Location Of Visual Stimulus Research Articles

A hard-wired priority map in the superior colliculus shaped by asymmetric inhibitory circuitry.

The mammalian superior colliculus (SC) is a laminar midbrain structure that translates visual signals into commands to shift the focus of attention and gaze. The SC plays an integral role in selecting targets and ultimately generating rapid eye movements to those targets. In all mammals studied to date, neurons in the SC are arranged topographically such that the location of visual stimuli and the endpoints of orienting movements form organized maps in superficial and deeper layers, respectively. The organization of these maps is thought to underlie attentional priority by assessing which regions of the visual field contain behaviorally relevant information. Using voltage imaging and patch-clamp recordings in parasagittal SC slices from the rat, we found the synaptic circuitry of the visuosensory map in the SC imposes a strong bias. Voltage imaging of responses to electrical stimulation revealed more spread in the caudal direction than the rostral direction. Pharmacological experiments demonstrated that this asymmetry arises from GABAA receptor activation rostral to the site of stimulation. Patch-clamp recordings confirmed this rostrally directed inhibitory circuit and showed that it is contained within the visuosensory layers of the SC. Stimulation of two sites showed that initial stimulation of a caudal site can take priority over subsequent stimulation of a rostral site. Taken together, our data indicate that the circuitry of the visuosensory SC is hard-wired to give higher priority to more peripheral targets, and this property is conferred by a uniquely structured, dedicated inhibitory circuit.

Vision: A Moving Hill for Spatial Updating on the Fly

A recent study reveals a dynamic neural map that provides a continuous representation of remembered visual stimulus locations with respect to constantly changing gaze. This finding suggests a new mechanistic framework for understanding the spatiotemporal dynamics of goal-directed action.

The amygdala and basal forebrain as a pathway for motivationally guided attention.

Visual stimuli associated with rewards attract spatial attention. Neurophysiological mechanisms that mediate this process must register both the motivational significance and location of visual stimuli. Recent neurophysiological evidence indicates that the amygdala encodes information about both of these parameters. Furthermore, the firing rate of amygdala neurons predicts the allocation of spatial attention. One neural pathway through which the amygdala might influence attention involves the intimate and bidirectional connections between the amygdala and basal forebrain (BF), a brain area long implicated in attention. Neurons in the rhesus monkey amygdala and BF were therefore recorded simultaneously while subjects performed a detection task in which the stimulus-reward associations of visual stimuli modulated spatial attention. Neurons in BF were spatially selective for reward-predictive stimuli, much like the amygdala. The onset of reward-predictive signals in each brain area suggested different routes of processing for reward-predictive stimuli appearing in the ipsilateral and contralateral fields. Moreover, neurons in the amygdala, but not BF, tracked trial-to-trial fluctuations in spatial attention. These results suggest that the amygdala and BF could play distinct yet inter-related roles in influencing attention elicited by reward-predictive stimuli.

Reward-priming of location in visual search.

Existing visual search research has demonstrated that the receipt of reward will be beneficial for subsequent perceptual and attentional processing of features that have characterized targets, but detrimental for processing of features that have characterized irrelevant distractors. Here we report a similar effect of reward on location. Observers completed a visual search task in which they selected a target, ignored a salient distractor, and received random-magnitude reward for correct performance. Results show that when target selection garnered rewarding outcome attention is subsequently a.) primed to return to the target location, and b.) biased away from the location that was occupied by the salient, task-irrelevant distractor. These results suggest that in addition to priming features, reward acts to guide visual search by priming contextual locations of visual stimuli.

Are patients with Parkinson's disease blind to blindsight?

In Parkinson's disease, visual dysfunction is prominent. Visual hallucinations can be a major hallmark of late stage disease, but numerous visual deficits also occur in early stage Parkinson's disease. Specific retinopathy, deficits in the primary visual pathway and the secondary ventral and dorsal pathways, as well as dysfunction of the attention pathways have all been posited as causes of hallucinations in Parkinson's disease. We present data from patients with Parkinson's disease that contrast with a known neuro-ophthalmological syndrome, termed 'blindsight'. In this syndrome, there is an absence of conscious object identification, but preserved 'guess' of the location of a stimulus, preserved reflexive saccades and motion perception and preserved autonomical and expressive reactions to negative emotional facial expressions. We propose that patients with Parkinson's disease have the converse of blindsight, being 'blind to blindsight'. As such they preserve conscious vision, but show erroneous 'guess' localization of visual stimuli, poor saccades and motion perception, and poor emotional face perception with blunted autonomic reaction. Although a large data set on these deficits in Parkinson's disease has been accumulated, consolidation into one specific syndrome has not been proposed. Focusing on neuropathological and physiological data from two phylogenetically old and subconscious pathways, the retino-colliculo-thalamo-amygdala and the retino-geniculo-extrastriate pathways, we propose that aberrant function of these systems, including pathologically inhibited superior colliculus activity, deficient corollary discharges to the frontal eye fields, dysfunctional pulvinar, claustrum and amygdaloid subnuclei of the amygdala, the latter progressively burdened with Lewy bodies, underlie this syndrome. These network impairments are further corroborated by the concept of the 'silent amygdala'. Functionally being 'blind to blindsight' may facilitate the highly distinctive 'presence' or 'passage' hallucinations of Parkinson's disease and can help to explain handicaps in driving capacities and dysfunctional 'theory of mind'. We propose this synthesis to prompt refined neuropathological and neuroimaging studies on the pivotal nuclei in these pathways in order to better understand the networks underpinning this newly conceptualized syndrome in Parkinson's disease.

Gaze-Dependent Topography in Human Posterior Parietal Cortex

The brain must convert retinal coordinates into those required for directing an effector. One prominent theory holds that, through a combination of visual and motor/proprioceptive information, head-/body-centered representations are computed within the posterior parietal cortex (PPC). An alternative theory, supported by recent visual and saccade functional magnetic resonance imaging (fMRI) topographic mapping studies, suggests that PPC neurons provide a retinal/eye-centered coordinate system, in which the coding of a visual stimulus location and/or intended saccade endpoints should remain unaffected by changes in gaze position. To distinguish between a retinal/eye-centered and a head-/body-centered coordinate system, we measured how gaze direction affected the representation of visual space in the parietal cortex using fMRI. Subjects performed memory-guided saccades from a central starting point to locations “around the clock.” Starting points varied between left, central, and right gaze relative to the head-/body midline. We found that memory-guided saccadotopic maps throughout the PPC showed spatial reorganization with very subtle changes in starting gaze position, despite constant retinal input and eye movement metrics. Such a systematic shift is inconsistent with models arguing for a retinal/eye-centered coordinate system in the PPC, but it is consistent with head-/body-centered coordinate representations.

Transformation of Visual Signals by Inhibitory Interneurons in Retinal Circuits

One of the largest mysteries of the brain lies in understanding how higher-level computations are implemented by lower-level operations in neurons and synapses. In particular, in many brain regions inhibitory interneurons represent a diverse class of cells, the individual functional roles of which are unknown. We discuss here how the operations of inhibitory interneurons influence the behavior of a circuit, focusing on recent results in the vertebrate retina. A key role in this understanding is played by a common representation of the visual stimulus that can be applied at different stages. By considering how this stimulus representation changes at each location in the circuit, we can understand how neuron-level operations such as thresholds and inhibition yield circuit-level computations such as how stimulus selectivity and gain are controlled by local and peripheral visual stimuli.

Distinct Acute Zones for Visual Stimuli in Different Visual Tasks in Drosophila

The fruit fly Drosophila melanogaster has a sophisticated visual system and exhibits complex visual behaviors. Visual responses, vision processing and higher cognitive processes in Drosophila have been studied extensively. However, little is known about whether the retinal location of visual stimuli can affect fruit fly performance in various visual tasks. We tested the response of wild-type Berlin flies to visual stimuli at several vertical locations. Three paradigms were used in our study: visual operant conditioning, visual object fixation and optomotor response. We observed an acute zone for visual feature memorization in the upper visual field when visual patterns were presented with a black background. However, when a white background was used, the acute zone was in the lower visual field. Similar to visual feature memorization, the best locations for visual object fixation and optomotor response to a single moving stripe were in the lower visual field with a white background and the upper visual field with a black background. The preferred location for the optomotor response to moving gratings was around the equator of the visual field. Our results suggest that different visual processing pathways are involved in different visual tasks and that there is a certain degree of overlap between the pathways for visual feature memorization, visual object fixation and optomotor response.

Collinear Stimuli Induce Local and Cross-Areal Coherence in the Visual Cortex of Behaving Monkeys

BackgroundCollinear patterns of local visual stimuli are used to study contextual effects in the visual system. Previous studies have shown that proximal collinear flankers, unlike orthogonal, can enhance the detection of a low contrast central element. However, the direct neural interactions between cortical populations processing the individual flanker elements and the central element are largely unknown.Methodology/Principal FindingsUsing voltage-sensitive dye imaging (VSDI) we imaged neural population responses in V1 and V2 areas in fixating monkeys while they were presented with collinear or orthogonal arrays of Gabor patches. We then studied the spatio-temporal interactions between neuronal populations processing individual Gabor patches in the two conditions. Time-frequency analysis of the stimulus-evoked VSDI signal showed power increase mainly in low frequencies, i.e., the alpha band (α; 7–14 Hz). Power in the α-band was more discriminative at a single trial level than other neuronal population measures. Importantly, the collinear condition showed an increased intra-areal (V1-V1 and V2-V2) and inter-areal (V1-V2) α-coherence with shorter latencies than the orthogonal condition, both before and after the removal of the stimulus contribution. α-coherence appeared between discrete neural populations processing the individual Gabor patches: the central element and the flankers.Conclusions/SignificanceOur findings suggest that collinear effects are mediated by synchronization in a distributed network of proximal and distant neuronal populations within and across V1 and V2.

Bioinspired computing nets for directionality in vision

Directional selectivity to local visual stimuli appears in various levels of the visual pathway, being in the retina very conspicuous. Neurophysiology suggests that directionality (as well as other local and quasi-global filtering properties) are based in the space–time interactions of processes with different “memory” (latency). We draw inspiration from the corresponding underlying biological mechanisms to propose two general schemes for directionality computation in nets, compatible with other space–time filtering properties. First, a connectivistic mechanism based on bipolar–amacrine–ganglion cell interaction is proposed, by formalizing the classical proposals of early vision neurophysiologists. Second, inspired initially in the more recently described intrinsic directionality of amacrines, novel schemes are proposed where directionality appear as the computing consequence of adding memory to spatial filtering structures. The mathematical formulations are achieved by means of Newton Filters and Hermite Functionals.

Generating a diverse repertoire of receptive fields in mouse visual cortex

Event Abstract Back to Event Generating a diverse repertoire of receptive fields in mouse visual cortex Dmitry Tsigankov1, Audrey Sederberg2 and Matthias Kaschube1* 1 Goethe University, Frankfurt Institute for Advanced Studies, Germany 2 University of Chicago, Department of Neurobiology, United States In mouse visual cortex (V1), the receptive fields and responses of neurons are highly diverse [1]. Selectivities for the orientation, direction and visual field location of visual stimuli are arranged nearly randomly across local groups of neurons. In this model study we show that to a very good approximation this organization naturally arises in a very large class of generic random recurrent networks without the need of any stimulus dependent plasticity. We consider a recurrent random network of neurons in V1 layer 4 receiving input from the LGN. Neurons are modeled as firing rate units with a nonlinearity. Assuming the network receives weakly orientation but not direction selective afferent inputs, we show that as a function of average strength of recurrent connections, most neurons increase their orientation selectivity and become also direction selective. For sufficiently strong recurrent connections the distributions of both orientation and direction selectivity closely approaches the experimentally observed distributions in mice [2]. In this regime, neurons show diverse levels of average activity with the majority of cells firing at relatively low rates. Computing the structure of the neurons’ receptive fields we find that they are often composed of several ON- and OFF regions reminiscent of cortical simple cells [1]. We discuss the effect of excitatory and inhibitory connections and the robustness of selectivities with respect to different recurrent connections and visual stimuli. We conclude that a diverse repertoire of receptive fields arises naturally in networks with sufficiently strong recurrent connections. Our results account for the recent observations that neurons in mouse V1 are orientation and direction selective already shortly after the time of eye opening and that dark rearing appears to have little effect on these properties [2]. Acknowledgements Bernstein Focus: Neurotechnology Frankfurt, FKZ 01GQ0840 References [1] Bonin et al., J Neurosc (2011) [2] Rochefort et al., Neuron (2011) Keywords: Dark Rearing, Direction Selectivity, firing rate, Mouse, orientation selectivity, Randomness, Recurrent network Conference: Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012. Presentation Type: Poster Topic: Sensory processing and perception Citation: Tsigankov D, Sederberg A and Kaschube M (2012). Generating a diverse repertoire of receptive fields in mouse visual cortex. Front. Comput. Neurosci. Conference Abstract: Bernstein Conference 2012. doi: 10.3389/conf.fncom.2012.55.00067 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 May 2012; Published Online: 12 Sep 2012. * Correspondence: Prof. Matthias Kaschube, Goethe University, Frankfurt Institute for Advanced Studies, Frankfurt am Main, 60438, Germany, kaschube@fias.uni-frankfurt.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Dmitry Tsigankov Audrey Sederberg Matthias Kaschube Google Dmitry Tsigankov Audrey Sederberg Matthias Kaschube Google Scholar Dmitry Tsigankov Audrey Sederberg Matthias Kaschube PubMed Dmitry Tsigankov Audrey Sederberg Matthias Kaschube Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The attentional repulsion effect distorts space but not objects

• A spatial consequence of allocating attention to peripheral locations  reflexive shifts of attention to the periphery create errors in the localization of visual stimuli in the direction opposite to the shift (Suzuki & Cavanagh, 1997) • Location : pay attention to the circles – ‘is the top circle to the left or right of the bottom circle?’ • Object : pay attention to the diamond – ‘is the diamond tilted to the left or to the right?’

A novel high-throughput imaging system for automated analyses of avoidance behavior in zebrafish larvae

Early brain development can be influenced by numerous genetic and environmental factors, with long-lasting effects on brain function and behavior. The identification of these factors is facilitated by recent innovations in high-throughput screening. However, large-scale screening in whole organisms remains challenging, in particular when studying changes in brain function or behavior in vertebrate model systems. In this study, we present a novel imaging system for high-throughput analyses of behavior in zebrafish larvae. The three-camera system can image 12 multiwell plates simultaneously and is unique in its ability to provide local visual stimuli in the wells of a multiwell plate. The acquired images are converted into a series of coordinates, which characterize the location and orientation of the larvae. The developed imaging techniques were tested by measuring avoidance behaviors in seven-day-old zebrafish larvae. The system effectively quantified larval avoidance and revealed an increased edge preference in response to a blue or red ‘bouncing ball’ stimulus. Larvae also avoid a bouncing ball stimulus when it is counter-balanced with a stationary ball, but do not avoid blinking balls counter-balanced with a stationary ball. These results indicate that the seven-day-old larvae respond specifically to movement, rather than color, size, or local changes in light intensity. The imaging system and assays for measuring avoidance behavior may be used to screen for genetic and environmental factors that cause developmental brain disorders and for novel drugs that could prevent or treat these disorders.

Neuronal code of spatial visual information in the caudate nucleus

Earlier reports described huge overlapping visual receptive fields and the absence of retinotopic organization in the dorsolateral, caudal part of the caudate nucleus. In the present study we suggest a possible alternative mechanism for the coding of spatial visual information. Extracellular microelectrode recordings were carried out in halothane-anesthetized, immobilized, artificially ventilated cats. In order to investigate the responsiveness of the single neurons to visual information arriving from different sites of the receptive field, we divided the visual fields to 20 parts of equal size and stimulated the individual parts one-by-one. We found that each single visual caudate nucleus (CN) neuron can carry information about stimulus locations throughout the whole physically approachable visual field of the investigated eye. A large majority (85%) of these neurons exhibited significantly different responses to stimuli appearing in different regions of their huge receptive field. Thus these neurons appear to have the ability to provide information on the site of the stimulus via their discharge rate. The huge receptive fields in combination with the spatial selectivity suggest that these caudate nucleus neurons may serve as panoramic localizers. On the population level, the sites of maximal responsiveness of the visual neurons are distributed over the whole extent of the receptive fields. We argue that groups of these panoramic localizer neurons with different locations of maximal stimulus preference should have the ability to accurately code the locations of visual stimuli. We propose this distributed population code of visual information as an alternative information processing mechanism.

The role of spatial attention in attentional control over pain: an experimental investigation

Distraction is a common method of pain control that is often found to be effective. However, it is still largely unexplored which components of distraction are responsible for its effects. This study investigated the role of the spatial location of task-relevant stimuli in the effectiveness of distraction. Two experiments were performed in which the spatial location of visual stimuli during nociceptive input was manipulated. In a first experiment, we tested whether the reaction to nociceptive information is slower when visual stimuli are presented at a different spatial location than at the same spatial location. In a second experiment, we examined whether the manipulation of spatial location affects the experience of pain. Overall, results indicated that directing attention away from the pain location results in a slower response to painful stimuli and a reduction in pain. It may be concluded that the analgesic effect of distraction is at least partly the result of the spatial location of the distracting information.

Adaptive actions on shading devices in response to local visual stimuli

Based on 6 years of continuous measurements, we have analysed in detail the occupancy, thermal and visual parameters influencing actions on shading devices in order to derive an accurate model for the prediction of their usage in office buildings. This article begins by presenting some of the key findings from these analyses. Informed by other developments in the literature, we go on to propose an approach for a comprehensive stochastic model for simulating blind usage. This model is based on a Markov process taking rigorously selected predictors (initial blind status, indoor and outdoor illuminance) as input variables to predict lowering and raising actions performed by occupants. A separate sub-model then predicts the chosen shaded fraction. An assessment of the predictive accuracy of simulations is then presented for several modelling variants using our measured data, from which the best performing model variant is selected.

Human thalamus contributes to perceptual stability across eye movements

We continuously move our eyes when we inspect a visual scene. Although this leads to a rapid succession of discontinuous and fragmented retinal snapshots, we perceive the world as stable and coherent. Neural mechanisms underlying visual stability may depend on internal monitoring of planned or ongoing eye movements. In the macaque brain, a pathway for the transmission of such signals has been identified that is relayed by central thalamic nuclei. Here, we studied a possible role of this pathway for perceptual stability in a patient with a selective lesion affecting homologous regions of the human thalamus. Compared with controls, the patient exhibited a unilateral deficit in monitoring his eye movements. This deficit was manifest by a systematic inaccuracy both in successive eye movements and in judging the locations of visual stimuli. In addition, perceptual consequences of oculomotor targeting errors were erroneously attributed to external stimulus changes. These findings show that the human brain draws on transthalamic monitoring signals to bridge the perceptual discontinuities generated by our eye movements.

Acquisition of the Head-Centered Peri-Personal Spatial Representation Found in VIP Neuron

Both body and visuo-spatial representations are supposed to be gradually acquired during the developmental process as described in cognitive and brain sciences. A typical example is face representation in a neuron (found in the ventral intraparietal (VIP) area) of which the function is not only to code for the location of visual stimuli in the head-centered reference frame, but also to connect visual sensation with tactile sensation. This paper presents a model that enables a robot to acquire such representation. The proprioception of arm posture is utilized as reference data through the ldquohand regard behavior,rdquo that is, the robot moves its hand in front of its face, and the self-organizing map (SOM) and Hebbian learning methods are applied. The simulation results are shown and discussions on the limitation of the current model and future issues are given.

Functional Selectivity of Interhemispheric Connections in Cat Visual Cortex

The functional specificity of callosal connections was investigated in visual areas 17 and 18 of adult cats, by combining in vivo optical imaging of intrinsic signals with labeling of callosal axons. Local injections of neuronal tracers were performed in one hemisphere and eight single callosal axons were reconstructed in the opposite hemisphere. The distributions of injection sites and callosal axon terminals were analyzed with respect to functional maps in both hemispheres. Typically, each callosal axon displayed 2 or 3 clusters of synaptic boutons in layer II/III and the upper part of layer IV. These clusters were preferentially distributed in regions representing the same orientation and the same visuotopic location as that at the corresponding injection sites in the opposite hemisphere. The spatial distribution of these clusters was elongated and its main axis correlated well with the preferred orientation at the injection site. These results demonstrate a specific organization of interhemispheric axons that link cortical regions representing the same orientation and the same location of visual stimuli. Visual callosal connections are thus likely involved in the processing of coherent information in terms of shape and position along the midline of the visual field, which may facilitate the fusion of both hemifields into the percept of a single visual scene.

FMRI reveals greater within‐ than between‐hemifield integration in the human lateral occipital cortex

Early visual areas within each hemisphere (V1, V2, V3/VP, V4v) contain distinct representations of the upper and lower quadrants of the contralateral hemifield. As receptive field size increases, the retinotopy in higher-tier visual areas becomes progressively less distinct. Using functional magnetic resonance imaging (fMRI) to map the visual fields, we found that an intermediate level visual area, the lateral occipital region (LO), contains retinotopic maps with a contralateral bias, but with a combined representation of the upper and lower visual field. Moreover, we used the technique of fMRI adaptation to determine whether neurons in LO code for both the upper and lower contralateral quadrants. We found that even when visual stimulus locations are equivalent across comparisons, the LO was more sensitive to location changes that crossed hemifields than location changes within a hemifield. These results suggested that within high-tier visual areas the increasing integration of visual field information is a two-stage process. The upper and lower visual representations are combined first, in LO, then the left and right representations. Furthermore, these results provided evidence for a neural mechanism to explain behavioral findings of greater integration within than between hemifields.