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1.
Nat Commun ; 12(1): 4816, 2021 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-34376652

RESUMO

Remapping refers to a decorrelation of hippocampal representations of similar spatial environments. While it has been speculated that remapping may contribute to the resolution of episodic memory interference in humans, direct evidence is surprisingly limited. We tested this idea using high-resolution, pattern-based fMRI analyses. Here we show that activity patterns in human CA3/dentate gyrus exhibit an abrupt, temporally-specific decorrelation of highly similar memory representations that is precisely coupled with behavioral expressions of successful learning. The magnitude of this learning-related decorrelation was predicted by the amount of pattern overlap during initial stages of learning, with greater initial overlap leading to stronger decorrelation. Finally, we show that remapped activity patterns carry relatively more information about learned episodic associations compared to competing associations, further validating the learning-related significance of remapping. Collectively, these findings establish a critical link between hippocampal remapping and episodic memory interference and provide insight into why remapping occurs.


Assuntos
Potenciais de Ação/fisiologia , Região CA3 Hipocampal/fisiologia , Giro Denteado/fisiologia , Aprendizagem/fisiologia , Memória/fisiologia , Adolescente , Adulto , Mapeamento Encefálico/métodos , Região CA3 Hipocampal/diagnóstico por imagem , Giro Denteado/diagnóstico por imagem , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Estimulação Luminosa/métodos , Adulto Jovem
2.
Nat Commun ; 12(1): 4714, 2021 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-34354071

RESUMO

Although the contents of working memory can be decoded from visual cortex activity, these representations may play a limited role if they are not robust to distraction. We used model-based fMRI to estimate the impact of distracting visual tasks on working memory representations in several visual field maps in visual and frontoparietal association cortex. Here, we show distraction causes the fidelity of working memory representations to briefly dip when both the memorandum and distractor are jointly encoded by the population activities. Distraction induces small biases in memory errors which can be predicted by biases in neural decoding in early visual cortex, but not other regions. Although distraction briefly disrupts working memory representations, the widespread redundancy with which working memory information is encoded may protect against catastrophic loss. In early visual cortex, the neural representation of information in working memory and behavioral performance are intertwined, solidifying its importance in visual memory.


Assuntos
Memória de Curto Prazo/fisiologia , Córtex Visual/fisiologia , Adulto , Atenção/fisiologia , Mapeamento Encefálico , Feminino , Neuroimagem Funcional , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Modelos Neurológicos , Modelos Psicológicos , Estimulação Luminosa , Análise e Desempenho de Tarefas
3.
Neuroscience ; 472: 138-156, 2021 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-34333061

RESUMO

Establishing consistent relationships between neural activity and behavior is a challenge in human cognitive neuroscience research. We addressed this issue using variable time constraints in an oddball frequency-sweep design for visual discrimination of complex images (face exemplars). Sixteen participants viewed sequences of ascending presentation durations, from 25 to 333 ms (40-3 Hz stimulation rate) while their electroencephalogram (EEG) was recorded. Throughout each sequence, the same unfamiliar face picture was repeated with variable size and luminance changes while different unfamiliar facial identities appeared every 1 s (1 Hz). A neural face individuation response, tagged at 1 Hz and its unique harmonics, emerged over the occipito-temporal cortex at 50 ms stimulus duration (25-100 ms across individuals), with an optimal response reached at 170 ms stimulus duration. In a subsequent experiment, identity changes appeared non-periodically within fixed-frequency sequences while the same participants performed an explicit face individuation task. The behavioral face individuation response also emerged at 50 ms presentation time, and behavioral accuracy correlated with individual participants' neural response amplitude in a weighted middle stimulus duration range (50-125 ms). Moreover, the latency of the neural response peaking between 180 and 200 ms correlated strongly with individuals' behavioral accuracy in this middle duration range, as measured independently. These observations point to the minimal (50 ms) and optimal (170 ms) stimulus durations for human face individuation and provide novel evidence that inter-individual differences in the magnitude and latency of early, high-level neural responses are predictive of behavioral differences in performance at this function.


Assuntos
Reconhecimento Facial , Discriminação Psicológica , Eletroencefalografia , Face , Humanos , Reconhecimento Visual de Modelos , Estimulação Luminosa
4.
Artigo em Inglês | MEDLINE | ID: mdl-34398754

RESUMO

Steady-state visual evoked potential (SSVEP) is widely used in electroencephalogram (EEG) control, medical detection, cognitive neuroscience, and other fields. However, successful application requires improving the detection performance of SSVEP signal frequency characteristics. Most strategies to enhance the signal-to-noise ratio of SSVEP utilize application of a spatial filter. Here, we propose a method for image filtering denoising (IFD) of the SSVEP signal from the perspective of image analysis, as a preprocessing step for signal analysis. Arithmetic mean, geometric mean, Gaussian, and non-local means filtering methods were tested, and the experimental results show that image filtering of SSVEP cannot effectively remove the noise. Thus, we proposed a reverse solution in which the SSVEP noise signal was obtained by image filtering, and then the noise was subtracted from the original signal. Comparison of the recognition accuracy of the SSVEP signal before and after denoising was used to evaluate the denoising performance for stimuli of different duration. After IFD processing, SSVEP exhibited higher recognition accuracy, indicating the effectiveness of this proposed denoising method. Application of this method improves the detection performance of SSVEP signal frequency characteristics, combines image processing and brain signal analysis, and expands the research scope of brain signal analysis for widespread application.


Assuntos
Interfaces Cérebro-Computador , Potenciais Evocados Visuais , Algoritmos , Eletroencefalografia , Humanos , Estimulação Luminosa , Razão Sinal-Ruído
5.
Sensors (Basel) ; 21(16)2021 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-34450713

RESUMO

Action observation (AO)-based brain-computer interface (BCI) is an important technology in stroke rehabilitation training. It has the advantage of simultaneously inducing steady-state motion visual evoked potential (SSMVEP) and activating sensorimotor rhythm. Moreover, SSMVEP could be utilized to perform classification. However, SSMVEP is composed of complex modulation frequencies. Traditional canonical correlation analysis (CCA) suffers from poor recognition performance in identifying those modulation frequencies at short stimulus duration. To address this issue, task-related component analysis (TRCA) was utilized to deal with SSMVEP for the first time. An interesting phenomenon was found: different modulated frequencies in SSMVEP distributed in different task-related components. On this basis, a multi-component TRCA method was proposed. All the significant task-related components were utilized to construct multiple spatial filters to enhance the detection of SSMVEP. Further, a combination of TRCA and CCA was proposed to utilize both advantages. Results showed that the accuracies using the proposed methods were significant higher than that using CCA at all window lengths and significantly higher than that using ensemble-TRCA at short window lengths (≤2 s). Therefore, the proposed methods further validate the induced modulation frequencies and will speed up the application of the AO-based BCI in rehabilitation.


Assuntos
Interfaces Cérebro-Computador , Potenciais Evocados Visuais , Algoritmos , Eletroencefalografia , Humanos , Movimento (Física) , Estimulação Luminosa
6.
Sensors (Basel) ; 21(16)2021 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-34450751

RESUMO

The steady-state visual evoked potential (SSVEP), which is a kind of event-related potential in electroencephalograms (EEGs), has been applied to brain-computer interfaces (BCIs). SSVEP-based BCIs currently perform the best in terms of information transfer rate (ITR) among various BCI implementation methods. Canonical component analysis (CCA) or spectrum estimation, such as the Fourier transform, and their extensions have been used to extract features of SSVEPs. However, these signal extraction methods have a limitation in the available stimulation frequency; thus, the number of commands is limited. In this paper, we propose a complex valued convolutional neural network (CVCNN) to overcome the limitation of SSVEP-based BCIs. The experimental results demonstrate that the proposed method overcomes the limitation of the stimulation frequency, and it outperforms conventional SSVEP feature extraction methods.


Assuntos
Interfaces Cérebro-Computador , Potenciais Evocados Visuais , Algoritmos , Eletroencefalografia , Redes Neurais de Computação , Estimulação Luminosa
7.
FASEB J ; 35(9): e21802, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34383984

RESUMO

Mutations in transcription factors often exhibit pleiotropic effects related to their complex expression patterns and multiple regulatory targets. One such mutation in the zinc finger homeobox 3 (ZFHX3) transcription factor, short circuit (Sci, Zfhx3Sci/+ ), is associated with significant circadian deficits in mice. However, given evidence of its retinal expression, we set out to establish the effects of the mutation on retinal function using molecular, cellular, behavioral and electrophysiological measures. Immunohistochemistry confirms the expression of ZFHX3 in multiple retinal cell types, including GABAergic amacrine cells and retinal ganglion cells including intrinsically photosensitive retinal ganglion cells (ipRGCs). Zfhx3Sci/+ mutants display reduced light responsiveness in locomotor activity and circadian entrainment, relatively normal electroretinogram and optomotor responses but exhibit an unexpected pupillary reflex phenotype with markedly increased sensitivity. Furthermore, multiple electrode array recordings of Zfhx3Sci/+ retina show an increased sensitivity of ipRGC light responses.


Assuntos
Ritmo Circadiano/fisiologia , Proteínas de Homeodomínio/metabolismo , Retina/metabolismo , Células Amácrinas/metabolismo , Animais , Luz , Locomoção/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Estimulação Luminosa/métodos , Células Ganglionares da Retina/metabolismo , Visão Ocular/fisiologia
8.
PLoS One ; 16(8): e0253738, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34432819

RESUMO

BACKGROUND: The recent COVID-19 pandemic has seen an explosion of coronavirus-related information. In many cases, this information was supported by images representing the SARS-CoV-2. AIM: To evaluate how attributes of images representing the SARS-CoV-2 coronavirus that were used in the initial phase of the coronavirus crisis in 2020 influenced the public's perceptions. METHODS: We have carried out an in-depth survey using 46 coronavirus images, asking individuals how beautiful, scientific, realistic, infectious, scary and didactic they appeared to be. RESULTS: We collected 91,908 responses, obtaining 15,315 associations for each category. While the reference image of SARS-CoV-2 used in the media is a three-dimensional, colour, illustration, we found that illustrations of the coronavirus were perceived as beautiful but not very realistic, scientific or didactic. By contrast, black and white coronavirus images are thought to be the opposite. The beauty of coronavirus images was negatively correlated with the perception of scientific realism and didactic value. CONCLUSION: Given these effects and the consequences on the individual's perception, it is important to evaluate the influence that different images of SARS-CoV-2 may have on the population.


Assuntos
Percepção , SARS-CoV-2/fisiologia , Adolescente , Adulto , Idoso , COVID-19/patologia , COVID-19/virologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estimulação Luminosa , SARS-CoV-2/isolamento & purificação , Inquéritos e Questionários , Adulto Jovem
9.
Medicine (Baltimore) ; 100(31): e26685, 2021 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-34397801

RESUMO

RATIONALE: It is estimated that about 6 million people suffer from severe traumatic brain injury (TBI) each year (73 cases per 100,000 people). TBI may affect emotional, sensory-motor, cognitive, and psychological functions with a consequent worsening of both patient and his/her caregiver's quality of life. In recent years, technological innovations allowed the development of new, advanced sensory stimulation systems, such as Neurowave, to further stimulate residual cognitive abilities and, at the same time, evaluate residual cognition. PATIENT CONCERN: An 69-year-old Italian man entered our neurorehabilitation unit with a diagnosis of minimally conscious state following severe TBI. He breathed spontaneously via tracheostomy and was fed via percutaneous gastrostomy. At the neurological examination, the patient showed severe tetraparesis as he showed fluctuating alertness and responsiveness to external stimuli and opened the eyes without stimulation. DIAGNOSIS: Patient was affected by subarachnoid hemorrhage and frontotemporal bilateral hematoma, which were surgically treated with decompressive craniotomy and subsequent cranioplasty about 6 months before. INTERVENTIONS: The patient underwent a neuropsychological and clinical evaluation before (T0) and after a conventional rehabilitation cycle (T1), and after a Neurowave emotional stimulation-supported rehabilitative cycle (T2). OUTCOMES: Following conventional rehabilitation (T1), the patient achieved a partial improvement in behavioral responsiveness; there was also a mild improvement in the caregiver's distress. Conversely, Neurowave emotional stimulation session determined (at T2) a significant improvement of the patient's behavioral responsiveness, cognition, and in the caregiver's distress. The P300 recording in response to the NES showed a significant change of P300 magnitude and latency. DISCUSSION: Our data suggest that emotional-integrated sensory stimulation using adequate visual stimuli represents a beneficial, complementary rehabilitative treatment for patients in minimally conscious state following a severe TBI. This may occur because stimuli with emotional salience can provide a reliable motivational resource to stimulate motor and cognitive recovery following severe TBI.


Assuntos
Estimulação Acústica , Lesões Encefálicas Traumáticas/reabilitação , Emoções , Estado Vegetativo Persistente/reabilitação , Estimulação Luminosa , Idoso , Lesões Encefálicas Traumáticas/complicações , Lesões Encefálicas Traumáticas/fisiopatologia , Cuidadores/psicologia , Cognição , Humanos , Masculino , Estado Vegetativo Persistente/etiologia , Estado Vegetativo Persistente/fisiopatologia , Angústia Psicológica , Recuperação de Função Fisiológica
10.
Sensors (Basel) ; 21(16)2021 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-34450750

RESUMO

This paper presents the implementation of nonlinear canonical correlation analysis (NLCCA) approach to detect steady-state visual evoked potentials (SSVEP) quickly. The need for the fast recognition of proper stimulus to help end an SSVEP task in a BCI system is justified due to the flickering external stimulus exposure that causes users to start to feel fatigued. Measuring the accuracy and exposure time can be carried out through the information transfer rate-ITR, which is defined as a relationship between the precision, the number of stimuli, and the required time to obtain a result. NLCCA performance was evaluated by comparing it with two other approaches-the well-known canonical correlation analysis (CCA) and the least absolute reduction and selection operator (LASSO), both commonly used to solve the SSVEP paradigm. First, the best average ITR value was found from a dataset comprising ten healthy users with an average age of 28, where an exposure time of one second was obtained. In addition, the time sliding window responses were observed immediately after and around 200 ms after the flickering exposure to obtain the phase effects through the coefficient of variation (CV), where NLCCA obtained the lowest value. Finally, in order to obtain statistical significance to demonstrate that all approaches differ, the accuracy and ITR from the time sliding window responses was compared using a statistical analysis of variance per approach to identify differences between them using Tukey's test.


Assuntos
Interfaces Cérebro-Computador , Potenciais Evocados Visuais , Algoritmos , Eletroencefalografia , Análise Multivariada , Estimulação Luminosa
11.
Nat Neurosci ; 24(9): 1280-1291, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34341586

RESUMO

Predictive motion encoding is an important aspect of visually guided behavior that allows animals to estimate the trajectory of moving objects. Motion prediction is understood primarily in the context of translational motion, but the environment contains other types of behaviorally salient motion correlation such as those produced by approaching or receding objects. However, the neural mechanisms that detect and predictively encode these correlations remain unclear. We report here that four of the parallel output pathways in the primate retina encode predictive motion information, and this encoding occurs for several classes of spatiotemporal correlation that are found in natural vision. Such predictive coding can be explained by known nonlinear circuit mechanisms that produce a nearly optimal encoding, with transmitted information approaching the theoretical limit imposed by the stimulus itself. Thus, these neural circuit mechanisms efficiently separate predictive information from nonpredictive information during the encoding process.


Assuntos
Percepção de Movimento/fisiologia , Células Ganglionares da Retina/fisiologia , Vias Visuais/fisiologia , Animais , Macaca , Estimulação Luminosa
12.
Sensors (Basel) ; 21(15)2021 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-34372256

RESUMO

For subjects with amyotrophic lateral sclerosis (ALS), the verbal and nonverbal communication is greatly impaired. Steady state visually evoked potential (SSVEP)-based brain computer interfaces (BCIs) is one of successful alternative augmentative communications to help subjects with ALS communicate with others or devices. For practical applications, the performance of SSVEP-based BCIs is severely reduced by the effects of noises. Therefore, developing robust SSVEP-based BCIs is very important to help subjects communicate with others or devices. In this study, a noise suppression-based feature extraction and deep neural network are proposed to develop a robust SSVEP-based BCI. To suppress the effects of noises, a denoising autoencoder is proposed to extract the denoising features. To obtain an acceptable recognition result for practical applications, the deep neural network is used to find the decision results of SSVEP-based BCIs. The experimental results showed that the proposed approaches can effectively suppress the effects of noises and the performance of SSVEP-based BCIs can be greatly improved. Besides, the deep neural network outperforms other approaches. Therefore, the proposed robust SSVEP-based BCI is very useful for practical applications.


Assuntos
Interfaces Cérebro-Computador , Eletroencefalografia , Potenciais Evocados , Potenciais Evocados Visuais , Humanos , Estimulação Luminosa
13.
Nat Commun ; 12(1): 4839, 2021 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-34376673

RESUMO

The ability to maintain a sequence of items in memory is a fundamental cognitive function. In the rodent hippocampus, the representation of sequentially organized spatial locations is reflected by the phase of action potentials relative to the theta oscillation (phase precession). We investigated whether the timing of neuronal activity relative to the theta brain oscillation also reflects sequence order in the medial temporal lobe of humans. We used a task in which human participants learned a fixed sequence of pictures and recorded single neuron and local field potential activity with implanted electrodes. We report that spikes for three consecutive items in the sequence (the preferred stimulus for each cell, as well as the stimuli immediately preceding and following it) were phase-locked at distinct phases of the theta oscillation. Consistent with phase precession, spikes were fired at progressively earlier phases as the sequence advanced. These findings generalize previous findings in the rodent hippocampus to the human temporal lobe and suggest that encoding stimulus information at distinct oscillatory phases may play a role in maintaining sequential order in memory.


Assuntos
Potenciais de Ação/fisiologia , Epilepsia/fisiopatologia , Aprendizagem/fisiologia , Neurônios/fisiologia , Ritmo Teta/fisiologia , Adolescente , Adulto , Epilepsia/diagnóstico , Feminino , Hipocampo/citologia , Hipocampo/fisiologia , Humanos , Masculino , Modelos Neurológicos , Neurônios/citologia , Estimulação Luminosa/métodos , Lobo Temporal/citologia , Lobo Temporal/fisiologia , Adulto Jovem
14.
Epilepsy Behav ; 122: 108189, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34252828

RESUMO

Sensory stimuli can induce seizures in patients with epilepsy and predisposed subjects. Visual stimuli are the most common triggers, provoking seizures through an abnormal response to light or pattern. Sensitive patients may intentionally provoke their seizures through visual stimuli. Self-induction methods are widely described in photo-sensitive patients, while there are only a few reports of those who are pattern-sensitive. We analyzed 73 images of environmental visual triggers collected from 14 pattern-sensitive patients with self-induced seizures. The images were categorized according to their topics: 29 Objects (43%); 19 Patterns (28%); 15 External scenes (22%); 4 TV or computer screens (6%). Six photos were of poor quality and were excluded from analysis. Images were analyzed by an algorithm that calculated the degree to which the Fourier amplitude spectrum differed from that in images from nature. The algorithm has been shown to predict discomfort in healthy observers. The algorithm identified thirty-one images (46%) as "uncomfortable". There were significant differences between groups of images (ANOVA p = .0036; Chi2 p < .0279), with higher values of difference from nature in the images classified as "Objects" (mean 6,81E+11; SD 6,72E+11; n.17, 59%) and "Pattern" (mean 9,05E+11; SD 6,86E+11; n.14, 74%). During the semi-structured face-to-face interviews, all patients described the visual triggers as 'uncomfortable'; the appearance of enjoyable visual epileptic symptoms (especially multi-colored hallucinations) transformed uncomfortable images into pleasant stimuli. Patients considered self-induction as the simplest and most effective way to overcome stressful situations, suggesting that self-inducing pattern-sensitive patients often use uncomfortable visual stimuli to trigger their seizures. Among the reasons for the self-inducing behavior, the accidental discovery of pleasurable epileptic symptoms related to these "uncomfortable" visual stimuli should be considered.


Assuntos
Epilepsia , Epilepsia/complicações , Humanos , Estimulação Luminosa , Convulsões
15.
J Neural Eng ; 18(4)2021 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-34229315

RESUMO

Objective.Optogenetics has emerged as a promising technique for neural prosthetics, especially retinal prostheses, with unprecedented spatiotemporal resolution. Newly discovered opsins with high light sensitivity and fast temporal kinetics can provide sufficient temporal resolution at safe light powers and overcome the limitations of presently used opsins. It is also important to formulate accurate mathematical models for optogenetic retinal prostheses, which can facilitate optimization of photostimulation factors to improve the performance.Approach.A detailed theoretical analysis of optogenetic excitation of model retinal ganglion neurons (RGNs) and hippocampal neurons expressed with already tested opsins for retinal prostheses, namely, ChR2, ReaChR and ChrimsonR, and also with recently discovered potent opsins CsChrimson, bReaChES and ChRmine, was carried out.Main results.Under continuous illumination, ChRmine-expressing RGNs begin to respond at very low irradiances ∼10-4mW mm-2, and evoke firing upto ∼280 Hz, highest among other opsin-expressing RGNs, at 10-2mW mm-2. Under pulsed illumination at randomized photon fluxes, ChRmine-expressing RGNs respond to changes in pulse to pulse irradiances upto four logs, although very bright pulses >1014photons mm-2s-1block firing in these neurons. The minimum irradiance threshold for ChRmine-expressing RGNs is lower by two orders of magnitude, whereas, the first spike latency in ChRmine-expressing RGNs is shorter by an order of magnitude, alongwith stable latency of subsequest spikes compared to others. Further, a good set of photostimulation parameters were determined to achieve high-frequency control with single spike resolution at minimal power. Although ChrimsonR enables spiking upto 100 Hz in RGNs, it requires very high irradiances. ChRmine provides control at light powers that are two orders of magnitude smaller than that required with experimentally studied opsins, while maintaining single spike temporal resolution upto 40 Hz.Significance.The present study highlights the importance of ChRmine as a potential opsin for optogenetic retinal prostheses.


Assuntos
Optogenética , Próteses Visuais , Opsinas/genética , Estimulação Luminosa , Células Ganglionares da Retina
16.
J Neural Eng ; 18(4)2021 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-34237711

RESUMO

Objective.Asynchronous brain-computer interfaces (BCIs) show significant advantages in many practical application scenarios. Compared with the rapid development of synchronous BCIs technology, the progress of asynchronous BCI research, in terms of containing multiple targets and training-free detection, is still relatively slow. In order to improve the practicability of the BCI, a spatio-temporal equalization multi-window algorithm (STE-MW) was proposed for asynchronous detection of steady-state visual evoked potential (SSVEP) without the need for acquiring calibration data.Approach.The algorithm used SIE strategy to intercept EEG signals of different lengths through multiple stacked time windows and statistical decisions-making based on Bayesian risk decision-making. Different from the traditional asynchronous algorithms based on the 'non-control state detection' methods, this algorithm was based on the 'statistical inspection-rejection decision' mode and did not require a separate classification of non-control states, so it can be effectively applied to detections for large-scale candidates.Main results.Online experimental results involving 14 healthy subjects showed that, in the continuously input experiments of 40 targets, the algorithm achieved the average recognition accuracy of97.2±2.6%and the average information transfer rate (ITR) of106.3±32.0 bitsmin-1. At the same time, the average false alarm rate in the 240 s resting state test was0.607±0.602 min-1. In the free spelling experiments involving patients with severe amyotrophic lateral sclerosis, the subjects achieved an accuracy of 92.7% and an average ITR of 43.65 bits min-1in two free spelling experiments.Significance.This algorithm can achieve high-performance, high-precision, and asynchronous detection of SSVEP signals with low algorithm complexity and false alarm rate under multi-targets and training-free conditions, which is helpful for the development of asynchronous BCI systems.


Assuntos
Interfaces Cérebro-Computador , Potenciais Evocados Visuais , Algoritmos , Teorema de Bayes , Eletroencefalografia , Humanos , Estimulação Luminosa
17.
Neuroscience ; 472: 1-10, 2021 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-34311017

RESUMO

Lifelong auditory and visual sensory deprivation have been demonstrated to alter both perceptual acuity and the neural processing of remaining senses. Recently, it was demonstrated that individuals with anosmia, i.e. complete olfactory sensory deprivation, displayed enhanced multisensory integration performance. Whether this ability is due to a reorganization of olfactory processing regions to focus on cross-modal multisensory information or whether it is due to enhanced processing within multisensory integration regions is not known. To dissociate these two outcomes, we investigated the neural processing of dynamic audio-visual stimuli in individuals with congenital anosmia and matched controls (both groups, n = 33) using functional magnetic resonance imaging. Specifically, we assessed whether the previously demonstrated multisensory enhancement is related to cross-modal processing of multisensory stimuli in olfactory associated regions, the piriform and olfactory orbitofrontal cortices, or enhanced multisensory processing in established multisensory integration regions, the superior temporal and intraparietal sulci. No significant group differences were found in the a priori hypothesized regions using region of interest analyses. However, exploratory whole-brain analysis suggested higher activation related to multisensory integration within the posterior superior temporal sulcus, in close proximity to the multisensory region of interest, in individuals with congenital anosmia. No group differences were demonstrated in olfactory associated regions. Although results were outside our hypothesized regions, combined, they tentatively suggest that enhanced processing of audio-visual stimuli in individuals with congenital anosmia may be mediated by multisensory, and not primary sensory, cerebral regions.


Assuntos
Privação Sensorial , Percepção Visual , Estimulação Acústica , Percepção Auditiva , Mapeamento Encefálico , Humanos , Imageamento por Ressonância Magnética , Estimulação Luminosa , Olfato
18.
Neuropsychologia ; 160: 107967, 2021 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-34303717

RESUMO

Human faces and bodies are environmental stimuli of special importance that the brain processes with selective attention and a highly specialized visual system. It has been shown recently that the human brain also has dedicated networks for perception of pluralities of human bodies in synchronous motion or in face-to-face interaction. Here we show that a plurality of human bodies that are merely in close spatial proximity are automatically integrated into a coherent perceptual unit. We used an EEG frequency tagging technique allowing the dissociation of the brain activity related to the component parts of an image from the activity related to the global image configuration. We presented to participants images of two silhouettes flickering at different frequencies (5.88 vs. 7.14 Hz). Clear response at these stimulation frequencies reflected response to each part of the dyad. An emerging intermodulation component (7.14 + 5.88 = 13.02 Hz), a nonlinear response regarded as an objective signature of holistic representation, was significantly enhanced in the (typical) upright relative to an (altered) inverted position. Moreover, the inversion effect was significant for the intermodulation component but not for the stimulation frequencies, suggesting a trade-off between the processing of the global dyad configuration and that of the structural properties of the dyad elements. Our results show that when presented with two humans merely in close proximity the perceptual visual system will bind them. Hence the perception of the human form might be of a fundamentally different nature when it is part of a plurality.


Assuntos
Encéfalo , Eletroencefalografia , Atenção , Encéfalo/diagnóstico por imagem , Fenômenos Eletrofisiológicos , Humanos , Reconhecimento Visual de Modelos , Percepção , Estimulação Luminosa , Percepção Visual
19.
Exp Brain Res ; 239(9): 2767-2779, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34241642

RESUMO

Analysing a visual scene requires the brain to briefly keep in memory potentially relevant items of that scene and then direct attention to their locations for detailed processing. To reveal the neuronal basis of the underlying working memory and top-down attention processes, we trained macaques to match two patterns presented with a delay between them. As the above processes are likely to require communication between brain regions, and the parietal cortex is known to be involved in spatial attention, we simultaneously recorded neuronal activities from the interconnected parietal and middle temporal areas. We found that mnemonic information about features of the first pattern was retained in coherent oscillating activity between the two areas in high-frequency bands, followed by coherent activity in lower frequency bands mediating top-down attention on the relevant spatial location. Oscillations maintaining featural information also modulated activity of the cells of the parietal cortex that mediate attention. This could potentially enable transfer of information to organize top-down signals necessary for selective attention. Our results provide evidence in support of a two-stage model of visual attention where the first stage involves creating a saliency map representing a visual scene and at the second stage attentional feedback is provided to cortical areas involved in detailed analysis of the attended parts of a scene.


Assuntos
Neurônios , Lobo Parietal , Animais , Encéfalo , Mapeamento Encefálico , Macaca , Imageamento por Ressonância Magnética , Memória de Curto Prazo , Estimulação Luminosa , Percepção Visual
20.
Cortex ; 142: 138-153, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34265736

RESUMO

The ability to differentiate between repeated and novel events represents a fundamental property of the visual system. Neural responses are typically reduced upon stimulus repetition, a phenomenon called Repetition Suppression (RS). On the contrary, following a novel visual stimulus, the neural response is generally enhanced, a phenomenon referred to as Novelty Detection (ND). Here, we aimed to investigate the impact of early deafness on the oscillatory signatures of RS and ND brain responses. To this aim, electrophysiological data were acquired in early deaf and hearing control individuals during processing of repeated and novel visual events unattended by participants. By studying evoked and induced oscillatory brain activities, as well as inter-trial phase coherence, we linked response modulations to feedback and/or feedforward processes. Results revealed selective experience-dependent changes on both RS and ND mechanisms. Compared to hearing controls, early deaf individuals displayed: (i) greater attenuation of the response following stimulus repetition, selectively in the induced theta-band (4-7 Hz); (ii) reduced desynchronization following the onset of novel visual stimuli, in the induced alpha and beta bands (8-12 and 13-25 Hz); (iii) comparable modulation of evoked responses and inter-trial phase coherence. The selectivity of the effects in the induced responses parallels findings observed in the auditory cortex of deaf animal models following intracochlear electric stimulation. The present results support the idea that early deafness alters induced oscillatory activity and the functional tuning of basic visual processing.


Assuntos
Córtex Auditivo , Surdez , Animais , Encéfalo , Eletroencefalografia , Humanos , Estimulação Luminosa , Percepção Visual
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