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1.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2946-2949, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018624

RESUMO

The steady-state visual evoked potential (SSVEP) is a robust brain activity that has been used in brain-computer interface (BCI) applications. However, previous studies of SSVEP-based BCIs give contradictory results on which stimulation medium provides the best performance. This paper describes a comparison of electroencephalography (EEG) decoding accuracy between using an LCD screen, clear LEDs, and frosted LEDs to deliver flashing light stimulation. The LCD screen and frosted LEDs achieved similar mean accuracies, and both of them were significantly better than clear LEDs. Background contrast with the LEDs did not significantly influence SSVEP decoding accuracy. A strong correlation was found between SSVEP accuracy and frequency domain magnitudes of EEG measurements.


Assuntos
Interfaces Cérebro-Computador , Potenciais Evocados Visuais , Eletroencefalografia , Exame Neurológico , Estimulação Luminosa
2.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2986-2990, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018633

RESUMO

Brain-computer interface (BCI) can provide a way for the disabled to interact with the outside world. Steady-state visual evoked potential (SSVEP), which evokes potential through visual stimulation is one of important BCI paradigms. In laboratory environment, the classification accuracy of SSVEPs is excellent. However, in motion state, the accuracy will be greatly affected and reduce quite a lot. In this paper, in order to improve the classification accuracy of the SSVEP signals in the motion state, we collected SSVEP data of five targets at three speeds of 0km/h, 2.5km/h and 5km/h. A compare network based on convolutional neural network (CNN) was proposed to learn the relationship between EEG signal and the template corresponding to each stimulus frequency and classify. Compared with traditional methods (i.e., CCA, FBCCA and SVM) and state-of-the-art method (CNN) on the collected SSVEP datasets of 20 subjects, the method we proposed always performed best at different speeds. Therefore, these results validated the effectiveness of the method. In addition, compared with the speed of 0 km / h, the accuracy of the compare network at a high walking rate (5km/h) did not decrease much, and it could still maintain a good performance.


Assuntos
Interfaces Cérebro-Computador , Caminhada , Eletroencefalografia , Potenciais Evocados Visuais , Humanos , Redes Neurais de Computação
3.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3003-3006, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018637

RESUMO

Exploring the brain response to stimuli of healthy people in passive state is helpful to understand the brain response mechanism of unresponsive people. Event-related potential (ERP) can reflect the time synchronization of potentials, which is a feasible objective electrophysiological index reflecting the functional status of the brain. In this paper, we used the subjects' own name (SON) as target stimuli and compared with the nontarget stimuli (others' name) of Three Chinese Characters (3CC) and Two Chinese Characters (2CC) with the same stimuli duration (600ms) and inter stimuli interval (500ms-800ms). Thirteen healthy subjects attended in this study with four conditions ( [active, passive]×[3CC, 2CC] ). We compared the ERP waveforms, the behavior performance, and the classification of four different conditions. ERP results show that the P300 amplitude of conditions with 3CC nontargets is higher than that of conditions with 2CC nontargets. Behavioral results show that the grand accuracy is 97% when the nontargets are 3CC, while the grand accuracy is only 94% when the nontargets are 2CC. The reaction time is also different from the two nontargets (605ms with 3CC vs 635ms with 2CC). Classification results illustrate that in active condition, the accuracy rate is 82.1% when the nontarget is 3CC, and that is 80.9% in passive condition, which are 4.2% and 6.4% higher than the accuracy rate under 2CC cases in both active and passive conditions. This study can provide a scheme for grading diagnosis of consciousness detection, and further applying to clinical evaluation.Clinical Relevance- This study can provide a better paradigm basis for clinical evaluation of unresponsive patients (such as disorder of consciousness, DOC) and may become an effective auxiliary means for clinical rating scales.


Assuntos
Potencial Evocado P300 , Potenciais Evocados , Encéfalo , Potenciais Evocados Auditivos , Potenciais Evocados Visuais , Humanos
4.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3031-3034, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018644

RESUMO

The mapping of visual space onto human striate cortex allows the location of stimuli to affect the scalp distributions of electroencephalogram (EEG). To clarify the relationship between the characteristics of elicited high-frequency steady-state visual evoked potentials (SSVEPs) and the polar angle of stimulus, this study divided the annulus into eight symmetrical annular sectors (i.e., octants) as separate visual stimuli. For both 30 Hz and 60 Hz, the response intensity and classification accuracy indicated that the annular sectors in the lower visual field evoked stronger responses than those in the upper visual field. This paper also evaluated the phase differences between SSVEPs at specific polar angles and found clear individual differences across subjects. These findings may lead to inspirations for the design of new space coding methods for the SSVEP-based brain-computer interfaces (BCIs).


Assuntos
Interfaces Cérebro-Computador , Córtex Visual , Eletroencefalografia , Potenciais Evocados Visuais , Humanos , Estimulação Luminosa
5.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3070-3073, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018653

RESUMO

Task-related component analysis (TRCA) has been the most effective spatial filtering method in implementing high-speed brain-computer interfaces (BCIs) based on steady-state visual evoked potentials (SSVEPs). TRCA is a data-driven method, in which spatial filters are optimized to maximize inter-trial covariance of time-locked electroencephalographic (EEG) data, formulated as a generalized eigenvalue problem. Although multiple eigenvectors can be obtained by TRCA, the traditional TRCA-based SSVEP detection considered only one that corresponds to the largest eigenvalue to reduce its computational cost. This study proposes using multiple eigen-vectors to classify SSVEPs. Specifically, this study integrates a task consistency test, which statistically identifies whether the component reconstructed by each eigenvector is task-related or not, with the TRCA-based SSVEP detection method. The proposed method was evaluated by using a 12-class SSVEP dataset recorded from 10 subjects. The study results indicated that the task consistency test usually identified and suggested more than one eigenvectors (i.e., spatial filters). Further, the use of additional spatial filters significantly improved the classification accuracy of the TRCA-based SSVEP detection.


Assuntos
Interfaces Cérebro-Computador , Potenciais Evocados Visuais , Algoritmos , Eletroencefalografia , Humanos , Exame Neurológico
6.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3359-3362, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018724

RESUMO

Steady-State Visual Evoked Potentials (SSVEPs) have become one of the most used neural signals for brain- computer interfaces (BCIs) due to their stability and high signal- to-noise rate. However, the performance of SSVEP-based BCIs would degrade with a few training samples. This study was proposed to enhance the detection of SSVEP by combining the supervised learning information from training samples and the unsupervised learning information from the trial to be tested. A new method, i.e. cyclic shift trials (CST), was proposed to generate new calibration samples from the test data, which were furtherly used to create the templates and spatial filters of task- related component analysis (TRCA). The test-trial templates and spatial filters were combined with training-sample templates and spatial filters to recognize SSVEP. The proposed algorithm was tested on a benchmark dataset. As a result, it reached significantly higher classification accuracy than traditional TRCA when only two training samples were used. Speciflcally, the accuracy was improved by 9.5% for 0.7s data. Therefore, this study demonstrates CST is effective to improve the performance of SSVEP-BCI.


Assuntos
Interfaces Cérebro-Computador , Algoritmos , Eletroencefalografia , Potenciais Evocados Visuais , Aprendizado de Máquina não Supervisionado
7.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3521-3524, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018763

RESUMO

Cortical visual prostheses could one day help restore sight to the blind by targeting the visual cortex with electrical stimulation. However, power consumption and limited spatial resolution impose limits on performance, while large amounts of electrical charge sometimes necessary to evoke phosphenes can cause seizures. Here, we propose the use of the local field potential as a control signal for the timing of stimulation to reduce charge requirements. In Sprague-Dawley rats, visual cortex was electrically stimulated at random times, and neural responses recorded. Electrical stimulation at specific phases of the local field potential required smaller amounts of charge to elicit spikes than naïve stimulation. Incorporating this into prosthesis design could improve their safety and efficacy.


Assuntos
Potenciais Evocados Visuais , Córtex Visual , Animais , Estimulação Elétrica , Fosfenos , Ratos , Ratos Sprague-Dawley
8.
Cesk Slov Oftalmol ; 76(2): 94-97, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33126804

RESUMO

PURPOSE: The purpose of the study was to evaluate influence of betaxolol, brimonidine and carteolol in the progression of the visual field defects during time at patients with normotensive glaucoma (NTG). MATERIALS AND METHODS: This study included (60 eyes of) 30 patients with NTG. First group consisted of 20 eyes of 10 patients of the average age of 58.5 years, who were treated by betaxolol. Second group also consisted of 20 eyes of 10 patients of the average age of 62.6 years and they were treated by brimonidine. Third group had the same count of the eyes and patients, the average age was 61.1 years and these patients were treated by carteolol. Diagnose of NTG was based on the comprehensive ophthalmological examination including electroretinography and visual evoked potentials. Visual fields were examined by fast threshold glaucoma test using Medmont M700 device. We compared pattern defect (PD) in the visual field for 3 years. The including criteria were: similar visual field findings at the beginning of the study, stable eye therapy (treatment was not changed during the study), uncorrected or best corrected (up to +-3 D) visual acuity of 1,0 of ETDRS, intraocular pressure between 10-15 mm Hg, if present, then compensated cardiovascular disease, no other internal or neurological disorders. RESULTS: We didnt notice any statistically important difference of PD. The study revealed that brimonidin (p=0,99) and betaxolol (p = 0,81) had the best effect. CONCLUSION: Local therapy of betaxolol, brimonidine and carteolol has an essential clinical value in normotensive glaucoma. All the mentioned treatments had a protective effect on the visual field. However, local side-effects of brimonidinu are a question.


Assuntos
Carteolol , Glaucoma de Ângulo Aberto , Glaucoma , Betaxolol , Potenciais Evocados Visuais , Humanos , Pressão Intraocular , Pessoa de Meia-Idade
9.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3019-3022, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018641

RESUMO

Steady-State Visual Evoked Potentials (SSVEP) Brain-Computer Interface (BCI) relies on overt spatial attention to exhibit reliable steady-state responses. There is a promising potential to employ the SSVEP paradigm in with vision research and clinical use, for instance, for visual field assessment. In this study, we investigate the SSVEP characteristics with different spatial attention, the different number of stimuli, and different viewing/visual angles. We collected data from eleven subjects in three experiment sessions, lasting about forty minutes, including the setup and calibration. Our evaluation results show similar SSVEP responses between overt and covert attention in multiple stimuli scenarios in most of the visual angles. We do not find any significant differences in SSVEP responses in visual angles between single and multi stimuli in covert attention. From this study, we found that reliable SSVEP responses can be achieved with covert spatial attention regardless of visual angles and stimulus spatial resolution.


Assuntos
Interfaces Cérebro-Computador , Potenciais Evocados Visuais , Atenção , Eletroencefalografia , Humanos , Campos Visuais
10.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3054-3057, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018649

RESUMO

In order to explore the effect of low frequency stimulation on pupil size and electroencephalogram (EEG), we presented subjects with 1-6Hz black-and-white-alternating flickering stimulus, and compared the differences of signal-to-noise ratio (SNR) and classification performance between pupil size and visual evoked potentials (VEPs). The results showed that the SNR of the pupillary response reached the highest at 1Hz (17.19± 0.10dB) and 100% accuracy was obtained at 1s data length, while the performance was poor at the stimulation frequency above 3Hz. In contrast, the SNR of VEPs reached the highest at 6Hz (18.57± 0.37dB), and the accuracy of all stimulus frequencies could reach 100%, with the minimum data length of 1.5s. This study lays a theoretical foundation for further implementation of a hybrid brain-computer interface (BCI) that integrates pupillometry and EEG.


Assuntos
Interfaces Cérebro-Computador , Potenciais Evocados Visuais , Eletroencefalografia , Humanos , Estimulação Luminosa , Pupila
11.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 3090-3093, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018658

RESUMO

Steady State Visual Evoked Potentials (SSVEPs) have been widely used in Brain-Computer Interfaces (BCIs). SSVEP-BCIs have advantages of high classification accuracy, high information transfer rate, and strong anti-interference ability. Traditional studies mostly used low/medium frequency SSVEPs as system control signals. However, visual flickers with low/medium frequencies are uncomfortable, and even cause visual fatigue and epilepsy seizure. High-frequency SSVEP is a promising approach to solve these problems, but its miniature amplitude and low signal-to-noise ratio (SNR) would pose great challenges for target recognition. This study developed an innovative BCI paradigm to enhance the SNR of high-frequency SSVEP, which is named Steady-State asymmetrically Visual Evoked Potential (SSaVEP). Ten characters were encoded by ten couples of asymmetric flickers whose durations only lasted one second and frequencies ranged from 31 to 40 Hz with a step of 1 Hz. Discriminative canonical pattern matching (DCPM) was used to decode the high-frequency SSaVEP signals. Four subjects participated in the offline experiment. As a result, the accuracy achieved an average of 87.5% with a peak of 97.1%. The simulated online information transfer rate reached 87.2 bits/min on average and 111.2 bits/min for maximum. The results of this study demonstrate the high-frequency SSaVEP paradigm is a promising approach to alleviate the discomfort caused by visual stimuli and thereby can broaden the applications of BCIs.


Assuntos
Interfaces Cérebro-Computador , Potenciais Evocados Visuais , Eletroencefalografia , Humanos , Fenômenos Físicos , Razão Sinal-Ruído
12.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 4745-4748, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33019051

RESUMO

Brain-computer interfaces (BCIs) allow for translating electroencephalogram (EEG) into control commands, e.g., to control a quadcopter. This study, we developed a practical BCI based on steady-state visually evoked potential (SSVEP) for continuous control of a quadcopter from the first-person perspective. Users watched with the video stream from a camera on the quadcopter. An innovative user interface was developed by embedding 12 SSVEP flickers into the video stream, which corresponded to the flight commands of 'take-off,' 'land,' 'hover,' 'keep-going,' 'clockwise,' 'counter-clockwise' and rectilinear motions in six directions, respectively. The command was updated every 400ms by decoding the collected EEG data using a combined classification algorithm based on task-related component analysis (TRCA) and linear discriminant analysis (LDA). The quadcopter flew in the 3-D space according to the control vector that was determined by the latest four commands. Three novices participated in this study. They were asked to control the quadcopter by either the brain or hands to fly through a circle and land on the target zone. As a result, the time consumption ratio of brain-control to hand-control was as low as 1.34, which means the BCI performance was close to hands. The information transfer rate reached a peak of 401.79 bits/min in the simulated online experiment. These results demonstrate the proposed SSVEP-BCI system is efficient for controlling the quadcopter.


Assuntos
Interfaces Cérebro-Computador , Eletroencefalografia , Potenciais Evocados , Potenciais Evocados Visuais , Humanos , Movimento (Física)
13.
PLoS One ; 15(9): e0237663, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32870908

RESUMO

The information available through our senses is noisy, incomplete, and to varying degrees ambiguous. The perceptual system must create stable and reliable percepts out of this restricted information. It solves this perceptual inference problem by integrating memories of previous percepts and making predictions about the perceptual future. Using ambiguous figures and a new experimental approach, we studied whether generating predictions based on regularities in the past affects processing of the present and how this is done. Event-related potentials (ERPs) were measured to investigate whether a highly regular temporal context of either ambiguous or unambiguous stimulus variants differently affects processing of a current stimulus and/or task execution. Further, we tested whether symbolic announcements about the immediate perceptual future can replace the past experience of regularities as a source for making predictions. Both ERP and reaction time varied as a function of stimulus ambiguity in the temporal context of a present stimulus. No such effects were found with symbolic announcements. Our results indicate that predictions about the future automatically alter processing of the present, even if the predictions are irrelevant for the present percept and task. However, direct experiences of past regularities are necessary for predicting the future whereas symbolic information about the future is not sufficient.


Assuntos
Potenciais Evocados Visuais , Memória , Percepção Visual , Adulto , Feminino , Humanos , Masculino , Tempo de Reação , Adulto Jovem
16.
Nat Commun ; 11(1): 3925, 2020 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-32764538

RESUMO

Adaptation is a ubiquitous property of sensory systems. It is typically considered that neurons adapt to dominant energy in the ambient environment to function optimally. However, perceptual representation of the stimulus, often modulated by feedback signals, sometimes do not correspond to the input state of the stimulus, which tends to be more linked with feedforward signals. Here we investigated the relative contributions to cortical adaptation from feedforward and feedback signals, taking advantage of a visual illusion, the Flash-Grab Effect, to disassociate the feedforward and feedback representation of an adaptor. Results reveal that orientation adaptation is exclusively dependent on the perceived rather than the retinal orientation of the adaptor. Combined fMRI and EEG measurements demonstrate that the perceived orientation of the Flash-Grab Effect is indeed supported by feedback signals in the cortex. These findings highlight the important contribution of feedback signals for cortical neurons to recalibrate their sensitivity.


Assuntos
Adaptação Fisiológica , Ilusões/fisiologia , Orientação Espacial/fisiologia , Adulto , Eletroencefalografia , Potenciais Evocados Visuais , Retroalimentação Fisiológica , Feminino , Neuroimagem Funcional , Humanos , Imagem por Ressonância Magnética , Masculino , Ilusões Ópticas/fisiologia , Estimulação Luminosa , Psicofísica , Retina/fisiologia , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Adulto Jovem
17.
PLoS One ; 15(8): e0236967, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32750065

RESUMO

Previous research has shown that visual attention does not always exactly follow gaze direction, leading to the concepts of overt and covert attention. However, it is not yet clear how such covert shifts of visual attention to peripheral regions impact the processing of the targets we directly foveate as they move in our visual field. The current study utilised the co-registration of eye-position and EEG recordings while participants tracked moving targets that were embedded with a 30 Hz frequency tag in a Steady State Visually Evoked Potentials (SSVEP) paradigm. When the task required attention to be divided between the moving target (overt attention) and a peripheral region where a second target might appear (covert attention), the SSVEPs elicited by the tracked target at the 30 Hz frequency band were significantly, but transiently, lower than when participants did not have to covertly monitor for a second target. Our findings suggest that neural responses of overt attention are only briefly reduced when attention is divided between covert and overt areas. This neural evidence is in line with theoretical accounts describing attention as a pool of finite resources, such as the perceptual load theory. Altogether, these results have practical implications for many real-world situations where covert shifts of attention may discretely reduce visual processing of objects even when they are directly being tracked with the eyes.


Assuntos
Atenção , Potenciais Evocados Visuais , Movimentos Oculares , Percepção Visual , Adulto , Eletroencefalografia , Feminino , Humanos , Masculino , Campos Visuais , Adulto Jovem
18.
Medicine (Baltimore) ; 99(27): e20754, 2020 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-32629652

RESUMO

INTRODUCTION: To describe an unusual case of binasal congruous hemianopia secondary to functional visual loss (FVL). PATIENT CONCERNS: A 24 year-old male was referred originally by his optician at the Emergency Eye Department of the Leicester Royal Infirmary in October 2018 with visual field changes affecting the nasal field of vision in both eyes on routine eye examination. The patient reported ongoing headaches over the last 6 weeks to 8 weeks associated with simultaneous peripheral visual field changes. He also reported rapid loss of weight over the same period of time. DIAGNOSIS: Binasal congruous hemianopia secondary to FVL. INTERVENTIONS: Full past medical and ocular history was obtained. The patient underwent full ophthalmic examination including dilated fundoscopy. Visual acuity was recorded with Snellen Chart. Color vision was assessed with Ishihara plates. Peripheral vision was assessed with both Humphrey visual fields and Goldmann visual fields. Optical coherence tomography of the macula and discs was also performed. Neuroimaging investigations included Computerized Tomography (CT) and Magnetic Resonance Imaging (MRI) of the Brain. Electrophysiology investigations included Electroretinogram and visual evoked potentials. Patient was also tested for syphilis. OUTCOMES: Humphrey visual fields and Goldmann visual fields confirmed the presence of complete binasal field defects. Optical coherence tomography, electroretinogram, visual evoked potentials, CT, MRI were all unremarkable. Ocular examination was normal. Finally, syphilis serology was negative. After 1 year of follow-up, the visual field changes have remained the same. CONCLUSION: To the best of our knowledge, this is the fourth case described in the literature with complete congruous binasal hemianopia due to FVL. We advocate thorough investigations with multimodal imaging of the fundus, neuroimaging and syphilis serology to exclude serious organic causes for binasal field defects prior to labeling such a field defect functional. Such patients may benefit from neuropsychological input to understand the psychological factors that may be contributing to the symptoms.


Assuntos
Hemianopsia/etiologia , Transtornos da Visão/complicações , Encéfalo/diagnóstico por imagem , Potenciais Evocados Visuais , Humanos , Imagem por Ressonância Magnética , Masculino , Neuroimagem , Tomografia de Coerência Óptica , Tomografia Computadorizada por Raios X , Testes de Campo Visual , Campos Visuais , Adulto Jovem
19.
PLoS One ; 15(7): e0235309, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32614860

RESUMO

Recent researches revealed that the EEG component caused by the flickering visual stimulus, which is called steady-state visually evoked potential (SSVEP), might be a potential index for object recognition. This study examined whether SSVEP reflects different states during object recognition. In one trial, a binary image (BI), which is difficult to recognize, was followed by a grayscale image (GI) of the same object as the answer. Both BI and GI were presented in a flickering manner at a frequency of 7.5 Hz. Participants were first asked to answer whether they could recognize BI. Then, after GI was shown, participants were requested to answer whether they recognized it. We analyzed the evoked and induced component of SSVEPs from the two recognition conditions. As a result, the SSVEPs to BI were significantly larger than that to GI. In addition, induced component to GI after the BI was unrecognized was smaller than after the BI was recognized. The present data provide evidence that SSVEPs reflect a transition of cognitive state to ambiguous figures is reflected.


Assuntos
Eletroencefalografia/métodos , Potenciais Evocados Visuais , Reconhecimento Visual de Modelos/fisiologia , Estimulação Luminosa/métodos , Córtex Visual/fisiologia , Adulto , Feminino , Humanos , Masculino , Adulto Jovem
20.
Neurology ; 95(10): e1333-e1340, 2020 09 08.
Artigo em Inglês | MEDLINE | ID: mdl-32641520

RESUMO

OBJECTIVE: To assess cerebrovascular reactivity in response to a visual task in participants with cerebral amyloid angiopathy (CAA), Alzheimer disease (AD), and mild cognitive impairment (MCI) using fMRI. METHODS: This prospective cohort study included 40 patients with CAA, 22 with AD, 27 with MCI, and 25 healthy controls. Each participant underwent a visual fMRI task using a contrast-reversing checkerboard stimulus. Visual evoked potentials (VEPs) were used to compare visual cortex neuronal activity in 83 participants. General linear models using least-squares means, adjusted for multiple comparisons with the Tukey test, were used to estimate mean blood oxygen level-dependent (BOLD) signal change during the task and VEP differences between groups. RESULTS: After adjustment for age and hypertension, estimated mean BOLD response amplitude was as follows: CAA 1.88% (95% confidence interval [CI] 1.60%-2.15%), AD 2.26% (1.91%-2.61%), MCI 2.15% (1.84%-2.46%), and control 2.65% (2.29%-3.00%). Only patients with CAA differed from controls (p = 0.01). In the subset with VEPs, group was not associated with prolonged latencies or lower amplitudes. Lower BOLD amplitude response was associated with higher white matter hyperintensity (WMH) volumes in CAA (for each 0.1% lower BOLD response amplitude, the WMH volume was 9.2% higher, 95% CI 6.0%-12.4%) but not other groups (p = 0.002 for interaction) when controlling for age and hypertension. CONCLUSIONS: Mean visual BOLD response amplitude was lowest in participants with CAA compared to controls, without differences in VEP latencies and amplitudes. This suggests that the impaired visual BOLD response is due to reduced vascular reactivity in CAA. In contrast to participants with CAA, the visual BOLD response amplitude did not differ between those with AD or MCI and controls.


Assuntos
Doença de Alzheimer/fisiopatologia , Angiopatia Amiloide Cerebral/fisiopatologia , Circulação Cerebrovascular/fisiologia , Disfunção Cognitiva/fisiopatologia , Idoso , Estudos de Coortes , Estudos Transversais , Imagem Ecoplanar , Potenciais Evocados Visuais/fisiologia , Feminino , Humanos , Interpretação de Imagem Assistida por Computador/métodos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Córtex Visual/fisiopatologia
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