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1.
Science ; 367(6482): 1112-1119, 2020 03 06.
Artigo em Inglês | MEDLINE | ID: mdl-32139539

RESUMO

The genome versus experience dichotomy has dominated understanding of behavioral individuality. By contrast, the role of nonheritable noise during brain development in behavioral variation is understudied. Using Drosophila melanogaster, we demonstrate a link between stochastic variation in brain wiring and behavioral individuality. A visual system circuit called the dorsal cluster neurons (DCN) shows nonheritable, interindividual variation in right/left wiring asymmetry and controls object orientation in freely walking flies. We show that DCN wiring asymmetry instructs an individual's object responses: The greater the asymmetry, the better the individual orients toward a visual object. Silencing DCNs abolishes correlations between anatomy and behavior, whereas inducing DCN asymmetry suffices to improve object responses.


Assuntos
Encéfalo/crescimento & desenvolvimento , Drosophila melanogaster/crescimento & desenvolvimento , Individualidade , Neurogênese , Campos Visuais/fisiologia , Vias Visuais/crescimento & desenvolvimento , Animais , Encéfalo/anatomia & histologia , Drosophila melanogaster/genética , Variação Genética , Orientação/fisiologia , Vias Visuais/anatomia & histologia
2.
Neural Netw ; 121: 339-355, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31593840

RESUMO

Previous research has shown that performance of a novice skill can be easily interfered with by subsequent training of another skill. We address the open questions whether extensively trained skills show the same vulnerability to interference as novice skills and which memory mechanism regulates interference between expert skills. We developed a recurrent neural network model of V1 able to learn from feedback experienced over the course of a long-term orientation discrimination experiment. After first exposing the model to one discrimination task for 3480 consecutive trials, we assessed how its performance was affected by subsequent training in a second, similar task. Training the second task strongly interfered with the first (highly trained) discrimination skill. The magnitude of interference depended on the relative amounts of training devoted to the different tasks. We used these and other model outcomes as predictions for a perceptual learning experiment in which human participants underwent the same training protocol as our model. Specifically, over the course of three months participants underwent baseline training in one orientation discrimination task for 15 sessions before being trained for 15 sessions on a similar task and finally undergoing another 15 sessions of training on the first task (to assess interference). Across all conditions, the pattern of interference observed empirically closely matched model predictions. According to our model, behavioral interference can be explained by antagonistic changes in neuronal tuning induced by the two tasks. Remarkably, this did not stem from erasing connections due to earlier learning but rather from a reweighting of lateral inhibition.


Assuntos
Memória/fisiologia , Orientação/fisiologia , Estimulação Luminosa/métodos , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Adulto , Feminino , Humanos , Masculino , Neurônios/fisiologia , Adulto Jovem
3.
PLoS Comput Biol ; 15(10): e1007370, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31581240

RESUMO

When probed with complex stimuli that extend beyond their classical receptive field, neurons in primary visual cortex display complex and non-linear response characteristics. Sparse coding models reproduce some of the observed contextual effects, but still fail to provide a satisfactory explanation in terms of realistic neural structures and cortical mechanisms, since the connection scheme they propose consists only of interactions among neurons with overlapping input fields. Here we propose an extended generative model for visual scenes that includes spatial dependencies among different features. We derive a neurophysiologically realistic inference scheme under the constraint that neurons have direct access only to local image information. The scheme can be interpreted as a network in primary visual cortex where two neural populations are organized in different layers within orientation hypercolumns that are connected by local, short-range and long-range recurrent interactions. When trained with natural images, the model predicts a connectivity structure linking neurons with similar orientation preferences matching the typical patterns found for long-ranging horizontal axons and feedback projections in visual cortex. Subjected to contextual stimuli typically used in empirical studies, our model replicates several hallmark effects of contextual processing and predicts characteristic differences for surround modulation between the two model populations. In summary, our model provides a novel framework for contextual processing in the visual system proposing a well-defined functional role for horizontal axons and feedback projections.


Assuntos
Modelos Neurológicos , Rede Nervosa/fisiologia , Percepção Visual/fisiologia , Potenciais de Ação/fisiologia , Animais , Axônios/fisiologia , Simulação por Computador , Humanos , Modelos Biológicos , Neurônios/fisiologia , Orientação/fisiologia , Estimulação Luminosa/métodos , Córtex Visual/fisiologia , Campos Visuais , Vias Visuais/fisiologia
4.
Acta Neurobiol Exp (Wars) ; 79(3): 225-231, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31587014

RESUMO

The present study used optical imaging to investigate the development of the optical signal within orientational columns in primary visual cortex of cats reared under conditions of rhythmic light stimulation. Results showed that, although inter-columnar spacing was unchanged, a 3-5-fold decrement in optical signal from orientation columns and a drastic decline in contrast sensitivity was observed in both areas 18 and 17. These data suggest the modification of cortical columnar functioning under artificially correlated synchronization of retinal input.


Assuntos
Orientação/fisiologia , Estimulação Luminosa , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Animais , Mapeamento Encefálico , Gatos , Processamento de Imagem Assistida por Computador/métodos , Estimulação Luminosa/métodos
5.
Nat Commun ; 10(1): 4745, 2019 10 18.
Artigo em Inglês | MEDLINE | ID: mdl-31628322

RESUMO

Measuring neuronal tuning curves has been instrumental for many discoveries in neuroscience but requires a priori assumptions regarding the identity of the encoded variables. We applied unsupervised learning to large-scale neuronal recordings in behaving mice from circuits involved in spatial cognition and uncovered a highly-organized internal structure of ensemble activity patterns. This emergent structure allowed defining for each neuron an 'internal tuning-curve' that characterizes its activity relative to the network activity, rather than relative to any predefined external variable, revealing place-tuning and head-direction tuning without relying on measurements of place or head-direction. Similar investigation in prefrontal cortex revealed schematic representations of distances and actions, and exposed a previously unknown variable, the 'trajectory-phase'. The internal structure was conserved across mice, allowing using one animal's data to decode another animal's behavior. Thus, the internal structure of neuronal activity itself enables reconstructing internal representations and discovering new behavioral variables hidden within a neural code.


Assuntos
Movimentos da Cabeça/fisiologia , Rede Nervosa/fisiologia , Neurônios/fisiologia , Córtex Pré-Frontal/fisiologia , Percepção Espacial/fisiologia , Potenciais de Ação/fisiologia , Algoritmos , Animais , Cognição/fisiologia , Hipocampo/citologia , Hipocampo/fisiologia , Masculino , Camundongos Endogâmicos C57BL , Modelos Neurológicos , Rede Nervosa/citologia , Orientação/fisiologia , Córtex Pré-Frontal/citologia
6.
J Vis ; 19(11): 2, 2019 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-31480073

RESUMO

Research has shown that participants can extract the average facial expression from a set of faces when these were presented at fixation. In this study, we investigated whether this performance would be modulated by eccentricity given that neural resources are limited outside the foveal region. We also examined whether or not there would be compulsory averaging in the parafovea as has been previously reported for the orientation of Gabor patches by Parkes, Lund, Angelucci, Solomon, and Morgan (2001). Participants were presented with expressive faces (alone or in sets of nine, at fixation or at 3° to the left or right) and were asked to identify the expression of the central target face or to estimate the average expression of the set. Our results revealed that, although participants were able to extract average facial expressions in central and parafoveal conditions, their performance was superior in the parafovea, suggesting facilitated averaging outside the fovea by peripheral mechanisms. Furthermore, regardless of whether the task was to judge the expression of the central target or set average, participants had a tendency to identify central targets' expressions in the fovea but were compelled to average in the parafovea, a finding consistent with compulsory averaging. The data also supported averaging over substitution models of crowding. We conclude that the ability to extract average expressions in sets of faces and identify single targets' facial expressions is influenced by eccentricity.


Assuntos
Expressão Facial , Reconhecimento Facial/fisiologia , Adulto , Análise de Variância , Emoções/fisiologia , Feminino , Fixação Ocular/fisiologia , Fóvea Central/fisiologia , Humanos , Masculino , Modelos Biológicos , Orientação/fisiologia , Adulto Jovem
7.
J Vis ; 19(11): 1, 2019 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-31480074

RESUMO

Although real-world environments are often multisensory, visual scientists typically study visual learning in unisensory environments containing visual signals only. Here, we use deep or artificial neural networks to address the question, Can multisensory training aid visual learning? We examine a network's internal representations of objects based on visual signals in two conditions: (a) when the network is initially trained with both visual and haptic signals, and (b) when it is initially trained with visual signals only. Our results demonstrate that a network trained in a visual-haptic environment (in which visual, but not haptic, signals are orientation-dependent) tends to learn visual representations containing useful abstractions, such as the categorical structure of objects, and also learns representations that are less sensitive to imaging parameters, such as viewpoint or orientation, that are irrelevant for object recognition or classification tasks. We conclude that researchers studying perceptual learning in vision-only contexts may be overestimating the difficulties associated with important perceptual learning problems. Although multisensory perception has its own challenges, perceptual learning can become easier when it is considered in a multisensory setting.


Assuntos
Aprendizagem Espacial/efeitos da radiação , Percepção Visual/fisiologia , Humanos , Orientação/fisiologia , Estimulação Luminosa , Visão Ocular/fisiologia
8.
Acta Psychol (Amst) ; 199: 102896, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31376724

RESUMO

We investigated somatically perceived inclination of a floor on which an observer was. In the first three experiments, using blindfolded observers, we determined the point of subjective equality (PSE) and the difference limen (DL) for horizontal floor. Orientation of the lying body relative to the axis around which the floor was rotated, distance of the lying body from the rotation axis, posture (standing, sitting, and lying), and age were varied. In the fourth experiment, effects of seeing the floor were examined. The mean PSEs were accurate within ±0.25° in all experiments. The mean DLs varied with condition: 1) The largest DLs were obtained for the blindfolded observers lying orthogonally or obliquely to the rotation axis, 2) the second largest DLs for the blindfolded observers lying parallel to the rotation axis, 3) medium DLs for the blindfolded observers sitting or standing, and 4) the smallest DLs for the standing observers with visual exposure to surroundings. In the last experiment, we determined a scale for inclination from verbally estimating apparent inclination with or without a blindfold. We concluded that the ratio of shear force to normal force was used for estimation of inclination. We discussed synergy of somatic inputs and visual inputs.


Assuntos
Orientação/fisiologia , Percepção/fisiologia , Postura/fisiologia , Percepção Espacial/fisiologia , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Rotação , Adulto Jovem
9.
Nat Commun ; 10(1): 3832, 2019 08 23.
Artigo em Inglês | MEDLINE | ID: mdl-31444323

RESUMO

Visual stimuli evoke heterogeneous responses across nearby neural populations. These signals must be locally integrated to contribute to perception, but the principles underlying this process are unknown. Here, we exploit the systematic organization of orientation preference in macaque primary visual cortex (V1) and perform causal manipulations to examine the limits of signal integration. Optogenetic stimulation and visual stimuli are used to simultaneously drive two neural populations with overlapping receptive fields. We report that optogenetic stimulation raises firing rates uniformly across conditions, but improves the detection of visual stimuli only when activating cells that are preferentially-tuned to the visual stimulus. Further, we show that changes in correlated variability are exclusively present when the optogenetically and visually-activated populations are functionally-proximal, suggesting that correlation changes represent a hallmark of signal integration. Our results demonstrate that information from functionally-proximal neurons is pooled for perception, but functionally-distal signals remain independent.


Assuntos
Potenciais Evocados Visuais/fisiologia , Modelos Neurológicos , Orientação/fisiologia , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Potenciais de Ação/fisiologia , Animais , Técnicas de Observação do Comportamento , Comportamento Animal/fisiologia , Mapeamento Encefálico , Macaca mulatta , Masculino , Neurônios/fisiologia , Optogenética , Estimulação Luminosa , Tempo de Reação , Córtex Visual/citologia , Córtex Visual/diagnóstico por imagem
10.
J Vis ; 19(7): 6, 2019 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-31287860

RESUMO

Are people biologically prepared for the rapid detection of threat posed by an angry facial expression, even when it is conveyed in the form of a schematic line drawing? Based on visual search times, the current literature would suggest that the answer is yes. But are there low-level explanations for this effect? Here, we present visual search results for schematic faces using current best practice, based on a concentric search array and set size manipulation. Using this approach, we replicate the classic search advantage for angry over happy faces. However, we also report a comparable effect when abstract plus- and square-shaped stimuli-derived from the angry and happy schematic faces respectively-are used within the same paradigm. We then go on to demonstrate that, while reduced, the effect remains after removal of the circular surround, bringing us closer to the source of the effect. We explore the possibility that the source of this search asymmetry could be the iso-feature suppression and collinear facilitation model proposed in Li's (1999a, 1999b, and 2002) bottom-up model of saliency. Simulations with this model using the abstract stimuli align with the corresponding behavioral results (i.e., the plus shape was found to be more salient than the square). Given the deliberate similarities between these abstract shapes and the respective face stimuli, we propose that the underlying cause for the asymmetries typically found using schematic faces, may be more related to early visual processing of line orientation than threat detection.


Assuntos
Ira/fisiologia , Expressão Facial , Adolescente , Adulto , Cognição/fisiologia , Aglomeração/psicologia , Emoções/fisiologia , Medo/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Orientação/fisiologia , Estimulação Luminosa , Processamento Espacial/fisiologia , Adulto Jovem
11.
PLoS Comput Biol ; 15(7): e1007123, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31318859

RESUMO

Many insects navigate by integrating the distances and directions travelled on an outward path, allowing direct return to the starting point. Fundamental to the reliability of this process is the use of a neural compass based on external celestial cues. Here we examine how such compass information could be reliably computed by the insect brain, given realistic constraints on the sky polarisation pattern and the insect eye sensor array. By processing the degree of polarisation in different directions for different parts of the sky, our model can directly estimate the solar azimuth and also infer the confidence of the estimate. We introduce a method to correct for tilting of the sensor array, as might be caused by travel over uneven terrain. We also show that the confidence can be used to approximate the change in sun position over time, allowing the compass to remain fixed with respect to 'true north' during long excursions. We demonstrate that the compass is robust to disturbances and can be effectively used as input to an existing neural model of insect path integration. We discuss the plausibility of our model to be mapped to known neural circuits, and to be implemented for robot navigation.


Assuntos
Comportamento Animal/fisiologia , Insetos/fisiologia , Modelos Biológicos , Animais , Encéfalo/fisiologia , Biologia Computacional , Simulação por Computador , Sinais (Psicologia) , Comportamento de Retorno ao Território Vital/fisiologia , Luz , Modelos Neurológicos , Lobo Óptico de Animais não Mamíferos/fisiologia , Orientação/fisiologia , Células Fotorreceptoras de Invertebrados/fisiologia , Comportamento Espacial/fisiologia , Luz Solar
12.
Acta Psychol (Amst) ; 198: 102870, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31301573

RESUMO

The standard visual search task is integral to the study of selective attention and in search tasks target present slopes are the primary index of attentional demand. However, there are times when similarities in slopes may obscure important differences between conditions. To demonstrate this point, we used the case of line-ending illusory contours, building on a study by Li, Cave, and Wolfe (2008) where orientation-based search for figures defined by line-ending illusory contours was compared to that for the corresponding real-contour controls. Consistent with Li et al. (2008), we found search to be efficient for both illusory contour figures and the corresponding real-contour controls, with no significant differences between them. However, major differences between illusory contours and the real-contour controls emerged in selective enumeration, a task where participants enumerated targets in a display of distractors, with the number of targets and distractors manipulated. When looking at the distractor slopes, the increase in RT to enumerate a single target as a function of the number of distractors (a direct analogue to target present trials, with identical displays), we found distractor costs for illusory contour figures to be over 100 ms/distractor higher than for the corresponding real-contour controls. Furthermore, the discrepancies in RT slope between 1-3 and 6-8 targets associated with subitizing were only seen in the real-contour controls. These results show that similarities in RT slopes in search may mask important differences between conditions that emerge in other tasks.


Assuntos
Percepção de Forma/fisiologia , Ilusões/psicologia , Reconhecimento Visual de Modelos/fisiologia , Desempenho Psicomotor/fisiologia , Adolescente , Atenção/fisiologia , Feminino , Previsões , Humanos , Ilusões/fisiologia , Masculino , Orientação/fisiologia , Estimulação Luminosa/métodos , Distribuição Aleatória , Adulto Jovem
13.
PLoS One ; 14(7): e0220414, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31348807

RESUMO

This study explored gender differences in correct response rates and response times on a task involving left or right arrow selection and another involving the transformation of mental rotation of the hand. We recruited 15 healthy, right-handed men (age 24.5 ± 6.4) and 15 healthy, right-handed women (age 21.3 ± 4.9). For the tasks, we used pictures of left and right arrows and 32 hand pictures (left and right, palm and back) placed in cons (each at 45° from 0° to 315°). Hand and arrow pictures alternated and were shown at random. Participants decided as quickly as possible whether each picture was left or right. To compare the time taken for the transformation of mental rotation of the hand, we subtracted the average arrow response time from that for the left and right hand pictures for each participant. Correct response rates did not differ significantly between men and women or left and right for either arrow or hand pictures. Regardless of gender, the response time was longer for the left arrow picture than right arrow picture. The response time for the hand picture was longest for both men and women for pictures at rotation angles that were most difficult to align with participants' hands. While there was no difference between men's responses for left and right hand pictures, the responses of women were longer for left than right hand pictures and also than those of men. These findings suggest that both men and women mainly perform the hand mental rotation task with implicit motor imagery. On the other hand, the gender difference in performance might be explained by the difference in balance with other strategies, such as visual imagery, and by cognitive, neurophysiological, and morphological differences.


Assuntos
Mãos/fisiologia , Orientação/fisiologia , Tempo de Reação/fisiologia , Caracteres Sexuais , Adolescente , Adulto , Feminino , Lateralidade Funcional/fisiologia , Humanos , Masculino , Desempenho Psicomotor , Rotação , Inquéritos e Questionários , Adulto Jovem
14.
PLoS Comput Biol ; 15(7): e1007254, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31356590

RESUMO

Orientation selectivity is a key property of primary visual cortex that contributes, downstream, to object recognition. The origin of orientation selectivity, however, has been debated for decades. It is known that on- and off-centre subcortical pathways converge onto single neurons in primary visual cortex, and that the spatial offset between these pathways gives rise to orientation selectivity. On- and off-centre pathways are intermingled, however, so it is unclear how their inputs to cortex come to be spatially segregated. We here describe a model in which the segregation occurs through Hebbian strengthening and weakening of geniculocortical synapses during the development of the visual system. Our findings include the following. 1. Neighbouring on- and off-inputs to cortex largely cancelled each other at the start of development. At each receptive field location, the Hebbian process increased the strength of one input sign at the expense of the other sign, producing a spatial segregation of on- and off-inputs. 2. The resulting orientation selectivity was precise in that the bandwidths of the orientation tuning functions fell within empirical estimates. 3. The model produced maps of preferred orientation-complete with iso-orientation domains and pinwheels-similar to those found in real cortex. 4. These maps did not originate in cortical processes, but from clustering of off-centre subcortical pathways and the relative location of neighbouring on-centre clusters. We conclude that a model with intermingled on- and off-pathways shaped by Hebbian synaptic plasticity can explain both the origin and development of orientation selectivity.


Assuntos
Modelos Neurológicos , Orientação/fisiologia , Córtex Visual/fisiologia , Animais , Gatos , Biologia Computacional , Corpos Geniculados/fisiologia , Plasticidade Neuronal/fisiologia , Estimulação Luminosa , Células Fotorreceptoras de Vertebrados/fisiologia , Células Ganglionares da Retina/fisiologia , Córtex Visual/crescimento & desenvolvimento , Campos Visuais/fisiologia , Vias Visuais/crescimento & desenvolvimento , Vias Visuais/fisiologia
15.
J Exp Psychol Gen ; 148(8): 1386-1406, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31259600

RESUMO

Voluminous research supports holistic processing of faces. However, little is known about how holistic processing affects recognition of newly learned faces, a question of importance for improving performance in police lineups and other real-world tasks. Drawing on cognitive and neuropsychological research, we suggest that holistic processing facilitates the formation of unitized representations that support discrimination between old and new faces-including new faces that contain old parts-through a unidimensional familiarity signal. In the absence of holistic processing, face recognition is based on relational representations that are relatively difficult to encode, but which allow flexible recognition decisions based on match-mismatch detection to be made. Unlike unitized representations, relational representations can support judgments that newly encountered faces match previously experienced faces in some respects (e.g., some of their features) and yet not in others (e.g., other features, global configuration). Four experiments clarified the relationship of holistic processing to the formation of unitized and relational representations of faces. By manipulating the extent of holistic processing while controlling for the overall level of recognition performance, we demonstrate qualitative effects of holistic processing on how recognition decisions are made with faces. (PsycINFO Database Record (c) 2019 APA, all rights reserved).


Assuntos
Reconhecimento Facial/fisiologia , Orientação/fisiologia , Percepção Visual/fisiologia , Adolescente , Feminino , Humanos , Julgamento/fisiologia , Masculino , Estimulação Luminosa , Adulto Jovem
16.
Sensors (Basel) ; 19(12)2019 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-31226796

RESUMO

The development of computer vision based systems dedicated to help visually impaired people to perceive the environment, to orientate and navigate has been the main research subject of many works in the recent years. A significant ensemble of resources has been employed to support the development of sensory substitution devices (SSDs) and electronic travel aids for the rehabilitation of the visually impaired. The Sound of Vision (SoV) project used a comprehensive approach to develop such an SSD, tackling all the challenging aspects that so far restrained the large scale adoption of such systems by the intended audience: Wearability, real-time operation, pervasiveness, usability, cost. This article is set to present the artificial vision based component of the SoV SSD that performs the scene reconstruction and segmentation in outdoor environments. In contrast with the indoor use case, where the system acquires depth input from a structured light camera, in outdoors SoV relies on stereo vision to detect the elements of interest and provide an audio and/or haptic representation of the environment to the user. Our stereo-based method is designed to work with wearable acquisition devices and still provide a real-time, reliable description of the scene in the context of unreliable depth input from the stereo correspondence and of the complex 6 DOF motion of the head-worn camera. We quantitatively evaluate our approach on a custom benchmarking dataset acquired with SoV cameras and provide the highlights of the usability evaluation with visually impaired users.


Assuntos
Inteligência Artificial , Auxiliares Sensoriais , Visão Ocular/fisiologia , Pessoas com Deficiência Visual , Humanos , Orientação/fisiologia , Interface Usuário-Computador , Dispositivos Eletrônicos Vestíveis
17.
Sensors (Basel) ; 19(13)2019 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-31248016

RESUMO

Features were developed which accounted for the changing orientation of the inertial measurement unit (IMU) relative to the body, and demonstrably improved the performance of models for human activity recognition (HAR). The method is proficient at separating periods of standing and sedentary activity (i.e., sitting and/or lying) using only one IMU, even if it is arbitrarily oriented or subsequently re-oriented relative to the body; since the body is upright during walking, learning the IMU orientation during walking provides a reference orientation against which sitting and/or lying can be inferred. Thus, the two activities can be identified (irrespective of the cohort) by analyzing the magnitude of the angle of shortest rotation which would be required to bring the upright direction into coincidence with the average orientation from the most recent 2.5 s of IMU data. Models for HAR were trained using data obtained from a cohort of 37 older adults (83.9 ± 3.4 years) or 20 younger adults (21.9 ± 1.7 years). Test data were generated from the training data by virtually re-orienting the IMU so that it is representative of carrying the phone in five different orientations (relative to the thigh). The overall performance of the model for HAR was consistent whether the model was trained with the data from the younger cohort, and tested with the data from the older cohort after it had been virtually re-oriented (Cohen's Kappa 95% confidence interval [0.782, 0.793]; total class sensitivity 95% confidence interval [84.9%, 85.6%]), or the reciprocal scenario in which the model was trained with the data from the older cohort, and tested with the data from the younger cohort after it had been virtually re-oriented (Cohen's Kappa 95% confidence interval [0.765, 0.784]; total class sensitivity 95% confidence interval [82.3%, 83.7%]).


Assuntos
Monitorização Fisiológica , Postura/fisiologia , Caminhada/fisiologia , Dispositivos Eletrônicos Vestíveis , Adulto , Idoso , Algoritmos , Fenômenos Biomecânicos , Feminino , Atividades Humanas , Humanos , Masculino , Orientação/fisiologia , Adulto Jovem
18.
J Vis ; 19(6): 23, 2019 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-31251807

RESUMO

Adaptation aftereffects are generally stronger for peripheral than for foveal viewing. We examined whether there are also differences in the dynamics of visual adaptation in central and peripheral vision. We tracked the time course of contrast adaptation to binocularly presented Gabor patterns in both the central visual field (within 5°) and in the periphery (beyond 10° eccentricity) using a yes/no detection task to monitor contrast thresholds. Consistent with previous studies, sensitivity losses were stronger in the periphery than in the center when adapting to equivalent high contrast (90% contrast) patterns. The time course of the threshold changes was fitted with separate exponential functions to estimate the time constants during the adapt and post-adapt phases. When adapting to equivalent high contrast, adaptation effects built up and decayed more slowly in the periphery compared with central adaptation. Surprisingly, the aftereffect in the periphery did not decay completely to the baseline within the monitored post-adapt period (400 s), and instead asymptoted to a higher level than for central adaptation. Even when contrast was reduced to one-third (30% contrast) of the central contrast, peripheral adaptation remained stronger and decayed more slowly. This slower dynamic was also confirmed at suprathreshold test contrasts by tracking tilt-aftereffects with a 2AFC orientation discrimination task. Our results indicate that the dynamics of contrast adaptation differ between central and peripheral vision, with the periphery adapting not only more strongly but also more slowly, and provide another example of potential qualitative processing differences between central and peripheral vision.


Assuntos
Adaptação Fisiológica , Sensibilidades de Contraste/fisiologia , Orientação/fisiologia , Campos Visuais/fisiologia , Percepção Visual/fisiologia , Feminino , Humanos , Masculino
19.
Comput Intell Neurosci ; 2019: 6989128, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31191633

RESUMO

Recognizing and tracking the direction of moving stimuli is crucial to the control of much animal behaviour. In this study, we examine whether a bio-inspired model of synaptic plasticity implemented in a robotic agent may allow the discrimination of motion direction of real-world stimuli. Starting with a well-established model of short-term synaptic plasticity (STP), we develop a microcircuit motif of spiking neurons capable of exhibiting preferential and nonpreferential responses to changes in the direction of an orientation stimulus in motion. While the robotic agent processes sensory inputs, the STP mechanism introduces direction-dependent changes in the synaptic connections of the microcircuit, resulting in a population of units that exhibit a typical cortical response property observed in primary visual cortex (V1), namely, direction selectivity. Visually evoked responses from the model are then compared to those observed in multielectrode recordings from V1 in anesthetized macaque monkeys, while sinusoidal gratings are displayed on a screen. Overall, the model highlights the role of STP as a complementary mechanism in explaining the direction selectivity and applies these insights in a physical robot as a method for validating important response characteristics observed in experimental data from V1, namely, direction selectivity.


Assuntos
Percepção de Movimento/fisiologia , Movimento (Física) , Plasticidade Neuronal/fisiologia , Robótica , Animais , Potenciais Evocados Visuais/fisiologia , Neurônios/fisiologia , Orientação/fisiologia , Córtex Visual/fisiologia , Percepção Visual/fisiologia
20.
Sensors (Basel) ; 19(11)2019 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-31174268

RESUMO

A device to train children in time orientation has been designed, developed and evaluated. It is framed within a long-term cooperation action between university and special education school. It uses a specific cognitive accessible time display: Time left in the day is represented by a row of luminous elements initially on. Time passing is represented by turning off sequentially and gradually each luminous element every 15 min. Agenda is displayed relating time to tasks with standard pictograms for further accessibility. Notifications of tasks-to-come both for management support and anticipation to changes uses visual and auditory information. Agenda can be described in an Alternative and Augmentative Communication pictogram language already used by children, supporting individual and class activities on agenda. Validation has been performed with 16 children in 12 classrooms of four special education schools. Methodology for evaluation compares both prior and posterior assessments which are based in the International Classification of Functioning, Disability and Health (ICF) from the World Health Organization (WHO), together with observation registers. Results show consistent improvement in performances related with time orientation.


Assuntos
Pessoas com Deficiência , Orientação/fisiologia , Tecnologia/métodos , Adolescente , Adulto , Criança , Assistência à Saúde , Feminino , Humanos , Instituições Acadêmicas , Tempo , Adulto Jovem
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