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1.
Neuroimage ; 228: 117571, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33412281

RESUMO

Brain oscillations, e.g. measured by electro- or magnetoencephalography (EEG/MEG), are causally linked to brain functions that are fundamental for perception, cognition and learning. Recent advances in neurotechnology provide means to non-invasively target these oscillations using frequency-tuned amplitude-modulated transcranial alternating current stimulation (AM-tACS). However, online adaptation of stimulation parameters to ongoing brain oscillations remains an unsolved problem due to stimulation artifacts that impede such adaptation, particularly at the target frequency. Here, we introduce a real-time compatible artifact rejection algorithm (Stimulation Artifact Source Separation, SASS) that overcomes this limitation. SASS is a spatial filter (linear projection) removing EEG signal components that are maximally different in the presence versus absence of stimulation. This enables the reliable removal of stimulation-specific signal components, while leaving physiological signal components unaffected. For validation of SASS, we evoked brain activity with known phase and amplitude using 10 Hz visual flickers across 7 healthy human volunteers. 64-channel EEG was recorded during and in absence of 10 Hz AM-tACS targeting the visual cortex. Phase differences between AM-tACS and the visual stimuli were randomized, so that steady-state visually evoked potentials (SSVEPs) were phase-locked to the visual stimuli but not to the AM-tACS signal. For validation, distributions of single-trial amplitude and phase of EEG signals recorded during and in absence of AM-tACS were compared for each participant. When no artifact rejection method was applied, AM-tACS stimulation artifacts impeded assessment of single-trial SSVEP amplitude and phase. Using SASS, amplitude and phase of single trials recorded during and in absence of AM-tACS were comparable. These results indicate that SASS can be used to establish adaptive (closed-loop) AM-tACS, a potentially powerful tool to target various brain functions, and to investigate how AM-tACS interacts with electric brain oscillations.


Assuntos
Algoritmos , Artefatos , Encéfalo/fisiologia , Processamento de Sinais Assistido por Computador , Estimulação Transcraniana por Corrente Contínua/métodos , Adulto , Potenciais Evocados Visuais/fisiologia , Feminino , Humanos , Masculino , Adulto Jovem
2.
Neurology ; 96(4): e482-e490, 2021 01 26.
Artigo em Inglês | MEDLINE | ID: mdl-33328323

RESUMO

OBJECTIVE: To assess the added value of the optic nerve region (by using visual evoked potentials [VEPs]) to the current diagnostic criteria. METHODS: From the Barcelona clinically isolated syndrome (CIS) cohort, patients with complete information to assess dissemination in space (DIS), the optic nerve region, and dissemination in time at baseline (n = 388) were selected. Modified DIS (modDIS) criteria were constructed by adding the optic nerve to the current DIS regions. The DIS and modDIS criteria were evaluated with univariable Cox proportional hazard regression analyses with the time to the second attack as the outcome. A subset of these patients who had at least 10 years of follow-up or a second attack occurring within 10 years (n = 151) were selected to assess the diagnostic performance. The analyses were also performed according to CIS topography (optic neuritis vs non-optic neuritis). RESULTS: The addition of the optic nerve as a fifth region improved the diagnostic performance by slightly increasing the accuracy (2017 DIS 75.5%, modDIS 78.1%) and the sensitivity (2017 DIS 79.2%, modDIS 82.3%) without lowering the specificity (2017 DIS 52.4%, modDIS 52.4%). When the analysis was conducted according to CIS topography, the modDIS criteria performed similarly in both optic neuritis and non-optic neuritis CIS. CONCLUSION: The addition of the optic nerve, assessed by VEP, as a fifth region in the current DIS criteria slightly improves the diagnostic performance because it increases sensitivity without losing specificity.


Assuntos
Potenciais Evocados Visuais/fisiologia , Esclerose Múltipla/diagnóstico por imagem , Esclerose Múltipla/fisiopatologia , Nervo Óptico/diagnóstico por imagem , Nervo Óptico/fisiopatologia , Adulto , Estudos de Coortes , Feminino , Seguimentos , Humanos , Masculino , Exame Neurológico/métodos , Neurite Óptica/diagnóstico por imagem , Neurite Óptica/fisiopatologia , Estudos Retrospectivos , Adulto Jovem
3.
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
4.
Proc Natl Acad Sci U S A ; 117(27): 16055-16064, 2020 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-32571942

RESUMO

Visual awareness is thought to result from integration of low- and high-level processing; instances of integration failure provide a crucial window into the cognitive and neural bases of awareness. We present neurophysiological evidence of complex cognitive processing in the absence of awareness, raising questions about the conditions necessary for visual awareness. We describe an individual with a neurodegenerative disease who exhibits impaired visual awareness for the digits 2 to 9, and stimuli presented in close proximity to these digits, due to perceptual distortion. We identified robust event-related potential responses indicating 1) face detection with the N170 component and 2) task-dependent target-word detection with the P3b component, despite no awareness of the presence of faces or target words. These data force us to reconsider the relationship between neural processing and visual awareness; even stimuli processed by a workspace-like cognitive system can remain inaccessible to awareness. We discuss how this finding challenges and constrains theories of visual awareness.


Assuntos
Cognição/fisiologia , Potenciais Evocados/fisiologia , Transtornos da Visão/metabolismo , Percepção Visual/fisiologia , Conscientização/fisiologia , Encéfalo/fisiologia , Eletroencefalografia , Potenciais Evocados Visuais/fisiologia , Face , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Doenças Neurodegenerativas , Estimulação Luminosa , Córtex Visual/fisiologia
5.
J Vis ; 20(6): 15, 2020 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-32574359

RESUMO

When a visual stimulus flickers periodically and rhythmically, the perceived duration tends to exceed its physical duration in the peri-second range. Although flicker-induced time dilation is a robust time illusion, its underlying neural mechanisms remain inconclusive. The neural entrainment account proposes that neural entrainment of the exogenous visual stimulus, marked by steady-state visual evoked potentials (SSVEPs) over the visual cortex, is the cause of time dilation. By contrast, the saliency account argues that the conscious perception of flicker changes is indispensable. In the current study, we examined these two accounts separately. The first two experiments manipulated the level of saliency around the critical fusion threshold (CFF) in a duration discrimination task to probe the effect of change saliency. The amount of dilation correlated with the level of change saliency. The next two experiments investigated whether neural entrainment alone could also induce perceived dilation. To preclude change saliency, we utilized a combination of two high-frequency flickers above the CFF, whereas their beat frequency still theoretically aroused neural entrainment at a low frequency. Results revealed a moderate time dilation induced by combinative high-frequency flickers. Although behavioral results suggested neural entrainment engagement, electroencephalography showed neither larger power nor inter-trial coherence (ITC) at the beat. In summary, change saliency was the most critical factor determining the perception and strength of time dilation, whereas neural entrainment had a moderate influence. These results highlight the influence of higher-level visual processing on time perception.


Assuntos
Fusão Flicker/fisiologia , Percepção do Tempo/fisiologia , Percepção Visual/fisiologia , Adulto , Estado de Consciência , Dilatação , Eletroencefalografia/métodos , Potenciais Evocados Visuais/fisiologia , Feminino , Humanos , Masculino , Estimulação Luminosa/métodos , Adulto Jovem
6.
Doc Ophthalmol ; 141(3): 259-267, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32506270

RESUMO

PURPOSE: Pre-term infants are at risk of abnormal visual development that can range from subtle to severe. The aim of this study was to compare flash VEPs in clinically stable pre-term and full-term infants at 6 months of age. METHODS: Twenty-five pre-term and 25 full-term infants underwent flash VEP testing at the age of 6 months. Monocular VEPs were recorded using flash goggles on a RETIscan system under normal sleeping conditions. Amplitude and peak time responses of the P2 component in the two eyes were averaged and compared between the two groups. Multiple regression analyses were performed to assess the relationship of the P2 responses with birth weight (BW) and gestational age (GA). RESULTS: At 6 months corrected age, pre-term infants had significantly delayed P2 peak times than full-term infants (mean difference: 10.88 [95% CI 4.00-17.76] ms, p = 0.005). Pre-term infants also showed significantly reduced P2 amplitudes as compared to full-term infants (mean difference: 2.36 [0.83-3.89] µV, p = 0.003). Although the regression model with GA and BW as fixed factors explained 20% of the variance in the P2 peak time (F2,47 = 5.98, p = .0045), only GA showed a significant negative relationship (ß = -2.66, p = .003). Neither GA (ß = 0.21, p = .28) nor BW (ß = 0.001, p = .32) showed any relationship with P2 amplitude. CONCLUSIONS: Our results demonstrate that, compared with full-term infants, clinically stable pre-term infants exhibit abnormal flash VEPs, with a delay in P2 peak time and a reduction in P2 amplitude. These findings support a potential dysfunction of the visual pathway in clinically stable pre-term infants as compared to full-term infants.


Assuntos
Potenciais Evocados Visuais/fisiologia , Recém-Nascido Prematuro/fisiologia , Nascimento a Termo/fisiologia , Peso ao Nascer , Eletrorretinografia , Feminino , Idade Gestacional , Humanos , Lactente , Recém-Nascido , Masculino , Estimulação Luminosa/métodos , Tempo de Reação/fisiologia , Vias Visuais/fisiologia
7.
Science ; 368(6495): 1108-1113, 2020 06 05.
Artigo em Inglês | MEDLINE | ID: mdl-32499439

RESUMO

Enabling near-infrared light sensitivity in a blind human retina may supplement or restore visual function in patients with regional retinal degeneration. We induced near-infrared light sensitivity using gold nanorods bound to temperature-sensitive engineered transient receptor potential (TRP) channels. We expressed mammalian or snake TRP channels in light-insensitive retinal cones in a mouse model of retinal degeneration. Near-infrared stimulation increased activity in cones, ganglion cell layer neurons, and cortical neurons, and enabled mice to perform a learned light-driven behavior. We tuned responses to different wavelengths, by using nanorods of different lengths, and to different radiant powers, by using engineered channels with different temperature thresholds. We targeted TRP channels to human retinas, which allowed the postmortem activation of different cell types by near-infrared light.


Assuntos
Cegueira/terapia , Ouro , Raios Infravermelhos , Nanotubos , Degeneração Retiniana/terapia , Limiar Sensorial/efeitos da radiação , Canais de Cátion TRPC/fisiologia , Visão Ocular/efeitos da radiação , Animais , Cegueira/fisiopatologia , Modelos Animais de Doenças , Potenciais Evocados Visuais/fisiologia , Potenciais Evocados Visuais/efeitos da radiação , Engenharia Genética , Células HEK293 , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Estimulação Luminosa , Ratos , Células Fotorreceptoras Retinianas Cones/fisiologia , Células Fotorreceptoras Retinianas Cones/efeitos da radiação , Degeneração Retiniana/fisiopatologia , Células Ganglionares da Retina/fisiologia , Células Ganglionares da Retina/efeitos da radiação , Limiar Sensorial/fisiologia , Serpentes , Canais de Cátion TRPC/genética , Canais de Cátion TRPV/genética , Canais de Cátion TRPV/fisiologia , Visão Ocular/fisiologia , Córtex Visual/fisiopatologia , Córtex Visual/efeitos da radiação
8.
J Vis ; 20(6): 3, 2020 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-32503040

RESUMO

Early visual processing is surprisingly flexible even in the adult brain. This flexibility involves both long-term structural plasticity and online adaptations conveyed by top-down feedback. Although this view is supported by rich evidence from both human behavioral studies and invasive electrophysiology in nonhuman models, it has proven difficult to close the gap between species. In particular, it remains debated whether noninvasive measures of neural activity can capture top-down modulations of the earliest stages of processing in the human visual cortex. We previously reported modulations of retinotopic C1, the earliest component of the human visual evoked potential. However, these effects were selectively observed in the upper visual field (UVF). Here we test whether this asymmetry is linked to an interaction between differences in spatial resolution across the visual field and the specific stimuli used in previous studies. We measured visual evoked potentials in response to task-irrelevant, high-contrast textures of different densities in a comparatively large sample of healthy volunteers (N = 31) using high-density electroencephalogram. Our results show differential response profiles for upper and lower hemifields, with UVF responses saturating at higher stimulus densities. In contrast, lower visual field responses did not increase, and even showed a tendency toward a decrease at the highest density tested. We propose that these findings reflect feature- and task-specific pooling of signals from retinotopic regions with different sensitivity profiles. Such complex interactions between anatomic and functional asymmetries need to be considered to resolve whether human early visual cortex activity is modulated by top-down factors.


Assuntos
Potenciais Evocados Visuais/fisiologia , Córtex Visual/fisiologia , Campos Visuais/fisiologia , Percepção Visual/fisiologia , Adolescente , Adulto , Atenção/fisiologia , Encéfalo/fisiologia , Mapeamento Encefálico/métodos , Eletroencefalografia/métodos , Feminino , Humanos , Masculino , Adulto Jovem
9.
Doc Ophthalmol ; 141(3): 237-251, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32405730

RESUMO

PURPOSE: There are several stimulus paradigms used in objective visual acuity assessment based on steady-state visual evoked potentials (SSVEPs). The aim of this study was to explore the difference and performance of common used six stimulus paradigms (reverse vertical sinusoidal gratings, reverse horizontal sinusoidal gratings, reverse vertical square-wave gratings, brief-onset vertical sinusoidal gratings, reversal checkerboards and oscillating expansion-contraction concentric-rings) of SSVEP acuity assessment. METHODS: We tested subjective visual acuity both by tumbling E and Freiburg Visual Acuity and Contrast Test (FrACT) in 11 subjects. SSVEPs were induced by 11 spatial frequencies for each paradigm, and then a threshold determination criterion was used to define the objective SSVEP visual acuity. RESULTS: After SSVEP signal analysis, we found there was difference in SSVEP response of harmonic components and no difference in sensitive electrode placement for the six paradigms. We selected six electrodes (PO3, POz, PO4, O1, Oz and O2) as the sensitive electrodes to use in data processing for each paradigm. The results showed that except for brief-onset vertical sinusoidal gratings, the correlation and agreement between objective SSVEP and subjective FrACT acuity were all quite good, demonstrating good performance in acuity detection for the rest five paradigms. CONCLUSION: Except for brief-onset vertical sinusoidal gratings, all the five stimulus paradigms of reverse vertical sinusoidal gratings, reverse horizontal sinusoidal gratings, reverse vertical square-wave gratings, reversal checkerboards and oscillating expansion-contraction concentric-rings performed quite well in objective SSVEP visual acuity assessment.


Assuntos
Potenciais Evocados Visuais/fisiologia , Estimulação Luminosa/métodos , Acuidade Visual/fisiologia , Adulto , Eletroencefalografia/métodos , Eletrorretinografia , Feminino , Humanos , Masculino , Retina/fisiologia , Testes Visuais/métodos , Adulto Jovem
10.
Int J Neural Syst ; 30(5): 2050020, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32380925

RESUMO

Canonical correlation analysis (CCA) is an effective spatial filtering algorithm widely used in steady-state visual evoked potential (SSVEP)-based brain-computer interfaces (BCIs). In existing CCA methods, training data are used for constructing templates of stimulus targets and the spatial filters are created between the template signals and a single-trial testing signal. The fact that spatial filters rely on testing data, however, results in low classification performance of CCA compared to other state-of-the-art algorithms such as task-related component analysis (TRCA). In this study, we proposed a novel CCA method in which spatial filters are estimated using training data only. This is achieved by using observed EEG training data and their SSVEP components as the two inputs of CCA and the objective function is optimized by averaging multiple training trials. In this case, we proved in theory that the two spatial filters estimated by the CCA are equivalent, and that the CCA and TRCA are also equivalent under certain hypotheses. A benchmark SSVEP data set from 35 subjects was used to compare the performance of the two algorithms according to different lengths of data, numbers of channels and numbers of training trials. In addition, the CCA was also compared with power spectral density analysis (PSDA). The experimental results suggest that the CCA is equivalent to TRCA if the signal-to-noise ratio of training data is high enough; otherwise, the CCA outperforms TRCA in terms of classification accuracy. The CCA is much faster than PSDA in detecting time of targets. The robustness of the training data-driven CCA to noise gives it greater potential in practical applications.


Assuntos
Algoritmos , Interfaces Cérebro-Computador , Córtex Cerebral/fisiologia , Eletroencefalografia , Potenciais Evocados Visuais/fisiologia , Reconhecimento Automatizado de Padrão , Adulto , Humanos
11.
J Neurosci ; 40(26): 5019-5032, 2020 06 24.
Artigo em Inglês | MEDLINE | ID: mdl-32350041

RESUMO

Even though the lateral geniculate nucleus of the thalamus (LGN) is associated with form vision, that is not its sole role. Only the dorsal portion of LGN (dLGN) projects to V1. The ventral division (vLGN) connects subcortically, sending inhibitory projections to sensorimotor structures, including the superior colliculus (SC) and regions associated with certain behavioral states, such as fear (Monavarfeshani et al., 2017; Salay et al., 2018). We combined computational, physiological, and anatomical approaches to explore visual processing in vLGN of mice of both sexes, making comparisons to dLGN and SC for perspective. Compatible with past, qualitative descriptions, the receptive fields we quantified in vLGN were larger than those in dLGN, and most cells preferred bright versus dark stimuli (Harrington, 1997). Dendritic arbors spanned the length and/or width of vLGN and were often asymmetric, positioned to collect input from large but discrete territories. By contrast, arbors in dLGN are compact (Krahe et al., 2011). Consistent with spatially coarse receptive fields in vLGN, visually evoked changes in spike timing were less precise than for dLGN and SC. Notably, however, the membrane currents and spikes of some cells in vLGN displayed gamma oscillations whose phase and strength varied with stimulus pattern, as for SC (Stitt et al., 2013). Thus, vLGN can engage its targets using oscillation-based and conventional rate codes. Finally, dark shadows activate SC and drive escape responses, whereas vLGN prefers bright stimuli. Thus, one function of long-range inhibitory projections from vLGN might be to enable movement by releasing motor targets, such as SC, from suppression.SIGNIFICANCE STATEMENT Only the dorsal lateral geniculate nucleus (dLGN) connects to cortex to serve form vision; the ventral division (vLGN) projects subcortically to sensorimotor nuclei, including the superior colliculus (SC), via long-range inhibitory connections. Here, we asked how vLGN processes visual information, making comparisons with dLGN and SC for perspective. Cells in vLGN versus dLGN had wider dendritic arbors, larger receptive fields, and fired with lower temporal precision, consistent with a modulatory role. Like SC, but not dLGN, visual stimuli entrained oscillations in vLGN, perhaps reflecting shared strategies for visuomotor processing. Finally, most neurons in vLGN preferred bright shapes, whereas dark stimuli activate SC and drive escape behaviors, suggesting that vLGN enables rapid movement by releasing target motor structures from inhibition.


Assuntos
Corpos Geniculados/fisiologia , Percepção Visual/fisiologia , Animais , Potenciais Evocados Visuais/fisiologia , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Vias Visuais/fisiologia
12.
World Neurosurg ; 139: 395-400, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32376380

RESUMO

BACKGROUND: Complete aneurysm obliteration is the goal of aneurysm treatment. In selected cases, a neck remnant may be left to preserve a critical branch. Literature on ophthalmic artery sacrifice in the treatment of cerebral aneurysms and subsequent risk of vision loss is limited. CASE DESCRIPTION: Herein, we describe 2 cases where the ophthalmic artery originated from the aneurysm dome, resulting in a situation where we either incompletely obliterate the aneurysm or sacrifice the ophthalmic artery in order to completely clip the lesion, risking visual function. CONCLUSIONS: We report for the first time the use of visual evoked potential monitoring and intraoperative awakening to test visual function following intentional ophthalmic artery sacrifice to demonstrate gross vision preservation.


Assuntos
Potenciais Evocados Visuais/fisiologia , Aneurisma Intracraniano/cirurgia , Monitorização Neurofisiológica Intraoperatória/métodos , Procedimentos Neurocirúrgicos/métodos , Artéria Oftálmica/cirurgia , Feminino , Humanos , Pessoa de Meia-Idade , Instrumentos Cirúrgicos
13.
Invest Ophthalmol Vis Sci ; 61(5): 37, 2020 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-32437548

RESUMO

Purpose: To determine the influence of RIBEYE deletion and the resulting absence of synaptic ribbons on retinal light signaling by electroretinography. Methods: Full-field flash electroretinograms (ERGs) were recorded in RIBEYE knock-out (KO) and wild-type (WT) littermate mice under photopic and scotopic conditions, with oscillatory potentials (OPs) extracted by digital filtering. Flicker ERGs and ERGs following intravitreal injection of pharmacological agents were also obtained under scotopic conditions. Results: The a-wave amplitudes were unchanged between RIBEYE KO and WT mice; however, the b-wave amplitudes were reduced in KOs under scotopic, but not photopic, conditions. Increasing stimulation frequency led to a greater reduction in RIBEYE KO b-wave amplitudes compared with WTs. Furthermore, we observed prominent, supernormal OPs in RIBEYE KO mice in comparison with WT mice. Following intravitreal injections with l-2 amino-4-phosphonobutyric acid and cis-2,3 piperidine dicarboxylic acid to block ON and OFF responses at photoreceptor synapses, OPs were completely abolished in both mice types, indicating a synaptic origin of the prominent OPs in the KOs. Conversely, tetrodotoxin treatment to block voltage-gated Na+ channels/spiking neurons did not differentially affect OPs in WT and KO mice. Conclusions: The decreased scotopic b-wave and decreased responses to increased stimulation frequencies are consistent with signaling malfunctions at photoreceptor and inner retinal ribbon synapses. Because phototransduction in the photoreceptor outer segments is unaffected in the KOs, their supernormal OPs presumably result from a dysfunction in retinal synapses. The relatively mild ERG phenotype in KO mice, particularly in the photopic range, is probably caused by compensatory mechanisms in retinal signaling pathways.


Assuntos
Oxirredutases do Álcool/fisiologia , Proteínas Correpressoras/fisiologia , Eletrorretinografia , Células Fotorreceptoras Retinianas Cones/fisiologia , Sinapses/fisiologia , Transmissão Sináptica , Visão Ocular/fisiologia , Aminobutiratos/farmacologia , Animais , Potenciais Evocados Visuais/fisiologia , Agonistas de Aminoácidos Excitatórios/farmacologia , Feminino , Deleção de Genes , Injeções Intravítreas , Masculino , Camundongos , Camundongos Knockout , Microscopia Eletrônica de Transmissão , Visão Noturna/fisiologia , Estimulação Luminosa , Piperidinas/farmacologia , Células Fotorreceptoras Retinianas Cones/ultraestrutura , Bloqueadores dos Canais de Sódio/farmacologia , Sinapses/efeitos dos fármacos , Sinapses/ultraestrutura , Tetrodotoxina/farmacologia
14.
PLoS One ; 15(5): e0232928, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32433672

RESUMO

The information available through our senses is noisy, incomplete, and ambiguous. Our perceptual systems have to resolve this ambiguity to construct stable and reliable percepts. Previous EEG studies found large amplitude differences in two event-related potential (ERP) components 200 and 400 ms after stimulus onset when comparing ambiguous with disambiguated visual information ("ERP Ambiguity Effects"). These effects so far generalized across classical ambiguous figures from different visual categories at lower (geometry, motion) and intermediate (Gestalt perception) levels. The present study aimed to examine whether these ERP Effects are restricted to ambiguous figures or whether they also occur for different degrees of visibility. Smiley faces with low and high visibility of emotional expressions, as well as abstract figures with low and high visibility of a target curvature were presented. We thus compared ambiguity effects in geometric cube stimuli with visibility in emotional faces, and with visibility in abstract figures. ERP Effects were replicated for the geometric stimuli and very similar ERP Effects were found for stimuli with emotional face expressions but also for abstract figures. Conclusively, the ERP amplitude effects generalize across fundamentally different stimulus categories and show highly similar effects for different degrees of stimulus ambiguity and stimulus visibility. We postulate the existence of a high-level/meta-perceptual evaluation instance, beyond sensory details, that estimates the certainty of a perceptual decision. The ERP Effects may reflect differences in evaluation results.


Assuntos
Potenciais Evocados Visuais/fisiologia , Percepção/fisiologia , Percepção Visual/fisiologia , Adulto , Eletroencefalografia , Emoções , Potenciais Evocados/fisiologia , Feminino , Humanos , Masculino , Ilusões Ópticas , Estimulação Luminosa/métodos , Sorriso
15.
Invest Ophthalmol Vis Sci ; 61(5): 5, 2020 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-32392311

RESUMO

Purpose: We investigated and characterized the patterns of meridional anisotropies in newly diagnosed refractive amblyopes using pattern onset-offset visual evoked potentials (POVEPs) and psychophysical grating acuity (GA). Methods: Twenty-five refractive amblyopes were recruited and compared with non-amblyopic controls from our previous study. Monocular POVEPs were recorded in response to sinewave 4 cycles per degree (cpd) grating stimuli oriented along each individual participants' principal astigmatic meridians, which were approximately horizontal (meridian 1) and vertical (meridian 2). Binocular POVEPs in response to the same stimuli, but oriented at 45°, 90°, 135°, and 180°, were recorded. Psychophysical GAs were assessed along the same meridians using a two-alternative non-forced-choice technique. The C3 amplitudes and peak latencies of the POVEPs and GAs were compared across meridians for both groups (refractive amblyopes and controls) using linear mixed models (monocular) and ANOVA (binocular), and post hoc analysis was conducted to determine if meridional anisotropies in this cohort of amblyopes were related to low (≤1.50 diopters [D]), moderate (1.75-2.75 D) and high (≥3.00 D) astigmatism. Results: In the newly diagnosed refractive amblyopes, there were no significant meridional anisotropies across all outcome measures, but the post hoc analysis demonstrated that C3 amplitude was significantly higher in those with low (P = 0.02) and moderate (P = 0.004) astigmatism compared to those with high astigmatism. Refractive amblyopes had poorer GA and C3 amplitudes compared to controls by approximately two lines on the logMAR chart (monocular: P = 0.013; binocular: P = 0.014) and approximately 6 µV (monocular: P = 0.009; binocular: P = 0.027), respectively. Conclusions: Deleterious effects of high astigmatism was evident in newly diagnosed refractive amblyopes, but the neural deficits do not seem to be orientation-specific for the stimulus parameters investigated.


Assuntos
Ambliopia/fisiopatologia , Potenciais Evocados Visuais/fisiologia , Orientação/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Anisotropia , Astigmatismo/fisiopatologia , Estudos de Casos e Controles , Criança , Pré-Escolar , Humanos , Psicofísica
16.
J Neurosci ; 40(27): 5283-5299, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32467356

RESUMO

Human scene categorization is characterized by its remarkable speed. While many visual and conceptual features have been linked to this ability, significant correlations exist between feature spaces, impeding our ability to determine their relative contributions to scene categorization. Here, we used a whitening transformation to decorrelate a variety of visual and conceptual features and assess the time course of their unique contributions to scene categorization. Participants (both sexes) viewed 2250 full-color scene images drawn from 30 different scene categories while having their brain activity measured through 256-channel EEG. We examined the variance explained at each electrode and time point of visual event-related potential (vERP) data from nine different whitened encoding models. These ranged from low-level features obtained from filter outputs to high-level conceptual features requiring human annotation. The amount of category information in the vERPs was assessed through multivariate decoding methods. Behavioral similarity measures were obtained in separate crowdsourced experiments. We found that all nine models together contributed 78% of the variance of human scene similarity assessments and were within the noise ceiling of the vERP data. Low-level models explained earlier vERP variability (88 ms after image onset), whereas high-level models explained later variance (169 ms). Critically, only high-level models shared vERP variability with behavior. Together, these results suggest that scene categorization is primarily a high-level process, but reliant on previously extracted low-level features.SIGNIFICANCE STATEMENT In a single fixation, we glean enough information to describe a general scene category. Many types of features are associated with scene categories, ranging from low-level properties, such as colors and contours, to high-level properties, such as objects and attributes. Because these properties are correlated, it is difficult to understand each property's unique contributions to scene categorization. This work uses a whitening transformation to remove the correlations between features and examines the extent to which each feature contributes to visual event-related potentials over time. We found that low-level visual features contributed first but were not correlated with categorization behavior. High-level features followed 80 ms later, providing key insights into how the brain makes sense of a complex visual world.


Assuntos
Percepção de Forma/fisiologia , Percepção Visual/fisiologia , Adolescente , Encéfalo/fisiologia , Cor , Eletroencefalografia , Potenciais Evocados Visuais/fisiologia , Feminino , Humanos , Masculino , Processos Mentais/fisiologia , Ruído , Estimulação Luminosa , Análise de Ondaletas , Adulto Jovem
17.
J Neurosci ; 40(27): 5214-5227, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32467358

RESUMO

The limitation of plasticity in the adult brain impedes functional recovery later in life from brain injury or disease. This pressing clinical issue may be resolved by enhancing plasticity in the adult brain. One strategy for triggering robust plasticity in adulthood is to reproduce one of the hallmark physiological events of experience-dependent plasticity observed during the juvenile critical period: to rapidly reduce the activity of parvalbumin (PV)-expressing interneurons and disinhibit local excitatory neurons. This may be achieved through the enhancement of local inhibitory inputs, particularly those of somatostatin (SST)-expressing interneurons. However, to date the means for manipulating SST interneurons for enhancing cortical plasticity in the adult brain are not known. We show that SST interneuron-selective overexpression of Lypd6, an endogenous nicotinic signaling modulator, enhances ocular dominance plasticity in the adult primary visual cortex (V1). Lypd6 overexpression mediates a rapid experience-dependent increase in the visually evoked activity of SST interneurons as well as a simultaneous reduction in PV interneuron activity and disinhibition of excitatory neurons. Recapitulating this transient activation of SST interneurons using chemogenetics similarly enhanced V1 plasticity. Notably, we show that SST-selective Lypd6 overexpression restores visual acuity in amblyopic mice that underwent early long-term monocular deprivation. Our data in both male and female mice reveal selective modulation of SST interneurons and a putative downstream circuit mechanism as an effective method for enhancing experience-dependent cortical plasticity as well as functional recovery in adulthood.SIGNIFICANCE STATEMENT The decline of cortical plasticity after closure of juvenile critical period consolidates neural circuits and behavior, but this limits functional recovery from brain diseases and dysfunctions in later life. Here we show that activation of cortical somatostatin (SST) interneurons by Lypd6, an endogenous modulator of nicotinic acetylcholine receptors, enhances experience-dependent plasticity and recovery from amblyopia in adulthood. This manipulation triggers rapid reduction of PV interneuron activity and disinhibition of excitatory neurons, which are known hallmarks of cortical plasticity during juvenile critical periods. Our study demonstrates modulation of SST interneurons by Lypd6 to achieve robust levels of cortical plasticity in the adult brain and may provide promising targets for restoring brain function in the event of brain trauma or disease.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/fisiologia , Proteínas Ligadas por GPI/fisiologia , Interneurônios/fisiologia , Plasticidade Neuronal/fisiologia , Somatostatina/fisiologia , Córtex Visual/fisiologia , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Dominância Ocular/genética , Potenciais Evocados Visuais/genética , Potenciais Evocados Visuais/fisiologia , Feminino , Proteínas Ligadas por GPI/genética , Imuno-Histoquímica , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Plasticidade Neuronal/genética , Fosfatidilinositóis/farmacologia , Receptores Nicotínicos/genética , Recuperação de Função Fisiológica/genética , Visão Monocular/genética , Visão Monocular/fisiologia , Acuidade Visual/genética
18.
Doc Ophthalmol ; 141(3): 269-278, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32468275

RESUMO

PURPOSE: The purpose of this study was to investigate the benefits of vision training with visual evoked potentials (VEP) biofeedback in amblyopia after the critical period in 8 to 17-year (11.5 ± 3.1) old children. METHODS: Ten participants with monocular amblyopia after the critical period underwent a 10-week, 20-session vision training program with the Retimax Vision Trainer device. During each session, the participants were instructed to be as focused as possible onto the fixation point in the middle of the screen. The size of the fixation point and the pitch of the background sound were changing according to VEP parameters and thus provided the participants real-time feedback of their visual performance. RESULTS: The mean BCVA improvement across our group was 0.12 LogMAR (p < 0.01). There was also a significant increase in contrast sensitivity to the FACT chart across all spatial frequencies (all p < 0.05). Electrophysiologic data revealed higher steady-state visual evoked potentials (SS-VEP) amplitudes and correspondingly lower fixation point values in the last 2 weeks of training compared to the first 2 weeks (both p < 0.01). Due to unexplainably low VEP amplitude levels in later trainings compared to those in the beginning in two participants, we have not found a significant correlation between the increase in BCVA and the increase in SS-VEP amplitude (p = 0.88). At the follow-up at 2 and 12 months following the end of training, both BCVA and contrast sensitivity remained within the levels achieved at the end of training. In some participants, however, no improvement of BCVA was observed. CONCLUSIONS: The tested vision training approach demonstrates modest but stable improvement of psychophysical parameters as well as objective characteristics in amblyopia after the critical period. Real-time SS-VEP can be used as an objective parameter to monitor participants' attention during vision training stimulation.


Assuntos
Ambliopia/fisiopatologia , Potenciais Evocados Visuais/fisiologia , Acuidade Visual/fisiologia , Adolescente , Criança , Sensibilidades de Contraste/fisiologia , Eletrorretinografia , Feminino , Humanos , Masculino , Neurorretroalimentação , Estimulação Luminosa , Testes Visuais , Baixa Visão/fisiopatologia
19.
Semin Ophthalmol ; 35(2): 116-125, 2020 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-32306804

RESUMO

Aim: To evaluate and compare structural and functional changes in macula and optic nerve in Alzheimer disease (AD) patients and healthy subjects.Methods: Both eyes of 20 AD patients and 40 age-matched healthy controls were evaluated. All subjects were evaluated by cognitive testing and comprehensive ophthalmological examination, including visual acuity, visual fields, color vision, contrast sensitivity, anterior, and posterior segment examination, optical coherence tomography, multifocal electroretinography (mfERG), and pattern-reversal visual evoked potential (pVEP).Results: AD patients showed significantly reduced contrast sensitivity, thinner nerve fiber layer, ganglion cell layer andmacular volume. Multifocal ERG wave amplitudes were significantly reduced with delayed implicit times, which correlated significantly with the inner retinal layer thinning and poorer disease severity scores. The correlation with structural changes and disease severity was highest for pVEP, which showed significant derangement in AD patients.Conclusion: Subclinical visual dysfunction may be present in AD patients, which may be detected as inner retinal thinning. A probable photoreceptor abnormality may also form a part of the AD disease process.


Assuntos
Doença de Alzheimer/fisiopatologia , Potenciais Evocados Visuais/fisiologia , Macula Lutea/fisiopatologia , Nervo Óptico/fisiopatologia , Transtornos da Visão/fisiopatologia , Adulto , Idoso , Visão de Cores/fisiologia , Eletrorretinografia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fibras Nervosas/patologia , Retina/fisiopatologia , Células Ganglionares da Retina/patologia , Tomografia de Coerência Óptica , Acuidade Visual/fisiologia , Campos Visuais/fisiologia
20.
J Clin Neurosci ; 75: 181-187, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32247741

RESUMO

Pattern reversal visual evoked potentials have been used to study optic neuritis. Although smaller check size in the central fields are more sensitive, larger check sizes can be advantageous for patient fixation and in poor vision. We compared sectorial central and peripheral hemisurround stimulus with commonly used full- and half- field stimulus using large check sizes (65') in the context of optic neuritis and multiple sclerosis. Of 19 female and 16 male control subjects studied, females had shorter P100 latencies and larger amplitudes than males. In 9 of the 18 patients with VEP abnormalities, the central field abnormalities were greater than those recorded with the full field response. The results confirm for the first time that central field stimulation using large checks can show a greater extent of abnormality than can be appreciated with large check full field stimulation alone, and could be commonly employed to improve yield in the investigation of optic neuritis. The data suggest that it is necessary to collect separate gender-specific laboratory normal values using this check size.


Assuntos
Potenciais Evocados Visuais/fisiologia , Esclerose Múltipla/fisiopatologia , Neurite Óptica/fisiopatologia , Estimulação Luminosa/métodos , Campos Visuais/fisiologia , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Esclerose Múltipla/diagnóstico , Neurite Óptica/diagnóstico , Adulto Jovem
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