Hans Supèr

Hans Supèr
Catalan Institution for Research and Advanced Studies | ICREA · Basic Psychology

PhD Neurobiology

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93
Publications
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Publications

Publications (93)
Article
We present a model connecting eye movements and cortical state. Its structure includes simulated retinal images, motion detection, feature detectors and layers of spiking neurons. The designed scheme shows how the effect of micro-saccadic scale eye movements can lead to successful figure segregation in a figure-ground paradigm, by inducing changes...
Article
Full-text available
Background Facial expression of emotion is fundamental to human social interactions. Attention to relevant cues in ADHD and ASD patients are believed to underlie difficulties in recognizing emotions. Cognitive vergence eye movements during gaze fixation have a role in attention. Here we evaluate a possible role of cognitive vergence in facial emoti...
Article
Figure-ground, that is the segmentation of visual information into objects and their surrounding backgrounds, provides structure for visual attention. Recent evidence shows a novel role of vergence eye movements in visual attention. In the present work, vergence responses during figure-ground segregation tasks are psychophysically investigated. We...
Article
Background: Alzheimer's disease (AD) is characterized by progressive deterioration of cognitive functions and may be preceded by mild cognitive impairment (MCI). Evidence shows changes in pupil and vergence responses related to cognitive processing of visual information. Objective: Here we test the hypothesis that MCI and AD are associated with...
Article
Full-text available
The visual system is highly sensitive to spatial context for encoding luminance patterns. Context sensitivity inspired the proposal of many neural mechanisms for explaining the perception of luminance (brightness). Here we propose a novel computational model for estimating the brightness of many visual illusions. We hypothesize that many aspects of...
Article
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Background Atypical arousal regulation may explain slower mean reaction times (MRT) in Autism Spectrum Disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD) compared to typically developing controls (TD). The Locus Coeruleus–Norepinephrine system (LC-NE) underlies arousal regulation and adapts its activity to the utility of a task. LC-...
Preprint
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The visual system is highly sensitive to spatial context for encoding luminance patterns. Context sensitivity inspired the proposal of many neural mechanisms for explaining the perception of luminance (brightness). Here we propose a novel computational model for estimating the brightness of many visual illusions. We hypothesize that many aspects of...
Article
Vergence eye movements are movements of both eyes in opposite directions. Vergence is known to have a role in binocular vision. However recent studies link vergence eye movements also to attention and attention disorders. As attention may be involved in dyslexia, it is sensible to guess that the presence of reading difficulties can be associated wi...
Article
Objective: ADHD patients show poor oculomotor control and recent studies show that attention-related eye vergence is weak in ADHD children. We aimed to assess vergence as a potential diagnostic biomarker for ADHD in adults. Method: We assessed the modulation in the angle of vergence while performing an attention task ( N = 144), comparing the resul...
Article
Objective: To assess whether the eye-tracking approach of the RECOGNeyes game has potential therapeutic benefits for children with neurodevelopmental disorders, in particular attention-deficit/hyperactivity disorder (ADHD). RECOGNeyes is a computer game that is played using the eyes as the game controller. The rationale behind the game is that ind...
Article
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Eye vergence is the slow movement of both eyes in opposite directions enabling binocular vision. Recently, it was suggested that vergence could be involved in orienting visual attention and memory having a role in cognitive processing of sensory information. In the present study, we assessed whether such vergence responses are observed in early chi...
Article
The brain analyses the visual world through the luminance patterns that reach the retina. Formally, luminance (as measured by the retina) is the product of illumination and reflectance. Whereas illumination is highly variable, reflectance is a physical property that characterizes each object surface. Due to memory constraints, it seems plausible th...
Article
Objective: ADHD youth show poor oculomotor control. Recent research shows that attention-related eye vergence is weak in ADHD children. Method: To validate vergence as a marker to classify ADHD, we assessed the modulation in the angle of vergence of children ( n = 43) previously diagnosed with ADHD while performing an attention task and compared...
Article
In line with a possible role of vergence in orienting visual attention, we sought to study this eye movement in young children to provide insights on face perception. For this purpose, we measured the modulation in the angle of eye vergence in a sample of 39 children aged 6-36 months and compared it when presenting static human face images versus t...
Article
Full-text available
We apply the competitive model of Loxley and Robinson (Phys Rev Lett 102:258701, 2009. doi: 10.1103/PhysRevLett.102.258701 ) to the study of a special case of visual rivalry. Three-peaked inputs with maxima at symmetrical locations are introduced, and the role of three-bump configurations is then considered. The model yields conditions for what can...
Article
Some forms of competition among activity bumps in a two-dimensional neural field are studied. First, threshold dynamics is included and rivalry evolutions are considered. The relations between parameters and dominance durations can match experimental observations about ageing. Next, the threshold dynamics is omitted from the model and we focus on t...
Article
Full-text available
Attention deficit hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorder. It is a chronic disease where 50–60% of ADHD cases persist into adult life. ADHD is associated with a range of clinical and psychosocial impairments. In children hyperactivity, impulsivity and inattention are the core symptoms of ADHD. In adults t...
Article
In a previous report it was shown that covertly attending visual stimuli produce small convergence of the eyes, and that visual stimuli can give rise to different modulations of the angle of eye vergence, depending on their power to capture attention. Working memory is highly dependent on attention. Therefore, in this study we assessed vergence res...
Article
Full-text available
Neural mechanisms of attention allow selective sensory information processing. Top-down deployment of visual-spatial attention is conveyed by cortical feedback connections from frontal regions to lower sensory areas modulating late stimulus responses. A recent study reported the occurrence of small eye vergence during orienting top-down attention....
Article
Full-text available
El Trastorno por Déficit de Atención con Hiperactividad (TDAH) es uno de los trastornos más comunes del neurodesarrollo. El diagnóstico actual se fundamenta en la presencia de síntomas de inatención, hiperactividad o impulsividad detectados a través de la anamnesis, la exploración, las entrevistas con padres y profesores y las escalas de evaluación...
Article
The role of sensory inputs in the modelling of synchrony regimes is exhibited by means of networks of spiking cells where the relative strength of the inhibitory interaction is controlled by the activation of a linear unit working as a gating variable. Adaptation to stimulus size is determined by the value of a changing length scale, modelled by th...
Article
Introduction Eye movement recordings can provide information about higher-level processing of visual information. Recent evidence shows a novel role for eye vergence in orienting attention (Solé Puig et al., 2013). Based on such eye tracking data, the BGaze method (Braingaze; Spain) detects visual attention. The outcomes of the BGaze method have be...
Article
We introduce a neural model capable of feature selectiveness by spike-mediated synchronization through lateral synaptic couplings. For a stimulus containing two features, the attended one elicits a higher response. In the case of sequential single-feature stimuli, repetition of the attended feature also results in an enhanced response, exhibited by...
Article
Full-text available
Recent evidence shows a novel role for eye vergence in orienting attention in adult subjects. Here we investigated whether such modulation in eye vergence by attention is present in children and whether it is altered in children with ADHD compared to control subjects. We therefore measured the angle of eye vergence in children previously diagnosed...
Chapter
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Orientation is one of the main elements that form our perceptual space. Many studies have shown that people misjudge orientation in the frontoparallel plane. Here we examined precision in matching oriented lines in a 3D environment. In Experiment 1 we used perspective as a pictorial cue to provide the impression of a surface inclined in depth. In t...
Article
Full-text available
The present study investigated the mechanisms involved in processing orientation on the frontal and ground planes. The stimuli comprised two yellow circles conceived as the endpoints of a segment and depicted on a black background. In Experiment 1, the observers performed two tasks on both planes (frontal and ground). In Task 1 they were asked to i...
Article
As a result of the spider experiments in Nagata et al. (2012), it was hypothesized that the depth perception mechanisms of these animals should be based on how much images are defocused. In the present paper, assuming that relative chromatic aberrations or blur radii values are known, we develop a formulation relating the values of these cues to th...
Article
In a three-dimensional (3D) world most saccades are made towards visual targets that are located at different distances. We previously demonstrated that gaze shifts within 3D space consist of two stages: a target saccade followed by a corrective saccade during gaze fixation that directs the eyes to the physical target location. We proposed that, by...
Article
Possible ways of obtaining information about the solutions of Izhikevich's "simple model" for a spiking neuron are considered. The method of power series in time is reviewed. From a different viewpoint, in the case of constant input and weak recovery scale effects, advantage is taken of a small-parameter expansion. The obtained approximations can b...
Article
Models for perceptual grouping and contour integration are presented. Connection weights depend on distances and angle differences, while neurons evolve following a spiking dynamics (Izhikevich's model in most of the considered cases). Although the studied synapses depend on discrete three-valued functions, simulations display the emergence of appr...
Article
Full-text available
Covert spatial attention produces biases in perceptual and neural responses in the absence of overt orienting movements. The neural mechanism that gives rise to these effects is poorly understood. Here we report the relation between fixational eye movements, namely eye vergence, and covert attention. Visual stimuli modulate the angle of eye vergenc...
Conference Paper
Full-text available
Background / Purpose: This talk presents evidence for a novel role of eye vergence in visual attention and perception. Main conclusion: We believe that we discovered a novel role of eye vergence in visual attention and perception; perhaps disengagement. We speculate that disparity neurons have a role in attention meaning that they form part o...
Article
Full-text available
The ability to recognize a shape is linked to figure-ground (FG) organization. Cell preferences appear to be correlated across contrast-polarity reversals and mirror reversals of polygon displays, but not so much across FG reversals. Here we present a network structure which explains both shape-coding by simulated IT cells and suppression of respon...
Article
What roles do the different cortical layers play in visual processing? We recorded simultaneously from all layers of the primary visual cortex while monkeys performed a figure-ground segregation task. This task can be divided into different subprocesses that are thought to engage feedforward, horizontal, and feedback processes at different time poi...
Article
The different sources of information that can be used to estimate time-to-contact may have different degrees of reliability across time. For example, after a given presentation or display time, an absolute change of angular size can be more reliable than the corresponding estimation of the rate of angular expansion (e.g. motion information). One co...
Article
Full-text available
Orienting visual attention is closely linked to the oculomotor system. For example, a shift of attention is usually followed by a saccadic eye movement and can be revealed by micro saccades. Recently we reported a novel role of another type of eye movement, namely eye vergence, in orienting visual attention. Shifts in visuospatial attention are cha...
Article
Attention deficit hyperactivity disorder (ADHD) is one of the main neurobiological disorders in young children. Despite its prevalence, current diagnosis is debated. In this study we tested whether measures of binocular rivalry (BR) can contribute to the diagnosis of ADHD. BR is a phenomenon that is produced when two different images are presented...
Article
3-D Vision, vergence eye movements, saccades
Article
Accurate saccadic and vergence eye movements towards selected visual targets are fundamental to perceive the 3-D environment. Despite this importance, shifts in eye gaze are not always perfect given that they are frequently followed by small corrective eye movements. The oculomotor system receives distinct information from various visual cues that...
Article
Full-text available
Covert spatial attention produces biases in perceptual and neural responses in the absence of overt orienting movements. The neural mechanism that gives rise to these effects is poorly understood. Here we report the relation between fixational eye movements, namely eye vergence, and covert attention. Visual stimuli modulate the angle of eye vergenc...
Article
In backward masking, a target stimulus is rendered invisible by the presentation of a second stimulus, the mask. When the mask is effective, neural responses to the target are suppressed. Nevertheless, weak target responses sometimes may produce a behavioural response. It remains unclear whether the reduced target response is a purely feedforward r...
Article
Full-text available
Figure-ground (FG) segmentation is the separation of visual information into background and foreground objects. In the visual cortex, FG responses are observed in the late stimulus response period, when neurons fire in tonic mode, and are accompanied by a switch in cortical state. When such a switch does not occur, FG segmentation fails. Currently,...
Article
Full-text available
Neurons in the primary visual cortex (V1) receive feedforward input from the thalamus, which shapes receptive-field properties. They additionally receive recurrent inputs via horizontal connections within V1 and feedback from higher visual areas that are thought to be important for conscious visual perception. Here, we investigated what roles diffe...
Article
Perception depends on proper recurrent interactions among separate visual areas. Within such a cooperative network, the primary visual cortex plays a unique part. It is the main recipient of visual information, and it is at the end stage of top-down influences. In recent years, it has become clear that the primary visual cortex plays a prominent ro...
Article
Full-text available
A visual stimulus can be made invisible, i.e. masked, by the presentation of a second stimulus. In the sensory cortex, neural responses to a masked stimulus are suppressed, yet how this suppression comes about is still debated. Inhibitory models explain masking by asserting that the mask exerts an inhibitory influence on the responses of a neuron e...
Article
Full-text available
In a three-dimensional (3-D) environment, sensory information is projected on a 2-D retina with the consequence that the visual system needs space information for accurately reconstructing the visual world. However, the 3-D environment is not accurately represented in the brain; in particular, the perception of distances in depth is imprecise. It h...
Article
Full-text available
In the visual cortex, feedback projections are conjectured to be crucial in figure-ground segregation. However, the precise function of feedback herein is unclear. Here we tested a hypothetical model of reentrant feedback. We used a previous developed 2-layered feedforward spiking network that is able to segregate figure from ground and included fe...
Article
Perceptual filling-in is the phenomenon where visual information is perceived although information is not physically present. For instance, the blind spot, which corresponds to the retinal location where there are no photoreceptor cells to capture the visual signals, is filled-in by the surrounding visual signals. The neural mechanism for such imme...
Article
We perceive the world by continually making saccadic eye movements. The primary role ofsaccadic eye movements is to bring the visual signals on the central part of the retina (fovea)where visual processing is superior and provides best visual capacities. It is therefore that thevisual signals at the foveal region will be more likely perceived consc...
Article
The visual scene is perceived as a composition of objects from which we select those that are meaningful to us. Sometimes this information needs to be maintained for a short period of time since in the constant and rapidly changing visual world a stimulus may have disappeared whereas a behavioral response to the stimulus still has to be made. Durin...
Article
In order to shift gaze the visual system first identifies the location of an object in the visual scene and then directs the eyes accordingly. Therefore, the neural responses signaling the perception of the object need to be coupled to motor activity. Here we studied the role of the primary visual cortex in the integration of visual and motor proce...
Article
We perceive our visual surrounding by continuously making saccadic eye movements. Saccades are guided by visual information that is previously selected by the visual system. Both bottom-up and top-down information guides saccades. The role of top-down control in gaze is demonstrated by studies showing that object perception, task demands, behaviora...
Article
Full-text available
The neural mechanisms of attention are closely related to oculomotor control of saccadic eye movements and vergence eye movements. Visual covert attention is a mechanism for mentally scanning the visual field to enhance the sensory signal. This shift in covert attention is linked to eye movement circuitry that prepares a saccadic eye movement to a...
Article
In backward masking, a target stimulus is rendered less perceptible or even invisible through the presentation of a second stimulus, the mask. Feedforward inhibitory models explain backward masking by asserting that the second stimulus exerts an inhibitory influence on the responses of a neuron evoked by the target. Another set of theories argue th...
Article
Full-text available
Figure-ground is the segmentation of visual information into objects and their surrounding backgrounds. Two main processes herein are boundary assignment and surface segregation, which rely on the integration of global scene information. Recurrent processing either by intrinsic horizontal connections that connect surrounding neurons or by feedback...
Article
The visual system binds and segments the elements of an image into coherent objects and their surroundings. Recent findings demonstrate that primary visual cortex is involved in this process of figure-ground organization. In the primary visual cortex the late part of a neural response to a stimulus correlates with figure-ground segregation and perc...
Article
When and where are decisions made? In the visual system a saccade, which is a fast shift of gaze toward a target in the visual scene, is the behavioral outcome of a decision. Current neurophysiological data and reaction time models show that saccadic reaction times are determined by a build-up of activity in motor-related structures, such as the fr...
Article
Every day we shift our gaze about 150.000 times mostly without noticing it. The direction of these gaze shifts are not random but directed by sensory information and internal factors. After each movement the eyes hold still for a brief moment so that visual information at the center of our gaze can be processed in detail. This means that visual inf...
Article
Full-text available
Behavioral measures such as expectancy and attention have been associated with the strength of synchronous neural activity. On this basis, it is hypothesized that synchronous activity affects our ability to detect and recognize visual objects. To investigate the role of synchronous activity in visual perception, we studied the magnitude and precisi...
Article
Recently neural activity related to visual working memory has been described in the primary visual cortex. These responses are observed during a delayed figure-ground response task where neural activity that segregates figure from ground continues after the removal of the figure. Attention influences the maintenance of the figure-ground signal duri...
Article
When in the brain is a decision made? In the visual domain, a behavioral outcome of a decision is a saccade, which is a fast shift of gaze towards a target in the visual scene. Making a saccade includes a sensory phase where a target is located and identified and a motor phase where an eye movement is prepared and executed. Current neurophysiologic...
Article
Cortical state is characterized by ongoing rhythmic neural activity. Changes in rhythmic activity and thus in cortical state are shown to occur spontaneously in the anesthetized cat. We were interested in whether these state changes have an affect on the cortical processing of sensory stimuli. This was investigated by recording spontaneous and stim...
Article
By simultaneous recording from neural responses at many different loci at the same time, we can understand the interaction between neurons, and thereby gain insight into the network properties of neural processing, instead of the functioning of individual neurons. Here we will discuss a method for recording in behaving animals that uses chronically...
Article
A recent study (Rossi et al. 2001) implied the absence of figure-ground based contextual modulation in macaque V1, in contrast to the study on which it was modelled (Zipser et al. 1996). We suggest that Rossi et al. may have underestimated the extent of modulation by considering only positive and not also negative modulation and that their data may...
Article
Full-text available
We continuously scan the visual world via rapid or saccadic eye movements. Such eye movements are guided by visual information, and thus the oculomotor structures that determine when and where to look need visual information to control the eye movements. To know whether visual areas contain activity that may contribute to the control of eye movemen...
Article
Aboitiz et al. describe a hypothesis on the origin of the isocortex. They propose the reptilian dorsal cortex to be the ancestral brain structure to the mammalian isocortex. But why did the dorsal cortex expand in mammals and not in reptiles? A change in development may have provided the mammalian cortex with the ability to organize and therefore t...
Article
he primary visual cortex is the first cortical area of the visual system that receives in- formation from the external visual world. Neurons in the primary visual cortex have small receptive fields and respond to basic elements of the visual scene. Recent find- ings, however, show that the primary visual cortex is also involved in cognitive pro- ce...
Article
To look at an object its position in the visual scene has to be localized and subsequently appropriate oculo-motor behavior needs to be initiated. This kind of behavior is largely controlled by the cortical executive system, such as the frontal eye field. In this report, we analyzed neural activity in the visual cortex in relation to oculo-motor be...
Article
Full-text available
When stimulus information enters the visual cortex, it is rapidly processed for identification. However, sometimes the processing of the stimulus is inadequate and the subject fails to notice the stimulus. Human psychophysical studies show that this occurs during states of inattention or absent-mindedness. At a neurophysiological level, it remains...
Article
The primary visual cortex is the first cortical area of the visual system that receives information from the external visual world. Based on the receptive field characteristics of the neurons in this area, it has been assumed that the primary visual cortex is a pure sensory area extracting basic elements of the visual scene. This information is the...
Article
Full-text available
During development, a cerebral cortex appears in the wall of the telencephalic vesicle in reptiles and mammals. It arises from a cell-dense cortical plate, which develops within a primordial preplate. The neurons of the preplate are essential for cortical development; they regulate the neuronal migration of the cortical plate neurons and form the f...