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Ophthalmologica. Journal International... 2011Degenerative retinal diseases like retinitis pigmentosa and age-related macular degeneration are among the most common causes of blindness worldwide. Electronic visual... (Review)
Review
Degenerative retinal diseases like retinitis pigmentosa and age-related macular degeneration are among the most common causes of blindness worldwide. Electronic visual prostheses represent a potential therapeutic option of increasing importance in otherwise incurably impaired patients. Based on extensive animal experiments, several devices are now being tested in clinical trials. According to the placement of the electrodes, possible stimulation sites are located subretinally, epiretinally, along the optic nerve or cortically. Anatomical, physiological and pathophysiological aspects must be considered in development and clinical application. To provide an appropriate retinal substitute, the optimal integration and adaptation of the prosthesis into the highly complex system of the visual pathway is important. This article aims to summarize the relevant studies and provides an overview of the current status of developments and challenges that still need to be mastered.
Topics: Blindness; Humans; Prosthesis Design; Retinal Diseases; Visual Acuity; Visual Pathways; Visual Prosthesis
PubMed: 21293161
DOI: 10.1159/000318042 -
Neuroscience Nov 2018In recent years, a growing body of research has addressed the nature and mechanism of material perception. Material perception entails perceiving and recognizing a... (Review)
Review
In recent years, a growing body of research has addressed the nature and mechanism of material perception. Material perception entails perceiving and recognizing a material, surface quality or internal state of an object based on sensory stimuli such as visual, tactile, and/or auditory sensations. This process is ongoing in every aspect of daily life. We can, for example, easily distinguish whether an object is made of wood or metal, or whether a surface is rough or smooth. Judging whether the ground is wet or dry or whether a fish is fresh also involves material perception. Information obtained through material perception can be used to govern actions toward objects and to make decisions about whether to approach an object or avoid it. Because the physical processes leading to sensory signals related to material perception is complicated, it has been difficult to manipulate experimental stimuli in a rigorous manner. However, that situation is now changing thanks to advances in technology and knowledge in related fields. In this article, we will review what is currently known about the neural mechanisms responsible for material perception. We will show that cortical areas in the ventral visual pathway are strongly involved in material perception. Our main focus is on vision, but every sensory modality is involved in material perception. Information obtained through different sensory modalities is closely linked in material perception. Such cross-modal processing is another important feature of material perception, and will also be covered in this review.
Topics: Animals; Brain; Form Perception; Humans; Macaca; Neurons; Pattern Recognition, Visual; Visual Cortex; Visual Pathways
PubMed: 30213767
DOI: 10.1016/j.neuroscience.2018.09.001 -
Journal of Neurotrauma Jun 2022The consequences of forceful rotational acceleration on the central nervous system are not fully understood. While traumatic brain injury (TBI) research primarily has...
Meningeal and Visual Pathway Magnetic Resonance Imaging Analysis after Single and Repetitive Closed-Head Impact Model of Engineered Rotational Acceleration (CHIMERA)-Induced Disruption in Male and Female Mice.
The consequences of forceful rotational acceleration on the central nervous system are not fully understood. While traumatic brain injury (TBI) research primarily has focused on effects related to the brain parenchyma, reports of traumatic meningeal enhancement in TBI patients may possess clinical significance. The objective of this study was to evaluate the meninges and brain for changes in dynamic contrast enhancement (DCE) magnetic resonance imaging (MRI) following closed-head impact model of engineered rotational acceleration (CHIMERA)-induced cerebral insult. Adult male and female mice received one (1 × ; = 19 CHIMERA, = 19 Sham) or four (4 × one/day; = 18 CHIMERA, = 12 Sham) injuries. Each animal underwent three MRI scans: 1 week before injury, immediately after the final injury, and 1 week post-injury. Compared with baseline readings and measures in sham animals, meningeal DCE in males was increased after single impact and repetitive injury. In female mice, DCE was elevated relative to their baseline level after a single impact. One week after CHIMERA, the meningeal enhancement returned to below baseline for single injured male mice, but compared with uninjured mice remained elevated in both sexes in the multiple impact groups. Pre-DCE meningeal T2-weighted relaxation time was increased only after 1 × CHIMERA in injured mice. Since vision is impaired after CHIMERA, visual pathway regions were analyzed through imaging and glial fibrillary acidic protein (GFAP) histology. Initial DCE in the lateral geniculate nucleus (LGN) and superior colliculus (SC) and T2 increases in the optic tract (OPT) and LGN were observed after injury with decreases in DCE and T2 1 week later. Astrogliosis was apparent in the OPT and SC with increased GFAP staining 7 days post-injury. To our knowledge, this is the first study to examine meningeal integrity after CHIMERA in both male and female rodents. DCE-MRI may serve as a useful approach for pre-clinical models of meningeal injury that will enable further evaluation of the underlying mechanisms.
Topics: Animals; Female; Humans; Male; Mice; Acceleration; Brain Injuries, Traumatic; Disease Models, Animal; Magnetic Resonance Imaging; Meninges; Mice, Inbred C57BL; Visual Pathways
PubMed: 35243900
DOI: 10.1089/neu.2021.0494 -
The Journal of Neuroscience : the... Jun 2022Although there is mounting evidence that input from the dorsal visual pathway is crucial for object processes in the ventral pathway, the specific functional...
Although there is mounting evidence that input from the dorsal visual pathway is crucial for object processes in the ventral pathway, the specific functional contributions of dorsal cortex to these processes remain poorly understood. Here, we hypothesized that dorsal cortex computes the spatial relations among an object's parts, a process crucial for forming global shape percepts, and transmits this information to the ventral pathway to support object categorization. Using fMRI with human participants (females and males), we discovered regions in the intraparietal sulcus (IPS) that were selectively involved in computing object-centered part relations. These regions exhibited task-dependent functional and effective connectivity with ventral cortex, and were distinct from other dorsal regions, such as those representing allocentric relations, 3D shape, and tools. In a subsequent experiment, we found that the multivariate response of posterior (p)IPS, defined on the basis of part-relations, could be used to decode object category at levels comparable to ventral object regions. Moreover, mediation and multivariate effective connectivity analyses further suggested that IPS may account for representations of part relations in the ventral pathway. Together, our results highlight specific contributions of the dorsal visual pathway to object recognition. We suggest that dorsal cortex is a crucial source of input to the ventral pathway and may support the ability to categorize objects on the basis of global shape. Humans categorize novel objects rapidly and effortlessly. Such categorization is achieved by representing an object's global shape structure, that is, the relations among object parts. Yet, despite their importance, it is unclear how part relations are represented neurally. Here, we hypothesized that object-centered part relations may be computed by the dorsal visual pathway, which is typically implicated in visuospatial processing. Using fMRI, we identified regions selective for the part relations in dorsal cortex. We found that these regions can support object categorization, and even mediate representations of part relations in the ventral pathway, the region typically thought to support object categorization. Together, these findings shed light on the broader network of brain regions that support object categorization.
Topics: Brain Mapping; Female; Humans; Magnetic Resonance Imaging; Male; Parietal Lobe; Pattern Recognition, Visual; Photic Stimulation; Visual Pathways
PubMed: 35508386
DOI: 10.1523/JNEUROSCI.2257-21.2022 -
The Journal of Comparative Neurology Jan 2021The extrageniculate visual pathway, which carries visual information from the retina through the superficial layers of the superior colliculus and the pulvinar, is...
The extrageniculate visual pathway, which carries visual information from the retina through the superficial layers of the superior colliculus and the pulvinar, is poorly understood. The pulvinar is thought to modulate information flow between cortical areas, and has been implicated in cognitive tasks like directing visually guided actions. In order to better understand the underlying circuitry, we performed retrograde injections of modified rabies virus in the visual cortex and pulvinar of the Long-Evans rat. We found a relatively small population of cells projecting to primary visual cortex (V1), compared to a much larger population projecting to higher visual cortex. Reciprocal corticothalamic projections showed a similar result, implying that pulvinar does not play as big a role in directly modulating rodent V1 activity as previously thought.
Topics: Animals; Female; Primary Visual Cortex; Pulvinar; Rats; Rats, Long-Evans; Visual Cortex; Visual Pathways
PubMed: 32361987
DOI: 10.1002/cne.24937 -
Proceedings of the National Academy of... Oct 2022Understanding the neural basis of the remarkable human cognitive capacity to learn novel concepts from just one or a few sensory experiences constitutes a fundamental...
Understanding the neural basis of the remarkable human cognitive capacity to learn novel concepts from just one or a few sensory experiences constitutes a fundamental problem. We propose a simple, biologically plausible, mathematically tractable, and computationally powerful neural mechanism for few-shot learning of naturalistic concepts. We posit that the concepts that can be learned from few examples are defined by tightly circumscribed manifolds in the neural firing-rate space of higher-order sensory areas. We further posit that a single plastic downstream readout neuron learns to discriminate new concepts based on few examples using a simple plasticity rule. We demonstrate the computational power of our proposal by showing that it can achieve high few-shot learning accuracy on natural visual concepts using both macaque inferotemporal cortex representations and deep neural network (DNN) models of these representations and can even learn novel visual concepts specified only through linguistic descriptors. Moreover, we develop a mathematical theory of few-shot learning that links neurophysiology to predictions about behavioral outcomes by delineating several fundamental and measurable geometric properties of neural representations that can accurately predict the few-shot learning performance of naturalistic concepts across all our numerical simulations. This theory reveals, for instance, that high-dimensional manifolds enhance the ability to learn new concepts from few examples. Intriguingly, we observe striking mismatches between the geometry of manifolds in the primate visual pathway and in trained DNNs. We discuss testable predictions of our theory for psychophysics and neurophysiological experiments.
Topics: Animals; Concept Formation; Humans; Learning; Macaca; Neural Networks, Computer; Plastics; Primates; Visual Pathways
PubMed: 36251997
DOI: 10.1073/pnas.2200800119 -
PloS One 2016Many structural and functional brain alterations accompany blindness, with substantial individual variation in these effects. In normally sighted people, there is...
Many structural and functional brain alterations accompany blindness, with substantial individual variation in these effects. In normally sighted people, there is correlated individual variation in some visual pathway structures. Here we examined if the changes in brain anatomy produced by blindness alter the patterns of anatomical variation found in the sighted. We derived eight measures of central visual pathway anatomy from a structural image of the brain from 59 sighted and 53 blind people. These measures showed highly significant differences in mean size between the sighted and blind cohorts. When we examined the measurements across individuals within each group we found three clusters of correlated variation, with V1 surface area and pericalcarine volume linked, and independent of the thickness of V1 cortex. These two clusters were in turn relatively independent of the volumes of the optic chiasm and lateral geniculate nucleus. This same pattern of variation in visual pathway anatomy was found in the sighted and the blind. Anatomical changes within these clusters were graded by the timing of onset of blindness, with those subjects with a post-natal onset of blindness having alterations in brain anatomy that were intermediate to those seen in the sighted and congenitally blind. Many of the blind and sighted subjects also contributed functional MRI measures of cross-modal responses within visual cortex, and a diffusion tensor imaging measure of fractional anisotropy within the optic radiations and the splenium of the corpus callosum. We again found group differences between the blind and sighted in these measures. The previously identified clusters of anatomical variation were also found to be differentially related to these additional measures: across subjects, V1 cortical thickness was related to cross-modal activation, and the volume of the optic chiasm and lateral geniculate was related to fractional anisotropy in the visual pathway. Our findings show that several of the structural and functional effects of blindness may be reduced to a smaller set of dimensions. It also seems that the changes in the brain that accompany blindness are on a continuum with normal variation found in the sighted.
Topics: Adolescent; Adult; Anisotropy; Blindness; Female; Humans; Male; Middle Aged; Visual Pathways; White Matter; Young Adult
PubMed: 27812129
DOI: 10.1371/journal.pone.0164677 -
Journal of Neuro-ophthalmology : the... Dec 2011Recent improvements in optical coherence tomographic (OCT) resolution and automated segmentation software have provided a means of relating visual pathway damage to... (Review)
Review
BACKGROUND
Recent improvements in optical coherence tomographic (OCT) resolution and automated segmentation software have provided a means of relating visual pathway damage to structural changes in the retinal nerve fiber layer (RNFL) and corresponding soma of the ganglion cells in the inner layers of the macula and also in the outer photoreceptor layer in the macula.
EVIDENCE ACQUISITION
Studies correlating retinal structure with function are reviewed in the context of OCT in optic nerve and retinal disorders.
RESULTS
Recently published work provides evidence showing a strong relationship not only between the RNFL and visual threshold in optic nerve disorders but also between visual sensitivity and the inner layers of the retina in the macula, where the cell bodies of ganglion cells reside. Acquired and genetic disorders affecting the outer retina show correlation between visual sensitivity and the thickness of the outer photoreceptors. These relationships help localize unknown causes of visual field loss through segmentation of the retinal layers using spectral domain OCT.
CONCLUSIONS
Advances in relating the structure of the ganglion cell layer in the macula to the corresponding axons in the RNFL and to visual function further our ability to differentiate and localize ambiguous causes of vision loss and visual field defects in neuro-ophthalmology. Ganglion cell layer analysis in volume OCT data may provide yet another piece of the puzzle to understanding structure-function relationships and its application to diagnosis and monitoring of optic nerve diseases, while similar structure-function relationships are also being elucidated in the outer retina for photoreceptor diseases.
Topics: Humans; Nerve Fibers; Optic Nerve Diseases; Retinal Diseases; Retinal Ganglion Cells; Tomography, Optical Coherence; Visual Fields; Visual Pathways
PubMed: 22089499
DOI: 10.1097/WNO.0b013e318238b9cb -
The Journal of Physiology Jun 2009The first paper of Hubel and Wiesel in The Journal of Physiology in 1959 marked the beginning of an exciting chapter in the history of visual neuroscience. Through a... (Review)
Review
The first paper of Hubel and Wiesel in The Journal of Physiology in 1959 marked the beginning of an exciting chapter in the history of visual neuroscience. Through a collaboration that lasted 25 years, Hubel and Wiesel described the main response properties of visual cortical neurons, the functional architecture of visual cortex and the role of visual experience in shaping cortical architecture. The work of Hubel and Wiesel transformed the field not only through scientific discovery but also by touching the life and scientific careers of many students. Here, I describe my personal experience as a postdoctoral student with Torsten Wiesel and how this experience influenced my own work.
Topics: Animals; Geniculate Bodies; History, 20th Century; Humans; Neural Pathways; Neurology; Retina; Visual Cortex; Visual Pathways
PubMed: 19525563
DOI: 10.1113/jphysiol.2009.169813 -
Multiple Sclerosis (Houndmills,... Apr 2022Decreased motion perception has been suggested as a marker for visual pathway demyelination in optic neuritis (ON) and/or multiple sclerosis (MS).
BACKGROUND
Decreased motion perception has been suggested as a marker for visual pathway demyelination in optic neuritis (ON) and/or multiple sclerosis (MS).
OBJECTIVES
To examine the influence of neuro-axonal damage on motion perception in MS and neuromyelitis optica spectrum disorders (NMOSD).
METHODS
We analysed motion perception with numbers-from-motion (NFM), visual acuity, (multifocal (mf)) VEP, optical coherence tomography in patients with MS ( = 38, confirmatory cohort = 43), NMOSD ( = 13) and healthy controls ( = 33).
RESULTS
NFM was lower compared with controls in MS ( = -12.37, < 0.001) and NMOSD ( = -34.5, < 0.001). NFM was lower in ON than in non-ON eyes ( = -30.95, = 0.041) in NMOSD, but not MS. In MS and NMOSD, lower NFM was associated with worse visual acuity ( = -139.4, < 0.001/ = -77.2, < 0.001) and low contrast letter acuity ( = 0.99, = 0.002/ = 1.6, < 0.001), thinner peripapillary retinal nerve fibre layer ( = 1.0, < 0.001/ = 0.92, = 0.016) and ganglion cell/inner plexiform layer ( = 64.8, < 0.001/ = 79.5, = 0.006), but not with VEP P100 latencies. In the confirmatory MS cohort, lower NFM was associated with thinner retinal nerve fibre layer ( = 1.351, < 0.001) and increased mfVEP P100 latencies ( = -1.159, < 0.001).
CONCLUSIONS
Structural neuro-axonal visual pathway damage is an important driver of motion perception impairment in MS and NMOSD.
Topics: Humans; Motion Perception; Multiple Sclerosis; Neuromyelitis Optica; Optic Neuritis; Tomography, Optical Coherence; Visual Pathways
PubMed: 34379018
DOI: 10.1177/13524585211032801