While the effects of visual deprivation have been well studied in animal models, much less is known about the effects of blindness on human early visual pathway...
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Decapod crustaceans, in particular semiterrestrial crabs, are highly visual animals that greatly rely on visual information. Their responsiveness to visual moving stimuli, with behavioral displays that can be easily and reliably elicited in the laboratory, together with their sturdiness for experimental manipulation and the accessibility of their nervous system for intracellular electrophysiological recordings in the intact animal, make decapod crustaceans excellent experimental subjects for investigating the neurobiology of visually guided behaviors. Investigations of crustaceans have elucidated the general structure of their eyes and some of their specializations, the anatomical organization of the main brain areas involved in visual processing and their retinotopic mapping of visual space, and the morphology, physiology, and stimulus feature preferences of a number of well-identified classes of neurons, with emphasis on motion-sensitive elements. This anatomical and physiological knowledge, ...
Brains visual pathways. Artwork of the visual pathways from the eyes (top) to the cortex of the brain (bottom), as seen from below. Nerve impulses produced when light falls on the retinas of the eyes travel along the optic nerves. The images are binocular. Light that falls on the right side of each retina (blue) from the left field of view, passes as impulses to the right visual cortex of the brain via the chiasma (crossing point of the optic nerves). This is reversed for light that falls on the left side of the retina (coloured red). The nerve impulses are processed in the brain to create a coherent image of what is seen by the eyes. - Stock Image C022/6388
A central feature of visual pathway development is its organization into retinotopic maps. The developmental process by which these maps form involves a transition from early patterning cues to arrays of axonal guidance factors allowing the relative order of retinotopic axons to be preserved. Mechanisms linking patterning molecules of early development to topographic wiring and subsequent functional responses are not well understood. In this thesis, I performed a microarray screen comparing gene expression in early visual and auditory regions of the thalamus in order to identify early patterning candidates with a potential role in visual pathway differentiation. Among the candidates enriched in the visual thalamus, the transcription factor, Zic4, was found to be expressed in gradients of the developing retina, lateral geniculate nucleus (LGN) and primary visual cortex (V 1). Mice lacking Zic4 exhibited a deficit in eye-specific patterning to the thalamus that was complementary to the phenotype ...
The transfer functions of Lateral Geniculate Nucleus and of Visual Cortex I have been determined under conditions of steady state flickering illumination at fixed intensity. The results are compared with those of steady non-flickering stimulation. Microelectrode recordings under conditions of steady illumination with non-flickering light of different intensities have been made from individual fibers in the geniculo-cortical and in the corticothalamic tracts. An analysis of mean discharge frequency and of interspike interval distribution has been performed. (Author)(*VISION
Visual pathways and acuity hooded rats.: Three experiments on the effects of lesions of the visual system on contrast-detection in hooded rats are described, in
Almost all fMRI studies of object recognition have focused on the geometric structure of objects. Little attention has been paid to the recognition of material properties from surface-based visual cues. Even when the processing of surface-based cues, such as colour and texture, has been studied, it has been in the context of using these cues to reveal the geometric structure of objects. Thus, the goal of the current experiment was to uncover the functional geography of occipito-temporal brain areas mediating the processing of stuff (material properties) versus things (geometric form). Using fMRI, we scanned participants as they attended to either the 3-D structure or the material properties of the same unfamiliar nonsense objects. Attention was manipulated by asking participants to perform a discrimination task in which they had to decide whether pairs of objects had the same or different 3-D geometry, or whether the objects shared the same or different material properties (wood, granite, ...
In natural environments, visual signals are highly redundant, so the representation of the input by the activity of photoreceptors is inefficient. Efficiency of information coding, however, potentially has significant evolutionary and computational advantages (Atick, 1992). It is thus reasonable to assume that an important task of the early stages of the visual pathway is to recode the incoming visual signals to improve efficiency (Barlow, 1961, 1989;Atick and Redlich, 1990; Atick, 1992).. The primary sources of redundancy in the visual signals at the level of the photoreceptors are the temporal and spatial correlations in natural scenes. The activity of photoreceptors is not independent at different times and between different cells. In other words, much information is represented repetitively over time and by different neurons. To improve efficiency, the neuronal signals must be recoded into a decorrelated form. When transformed into the frequency domain, this decorrelation is expressed as the ...
In vivo imaging reveals how grafted embryonic brain cells grow, connect, and mature into contributing members of damaged visual pathways in adult mice.. 0 Comments. ...
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Brodsky presents evidence that the accessory optic system is uniquely suited to provide an innervational substrate for visuovestibular eye movements in humans w
The study looks closely at the neural connections that start at the lateral geniculate nucleus (LGN), a thalamic region that receives inputs from the retinal cells, and end in a late-developing area of the visual cortex labeled layer 4. From there, highly specialized columns of cells form, which are involved in analyzing visual stimuli. Nobel prize-winning work by David Hubel and Torsten Wiesel at Harvard Medical School demonstrated that the thalamic connections to the nerve cells in the cortex help form these columns. One type of column, for determining ocular dominance, forms based on visual signals it receives from either the left or right eye. Another kind of column forms in response to bars of light presented to the eyes at different orientations--for example, neurons in one such column may respond to vertical lines like telephone poles, while cells of another column may recognize horizontal lines like the wires crossing between the poles ...
Nov. 17, 2015, 5:00 pm - 6:00 pm | LH-3.Please join Bas Rokers, Brain and Cognition Sciences, MIT and Department of Psychology, University of Wisconsin - Madison, for a presentation entitled
Vision provides a critical interface with the physical world. This work examines visual development and vision loss in mice to glean the influence of the retinal state on visual connections. I first assessed the impact of retinal activity on the eye-specific segregation of retinal afferents in the lateral geniculate nucleus (LGN) of young Gβ5 -/- mice. Gβ5 is the fifth member of the β subfamily of heterotrimeric G proteins. Gβ5 binds and stabilizes the R7 family of regulators of G-protein signaling (RGS), which accelerate Gi/o GTP hydrolysis. Gβ5 -/- mice, which lack R7RGS activity, have malformed synapses in the outer plexiform layer (OPL) and impaired OPL transmission. Altered spontaneous retinal activity in Gβ5-/- mice at P7, P12, P14, and P28 correlates with impaired eye-specific segregation of retinal afferents in the LGN at corresponding timepoints. However, Gβ5-/- mice exhibit a normal transition from cholinergic to glutamatergic drive that corresponds with a temporary recovery of
This book provides the essential facts about how visual information is processed in the brain. The book has 16 chapters. Chapter 1 provides basic information about the methods that are used by ... More. This book provides the essential facts about how visual information is processed in the brain. The book has 16 chapters. Chapter 1 provides basic information about the methods that are used by investigators to find out how visual information is processed in living organisms. Chapter 2 outlines the brain areas that process visual information and specifies how these areas are interconnected in the mammalian visual system. Chapter 3 describes in detail the structural and functional organization of the retina. Chapter 4 describes the lateral geniculate nucleus. Chapter 5 delineates the manner in which the primary visual cortex, area V1, is organized. Chapter 6 examines the organization and function of higher cortical visual areas. In Chapter 7 the ON and OFF channels that originate in the retina are ...
In order to investigate potential effects of visual experience vs. preprogrammed mechanisms on visual development, we have investigated how well variation in contrast sensitivity (CS) across a large group of typical infants (n = 182) can be accounted for by a variety of factors that differ in the extent to which they are tied to visual experience. Using multiple regression analyses, we find that gestational length and gender, which are unlikely to be tied to visual experience, predict Luminance CS (thought to be mediated by the Magnocellular pathway). Other factors, which might be tied to either preprogrammed mechanisms or visual experience, specifically, birth order and small variations in postnatal age, predict Chromatic CS (thought to be mediated by the Parvocellular pathway) and Luminance CS. In addition, we have investigated effects of visual experience vs. preprogrammed mechanisms by studying CS in infant twins (n = 64). Our results show that the CS of both monozygotic (Mz) and dizygotic ...
Presentation Description : Visual information is first processed in the retina where different subtypes of retinal ganglion cells (RGCs) encode specific features of the visual scene. The signals encoded by RGC subtypes are further integrated and transformed in various retinal targets in the brain to give rise to specific visual response properties. Recently, mouse has become a useful model in vision research due to the technical advances in genetic, imaging, and physiological methodologies. In mice, more than 70% RGCs project to the superior colliculus (SC), a midbrain structure important for multimodal integration and sensorimotor transformation. The significance of the SC in mouse vision thus makes it an important system to study visual transformation and its underlying mechanisms. In this talk, I will present our recent discoveries of visual response properties in the mouse SC and our ongoing effort to study retinocollicular transformation, with a focus on the processing of motion direction. ...
Even when the primary visual cortical area is absent bilaterally from early life, the rest of a primate visual brain can develop and function normally to support day-to-day visual behaviour.
How does a neural circuit get wired up to perform specific computations? The Feller lab recently addressed this question by studying the circuit mediates direction selectivity in the retina (Wei et al, Nature, 2010). Direction-selective neurons, which respond selectively to motion in one direction, have been characterized in visual circuits across many species. In the retina, it has been postulated that the ability to discern the direction of motion of an object required asymmetric wiring between the retinal neurons. However, the mechanisms that instruct this asymmetric wiring during development were completely unknown.
The major mammalian subcortical visual structures receive topographically ordered projections from both eyes. In the adult dorsal lateral geniculate nucleu
The optic tract conducts information from the chiasm to the lateral geniculate body. ... Fibers from the Lateral Geniculate Body curve around the lateral ventricle in ... – A free PowerPoint PPT presentation (displayed as a Flash slide show) on PowerShow.com - id: 104c4e-NDMyY
Lateral geniculate nucleus aka Corpus geniculatum laterale in the latin terminology and part of brainstem and related structures. Learn more now!
could you please tell why the lesion at proximal part of optic nerve (labelled 2 in the pic) would lead to ipsilateral central scotoma ...
Children are different than adults in that a childs brain develops more rapidly. Any problems a child may experience with his/her vision may disrupt the development of visual pathways to the brain. A critical stage of visual development occurs between birth and age three to four months, during which time the brain must receive clear visual messages from both eyes. Early detection and treatment can prevent loss of vision, learning difficulties, and delayed development.. The American Academy of Ophthalmology, the American Optometric Association, and the American Academy of Pediatrics have recommended the following screening stages:. ...
This might not be the right group for this, but... Im looking for papers or any information about where the brain creates/has visual and audio stimulation/activity during dreaming. Specifically, what parts along the visual pathway (if any) are stimulated or active to the point that it might be inferred that those parts are actively visualizing or creating the image the dreamer is perceiving? Is the striate cortex active? It may seem far fetched, but has anyone been able to measure retinal activity during dreaming? Or have dreams been proven to be a more symbolic, higher level cortical function? I am wondering if the circuit could look something vaguely like this *logical* diagram: S W I (or filter?) receptor (environmental) input T eyes ---------,[LGC]-----------,\ C \ H ,---,StriateCortex,---+ Symbolic (Dreaming) input / , +------------------------,/ , , , , / ^ / Higher cortical area(s). ,---------------------/ And could there be an analogous representation for audio? I know there is much ...
Ophthalmology is a branch of medicine dealing with the diagnosis, treatment, and prevention of diseases of the eye and visual system. Ophthalmology is unique among medical specialties. The eye, its surrounding structures and the visual pathways may be affected by a great variety of clinical conditions.
Introduces the visual pathways and visual fields and what happens when they are damaged. By using a number of case histories and interactive testing, the learner is guided through the process of determining... ...
Reorientation tasks, in which disoriented participants attempt to relocate objects using different visual cues, have previously been understood to depend on representing aspects of the global organisation of the space, for example its major axis for judgements based on geometry. Careful analysis of the visual information available for these tasks shows that successful performance could be based on the much simpler process of storing a visual snapshot at the target location, and subsequently moving in order to match it. We tested 4-8-year olds on a new spatial reorientation task that could not be solved based on information directly contained in any retinal projection that they had been exposed to, but required participants to infer how the space is structured. Only 6-8-year olds showed flexible recall from novel viewpoints. Five-year olds were able to recall locations given movement information or a unique proximal landmark, but without these they could not do so, even when they were not disoriented
The Neurology of Vision sets out the principles and information needed to understand and manage disorders of the visual pathways in the brain.
ABSTRACT. Aging often results in reduced visual acuity from changes in both the eye and neural circuits [1-4]. In normally aging subjects, primary visual cortex has been shown to have reduced responses to visual stimulation [5]. It is not known, however, to what extent aging affects visual field representations and population receptive sizes in human primary visual cortex. Here we use functional MRI (fMRI) and population receptive field (pRF) modeling [6] to measure angular and eccentric retinotopic representations and population receptive fields in primary visual cortex in healthy aging subjects ages 57 - 70 and in healthy young volunteers ages 24 - 36 (n = 9). Retinotopic stimuli consisted of black and white, drifting checkerboards comprising moving bars 11 deg in radius. Primary visual cortex (V1) was clearly identifiable along the calcarine sulcus in all hemispheres. There was a significant decrease in the surface area of V1 from 0 to 3 deg eccentricity in the aging subjects with respect to ...
Aging often results in reduced visual acuity from changes in both the eye and neural circuits [1-4]. In normally aging subjects, primary visual cortex has been shown to have reduced responses to visual stimulation [5]. It is not known, however, to what extent aging affects visual field repre-sentations and population receptive sizes in human primary visual cortex. Here we use func-tional MRI (fMRI) and population receptive field (pRF) modeling [6] to measure angular and ec-centric retinotopic representations and population receptive fields in primary visual cortex in healthy aging subjects ages 57 - 70 and in healthy young volunteers ages 24 - 36 (n = 9). Retinotopic stimuli consisted of black and white, drifting checkerboards comprising moving bars 11 deg in radius. Primary visual cortex (V1) was clearly identifiable along the calcarine sulcus in all hemispheres. There was a significant decrease in the surface area of V1 from 0 to 3 deg eccentricity in the aging subjects with respect to the young
The cerebral cortex changes throughout the lifespan, and the cortical grey matter in many brain regions becomes thinner with advancing age. Effects of aging on cortical thickness have been observed in many brain regions, including areas involved in basic perceptual functions such as processing visual inputs. An important property of early visual cortices is their topographic organization - the cortical structure of early visual areas forms a topographic map of retinal inputs. Primary visual cortex (V1) is considered to be the most basic cortical area in the visual processing hierarchy, and is topographically organized from posterior (central visual representation) to anterior (peripheral visual representation) along the calcarine sulcus. Some studies have reported strong age-dependent cortical thinning in portions of V1 that likely correspond to peripheral visual representations, while there is less evidence of substantial cortical thinning in central V1. However, the effect of aging on cortical
Flies are highly visually guided animals. In this thesis, I have used hoverflies as a model for studying motion vision. Flies process motion vision in three visual ganglia: the lamina, the medulla, and the lobula complex. In the posterior part of lobula complex, there are around 60 lobula plate tangential cells (LPTCs). Most of LPTCs have large receptive fields where the local direction sensitivity suggests that they function as matched filters to specific types of optic flow. LPTCs connect to descending or neck motor neurons that control wing and head movements, respectively. Therefore, in this thesis I have focused on the electrophysiological responses of LPTCs to gain understanding of visual behaviors in flies.. The elementary motion detector (EMD) is a model that can explain the formation of local motion sensitivity. However, responses to higher order motion, where the direction of luminance change is uncorrelated with the direction of movement, cannot be predicted by classic EMDs. ...
Flies are highly visually guided animals. In this thesis, I have used hoverflies as a model for studying motion vision. Flies process motion vision in three visual ganglia: the lamina, the medulla, and the lobula complex. In the posterior part of lobula complex, there are around 60 lobula plate tangential cells (LPTCs). Most of LPTCs have large receptive fields where the local direction sensitivity suggests that they function as matched filters to specific types of optic flow. LPTCs connect to descending or neck motor neurons that control wing and head movements, respectively. Therefore, in this thesis I have focused on the electrophysiological responses of LPTCs to gain understanding of visual behaviors in flies.. The elementary motion detector (EMD) is a model that can explain the formation of local motion sensitivity. However, responses to higher order motion, where the direction of luminance change is uncorrelated with the direction of movement, cannot be predicted by classic EMDs. ...
Visual disturbances may be caused by diseases of the optic disc, optic nerve, optic chiasm, optic tract, lateral geniculate nucleus, optic radiations, and occipital lobe of the brain, as well as other brain areas involved in complex visual processing.Diagnosis of disturbances of the visual pathways requires both knowledge of their anatomy and physiology, and the ability to carry out a thorough neuro-ophthalmological examination which should enable (1) documentation of the character and extent of the visual disturbance, and (2) topographic localization of the lesion, so that the relevant investigative techniques, such as radiological imaging, can be appropriately requested....
The visual thalamus of rodents has served as an important model for exploring the cellular and molecular mechanisms that underlie neural circuit formation. The overwhelming majority of these studies have focused on inputs to and projections from the dorsal lateral geniculate nucleus (dLGN). Relay neurons within dLGN receive strong glutamatergic inputs from retinal ganglion cells (RGCs) and serve as the principle conduit of visual signaling to the cortex. However, relay neurons do not act as passive relays of visual information. The gain of retinogeniculate signal transmission is modulated by nonretinal inputs to dLGN. These nonretinal inputs arise from visual cortex, pretectum, brainstem, thalamic reticular nuclei, and local dLGN interneurons, and they far outnumber the more powerful retinal inputs [1, 2]. In fact, nonretinal inputs account for as much as 95% of the nerve terminals in dLGN [1, 3-6].. Differences in the functional properties of inputs to dLGN translate into distinct neurochemical ...
The simple-cell receptive field (RF) structure is an attractive and unique feature of the primary visual cortex, which is thought to reflect the circuitry principles governing orientation selectivity. Synaptic inputs underlying spike RFs are key to understanding mechanisms for neuronal processing. The well-known push-pull model, which is proposed to explain the synaptic mechanism under simple-cell RFs, predicts that in simple cells the spatially separated excitation and inhibition does not interact with each other and that simple inhibitory neurons exist in the primary visual cortex (V1). However, previous experimental results suggest that synaptic inhibition plays an important role in shaping RF properties in the visual cortex. The synaptic mechanisms underlying simple-cell RFs remain not well understood, partly due to difficulties in systematically studying functional properties of cortical inhibitory neurons and precisely measuring excitatory and inhibitory synaptic inputs in vivo.; In the ...
Visual area MT is a model of choice in primate neurophysiological and human imaging research of visual perception, due to its considerable sensitivity to moving stimuli and the strong direction selectivity of its neurons. While the location of MT(V5) in the non-human primate is easily identifiable based on gross anatomy and appears consistent between animals, this is less the case in human subjects. Functional localisation of human MT+ with moving stimuli can identify a group of motion-sensitive regions, but defining MT proper has proved more challenging. In this review we consider approaches to studying the cyto- and myleoarchitecture of this cortical area that may, in the future, allow identification of human MT in vivo based on anatomy.
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Spike count correlations (SCCs), covariation of neuronal responses across multiple presentations of the same stimulus, are ubiquitous in sensory cortices and span different modalities (1⇓-3) and processing stages (4⇓⇓-7). In the visual system, SCCs, also termed noise correlations, have traditionally been considered to be independent of the stimulus and hence have been thought to impede stimulus encoding (8). Studies on stimulus-independent aspects of SCCs in the primary visual cortex (V1) sought to capture correlation patterns that were solely accounted for by differences in receptive field structure (9, 10). Initial investigations of dependence of SCCs on low-level stimulus features, such as orientation and contrast, focused on the population mean of SCCs (11⇓-13), but stimulus-dependent changes in the mean are modest in awake animals (9, 14). Only recently has orientation and contrast dependence of the fine structure of SCCs been demonstrated in anesthetized cats and awake mice (15). ...
Background The dorsal lateral geniculate nucleus (dLGN) of the mouse has been an important experimental model for understanding thalamic circuit development. The developmental remodeling of retinal projections has been the primary focus, however much less is known about the maturation of their synaptic targets, the relay cells of the dLGN. Here we examined the growth and maturation of relay cells during the first few weeks of life and addressed whether early retinal innervation affects their development. To accomplish this we utilized themath5 null (math5−/−) mouse, a mutant lacking retinal ganglion cells and central projections. Results The absence of retinogeniculate axon innervation led to an overall shrinkage of dLGN and disrupted the pattern of dendritic growth among developing relay cells. 3-D reconstructions of biocytin filled neurons frommath5−/− mice showed that in the absence of retinal input relay cells undergo a period of exuberant dendritic growth and branching, followed by branch
Coordinated changes in gene expression underlie the early patterning and cell-type specification of the central nervous system. However, much less is known about how such changes contribute to later stages of circuit assembly and refinement. In this study, we employ single-cell RNA sequencing to develop a detailed, whole-transcriptome resource of gene expression across four time points in the developing dorsal lateral geniculate nucleus (LGN), a visual structure in the brain that undergoes a well-characterized program of postnatal circuit development. This approach identifies markers defining the major LGN cell types, including excitatory relay neurons, oligodendrocytes, astrocytes, microglia, and endothelial cells. Most cell types exhibit significant transcriptional changes across development, dynamically expressing genes involved in distinct processes including retinotopic mapping, synaptogenesis, myelination, and synaptic refinement. Our data suggest that genes associated with synapse and ...
The visual system transmits visual information from the retina within the eyes to the primary visual cortex of the occipital lobe as well as the pretectal nuclei and superior colliculi of the midbrain. Gross anatomy Below the visual pathway is ...
In this experiment we contrast the neural activity associated with reporting a stimulus attribute with the activity that occurs when the same stimulus attribute is used to guide behavior. Reporting the characteristics of a stimulus differs from simply tracking that stimulus since reporting requires that a stimulus is explicitly recognized and associated with an arbitrary response. In one condition the subject used his right finger to follow a square that moved randomly on a screen. In a second condition he had to indicate changes in the direction of the squares movements by touching one of two report buttons with his right finger. Two other conditions were added to control for the differences in the form of movement between the two primary conditions. When the reporting condition was contrasted with the tracking condition (controlling for the differences in the form of movement), areas in the ventral visual system (the left ventral prefrontal cortex and the left inferior temporal cortex) were activated
RGCs in mice and other mammals project to numerous central targets, including the suprachiasmatic nucleus, accessory optic nuclei, pretectal nuclei, superior colliculus, ventral LGN, and dorsal LGN (Rodieck, 1979). In C57BL/6J mice, ∼70% of ganglion cells project to the LGN as well as the superior colliculus (Drager and Olsen, 1980; Hofbauer and Drager, 1985). This leaves open the possibility that a positive correlation between geniculate neurons and a specific subpopulation of RGCs is masked or degraded by strain variability and heterogeneity of retinal projections. However, we are swayed against this argument for several reasons. First, we are able to detect a significant positive correlation between numbers of RGCs and glial cells in the LGN. The RGC-to-glial cell correlation is 0.33 (Table 4) and reaches a p value of ,0.01. This observation is difficult to reconcile with large strain differences in the projections to different nuclei that obscure an RGC-to-neuron correlation. Instead, this ...