the most frequent diagnoses being neurosyphilis (nine cases) and hydrocephalus (six cases). Full recovery was observed in two patients and partial recovery in 10 patients. Two cases were not treated and eight cases were lost on follow-up. The prevalence found in the present study falls within the range reported in previous studies (0-30%).
Generalized periodic EEG activity in two cases of neurosyphilis
Anghinah, Renato;Camargo, érica C.S.;Braga, Nádia I.;Waksman, Simone;Nitrini, Ricardo;
Arquivos de Neuro-Psiquiatria , 2006, DOI: 10.1590/S0004-282X2006000100025
Abstract: neurosyphilis is a recognized cause of epileptic seizures and cognitive impairment, but is not usually associated with the finding of generalized periodic activity in the eeg. we report two similar cases characterized by progressive cognitive impairment followed by partial complex seizures, in whom the eeg showed generalized periodic activity. both cerebrospinal fluid and the response to penicillin therapy confirmed the diagnoses of neurosyphilis in the two cases. the finding of eeg generalized periodic activity in patients with cognitive or behavioral disorders is usually associated with creutzfeldt-jakob disease, although there are other conditions, some of them potentially reversible, which may also present this eeg abnormality. neurosyphilis has tended not to be included among them, and our present findings support the importance of first ruling out neurosyphilis in those patients with cognitive or behavioral disorders associated with generalized periodic epileptiform discharges.
Estudo da coerência do eletrencefalograma na banda de frequência alfa em indivíduos adultos normais: resultados preliminares em 10 casos
Anghinah, Renato;Caramelli, Paulo;Takahashi, Daniel Yassumasa;Nitrini, Ricardo;Sameshima, Koichi;
Arquivos de Neuro-Psiquiatria , 2005, DOI: 10.1590/S0004-282X2005000100015
Abstract: we studied the occipital inter-hemispheric coherence of electroencephalogram (electrodes o1-o2) for alpha band (alpha1 - 8,0 to 10,0 hz and alpha2 - 10,1 to 12,5 hz) in two groups of healthy individuals (young adults and subjects older than 50 years-old), to assess if there is significant difference between this two age groups. no significant difference in alpha band coherences was found between these two age groups.
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