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Parkinsonism & Related Disorders Jul 2017Patients with Parkinson's disease (PD) often compensate for their motor deficits by guiding their movements visually. A wide range of ocular and visual disorders... (Review)
Review
Patients with Parkinson's disease (PD) often compensate for their motor deficits by guiding their movements visually. A wide range of ocular and visual disorders threatens the patients' ability to benefit optimally from visual feedback. These disorders are common in patients with PD, yet they have received little attention in both research and clinical practice, leading to unnecessary - but possibly treatable - disability. Based on a literature search covering 50 years, we review the range of ocular and visual disorders in patients with PD, and classify these according to anatomical structures of the visual pathway. We discuss six common disorders in more detail: dry eyes; diplopia; glaucoma and glaucoma-like visual problems; impaired contrast and colour vision; visuospatial and visuoperceptual impairments; and visual hallucinations. In addition, we review the effects of PD-related pharmacological and surgical treatments on visual function, and we offer practical recommendations for clinical management. Greater awareness and early recognition of ocular and visual problems in PD might enable timely instalment of tailored treatments, leading to improved patient safety, greater independence, and better quality of life.
Topics: Humans; Parkinson Disease; Quality of Life; Vision Disorders; Vision, Ocular; Visual Pathways; Visual Perception
PubMed: 28284903
DOI: 10.1016/j.parkreldis.2017.02.014 -
Trends in Cognitive Sciences Nov 2015Recognising objects goes beyond vision, and requires models that incorporate different aspects of meaning. Most models focus on superordinate categories (e.g., animals,... (Review)
Review
Recognising objects goes beyond vision, and requires models that incorporate different aspects of meaning. Most models focus on superordinate categories (e.g., animals, tools) which do not capture the richness of conceptual knowledge. We argue that object recognition must be seen as a dynamic process of transformation from low-level visual input through categorical organisation to specific conceptual representations. Cognitive models based on large normative datasets are well-suited to capture statistical regularities within and between concepts, providing both category structure and basic-level individuation. We highlight recent research showing how such models capture important properties of the ventral visual pathway. This research demonstrates that significant advances in understanding conceptual representations can be made by shifting the focus from studying superordinate categories to basic-level concepts.
Topics: Brain; Comprehension; Humans; Pattern Recognition, Visual; Semantics; Vision, Ocular; Visual Pathways
PubMed: 26440124
DOI: 10.1016/j.tics.2015.08.008 -
Shaping the visual system: cortical and subcortical plasticity in the intact and the lesioned brain.Neuropsychologia May 2020Visual system is endowed with an incredibly complex organization composed of multiple visual pathway affording both hierarchical and parallel processing. Even if most of... (Review)
Review
Visual system is endowed with an incredibly complex organization composed of multiple visual pathway affording both hierarchical and parallel processing. Even if most of the visual information is conveyed by the retina to the lateral geniculate nucleus of the thalamus and then to primary visual cortex, a wealth of alternative subcortical pathways is present. This complex organization is experience dependent and retains plastic properties throughout the lifespan enabling the system with a continuous update of its functions in response to variable external needs. Changes can be induced by several factors including learning and experience but can also be promoted by the use non-invasive brain stimulation techniques. Furthermore, besides the astonishing ability of our visual system to spontaneously reorganize after injuries, we now know that the exposure to specific rehabilitative training can produce not only important functional modifications but also long-lasting changes within cortical and subcortical structures. The present review aims to update and address the current state of the art on these topics gathering studies that reported relevant modifications of visual functioning together with plastic changes within cortical and subcortical structures both in the healthy and in the lesioned visual system.
Topics: Geniculate Bodies; Humans; Retina; Thalamus; Visual Cortex; Visual Pathways
PubMed: 32289349
DOI: 10.1016/j.neuropsychologia.2020.107464 -
Sheng Li Xue Bao : [Acta Physiologica... Feb 2018Superior colliculus-pulvinar-amygdala pathway is one of the subcortical visual pathways in mammalian brain. Some recent studies suggest that this pathway is involved in... (Review)
Review
Superior colliculus-pulvinar-amygdala pathway is one of the subcortical visual pathways in mammalian brain. Some recent studies suggest that this pathway is involved in processing emotion-related visual information. This review discusses the possibility that this pathway is more related to visual alert rather than simply the early visual information processing. The biological significance of this pathway is also discussed. Instead of detecting "where" or "what" the visual target is, the task of this early visual stage is to send out a warning signal, i.e., "something appears", so that the brain can be set up in a state of alert, which is important for the survival of animals. Thus, in the early visual information process, detection of new object "emerging" or "disappearing" takes priority over the acquisition of its feature information of "texture" and "shape", etc. The subcortical pathway may provide the neural basis of early visual warning in topological perception, a biological significance critical for animal survival.
Topics: Amygdala; Animals; Brain; Emotions; Humans; Perception; Pulvinar; Superior Colliculi; Visual Pathways
PubMed: 29492518
DOI: No ID Found -
The Journal of Comparative Neurology Dec 2020Visual perception requires both visual information and attention. This review compares, across classes of vertebrates, the functional and anatomical characteristics of... (Review)
Review
Visual perception requires both visual information and attention. This review compares, across classes of vertebrates, the functional and anatomical characteristics of (a) the neural pathways that process visual information about objects, and (b) stimulus selection pathways that determine the objects to which an animal attends. Early in the evolution of vertebrate species, visual perception was dominated by information transmitted via the midbrain (retinotectal) visual pathway, and attention was probably controlled primarily by a selection network in the midbrain. In contrast, in primates, visual perception is dominated by information transmitted via the forebrain (retinogeniculate) visual pathway, and attention is mediated largely by networks in the forebrain. In birds and nonprimate mammals, both the retinotectal and retinogeniculate pathways contribute critically to visual information processing, and both midbrain and forebrain networks play important roles in controlling attention. The computations and processing strategies in birds and mammals share some strikingly similar characteristics despite over 300 million years of independent evolution and being implemented by distinct brain architectures. The similarity of these functional characteristics suggests that they provide valuable advantages to visual perception in advanced visual systems. A schema is proposed that describes the evolution of the pathways and computations that enable visual perception in vertebrate species.
Topics: Animals; Biological Evolution; Birds; Brain; Humans; Mammals; Nerve Net; Retina; Retinal Neurons; Superior Colliculi; Vertebrates; Visual Pathways; Visual Perception
PubMed: 32003466
DOI: 10.1002/cne.24871 -
Trends in Cognitive Sciences Oct 2016The cortical visual system is almost universally thought to be segregated into two anatomically and functionally distinct pathways: a ventral occipitotemporal pathway... (Review)
Review
The cortical visual system is almost universally thought to be segregated into two anatomically and functionally distinct pathways: a ventral occipitotemporal pathway that subserves object perception, and a dorsal occipitoparietal pathway that subserves object localization and visually guided action. Accumulating evidence from both human and non-human primate studies, however, challenges this binary distinction and suggests that regions in the dorsal pathway contain object representations that are independent of those in ventral cortex and that play a functional role in object perception. We review here the evidence implicating dorsal object representations, and we propose an account of the anatomical organization, functional contributions, and origins of these representations in the service of perception.
Topics: Animals; Humans; Pattern Recognition, Visual; Perception; Visual Pathways; Visual Perception
PubMed: 27615805
DOI: 10.1016/j.tics.2016.08.003 -
Annual Review of Vision Science Sep 2018Inferior temporal cortex (IT) is a key part of the ventral visual pathway implicated in object, face, and scene perception. But how does IT work? Here, I describe an... (Review)
Review
Inferior temporal cortex (IT) is a key part of the ventral visual pathway implicated in object, face, and scene perception. But how does IT work? Here, I describe an organizational scheme that marries form and function and provides a framework for future research. The scheme consists of a series of stages arranged along the posterior-anterior axis of IT, defined by anatomical connections and functional responses. Each stage comprises a complement of subregions that have a systematic spatial relationship. The organization of each stage is governed by an eccentricity template, and corresponding eccentricity representations across stages are interconnected. Foveal representations take on a role in high-acuity object vision (including face recognition); intermediate representations compute other aspects of object vision such as behavioral valence (using color and surface cues); and peripheral representations encode information about scenes. This multistage, parallel-processing model invokes an innately determined organization refined by visual experience that is consistent with principles of cortical development. The model is also consistent with principles of evolution, which suggest that visual cortex expanded through replication of retinotopic areas. Finally, the model predicts that the most extensively studied network within IT-the face patches-is not unique but rather one manifestation of a canonical set of operations that reveal general principles of how IT works.
Topics: Animals; Color Perception; Facial Recognition; Humans; Models, Neurological; Temporal Lobe; Visual Cortex; Visual Pathways; Visual Perception
PubMed: 30059648
DOI: 10.1146/annurev-vision-091517-034202 -
Journal of Vision Aug 2020The crowding effect, defined as the detrimental effects of nearby items on visual object recognition, has been extensively investigated. Previous studies have primarily...
The crowding effect, defined as the detrimental effects of nearby items on visual object recognition, has been extensively investigated. Previous studies have primarily focused on finding the stage(s) in the visual hierarchy where crowding starts to limit target processing, while little attention has been focused on potential differences between the parvocellular (P) and magnocellular (M) pathways in crowding mechanisms. Here, we investigated the crowding effect in these parallel visual pathways. In Experiment 1, stimuli were designed to separately engage the P or M pathway, by tuning stimulus and background features (e.g., temporal frequency and color) to activate the targeted pathway and saturate the other pathway, respectively. Results showed that at the same eccentricity and with the same tasks, targets processed in the M pathway appeared to be more vulnerable to crowding effect. In Experiment 2, crowding effects were studied using three different types of stimuli and visual tasks (form, color, and motion), presumably with different degrees of dependence on the P and M pathways. Results revealed that color, motion, and form discrimination were increasingly more affected by crowding. We conclude that processing in the M and P pathways are differentially impacted by crowding; and importantly, crowding seems to affect processing of spatial forms more than other stimulus properties.
Topics: Adolescent; Adult; Attention; Color; Color Perception; Crowding; Female; Form Perception; Humans; Male; Motion Perception; Pattern Recognition, Visual; Photic Stimulation; Visual Pathways; Young Adult
PubMed: 32749447
DOI: 10.1167/jov.20.8.6 -
Ophthalmic & Physiological Optics : the... May 2016Over the last two decades, magnetic resonance imaging (MRI) has been widely used in neuroscience research to assess both structure and function in the brain in health... (Review)
Review
PURPOSE
Over the last two decades, magnetic resonance imaging (MRI) has been widely used in neuroscience research to assess both structure and function in the brain in health and disease. With regard to vision research, prior to the advent of MRI, researchers relied on animal physiology and human post-mortem work to assess the impact of eye disease on visual cortex and connecting structures. Using MRI, researchers can non-invasively examine the effects of eye disease on the whole visual pathway, including the lateral geniculate nucleus, striate and extrastriate cortex. This review aims to summarise research using MRI to investigate structural, chemical and functional effects of eye diseases, including: macular degeneration, retinitis pigmentosa, glaucoma, albinism, and amblyopia.
RECENT FINDINGS
Structural MRI has demonstrated significant abnormalities within both grey and white matter densities across both visual and non-visual areas. Functional MRI studies have also provided extensive evidence of functional changes throughout the whole of the visual pathway following visual loss, particularly in amblyopia. MR spectroscopy techniques have also revealed several abnormalities in metabolite concentrations in both glaucoma and age-related macular degeneration. GABA-edited MR spectroscopy on the other hand has identified possible evidence of plasticity within visual cortex.
SUMMARY
Collectively, using MRI to investigate the effects on the visual pathway following disease and dysfunction has revealed a rich pattern of results allowing for better characterisation of disease. In the future MRI will likely play an important role in assessing the impact of eye disease on the visual pathway and how it progresses over time.
Topics: Animals; Humans; Magnetic Resonance Imaging; Vision Disorders; Visual Cortex; Visual Pathways
PubMed: 27112223
DOI: 10.1111/opo.12293 -
Seminars in Cell & Developmental Biology Nov 2014
Topics: Animals; Brain; Brain Mapping; Humans; Models, Neurological; Neural Pathways; Visual Pathways
PubMed: 25171872
DOI: 10.1016/j.semcdb.2014.08.012