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1.
Nat Commun ; 11(1): 5109, 2020 10 09.
Artigo em Inglês | MEDLINE | ID: mdl-33037209

RESUMO

Perceptual decisions entail the accumulation of sensory evidence for a particular choice towards an action plan. An influential framework holds that sensory cortical areas encode the instantaneous sensory evidence and downstream, action-related regions accumulate this evidence. The large-scale distribution of this computation across the cerebral cortex has remained largely elusive. Here, we develop a regionally-specific magnetoencephalography decoding approach to exhaustively map the dynamics of stimulus- and choice-specific signals across the human cortical surface during a visual decision. Comparison with the evidence accumulation dynamics inferred from behavior disentangles stimulus-dependent and endogenous components of choice-predictive activity across the visual cortical hierarchy. We find such an endogenous component in early visual cortex (including V1), which is expressed in a low (<20 Hz) frequency band and tracks, with delay, the build-up of choice-predictive activity in (pre-) motor regions. Our results are consistent with choice- and frequency-specific cortical feedback signaling during decision formation.


Assuntos
Córtex Cerebral/fisiologia , Tomada de Decisões , Magnetoencefalografia/métodos , Percepção Visual/fisiologia , Comportamento de Escolha , Feminino , Humanos , Masculino , Experimentação Humana não Terapêutica , Processamento de Sinais Assistido por Computador , Córtex Visual/fisiologia
2.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 6054-6057, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33019351

RESUMO

Contrast sensitivity is a key visual ability for everyday tasks, as well as a potential indicator of important optical and neurological diseases. Current clinical standards, based on visual discrimination performance on printed charts, present problems that could be bypassed using electronic devices. This work describes the development of new tests for contrast sensitivity, based on the detection of a moving target on a computer screen and in virtual reality headset. It presents preliminary evaluation of these innovations by comparison of their performance, using healthy adults with normal vision and by artificially altering their contrast sensitivity. The results demonstrate consistent correlation between all test modalities explored.


Assuntos
Sensibilidades de Contraste , Realidade Virtual , Teste de Realidade , Percepção Visual
3.
Nat Commun ; 11(1): 5440, 2020 10 28.
Artigo em Inglês | MEDLINE | ID: mdl-33116148

RESUMO

Despite recent progress in understanding multisensory decision-making, a conclusive mechanistic account of how the brain translates the relevant evidence into a decision is lacking. Specifically, it remains unclear whether perceptual improvements during rapid multisensory decisions are best explained by sensory (i.e., 'Early') processing benefits or post-sensory (i.e., 'Late') changes in decision dynamics. Here, we employ a well-established visual object categorisation task in which early sensory and post-sensory decision evidence can be dissociated using multivariate pattern analysis of the electroencephalogram (EEG). We capitalize on these distinct neural components to identify when and how complementary auditory information influences the encoding of decision-relevant visual evidence in a multisensory context. We show that it is primarily the post-sensory, rather than the early sensory, EEG component amplitudes that are being amplified during rapid audiovisual decision-making. Using a neurally informed drift diffusion model we demonstrate that a multisensory behavioral improvement in accuracy arises from an enhanced quality of the relevant decision evidence, as captured by the post-sensory EEG component, consistent with the emergence of multisensory evidence in higher-order brain areas.


Assuntos
Percepção Auditiva/fisiologia , Tomada de Decisões/fisiologia , Percepção Visual/fisiologia , Estimulação Acústica , Adolescente , Adulto , Comportamento de Escolha/fisiologia , Eletroencefalografia/estatística & dados numéricos , Feminino , Humanos , Masculino , Modelos Neurológicos , Modelos Psicológicos , Análise Multivariada , Estimulação Luminosa , Adulto Jovem
4.
PLoS One ; 15(9): e0239226, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32956420

RESUMO

Although there are many virtual reality (VR) applications in sports, only a handful of studies visualized the whole body. There is still a lack of understanding, how much of the own body must be visualized in the head-mounted display (HMD) based VR, to ensure fidelity and similar performance outcome as in the real-world. In the current study, 20 young and healthy participants completed three tasks in a real and virtual environment: balance task, grasping task, and throwing task with a ball. The aim was to find out the meaning of the visualization of different body parts for the quality of movement execution and to derive future guidelines for virtual body presentation. In addition, a comparison of human performance between reality and VR, with whole-body visualization was made. Focusing on the main goal of the current study, there were differences within the measured parameters due to the visualization of different body parts. In the balance task, the differences within the VR body visualization consisted mainly through no-body visualization (NB) compared to the other visualization types defined as whole-body (WB), WB except feet (NF), as well as WB except feet and legs (NLF). In the grasping task, the different body visualization seemed to have no impact on the participants' performances. In the throwing task, the whole-body visualization led to higher accuracy compared to the other visualization types. Regarding the comparison between the conditions, we found significant differences between reality and VR, which had a large effect on the parameters time for completion in the balance and grasping task, the number of foot strikes on the beam in the balance task, as well as the subjective estimation of the difficulty for all tasks. However, the number of errors and the quality of the performances did not differ significantly. The current study was the first study comparing sports-related tasks in VR and reality with further manipulations (occlusions of body parts) of the virtual body. For studies analyzing perception and sports performance or for VR sports interventions, we recommend the visualization of the whole body in real-time.


Assuntos
Desempenho Atlético , Exercício Físico , Realidade Virtual , Percepção Visual , Adulto , Feminino , Voluntários Saudáveis , Humanos , Masculino , Adulto Jovem
5.
PLoS One ; 15(9): e0238367, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32941453

RESUMO

PURPOSE: The purpose of this study was to examine how different threshold ranges of online-bandwidth visual feedback influence unilateral force control capabilities in healthy young women. METHODS: Twenty-five right-handed young women (mean±standard deviation age = 23.6±1.5 years) participated in this study. Participants unilaterally executed hand-grip force control tasks with their dominant and non-dominant hands, respectively. Each participant completed four experimental blocks in a different order of block presentation for each hand condition: (a) 10% of maximum voluntary contraction (MVC) with ±5% bandwidth threshold range (BTR), (b) 10% of MVC with ±10% BTR, (c) 40% of MVC with ±5% BTR, and (d) 40% of MVC with ±10% BTR. Outcome measures on force control capabilities included: (a) force accuracy, (b) force variability, (c) force regularity, and (d) the number of times and duration out of BTR. RESULTS: The non-dominant hand showed significant improvements in force control capabilities, as indicated by higher force accuracy, less force variability, and decreased force regularity from ±10% BTR to ±5% BTR during higher targeted force level task. For both hands, the number of times and duration out of BTR increased from ±10% BTR to ±5% BTR. CONCLUSIONS: The current findings suggested that the narrow threshold range of online-bandwidth visual feedback effectively revealed transient improvements in unilateral isometric force control capabilities during higher targeted force level tasks.


Assuntos
Retroalimentação Sensorial/fisiologia , Lateralidade Funcional , Força da Mão/fisiologia , Músculo Esquelético/fisiologia , Desempenho Psicomotor/fisiologia , Percepção Visual/fisiologia , Adulto , Feminino , Humanos , Contração Isométrica , Adulto Jovem
6.
Proc Biol Sci ; 287(1934): 20201189, 2020 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-32873203

RESUMO

Specific features of visual objects innately draw approach responses in animals, and provide natural signals of potential reward. However, visual sampling behaviours and the detection of salient, rewarding stimuli are context and behavioural state-dependent and it remains unclear how visual perception and orienting responses change with specific expectations. To start to address this question, we employed a virtual stimulus orienting paradigm based on prey capture to quantify the conditional expression of visual stimulus-evoked innate approaches in freely moving mice. We found that specific combinations of stimulus features selectively evoked innate approach or freezing responses when stimuli were unexpected. We discovered that prey capture experience, and therefore the expectation of prey in the environment, selectively modified approach frequency, as well as altered those visual features that evoked approach. Thus, we found that mice exhibit robust and selective orienting responses to parameterized visual stimuli that can be robustly and specifically modified via natural experience. This work provides critical insight into how natural appetitive behaviours are driven by both specific features of visual motion and internal states that alter stimulus salience.


Assuntos
Comportamento de Escolha , Animais , Camundongos , Orientação , Orientação Espacial , Visão Ocular , Percepção Visual
7.
Nat Commun ; 11(1): 4763, 2020 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-32958765

RESUMO

Many animal species remain separate not because their individuals fail to produce viable hybrids but because they "choose" not to mate. However, we still know very little of the genetic mechanisms underlying changes in these mate preference behaviours. Heliconius butterflies display bright warning patterns, which they also use to recognize conspecifics. Here, we couple QTL for divergence in visual preference behaviours with population genomic and gene expression analyses of neural tissue (central brain, optic lobes and ommatidia) across development in two sympatric Heliconius species. Within a region containing 200 genes, we identify five genes that are strongly associated with divergent visual preferences. Three of these have previously been implicated in key components of neural signalling (specifically an ionotropic glutamate receptor and two regucalcins), and overall our candidates suggest shifts in behaviour involve changes in visual integration or processing. This would allow preference evolution without altering perception of the wider environment.


Assuntos
Borboletas/fisiologia , Genes de Insetos , Especiação Genética , Preferência de Acasalamento Animal , Percepção Visual/genética , Animais , Borboletas/genética , Feminino , Regulação da Expressão Gênica , Fluxo Gênico , Genes de Insetos/genética , Genoma de Inseto/genética , Masculino , Mutação , Locos de Características Quantitativas , Especificidade da Espécie , Simpatria , Asas de Animais
8.
Nat Commun ; 11(1): 4553, 2020 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-32917902

RESUMO

Eye tracking has been widely used for decades in vision research, language and usability. However, most prior research has focused on large desktop displays using specialized eye trackers that are expensive and cannot scale. Little is known about eye movement behavior on phones, despite their pervasiveness and large amount of time spent. We leverage machine learning to demonstrate accurate smartphone-based eye tracking without any additional hardware. We show that the accuracy of our method is comparable to state-of-the-art mobile eye trackers that are 100x more expensive. Using data from over 100 opted-in users, we replicate key findings from previous eye movement research on oculomotor tasks and saliency analyses during natural image viewing. In addition, we demonstrate the utility of smartphone-based gaze for detecting reading comprehension difficulty. Our results show the potential for scaling eye movement research by orders-of-magnitude to thousands of participants (with explicit consent), enabling advances in vision research, accessibility and healthcare.


Assuntos
Confiabilidade dos Dados , Medições dos Movimentos Oculares , Movimentos Oculares , Smartphone , Adolescente , Adulto , Compreensão , Feminino , Fixação Ocular , Humanos , Masculino , Pessoa de Meia-Idade , Leitura , Visão Ocular , Percepção Visual , Adulto Jovem
9.
PLoS Genet ; 16(8): e1009003, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32866139

RESUMO

Sensory systems rely on neuromodulators, such as serotonin, to provide flexibility for information processing as stimuli vary, such as light intensity throughout the day. Serotonergic neurons broadly innervate the optic ganglia of Drosophila melanogaster, a widely used model for studying vision. It remains unclear whether serotonin modulates the physiology of interneurons in the optic ganglia. To address this question, we first mapped the expression patterns of serotonin receptors in the visual system, focusing on a subset of cells with processes in the first optic ganglion, the lamina. Serotonin receptor expression was found in several types of columnar cells in the lamina including 5-HT2B in lamina monopolar cell L2, required for spatiotemporal luminance contrast, and both 5-HT1A and 5-HT1B in T1 cells, whose function is unknown. Subcellular mapping with GFP-tagged 5-HT2B and 5-HT1A constructs indicated that these receptors localize to layer M2 of the medulla, proximal to serotonergic boutons, suggesting that the medulla neuropil is the primary site of serotonergic regulation for these neurons. Exogenous serotonin increased basal intracellular calcium in L2 terminals in layer M2 and modestly decreased the duration of visually induced calcium transients in L2 neurons following repeated dark flashes, but otherwise did not alter the calcium transients. Flies without functional 5-HT2B failed to show an increase in basal calcium in response to serotonin. 5-HT2B mutants also failed to show a change in amplitude in their response to repeated light flashes but other calcium transient parameters were relatively unaffected. While we did not detect serotonin receptor expression in L1 neurons, they, like L2, underwent serotonin-induced changes in basal calcium, presumably via interactions with other cells. These data demonstrate that serotonin modulates the physiology of interneurons involved in early visual processing in Drosophila.


Assuntos
Receptor 5-HT1B de Serotonina/genética , Receptores 5-HT1 de Serotonina/genética , Receptores 5-HT2 de Serotonina/genética , Neurônios Serotoninérgicos/metabolismo , Serotonina/metabolismo , Animais , Ritmo Circadiano/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Regulação da Expressão Gênica/genética , Interneurônios/metabolismo , Proteínas de Membrana/genética , Proteínas do Tecido Nervoso/genética , Neurotransmissores/genética , Receptores de Serotonina/genética , Serotonina/genética , Percepção Visual/genética
10.
Proc Biol Sci ; 287(1935): 20201884, 2020 09 30.
Artigo em Inglês | MEDLINE | ID: mdl-32962551

RESUMO

Fast saccades are rapid automatic oculomotor responses to salient and ecologically important visual stimuli such as animals and faces. Discriminating the number of friends, foe, or prey may also have an evolutionary advantage. In this study, participants were asked to saccade rapidly towards the more numerous of two arrays. Participants could discriminate numerosities with high accuracy and great speed, as fast as 190 ms. Intermediate numerosities were more likely to elicit fast saccades than very low or very high numerosities. Reaction-times for vocal responses (collected in a separate experiment) were slower, did not depend on numerical range, and correlated only with the slow not the fast saccades, pointing to different systems. The short saccadic reaction-times we observe are surprising given that discrimination using numerosity estimation is thought to require a relatively complex neural circuit, with several relays of information through the parietal and prefrontal cortex. Our results suggest that fast numerosity-driven saccades may be generated on a single feed-forward pass of information recruiting a primitive system that cuts through the cortical hierarchy and rapidly transforms the numerosity information into a saccade command.


Assuntos
Movimentos Sacádicos , Adulto , Animais , Feminino , Humanos , Masculino , Tempo de Reação , Percepção Visual , Adulto Jovem
11.
PLoS One ; 15(9): e0237663, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32870908

RESUMO

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


Assuntos
Potenciais Evocados Visuais , Memória , Percepção Visual , Adulto , Feminino , Humanos , Masculino , Tempo de Reação , Adulto Jovem
12.
PLoS Biol ; 18(9): e3000854, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32898172

RESUMO

Working memory is imprecise, and these imprecisions can be explained by the combined influences of random diffusive error and systematic drift toward a set of stable states ("attractors"). However, the neural correlates of diffusion and drift remain unknown. Here, we investigated how delay-period activity in frontal and parietal cortex, which is known to correlate with the decline in behavioral memory precision observed with increasing memory load, might relate to diffusion and drift. We analyzed data from an existing experiment in which subjects performed delayed recall for line orientation, at different loads, during functional magnetic resonance imaging (fMRI) scanning. To quantify the influence of drift and diffusion, we modeled subjects' behavior using a discrete attractor model and calculated within-subject correlation between frontal and parietal delay-period activity and whole-trial estimates of drift and diffusion. We found that although increases in frontal and parietal activity were associated with increases in both diffusion and drift, diffusion explained the most variance in frontal and parietal delay-period activity. In comparison, a subsequent whole-brain regression analysis showed that drift, rather than diffusion, explained the most variance in delay-period activity in lateral occipital cortex. These results are consistent with a model of the differential recruitment of general frontoparietal mechanisms in response to diffusive noise and of stimulus-specific biases in occipital cortex.


Assuntos
Lobo Frontal/fisiologia , Memória de Curto Prazo/fisiologia , Lobo Occipital/fisiologia , Lobo Parietal/fisiologia , Percepção Visual/fisiologia , Adolescente , Adulto , Viés , Mapeamento Encefálico/métodos , Feminino , Lobo Frontal/anatomia & histologia , Lobo Frontal/diagnóstico por imagem , Humanos , Imagem por Ressonância Magnética , Masculino , Rememoração Mental/fisiologia , Lobo Occipital/anatomia & histologia , Lobo Occipital/diagnóstico por imagem , Lobo Parietal/anatomia & histologia , Lobo Parietal/diagnóstico por imagem , Estimulação Luminosa , Razão Sinal-Ruído , Fatores de Tempo , Vias Visuais/anatomia & histologia , Vias Visuais/diagnóstico por imagem , Vias Visuais/fisiologia , Adulto Jovem
13.
Exp Psychol ; 67(3): 161-168, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32900298

RESUMO

Dynamic visual noise (DVN) selectively impairs memory for some types of stimuli (e.g., colors, textures, concrete words), but not for others (e.g., matrices, Chinese characters, simple shapes). According to the image definition hypothesis, the key difference is whether the stimulus leads to images that are ill-defined or well-defined. The former will be affected because the addition of noise quickly reduces the usefulness of the image in supplying information about the item's identity. The image definition hypothesis predicts that fonts should lead to ill-defined images and therefore should be affected by DVN, and although three previous studies appear to show this result, they lack a key control condition and report only proportion correct. Two experiments reassessed whether DVN affects memory for fonts, but, unlike the previous studies, both included a static visual noise condition and both were analyzed using signal detection measures. There was no evidence that DVN affected memory for font information, thus disconfirming a prediction of the original version of image definition hypothesis. We suggest a revised version that focuses on redintegration can explain the results.


Assuntos
Memória de Curto Prazo/fisiologia , Ruído , Percepção Visual/fisiologia , Adulto , Feminino , Humanos , Masculino , Adulto Jovem
14.
Hum Factors ; 62(7): 1095-1101, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32902338

RESUMO

BACKGROUND: Mandatory rules for social distancing to curb the SARS-CoV-2 pandemic require individuals to maintain a critical interpersonal distance above 1.5 m. However, this contradicts our natural preference, which is closer to 1 m for non-intimate encounters, for example, when asking a stranger for directions. OBJECTIVE: This review addresses how humans typically regulate interpersonal distances, in order to highlight the challenges of enforcing atypically large interpersonal distances. METHOD: To understand the challenges posed by social distancing requirements, we integrate relevant contributions from visual perception, social perception, and human factors. RESULTS: To date, research on preferred interpersonal distances suggests that social distancing could induce discomfort, heighten arousal, and decrease social signaling in the short term. While the protracted effects of social distancing are unclear, we propose hypotheses on the mid- to long-term consequences of violating preferred norms of interpersonal distances. CONCLUSION: We suggest that enforcing a physical distance of 1.5-2 m presents a serious challenge to behavioral norms. APPLICATION: We address how notifications, architectural design, and visualizations could be effectively applied to promote interpersonal distance requirements.


Assuntos
Infecções por Coronavirus/prevenção & controle , Programas Obrigatórios , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Distância Social , Ciências do Comportamento , Comunicação , Infecções por Coronavirus/transmissão , Humanos , Espaço Pessoal , Pneumonia Viral/transmissão , Comportamento Social , Mudança Social , Percepção Visual
15.
PLoS One ; 15(9): e0238976, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32925930

RESUMO

The use of pictures as experimental stimuli is a frequent practice in psychological and educational research. In addition, picture-naming task allows the study of different cognitive processes such as perception, attention, memory and language. Line drawings have been widely used in research to date but it has begun to be highlighted the need for more ecological stimuli such as photographs. However, normative data of a photographic set has not been published yet for use with children. We present PicPsy, a new standardized bank of photographs and matched line drawing. We collected written picture-naming norms for name agreement, unknown responses, alternative names, familiarity and visual complexity. A total of 118 native Spanish-speaking children in grades 3-4 participated in the study. For comparison purposes, 89 adults were also included in the study. Child and adult performance was highly correlated, but we found significant age group differences in all variables examined except for visual complexity. Researchers and teachers could benefit from using the new standardized bank reported here which is published under public domain license. The data and materials for this research are available at the Open Science Framework, https://osf.io/nyf3t/.


Assuntos
Nomes , Reconhecimento Visual de Modelos/classificação , Adolescente , Criança , Pré-Escolar , Bases de Dados Factuais , Feminino , Percepção de Forma/fisiologia , Humanos , Idioma , Desenvolvimento da Linguagem , Masculino , Reconhecimento Visual de Modelos/fisiologia , Reconhecimento Psicológico , Traduções , Percepção Visual/fisiologia , Redação
16.
Proc Natl Acad Sci U S A ; 117(34): 20959-20968, 2020 08 25.
Artigo em Inglês | MEDLINE | ID: mdl-32788373

RESUMO

Research into human working memory limits has been shaped by the competition between different formal models, with a central point of contention being whether internal representations are continuous or discrete. Here we describe a sampling approach derived from principles of neural coding as a framework to understand working memory limits. Reconceptualizing existing models in these terms reveals strong commonalities between seemingly opposing accounts, but also allows us to identify specific points of difference. We show that the discrete versus continuous nature of sampling is not critical to model fits, but that, instead, random variability in sample counts is the key to reproducing human performance in both single- and whole-report tasks. A probabilistic limit on the number of items successfully retrieved is an emergent property of stochastic sampling, requiring no explicit mechanism to enforce it. These findings resolve discrepancies between previous accounts and establish a unified computational framework for working memory that is compatible with neural principles.


Assuntos
Memória de Curto Prazo/fisiologia , Rememoração Mental/fisiologia , Percepção Visual/fisiologia , Humanos , Modelos Neurológicos , Modelos Teóricos
17.
Proc Natl Acad Sci U S A ; 117(37): 23011-23020, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32839334

RESUMO

The fusiform face area responds selectively to faces and is causally involved in face perception. How does face-selectivity in the fusiform arise in development, and why does it develop so systematically in the same location across individuals? Preferential cortical responses to faces develop early in infancy, yet evidence is conflicting on the central question of whether visual experience with faces is necessary. Here, we revisit this question by scanning congenitally blind individuals with fMRI while they haptically explored 3D-printed faces and other stimuli. We found robust face-selective responses in the lateral fusiform gyrus of individual blind participants during haptic exploration of stimuli, indicating that neither visual experience with faces nor fovea-biased inputs is necessary for face-selectivity to arise in the lateral fusiform gyrus. Our results instead suggest a role for long-range connectivity in specifying the location of face-selectivity in the human brain.


Assuntos
Face/fisiologia , Reconhecimento Facial/fisiologia , Lobo Temporal/fisiologia , Percepção Visual/fisiologia , Adulto , Mapeamento Encefálico/métodos , Feminino , Humanos , Imagem por Ressonância Magnética/métodos , Masculino , Reconhecimento Visual de Modelos/fisiologia , Estimulação Luminosa/métodos , Reconhecimento Psicológico/fisiologia
18.
Nat Commun ; 11(1): 4014, 2020 08 11.
Artigo em Inglês | MEDLINE | ID: mdl-32782303

RESUMO

Perception reflects not only sensory inputs, but also the endogenous state when these inputs enter the brain. Prior studies show that endogenous neural states influence stimulus processing through non-specific, global mechanisms, such as spontaneous fluctuations of arousal. It is unclear if endogenous activity influences circuit and stimulus-specific processing and behavior as well. Here we use intracranial recordings from 30 pre-surgical epilepsy patients to show that patterns of endogenous activity are related to the strength of trial-by-trial neural tuning in different visual category-selective neural circuits. The same aspects of the endogenous activity that relate to tuning in a particular neural circuit also correlate to behavioral reaction times only for stimuli from the category that circuit is selective for. These results suggest that endogenous activity can modulate neural tuning and influence behavior in a circuit- and stimulus-specific manner, reflecting a potential mechanism by which endogenous neural states facilitate and bias perception.


Assuntos
Rede Nervosa/fisiologia , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Adulto , Eletrocorticografia , Epilepsia/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Neurológicos , Reconhecimento Visual de Modelos/fisiologia , Estimulação Luminosa , Tempo de Reação/fisiologia
19.
PLoS Comput Biol ; 16(8): e1008018, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32813688

RESUMO

Visually inferring material properties is crucial for many tasks, yet poses significant computational challenges for biological vision. Liquids and gels are particularly challenging due to their extreme variability and complex behaviour. We reasoned that measuring and modelling viscosity perception is a useful case study for identifying general principles of complex visual inferences. In recent years, artificial Deep Neural Networks (DNNs) have yielded breakthroughs in challenging real-world vision tasks. However, to model human vision, the emphasis lies not on best possible performance, but on mimicking the specific pattern of successes and errors humans make. We trained a DNN to estimate the viscosity of liquids using 100.000 simulations depicting liquids with sixteen different viscosities interacting in ten different scenes (stirring, pouring, splashing, etc). We find that a shallow feedforward network trained for only 30 epochs predicts mean observer performance better than most individual observers. This is the first successful image-computable model of human viscosity perception. Further training improved accuracy, but predicted human perception less well. We analysed the network's features using representational similarity analysis (RSA) and a range of image descriptors (e.g. optic flow, colour saturation, GIST). This revealed clusters of units sensitive to specific classes of feature. We also find a distinct population of units that are poorly explained by hand-engineered features, but which are particularly important both for physical viscosity estimation, and for the specific pattern of human responses. The final layers represent many distinct stimulus characteristics-not just viscosity, which the network was trained on. Retraining the fully-connected layer with a reduced number of units achieves practically identical performance, but results in representations focused on viscosity, suggesting that network capacity is a crucial parameter determining whether artificial or biological neural networks use distributed vs. localized representations.


Assuntos
Modelos Neurológicos , Redes Neurais de Computação , Viscosidade , Percepção Visual/fisiologia , Adulto , Biologia Computacional , Feminino , Humanos , Masculino , Adulto Jovem
20.
PLoS One ; 15(8): e0226122, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32853238

RESUMO

Essential for successful interaction with the environment is the human capacity to resolve events in time. Typical event timing paradigms are judgements of simultaneity (SJ) and of temporal order (TOJ). It remains unclear whether SJ and TOJ are based on the same underlying mechanism and whether there are fixed thresholds for resolution. The current study employed four visual event timing task versions: horizontal and vertical SJ and TOJ. Binary responses were analysed using multilevel binary regression modelling. Modulatory effects of potential explanatory variables on event timing perception were investigated: (1) Individual factors (sex and age), (2) temporal factors (SOA, trial number, order of experiment, order of stimuli orientation, time of day) and (3) spatial factors (left or right stimulus first, top or bottom stimulus first, horizontal vs. vertical orientation). The current study directly compares for the first time, performance on SJ and TOJ tasks using the same paradigm and presents evidence that a variety of factors and their interactions selectively modulate event timing functions in humans, explaining the variance found in previous studies. We conclude that SJ and TOJ are partially independent functions, because they are modulated differently by individual and contextual variables.


Assuntos
Percepção do Tempo/fisiologia , Visão Ocular/fisiologia , Percepção Visual/fisiologia , Adulto , Percepção Auditiva/fisiologia , Feminino , Humanos , Julgamento/fisiologia , Masculino , Orientação , Tempo de Reação/fisiologia
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