Searching for object pointers in the visual cortex.

Visual search performance varies with stimulus and response history. Priming of pop-out refers to increased accuracy and reduced response time with repeated presentation of particular singleton and distractor features (e.g., a red target among green distractor stimuli), which are abruptly impaired when singleton and distractor features swap (e.g., green target among red distractors). Meanwhile, inhibition of return refers to the slowing of response time when target location repeats. Neurophysiological correlates of both these phenomena have been reported in the frontal eye field (FEF), an area in the frontal lobe contributing to attentional selection and eye movement planning. To understand the mechanistic origin of these adaptive behaviors, we investigated visual cortical area V4, an area providing input to and receiving feedback from FEF, during feature-based priming of pop-out and location-based inhibition of return. Performing a color pop-out task, monkeys exhibited pronounced priming of pop-out and inhibition of return. Neural spiking from V4 revealed earlier target selection associated with priming of pop-out and delayed selection associated with inhibition of return. These results demonstrate substantial involvement of extrastriate visual cortex in behavioral priming and inhibition of return.

The responses of the rabbit's visual cortical neurons to paired and rhythmic punctiform stimulation of their receptive fields were compared with responses to diffuse photic stimuli and the electric stimulation of the optic nerve. Diffuse photic and electric stimuli evoke a short-lasting initial activation of a neuron, followed by an inhibitory phase, during which the response to repetitive stimulation is suppressed. By contrast, localized stimulation of the neuron's receptive field with a spot of light produces an intensive and longer-lasting activation which is not followed by profound inhibition. Fusion of the responses to paired and rhythmic localized stimuli is therefore possible when the intervals between stimuli are brief enough. Rhythmic stimulation is capable of evoking sustained activation of a neuron during the entire duration of light flicker. During stimulation of a single point of the receptive field such prolonged activation can take place only within a limited range of stimulation frequencies (up to 15/sec), while higher frequencies evoke responses to the onset and offset of sequences of light flashes only. If, however, rhythmic stimuli alternate between the various points of a receptive field, prolonged neuronal activation is observed with any frequency of stimulation.

. We constantly move our eyes to new information while inspecting a scene, but these patterns of eye movements change based on the task and goals of the observer. Inhibition of return (IOR) may facilitate visual search by reducing the likelihood of revisiting previously attended locations. However, IOR may present in any visual task, or it may be search-specific. We investigated the presence of IOR in foraging, memorization, change detection, and two versions of visual search. One version of search used a static search array that remained stable throughout the trial, but the second used a scene flickering paradigm similar to the change detection task. IOR was observed in both versions of visual search, memorization, and foraging, but not in change detection. Visual search and change detection both had temporal nonscene components, and we observed that IOR could be maintained despite the scene removal but only for search. Although IOR is maintained in scene coordinates, short disruptions to this scene are insufficient to completely remove the inhibitory tags. Finally, we compare return saccades in trials without a probe and observe fewer return saccades in tasks for which IOR was observed, providing further evidence that IOR might serve as a novelty drive.

Inhibition of return (IOR) is a bias against reorienting attention to a previously cued location. In this study, using single-pulse transcranial magnetic stimulation (TMS), we show that the human frontal eye fields (FEF) play a crucial role in the generation of IOR. When TMS was applied over the right FEF at a time interval after a visual cue but shortly before the target, IOR was modulated in the hemifield ipsilateral to the TMS such that responses to a previously cued target were no longer slower than responses to uncued targets. Control TMS over the superior parietal lobule, as well as TMS of the FEF shortly after the cue but well before the target, had no influence on IOR. We further show that the FEF is involved with visual selection as responses to targets appearing contralateral to the TMS of the FEF, but not the control site, were delayed. These results suggest that the FEF produces IOR by biasing attention and eye movements away from a previously attended location and facilitating target detection at novel locations.

Acidic amino acids, such as glutamate and aspartate, are thought to be excitatory transmitters in the cerebral neocortex and hippocampus. Receptors for these amino acids can be classified into at least three types on the basis of their agonists. Quisqualate-preferring receptors and kainate-preferring receptors are implicated in the mediation of synaptic transmission in many regions including the hippocampus and visual cortex, whereas N-methyl-D-aspartate (NMDA)-preferring receptors are thought to be involved in modulating synaptic efficacy, for example in longterm potentiation, a form of synaptic plasticity in the hippocampus. In the visual cortex of the cat and monkey, it is well established that synaptic plasticity, estimated by susceptibility of binocular responsiveness of cortical neurons to monocular visual deprivation, disappears after the 'critical' period of postnatal development. Here we report that during the critical period in young kittens, a selective NMDA-receptor antagonist blocks visual responses of cortical neurons much more effectively than it does in the adult cat. This suggests that NMDA receptors may be involved in establishing synaptic plasticity in the kitten visual cortex.

Oculomotor inhibition of return (O-IOR) is an increase in saccade latency when returning to a recently fixated location relative to other locations. It has been proposed that this temporal O-IOR has spatial consequences, facilitating foraging by inhibiting return to previously attended regions (Klein & MacInnes, 1998). Models of visual attention incorporate this spatial IOR effect to drive attention to new locations. However, the foraging facilitator hypothesis has been a matter of debate recently in the scene literature, with several studies observing increased rather than decreased return probability (Hooge et al., 2005; Smith & Henderson, 2009, 2011a,b). To test whether spatial O-IOR occurs and can facilitate foraging, we monitored participants’ eye movements while they viewed arrays of objects or words. Arrays were chosen over scenes because arrays offer the advantage that fixation locations can be unambiguously assigned to specific objects. Temporal O-IOR was observed for both objects and words, but there was no evidence for spatial O-IOR. Instead, we observed spatial facilitation of return; participants were more likely than chance to refixate just-visited locations. Further, the likelihood of making a return saccade to an object or word was contingent on time spent previously on that object or word, suggesting that return saccades are triggered when further visual information is needed. The results also revealed strong evidence for saccadic momentum, an oculomotor bias to repeat the most recently executed saccade program. Such repetitions were the most frequently-occurring saccades in our data. Taken together, these results suggest that inhibition of return is not a foraging facilitator. We suggest that models of visual attention could incorporate saccadic momentum as a foraging facilitator instead of O-IOR. We further suggest that such models should incorporate a mechanism that triggers return saccades when more information is needed from a location. Meeting abstract presented at VSS 2013

ArticlesVision during saccadic eye movements. I. Visual interactions in striate cortexS. J. Judge, R. H. Wurtz, and B. J. RichmondS. J. Judge, R. H. Wurtz, and B. J. RichmondPublished Online:01 Apr 1980https://doi.org/10.1152/jn.1980.43.4.1133MoreSectionsPDF (4 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited BySparse coding in striate and extrastriate visual cortexBen D. B. Willmore, James A. Mazer, and Jack L. Gallant1 June 2011 | Journal of Neurophysiology, Vol. 105, No. 6Exploring the Superior Colliculus In VitroTadashi Isa, and William C. Hall1 November 2009 | Journal of Neurophysiology, Vol. 102, No. 5Neuronal Adaptation Caused by Sequential Visual Stimulation in the Frontal Eye FieldJ. Patrick Mayo, and Marc A. 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Schiff1 November 2003 | Journal of Neurophysiology, Vol. 90, No. 5Single-unit recording in the lateral geniculate nucleus of the awake behaving monkeyMethods, Vol. 30, No. 2Sensory-Motor Interaction in the Primate Auditory Cortex During Self-Initiated VocalizationsSteven J. Eliades, and Xiaoqin Wang1 April 2003 | Journal of Neurophysiology, Vol. 89, No. 4Neuronal mechanisms for detection of motion in the field of viewNeuropsychologia, Vol. 41, No. 13The responses of visual cortical neurons encode differences across saccadesNeuroReport, Vol. 14, No. 1Motion perception of saccade-induced retinal translation4 November 2002 | Proceedings of the National Academy of Sciences, Vol. 99, No. 23The effect of stimulus blanking on the detection of intrasaccadic displacements of translating objectsVision Research, Vol. 42, No. 16Cerebellar Flocculus and Paraflocculus Purkinje Cell Activity During Circular Pursuit in MonkeyH.-C. Leung, M. Suh, and R. E. Kettner1 January 2000 | Journal of Neurophysiology, Vol. 83, No. 1Neural Activity in the Primate Prefrontal Cortex during Associative LearningNeuron, Vol. 21, No. 6Neural activity in areas V1, V2 and V4 during free viewing of natural scenes compared to controlled viewingNeuroReport, Vol. 9, No. 7Effects of Saccades on the Activity of Neurons in the Cat Lateral Geniculate NucleusDaeyeol Lee, and Joseph G. Malpeli1 February 1998 | Journal of Neurophysiology, Vol. 79, No. 2Neural activity in areas V1, V2 and V4 during free viewing of natural scenes compared to controlled viewingNeuroReport, Vol. 9, No. 1Insensitivity of V1 Complex Cell Responses to Small Shifts in the Retinal Image of Complex PatternsTroels W. Kjaer, Timothy J. Gawne, John A. Hertz, and Barry J. Richmond1 December 1997 | Journal of Neurophysiology, Vol. 78, No. 6Central Versus Peripheral Determinants of Patterned Spike Activity in Rat Vibrissa Cortex During WhiskingMichale S. Fee, Partha P. Mitra, and David Kleinfeld1 August 1997 | Journal of Neurophysiology, Vol. 78, No. 2Sensory and attentional components of slowing of manual reaction time to non-fixated visual targets by ipsilateral primesVision Research, Vol. 33, No. 11Studying striate cortex neurons in behaving monkeys: Benefits of image stabilizationVision Research, Vol. 27, No. 12‘Real-motion’ cells in the primary visual cortex of macaque monkeysBrain Research, Vol. 301, No. 1Retinotopic organization of extra-retinal saccade-related input to the visual cortex in the cat3 September 2013 | Experimental Brain Research, Vol. 46, No. 3 More from this issue > Volume 43Issue 4April 1980Pages 1133-1155 Copyright & PermissionsCopyright © 1980 the American Physiological Societyhttps://doi.org/10.1152/jn.1980.43.4.1133PubMed6766996History Published online 1 April 1980 Published in print 1 April 1980 Metrics

Saccades toward previously cued or fixated locations typically have longer latencies than those toward novel locations, a phenomenon known as inhibition of return (IOR). Despite extensive debate on its potential function, it remains unclear what the role of IOR in the oculomotor decision process is. Here, we ask whether the effect on eye movement planning is best characterized as a delay in visual target discrimination or as a reduction in readiness to execute the movement (saccade readiness). To evaluate this question, we use target-distractor tasks with clear speed-accuracy trade-offs. Simultaneously cueing both the target and distractor (or neither) we find longer latencies at the cued locations. Despite this delay in latencies, accuracy improves in line with the speed-accuracy trade-off curve (Experiment 1). This suggests that while visual target discrimination can progress unimpeded, saccade readiness is reduced. Based on this reduction in readiness we predict that the more saccades rely on visual target discrimination, the less their destination will be affected by inducing IOR. Indeed, after cueing either the target or an onset distractor (Experiment 2), short-latency, stimulus-driven, saccades are strongly biased away from the cued location, while the destinations of longer latency goal-driven saccades are affected only minimally. The fact that primarily stimulus-driven saccades are affected by inducing IOR is interesting as it can explain why the spatial bias associated with IOR is not consistently found. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Modulation of rat cortical area 17 neuronal responses to moving visual stimuli during norepinephrine and serotonin microiontophoresis

The responses of visual cortical neurons to natural stimuli are both reliable and sparse. These properties require inhibition, yet the contribution of specific types of inhibitory neurons is not well understood. Here we demonstrate that optogenetic suppression of parvalbumin (PV)- but not somatostatin (SOM)-expressing interneurons reduces response reliability in the primary visual cortex of anaesthetized and awake mice. PV suppression leads to increases in the low firing rates and decreases in the high firing rates of cortical neurons, resulting in an overall reduction of the signal-to-noise ratio (SNR). In contrast, SOM suppression generally increases the overall firing rate for most neurons, without affecting the SNR. Further analysis reveals that PV, but not SOM, suppression impairs neural discrimination of natural stimuli. Together, these results reveal a critical role for PV interneurons in the formation of reliable visual cortical representations of natural stimuli.

The responses of visual cortical neurons during fixation tasks can be significantly modulated by stimuli from beyond the classical receptive field. Modulatory effects in neural responses have also been recently reported in a task where a monkey freely views a natural scene. In this article, we describe a hierarchical network model of visual recognition that explains these experimental observations by using a form of the extended Kalman filter as given by the minimum description length (MDL) principle. The model dynamically combines input-driven bottom-up signals with expectation-driven top-down signals to predict current recognition state. Synaptic weights in the model are adapted in a Hebbian manner according to a learning rule also derived from the MDL principle. The resulting prediction-learning scheme can be viewed as implementing a form of expectation-maximization (EM) algorithm. The architecture of the model posits an active computational role of the reciprocal connections between adjoining visual cortical areas in determining neural response properties. In particular, the model demonstrates the possible role of feedback from higher cortical areas in mediating neurophysiological effects due to stimuli from beyond the classical receptive field. Simulations of the model are provided that help explain the experimental observations regarding neural responses in both free viewing and fixation conditions.

The identification of brain regions that are associated with the conscious perception of visual stimuli is a major goal in neuroscience. Here we present a test of whether the signals on neurons in cortical area V1 correspond directly to our conscious perception of binocular stereoscopic depth. Depth perception requires that image features on one retina are first matched with appropriate features on the other retina. The mechanisms that perform this matching can be examined by using random-dot stereograms, in which the left and right eyes view randomly positioned but binocularly correlated dots. We exploit the fact that anticorrelated random-dot stereograms (in which dots in one eye are matched geometrically to dots of the opposite contrast in the other eye) do not give rise to the perception of depth because the matching process does not find a consistent solution. Anti-correlated random-dot stereograms contain binocular features that could excite neurons that have not solved the correspondence problem. We demonstrate that disparity-selective neurons in V1 signal the disparity of anticorrelated random-dot stereograms, indicating that they do not unambiguously signal stereoscopic depth. Hence single V1 neurons cannot account for the conscious perception of stereopsis, although combining the outputs of many V1 neurons could solve the matching problem. The accompanying paper suggests an additional function for disparity signals from V1: they may be important for the rapid involuntary control of vergence eye movements (eye movements that bring the images on the two foveae into register).

1. Luis H. Ospina, MD* 1. *Assistant Professor, Pediatric Ophthalmology and Neuro-ophthalmology, Ste-Justine Hospital, University de Montreal, Montreal, Quebec, Canada After completing this article, readers should be able to: 1. Recognize cortical visual impairment (CVI) as an important cause of pediatric visual loss. 2. Identify the most frequent causes of pediatric CVI and, more specifically, understand the role of hypoxia as a cause of central visual damage. 3. Describe the different patterns and implications for future vision of hypoxic central visual damage occurring in preterm compared with term babies. 4. Know the clinical signs suggestive of CVI in children. 5. Discuss the involvement of visual functions other than visual acuity (ie, cognitive visual aspects) in CVI and correlate them with the likely affected neuroanatomic substrates. 6. Explain the value of using a multidisciplinary approach in rehabilitating children who have CVI early in their development. Vision loss caused by central nervous system damage often is referred to as CVI but also may be referred to as cerebral visual impairment or neurologic visual impairment. These terms refer to the fact that the primary defect may not necessarily be limited to the striate (primary visual) cortex and may affect other areas subserving vision, such as the visual associative cortex, optic radiations, and visual attention pathways. Although it is not yet certain which of these three terms best describes the visual deficit, it is clear that use of the label cortical blindness must be abandoned. That term not only evokes negative connotations for the child and the family but is inaccurate because in almost every instance, some degree of residual vision remains, and visual improvement can occur. CVI has become the greatest cause of pediatric visual impairment in developed countries (1)(2)(3)(4)(5) and is becoming increasingly prevalent in developing nations. CVI is a problem of increasing frequency for two primary reasons. First, the progress in neonatal care has resulted in improved survival of …

The visual system needs to identify perceptually relevant borders to segment complex natural scenes. The primary visual cortex (V1) is thought to extract local borders, and higher visual areas are thought to identify the perceptually relevant borders between objects and the background. To test this conjecture, we used natural images that had been annotated by human observers who marked the perceptually relevant borders. We assessed the effect of perceptual relevance on V1 responses using human neuroimaging, macaque electrophysiology, and computational modeling. We report that perceptually relevant borders elicit stronger responses in the early visual cortex than irrelevant ones, even if simple features, such as contrast and the energy of oriented filters, are matched. Moreover, V1 neurons discriminate perceptually relevant borders surprisingly fast, during the early feedforward-driven activity at a latency of ~50 ms, indicating that they are tuned to the features that characterize them. We also revealed a delayed, contextual effect that enhances the V1 responses that are elicited by perceptually relevant borders at a longer latency. Our results reveal multiple mechanisms that allow V1 neurons to infer the layout of objects in natural images.

Not all attention orienting is created equal: Recognition memory is enhanced when attention orienting involves distractor suppression