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1.
Sci Rep ; 14(1): 10593, 2024 05 08.
Artigo em Inglês | MEDLINE | ID: mdl-38719939

RESUMO

Previous research on the neural correlates of consciousness (NCC) in visual perception revealed an early event-related potential (ERP), the visual awareness negativity (VAN), to be associated with stimulus awareness. However, due to the use of brief stimulus presentations in previous studies, it remains unclear whether awareness-related negativities represent a transient onset-related response or correspond to the duration of a conscious percept. Studies are required that allow prolonged stimulus presentation under aware and unaware conditions. The present ERP study aimed to tackle this challenge by using a novel stimulation design. Male and female human participants (n = 62) performed a visual task while task-irrelevant line stimuli were presented in the background for either 500 or 1000 ms. The line stimuli sometimes contained a face, which needed so-called visual one-shot learning to be seen. Half of the participants were informed about the presence of the face, resulting in faces being perceived by the informed but not by the uninformed participants. Comparing ERPs between the informed and uninformed group revealed an enhanced negativity over occipitotemporal electrodes that persisted for the entire duration of stimulus presentation. Our results suggest that sustained visual awareness negativities (SVAN) are associated with the duration of stimulus presentation.


Assuntos
Estado de Consciência , Eletroencefalografia , Potenciais Evocados , Percepção Visual , Humanos , Masculino , Feminino , Estado de Consciência/fisiologia , Percepção Visual/fisiologia , Adulto , Adulto Jovem , Potenciais Evocados/fisiologia , Estimulação Luminosa , Conscientização/fisiologia , Potenciais Evocados Visuais/fisiologia
2.
Sci Rep ; 14(1): 11188, 2024 05 16.
Artigo em Inglês | MEDLINE | ID: mdl-38755251

RESUMO

In primates, foveal and peripheral vision have distinct neural architectures and functions. However, it has been debated if selective attention operates via the same or different neural mechanisms across eccentricities. We tested these alternative accounts by examining the effects of selective attention on the steady-state visually evoked potential (SSVEP) and the fronto-parietal signal measured via EEG from human subjects performing a sustained visuospatial attention task. With a negligible level of eye movements, both SSVEP and SND exhibited the heterogeneous patterns of attentional modulations across eccentricities. Specifically, the attentional modulations of these signals peaked at the parafoveal locations and such modulations wore off as visual stimuli appeared closer to the fovea or further away towards the periphery. However, with a relatively higher level of eye movements, the heterogeneous patterns of attentional modulations of these neural signals were less robust. These data demonstrate that the top-down influence of covert visuospatial attention on early sensory processing in human cortex depends on eccentricity and the level of saccadic responses. Taken together, the results suggest that sustained visuospatial attention operates differently across different eccentric locations, providing new understanding of how attention augments sensory representations regardless of where the attended stimulus appears.


Assuntos
Atenção , Eletroencefalografia , Potenciais Evocados Visuais , Humanos , Atenção/fisiologia , Masculino , Feminino , Potenciais Evocados Visuais/fisiologia , Adulto , Adulto Jovem , Estimulação Luminosa , Percepção Visual/fisiologia , Movimentos Oculares/fisiologia
3.
Elife ; 122024 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-38564237

RESUMO

When observers have prior knowledge about the likely outcome of their perceptual decisions, they exhibit robust behavioural biases in reaction time and choice accuracy. Computational modelling typically attributes these effects to strategic adjustments in the criterion amount of evidence required to commit to a choice alternative - usually implemented by a starting point shift - but recent work suggests that expectations may also fundamentally bias the encoding of the sensory evidence itself. Here, we recorded neural activity with EEG while participants performed a contrast discrimination task with valid, invalid, or neutral probabilistic cues across multiple testing sessions. We measured sensory evidence encoding via contrast-dependent steady-state visual-evoked potentials (SSVEP), while a read-out of criterion adjustments was provided by effector-selective mu-beta band activity over motor cortex. In keeping with prior modelling and neural recording studies, cues evoked substantial biases in motor preparation consistent with criterion adjustments, but we additionally found that the cues produced a significant modulation of the SSVEP during evidence presentation. While motor preparation adjustments were observed in the earliest trials, the sensory-level effects only emerged with extended task exposure. Our results suggest that, in addition to strategic adjustments to the decision process, probabilistic information can also induce subtle biases in the encoding of the evidence itself.


Assuntos
Sinais (Psicologia) , Potenciais Evocados Visuais , Humanos , Viés , Simulação por Computador , Probabilidade
4.
Artigo em Inglês | MEDLINE | ID: mdl-38557619

RESUMO

Visual selective attention studies generally tend to apply cuing paradigms to instructively direct observers' attention to certain locations, features or objects. However, in real situations, attention in humans often flows spontaneously without any specific instructions. Recently, a concept named "willed attention" was raised in visuospatial attention, in which participants are free to make volitional attention decisions. Several ERP components during willed attention were found, along with a perspective that ongoing alpha activity may bias the subsequent attentional choice. However, it remains unclear whether similar neural mechanisms exist in feature- or object-based willed attention. Here, we included choice cues and instruct cues in a feature-based selective attention paradigm, allowing participants to freely choose or to be instructed to attend a color for the subsequent target detection task. Pre-cue ongoing alpha oscillations, cue-evoked potentials and target-related steady-state visual evoked potentials (SSVEPs) were simultaneously measured as markers of attentional processing. As expected, SSVEP responses were similarly modulated by attention between choice and instruct cue trials. Similar to the case of spatial attention, a willed-attention component (Willed Attention Component, WAC) was isolated during the cue-related choice period by comparing choice and instruct cues. However, pre-cue ongoing alpha oscillations did not predict the color choice (yellow vs blue), as indicated by the chance level decoding accuracy (50%). Overall, our results revealed both similarities and differences between spatial and feature-based willed attention, and thus extended the understanding toward the neural mechanisms of volitional attention.


Assuntos
Eletroencefalografia , Potenciais Evocados Visuais , Humanos , Potenciais Evocados/fisiologia , Sinais (Psicologia) , Estimulação Luminosa , Percepção Visual/fisiologia
5.
Artigo em Inglês | MEDLINE | ID: mdl-38598402

RESUMO

Canonical correlation analysis (CCA), Multivariate synchronization index (MSI), and their extended methods have been widely used for target recognition in Brain-computer interfaces (BCIs) based on Steady State Visual Evoked Potentials (SSVEP), and covariance calculation is an important process for these algorithms. Some studies have proved that embedding time-local information into the covariance can optimize the recognition effect of the above algorithms. However, the optimization effect can only be observed from the recognition results and the improvement principle of time-local information cannot be explained. Therefore, we propose a time-local weighted transformation (TT) recognition framework that directly embeds the time-local information into the electroencephalography signal through weighted transformation. The influence mechanism of time-local information on the SSVEP signal can then be observed in the frequency domain. Low-frequency noise is suppressed on the premise of sacrificing part of the SSVEP fundamental frequency energy, the harmonic energy of SSVEP is enhanced at the cost of introducing a small amount of high-frequency noise. The experimental results show that the TT recognition framework can significantly improve the recognition ability of the algorithms and the separability of extracted features. Its enhancement effect is significantly better than the traditional time-local covariance extraction method, which has enormous application potential.


Assuntos
Interfaces Cérebro-Computador , Humanos , Potenciais Evocados Visuais , Reconhecimento Automatizado de Padrão/métodos , Reconhecimento Psicológico , Eletroencefalografia/métodos , Algoritmos , Estimulação Luminosa
6.
Artigo em Inglês | MEDLINE | ID: mdl-38598403

RESUMO

Steady-state visual evoked potential (SSVEP), one of the most popular electroencephalography (EEG)-based brain-computer interface (BCI) paradigms, can achieve high performance using calibration-based recognition algorithms. As calibration-based recognition algorithms are time-consuming to collect calibration data, the least-squares transformation (LST) has been used to reduce the calibration effort for SSVEP-based BCI. However, the transformation matrices constructed by current LST methods are not precise enough, resulting in large differences between the transformed data and the real data of the target subject. This ultimately leads to the constructed spatial filters and reference templates not being effective enough. To address these issues, this paper proposes multi-stimulus LST with online adaptation scheme (ms-LST-OA). METHODS: The proposed ms-LST-OA consists of two parts. Firstly, to improve the precision of the transformation matrices, we propose the multi-stimulus LST (ms-LST) using cross-stimulus learning scheme as the cross-subject data transformation method. The ms-LST uses the data from neighboring stimuli to construct a higher precision transformation matrix for each stimulus to reduce the differences between transformed data and real data. Secondly, to further optimize the constructed spatial filters and reference templates, we use an online adaptation scheme to learn more features of the EEG signals of the target subject through an iterative process trial-by-trial. RESULTS: ms-LST-OA performance was measured for three datasets (Benchmark Dataset, BETA Dataset, and UCSD Dataset). Using few calibration data, the ITR of ms-LST-OA achieved 210.01±10.10 bits/min, 172.31±7.26 bits/min, and 139.04±14.90 bits/min for all three datasets, respectively. CONCLUSION: Using ms-LST-OA can reduce calibration effort for SSVEP-based BCIs.


Assuntos
Interfaces Cérebro-Computador , Potenciais Evocados Visuais , Humanos , Calibragem , Estimulação Luminosa/métodos , Eletroencefalografia/métodos , Algoritmos
7.
Rom J Ophthalmol ; 68(1): 19-24, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38617718

RESUMO

Aim: The research aimed to establish reference values of visual evoked potentials among school-aged children after brain injury. Methods: Eighteen patients with persisting visual symptoms after brain injury have been examined. A pattern-VEP test has been used during the examination. Results: The prolongation of the N2 wave in 55,6%-66,6%, P wave in 55,7%-66,7%, and N3 wave in 16,7%-22,2% was determined in the research group. Likewise, the decrease in the amplitude of the P wave was determined in the case of 16,7%-33,3%. According to the topography, we concluded that the prechiasmatic alteration was predominantly determined as bilateral in the optic pathways, with emphasis equally on the right and left. Conclusions: VEP evaluation remains one of the most credible methods of examination. In the case of moderate or severe traumatic optic neuropathy, it allows the detection of damage to the optic pathways before the appearance of organic changes that are often irreversible. The possibility of early detection of such modifications could justify the initiation of a dosed stimulatory treatment, to avoid damage to the optic pathways that would induce secondary optic atrophy. Abbreviations: VEP = visual evoked potentials, MRI = magnetic resonance imaging.


Assuntos
Lesões Encefálicas , Atrofia Óptica , Criança , Humanos , Potenciais Evocados Visuais
8.
Rom J Ophthalmol ; 68(1): 65-71, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38617721

RESUMO

Leber's hereditary optic neuropathy (LHON) is the most common maternally inherited disease linked to mitochondrial DNA (mtDNA). The patients present with subacute asymmetric bilateral vision loss. Approximately 95% of the LHON cases are caused by m.3460G>A (MTND1), m.11778G>A (MTND4), and m.14484T>C (MTND6) mutations. The hallmark of hereditary optic neuropathies determined by mitochondrial dysfunction is the vulnerability and degeneration of retinal ganglion cells (RGC). We present the case of a 28-year-old man who came to our clinic complaining of a subacute decrease in visual acuity of his left eye. From his medical history, we found out that one month before he had the same symptoms in the right eye. From the family history, we noted that an uncle has had vision problems since childhood. We carried out complete blood tests, including specific antibodies for autoimmune and infectious diseases. Laboratory tests and MRI were within normal limits. A blood test of the mtDNA showed the presence of 11778 G>A mutation on the mtND6 gene. The medical history, the fundus appearance, the OCT, and the paraclinical investigations, made us diagnose our patient with Leber's hereditary optic neuropathy. As soon as possible, we began the treatment with systemic idebenone, 900 mg/day. We examined the patient 2, 6, and 10 weeks after initiating the treatment. Abbreviations: LHON = Leber's Hereditary Optic Neuropathy, mtDNA = mitochondrial DNA, VA = visual acuity, RE = right eye, LE = left eye, OCT = Optical coherence tomography, pRNFL = peripapillary retinal nerve fiber layer, GCL = retinal ganglion cells layer, MRI = magnetic resonance imaging, VEP = visual evoked potentials, VEP IT = VEP implicit time, VEP A = VEP amplitude.


Assuntos
Atrofia Óptica Hereditária de Leber , Doenças do Nervo Óptico , Masculino , Humanos , Criança , Adulto , Atrofia Óptica Hereditária de Leber/diagnóstico , Atrofia Óptica Hereditária de Leber/genética , Diagnóstico Diferencial , Potenciais Evocados Visuais , DNA Mitocondrial/genética
9.
Neurol Neuroimmunol Neuroinflamm ; 11(3): e200223, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38588480

RESUMO

BACKGROUND AND OBJECTIVES: Optic neuritis is the most common optic neuropathy in young adults and a frequent manifestation of multiple sclerosis. Its clinical course is pertinent to the design of visual pathway neuroprotection trials. METHODS: This is a secondary analysis of longitudinal data from the TONE trial, which included 103 patients from 12 German academic tertiary centers with acute unilateral optic neuritis as a clinically isolated syndrome and baseline high-contrast visual acuity <0.5 decimal. Patients were randomized to 1,000 mg methylprednisolone i.v./d plus either erythropoietin (33,000 IU/d) or placebo (saline solution) for 3 days. They were followed up at standardized intervals with a battery of tests including high-contrast visual acuity, low-contrast letter acuity, contrast sensitivity, visual fields, visual evoked potentials, and retinal optical coherence tomography. At 6 months, participants answered a standardized questionnaire on vision-related quality of life (NEI-VFQ 25). We describe the disease course with mixed-effects piecewise linear models and calculate structure-function correlations using Pearson r. Because erythropoietin had no effect on the visual system, we use pooled (treatment-agnostic) data. RESULTS: Patients experienced initial rapid and then decelerating improvements of visual function with thinning of inner and thickening of outer retinal layers. At 6 months, visual parameters were positively correlated with inner and negatively correlated with outer retinal thickness changes. Peripapillary retinal nerve fiber layer thinning predominantly occurred in sectors without previous swelling. At 6 months, macular ganglion cell and inner plexiform layer thinning was weakly correlated with the P100 peak time (r = -0.11) and moderately correlated with the amplitude of visual evoked potentials (r = 0.35). Only functional outcomes were at least moderately correlated with vision-related quality of life. DISCUSSION: The longitudinal data from this large study cohort may serve as a reference for the clinical course of acute optic neuritis. The pattern of correlation between visual evoked potentials and inner retinal thinning may argue that the latter is mostly due to ganglion cell loss, rather than dysfunction. Visual pathway neuroprotection trials with functional outcomes are needed to confirm that candidate drugs will benefit patients' vision-related quality of life. TRIAL REGISTRATION INFORMATION: ClinicalTrials.gov, NCT01962571.


Assuntos
Eritropoetina , Neurite Óptica , Humanos , Adulto Jovem , Progressão da Doença , Eritropoetina/uso terapêutico , Potenciais Evocados Visuais , Neurite Óptica/tratamento farmacológico , Qualidade de Vida
10.
Doc Ophthalmol ; 148(3): 155-166, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38622306

RESUMO

PURPOSE: The aim of this neurophysiological study was to retrospectively analyze visual evoked potentials (VEPs) acquired during an examination for diagnosing optic nerve involvement in patients with Lyme neuroborreliosis (LNB). Attention was focused on LNB patients with peripheral facial palsy (PFP) and optic nerve involvement. METHODS: A total of 241 Czech patients were classified as having probable/definite LNB (193/48); of these, 57 were younger than 40 years, with a median age of 26.3 years, and 184 were older than 40 years, with a median age of 58.8 years. All patients underwent pattern-reversal (PVEP) and motion-onset (MVEP) VEP examinations. RESULTS: Abnormal VEP results were observed in 150/241 patients and were noted more often in patients over 40 years (p = 0.008). Muscle/joint problems and paresthesia were observed to be significantly more common in patients older than 40 years (p = 0.002, p = 0.030), in contrast to headache and decreased visual acuity, which were seen more often in patients younger than 40 years (p = 0.001, p = 0.033). Peripheral facial palsy was diagnosed in 26/241 LNB patients. Among patients with PFP, VEP peak times above the laboratory limit was observed in 22 (84.6%) individuals. Monitoring of patients with PFP and pathological VEP showed that the adjustment of visual system function occurred in half of the patients in one to more years, in contrast to faster recovery from peripheral facial palsy within months in most patients. CONCLUSION: In LNB patients, VEP helps to increase sensitivity of an early diagnostic process.


Assuntos
Potenciais Evocados Visuais , Neuroborreliose de Lyme , Doenças do Nervo Óptico , Humanos , Neuroborreliose de Lyme/fisiopatologia , Neuroborreliose de Lyme/diagnóstico , Neuroborreliose de Lyme/complicações , Pessoa de Meia-Idade , Adulto , Potenciais Evocados Visuais/fisiologia , Estudos Retrospectivos , Masculino , Feminino , Doenças do Nervo Óptico/fisiopatologia , Doenças do Nervo Óptico/diagnóstico , Idoso , Adulto Jovem , Adolescente , Paralisia Facial/fisiopatologia , Paralisia Facial/diagnóstico , Criança , Idoso de 80 Anos ou mais , Acuidade Visual/fisiologia , Nervo Óptico/fisiopatologia
11.
J Neural Eng ; 21(3)2024 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-38688262

RESUMO

Objective.The rapid serial visual presentation (RSVP) paradigm, which is based on the electroencephalogram (EEG) technology, is an effective approach for object detection. It aims to detect the event-related potentials (ERP) components evoked by target images for rapid identification. However, the object detection performance within this paradigm is affected by the visual disparity between adjacent images in a sequence. Currently, there is no objective metric to quantify this visual difference. Consequently, a reliable image sorting method is required to ensure the generation of a smooth sequence for effective presentation.Approach. In this paper, we propose a novel semantic image sorting method for sorting RSVP sequences, which aims at generating sequences that are perceptually smoother in terms of the human visual experience.Main results. We conducted a comparative analysis between our method and two existing methods for generating RSVP sequences using both qualitative and quantitative assessments. A qualitative evaluation revealed that the sequences generated by our method were smoother in subjective vision and were more effective in evoking stronger ERP components than those generated by the other two methods. Quantitatively, our method generated semantically smoother sequences than the other two methods. Furthermore, we employed four advanced approaches to classify single-trial EEG signals evoked by each of the three methods. The classification results of the EEG signals evoked by our method were superior to those of the other two methods.Significance. In summary, the results indicate that the proposed method can significantly enhance the object detection performance in RSVP-based sequences.


Assuntos
Eletroencefalografia , Potenciais Evocados Visuais , Estimulação Luminosa , Semântica , Humanos , Eletroencefalografia/métodos , Masculino , Feminino , Estimulação Luminosa/métodos , Adulto Jovem , Adulto , Potenciais Evocados Visuais/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Algoritmos
12.
Brain Behav ; 14(4): e3493, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38641893

RESUMO

INTRODUCTION: Generalized joint hypermobility (GJH) can be the result of several hereditary connective tissue disorders, especially Ehlers-Danlos syndrome. Cerebrovascular manifestations are among the most common complications in this disorder, and understanding their extent can help better diagnosis and prevention of hazardous events. We investigated visual evoked potential (VEP) changes in patients with GJH and compared them with healthy individuals. METHODS: Our case-control study included 90 patients who fulfilled the Beighton score (B score) for joint hypermobility and other 90 healthy participants. All of them went under VEP study, and the amplitude and latency of the evoked potential (P100) were compared to each other. RESULTS: The Case group had significantly higher B score (7.18 ± 0.967 vs. 1.18 ± 0.712), P100 latency (110.23 ± 6.64 ms vs. 100.18 ± 4.273 ms), and amplitude (6.54 ± 1.26 mv vs. 6.50 ± 1.29 mv) compared with the Control group, but the difference was only significant regarding B score, and P100 latency (p-value <.0001). Moreover, both latency and amplitude of P100 had significantly positive correlations with the B score in the Case group (p-value <.0001), but such correlations were not found in the Control group (p-value = .059). CONCLUSION: Our study could reveal VEP changes, especially significant P100 latency in GJH patients without previous neurologic or musculoskeletal disorders. Whether these changes are due to GJH itself or are predictive of inevitable neurologic disease or visual pathway involvement, particularly Multiple Sclerosis needs further investigation with longer follow-up periods.


Assuntos
Síndrome de Ehlers-Danlos , Instabilidade Articular , Humanos , Potenciais Evocados Visuais , Instabilidade Articular/diagnóstico , Estudos de Casos e Controles , Potenciais Evocados
13.
Sci Rep ; 14(1): 9281, 2024 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-38654008

RESUMO

Steady-state visual evoked potentials (SSVEP) are electroencephalographic signals elicited when the brain is exposed to a visual stimulus with a steady frequency. We analyzed the temporal dynamics of SSVEP during sustained flicker stimulation at 5, 10, 15, 20 and 40 Hz. We found that the amplitudes of the responses were not stable over time. For a 5 Hz stimulus, the responses progressively increased, while, for higher flicker frequencies, the amplitude increased during the first few seconds and often showed a continuous decline afterward. We hypothesize that these two distinct sets of frequency-dependent SSVEP signal properties reflect the contribution of parvocellular and magnocellular visual pathways generating sustained and transient responses, respectively. These results may have important applications for SSVEP signals used in research and brain-computer interface technology and may contribute to a better understanding of the frequency-dependent temporal mechanisms involved in the processing of prolonged periodic visual stimuli.


Assuntos
Eletroencefalografia , Potenciais Evocados Visuais , Estimulação Luminosa , Potenciais Evocados Visuais/fisiologia , Humanos , Masculino , Feminino , Adulto , Adulto Jovem , Interfaces Cérebro-Computador , Córtex Visual/fisiologia
14.
Proc Natl Acad Sci U S A ; 121(16): e2309975121, 2024 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-38588433

RESUMO

Research on attentional selection of stimulus features has yielded seemingly contradictory results. On the one hand, many experiments in humans and animals have observed a "global" facilitation of attended features across the entire visual field, even when spatial attention is focused on a single location. On the other hand, several event-related potential studies in humans reported that attended features are enhanced at the attended location only. The present experiment demonstrates that these conflicting results can be explained by differences in the timing of attentional allocation inside and outside the spatial focus of attention. Participants attended to fields of either red or blue randomly moving dots on either the left or right side of fixation with the task of detecting brief coherent motion targets. Recordings of steady-state visual evoked potentials elicited by the flickering stimuli allowed concurrent measurement of the time course of feature-selective attention in visual cortex on both the attended and the unattended sides. The onset of feature-selective attentional modulation on the attended side occurred around 150 ms earlier than on the unattended side. This finding that feature-selective attention is not spatially global from the outset but extends to unattended locations after a temporal delay resolves previous contradictions between studies finding global versus hierarchical selection of features and provides insight into the fundamental relationship between feature-based and location-based (spatial) attention mechanisms.


Assuntos
Eletroencefalografia , Potenciais Evocados Visuais , Humanos , Potenciais Evocados , Campos Visuais , Atenção , Estimulação Luminosa/métodos
15.
Neurosci Lett ; 830: 137777, 2024 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-38621505

RESUMO

Omitted stimulus potentials (OSPs) are elicited in response to the omission of expected stimuli and are thought to reflect prediction errors. If prediction errors are signaled in the sensory cortex, OSPs are expected to be generated in the sensory cortex. The present study investigated the involvement of the early visual cortex in the generation of OSPs by testing whether omitted visual stimuli elicit brain responses in a spatially specific manner. Checkerboard pattern stimuli were presented alternately in the upper and lower visual fields, and the stimuli were omitted in 10 % of the trials. Event-related potentials were recorded from 33 participants. While a retinotopic C1 component was evoked by real visual stimuli, omitted stimuli did not produce any response reflecting retinotopy but did elicit a visual mismatch negativity, which was larger for omitted stimuli expected in the lower visual field than for those in the upper visual field. These results suggest that omitted visual stimuli are processed in a different pathway than actual stimuli.


Assuntos
Potenciais Evocados Visuais , Estimulação Luminosa , Córtex Visual , Campos Visuais , Humanos , Masculino , Feminino , Adulto Jovem , Estimulação Luminosa/métodos , Potenciais Evocados Visuais/fisiologia , Adulto , Campos Visuais/fisiologia , Córtex Visual/fisiologia , Eletroencefalografia/métodos , Percepção Visual/fisiologia , Vias Visuais/fisiologia , Retina/fisiologia
16.
J Integr Neurosci ; 23(4): 73, 2024 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-38682224

RESUMO

BACKGROUND: To enhance the information transfer rate (ITR) of a steady-state visual evoked potential (SSVEP)-based speller, more characters with flickering symbols should be used. Increasing the number of symbols might reduce the classification accuracy. A hybrid brain-computer interface (BCI) improves the overall performance of a BCI system by taking advantage of two or more control signals. In a simultaneous hybrid BCI, various modalities work with each other simultaneously, which enhances the ITR. METHODS: In our proposed speller, simultaneous combination of electromyogram (EMG) and SSVEP was applied to increase the ITR. To achieve 36 characters, only nine stimulus symbols were used. Each symbol allowed the selection of four characters based on four states of muscle activity. The SSVEP detected which symbol the subject was focusing on and the EMG determined the target character out of the four characters dedicated to that symbol. The frequency rate for character encoding was applied in the EMG modality and latency was considered in the SSVEP modality. Online experiments were carried out on 10 healthy subjects. RESULTS: The average ITR of this hybrid system was 96.1 bit/min with an accuracy of 91.2%. The speller speed was 20.9 char/min. Different subjects had various latency values. We used an average latency of 0.2 s across all subjects. Evaluation of each modality showed that the SSVEP classification accuracy varied for different subjects, ranging from 80% to 100%, while the EMG classification accuracy was approximately 100% for all subjects. CONCLUSIONS: Our proposed hybrid BCI speller showed improved system speed compared with state-of-the-art systems based on SSVEP or SSVEP-EMG, and can provide a user-friendly, practical system for speller applications.


Assuntos
Interfaces Cérebro-Computador , Eletroencefalografia , Eletromiografia , Potenciais Evocados Visuais , Humanos , Potenciais Evocados Visuais/fisiologia , Adulto , Masculino , Eletroencefalografia/métodos , Feminino , Adulto Jovem , Encéfalo/fisiologia
17.
J Neurosci Methods ; 406: 110132, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38604523

RESUMO

BACKGROUND: Traditional therapist-based rehabilitation training for patients with movement impairment is laborious and expensive. In order to reduce the cost and improve the treatment effect of rehabilitation, many methods based on human-computer interaction (HCI) technology have been proposed, such as robot-assisted therapy and functional electrical stimulation (FES). However, due to the lack of active participation of brain, these methods have limited effects on the promotion of damaged nerve remodeling. NEW METHOD: Based on the neurofeedback training provided by the combination of brain-computer interface (BCI) and exoskeleton, this paper proposes a multimodal brain-controlled active rehabilitation system to help improve limb function. The joint control mode of steady-state visual evoked potential (SSVEP) and motor imagery (MI) is adopted to achieve self-paced control and thus maximize the degree of brain involvement, and a requirement selection function based on SSVEP design is added to facilitate communication with aphasia patients. COMPARISON WITH EXISTING METHODS: In addition, the Transformer is introduced as the MI decoder in the asynchronous online BCI to improve the global perception of electroencephalogram (EEG) signals and maintain the sensitivity and efficiency of the system. RESULTS: In two multi-task online experiments for left hand, right hand, foot and idle states, subject achieves 91.25% and 92.50% best accuracy, respectively. CONCLUSION: Compared with previous studies, this paper aims to establish a high-performance and low-latency brain-controlled rehabilitation system, and provide an independent and autonomous control mode of the brain, so as to improve the effect of neural remodeling. The performance of the proposed method is evaluated through offline and online experiments.


Assuntos
Interfaces Cérebro-Computador , Eletroencefalografia , Exoesqueleto Energizado , Neurorretroalimentação , Humanos , Eletroencefalografia/métodos , Masculino , Neurorretroalimentação/métodos , Neurorretroalimentação/instrumentação , Potenciais Evocados Visuais/fisiologia , Adulto , Encéfalo/fisiologia , Encéfalo/fisiopatologia , Feminino , Adulto Jovem , Imaginação/fisiologia , Imagens, Psicoterapia/métodos
18.
Indian J Ophthalmol ; 72(Suppl 3): S509-S513, 2024 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-38648460

RESUMO

PURPOSE: Mutations of G protein-coupled receptor 143 (GPR143) and FERM domain containing 7 (FRMD7) may result in congenital nystagmus (CN) in the first 6 months of life. We aimed to compare the differences in ocular oscillations between patients with these two gene mutations as well as the functional and structural changes in their retinas and visual pathways. METHODS: Medical records were retrospectively reviewed to identify patients of congenital nystagmus with confirmed mutations in either GPR143 or FMRD7 genes from January 2018 to May 2023. The parameters of the ocular oscillations were recorded using Eyelink 1000 Plus. The retinal structure and function were evaluated using optical coherence tomography and multi-focal electroretinography (mERG). The visual pathway and optical nerve projection were evaluated using visual evoked potentials. The next-generation sequencing technique was used to identify the pathogenic variations in the disease-causing genes for CN. RESULTS: Twenty nystagmus patients of GPR143 and 21 patients of FMRD7 who had been confirmed by molecular testing between January 2018 and May 2023 were included. Foveal hypoplasia was detected only in patients with the GPR143 pathogenic variant. mERG examination showed a flat response topography in the GPR143 group compared to the FRMD7 group. VEP showed that bilateral amplitude inconsistency was detected only in the patients with GPR143 gene mutation. The amplitude and frequency of the ocular oscillations were not found to differ between patients with two different genetic mutations. CONCLUSIONS: Although the etiology and molecular mechanisms are completely different between CN patients, they may have similar ocular oscillations. A careful clinical examination and electrophysiological test will be helpful in making a differential diagnosis. Our novel identified variants will further expand the spectrum of the GPR143 and FRMD7 variants.


Assuntos
Proteínas do Citoesqueleto , Proteínas de Membrana , Nistagmo Congênito , Feminino , Humanos , Masculino , Proteínas do Citoesqueleto/genética , DNA/genética , Análise Mutacional de DNA , Eletrorretinografia , Potenciais Evocados Visuais/fisiologia , Movimentos Oculares/fisiologia , Proteínas do Olho/genética , Glicoproteínas de Membrana/genética , Proteínas de Membrana/genética , Mutação , Nistagmo Congênito/genética , Nistagmo Congênito/fisiopatologia , Nistagmo Congênito/diagnóstico , Retina/fisiopatologia , Estudos Retrospectivos , Tomografia de Coerência Óptica/métodos
19.
J Neural Eng ; 21(3)2024 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-38639058

RESUMO

Objective.Brain-computer interface (BCI) systems with large directly accessible instruction sets are one of the difficulties in BCI research. Research to achieve high target resolution (⩾100) has not yet entered a rapid development stage, which contradicts the application requirements. Steady-state visual evoked potential (SSVEP) based BCIs have an advantage in terms of the number of targets, but the competitive mechanism between the target stimulus and its neighboring stimuli is a key challenge that prevents the target resolution from being improved significantly.Approach.In this paper, we reverse the competitive mechanism and propose a frequency spatial multiplexing method to produce more targets with limited frequencies. In the proposed paradigm, we replicated each flicker stimulus as a 2 × 2 matrix and arrange the matrices of all frequencies in a tiled fashion to form the interaction interface. With different arrangements, we designed and tested three example paradigms with different layouts. Further we designed a graph neural network that distinguishes between targets of the same frequency by recognizing the different electroencephalography (EEG) response distribution patterns evoked by each target and its neighboring targets.Main results.Extensive experiment studies employing eleven subjects have been performed to verify the validity of the proposed method. The average classification accuracies in the offline validation experiments for the three paradigms are 89.16%, 91.38%, and 87.90%, with information transfer rates (ITR) of 51.66, 53.96, and 50.55 bits/min, respectively.Significance.This study utilized the positional relationship between stimuli and did not circumvent the competing response problem. Therefore, other state-of-the-art methods focusing on enhancing the efficiency of SSVEP detection can be used as a basis for the present method to achieve very promising improvements.


Assuntos
Interfaces Cérebro-Computador , Eletroencefalografia , Potenciais Evocados Visuais , Estimulação Luminosa , Humanos , Potenciais Evocados Visuais/fisiologia , Eletroencefalografia/métodos , Masculino , Estimulação Luminosa/métodos , Feminino , Adulto , Adulto Jovem , Algoritmos
20.
Artigo em Inglês | MEDLINE | ID: mdl-38625770

RESUMO

This study embarks on a comprehensive investigation of the effectiveness of repetitive transcranial direct current stimulation (tDCS)-based neuromodulation in augmenting steady-state visual evoked potential (SSVEP) brain-computer interfaces (BCIs), alongside exploring pertinent electroencephalography (EEG) biomarkers for assessing brain states and evaluating tDCS efficacy. EEG data were garnered across three distinct task modes (eyes open, eyes closed, and SSVEP stimulation) and two neuromodulation patterns (sham-tDCS and anodal-tDCS). Brain arousal and brain functional connectivity were measured by extracting features of fractal EEG and information flow gain, respectively. Anodal-tDCS led to diminished offsets and enhanced information flow gains, indicating improvements in both brain arousal and brain information transmission capacity. Additionally, anodal-tDCS markedly enhanced SSVEP-BCIs performance as evidenced by increased amplitudes and accuracies, whereas sham-tDCS exhibited lesser efficacy. This study proffers invaluable insights into the application of neuromodulation methods for bolstering BCI performance, and concurrently authenticates two potent electrophysiological markers for multifaceted characterization of brain states.


Assuntos
Interfaces Cérebro-Computador , Eletroencefalografia , Potenciais Evocados Visuais , Fractais , Estimulação Transcraniana por Corrente Contínua , Humanos , Estimulação Transcraniana por Corrente Contínua/métodos , Potenciais Evocados Visuais/fisiologia , Masculino , Adulto , Feminino , Adulto Jovem , Nível de Alerta/fisiologia , Encéfalo/fisiologia , Voluntários Saudáveis , Algoritmos
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