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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 -
Neurosurgical Review Apr 2018The objective of this systematic literature review is to assess the role of retinal optical coherence tomography (OCT) in the evaluation of patients with tumors of the... (Review)
Review
The objective of this systematic literature review is to assess the role of retinal optical coherence tomography (OCT) in the evaluation of patients with tumors of the visual pathway. We performed a PubMed database search according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. The search was restricted to articles published in English between 2000 and 2016, with at least 10 human adult participants enrolled. Twenty-seven articles met the eligibility criteria. All studies investigated tumors of the anterior visual pathway. Both time-domain and spectral-domain OCT technologies were used and the role of OCT as diagnostic and/or prognostic tool was studied. Retinal OCT provides structural information about ganglion cell axon integrity and is complementary to visual function examination. OCT is a prognostic factor for post-operative visual outcome.
Topics: Humans; Nerve Compression Syndromes; Occipital Lobe; Optic Chiasm; Optic Nerve Neoplasms; Postoperative Complications; Retina; Retinal Ganglion Cells; Tomography, Optical Coherence; Visual Cortex; Visual Pathways
PubMed: 27465394
DOI: 10.1007/s10143-016-0772-1 -
Neuropsychologia Oct 2017A dominant view in the cognitive neuroscience of object vision is that regions of the ventral visual pathway exhibit some degree of category selectivity. However, recent... (Review)
Review
A dominant view in the cognitive neuroscience of object vision is that regions of the ventral visual pathway exhibit some degree of category selectivity. However, recent findings obtained with multivariate pattern analyses (MVPA) suggest that apparent category selectivity in these regions is dependent on more basic visual features of stimuli. In which case a rethinking of the function and organization of the ventral pathway may be in order. We suggest that addressing this issue of functional specificity requires clear coding hypotheses, about object category and visual features, which make contrasting predictions about neuroimaging results in ventral pathway regions. One way to differentiate between categorical and featural coding hypotheses is to test for residual categorical effects: effects of category selectivity that cannot be accounted for by visual features of stimuli. A strong method for testing these effects, we argue, is to make object category and target visual features orthogonal in stimulus design. Recent studies that adopt this approach support a feature-based categorical coding hypothesis according to which regions of the ventral stream do indeed code for object category, but in a format at least partially based on the visual features of stimuli.
Topics: Brain Mapping; Humans; Pattern Recognition, Visual; Photic Stimulation; Visual Cortex; Visual Pathways
PubMed: 28619529
DOI: 10.1016/j.neuropsychologia.2017.06.010 -
Journal of Molecular Neuroscience : MN Jun 2022A change in visual perception is a frequent early symptom of multiple sclerosis (MS), the pathoaetiology of which remains unclear. Following a slow demyelination process...
A change in visual perception is a frequent early symptom of multiple sclerosis (MS), the pathoaetiology of which remains unclear. Following a slow demyelination process caused by 12 weeks of low-dose (0.1%) cuprizone (CPZ) consumption, histology and proteomics were used to investigate components of the visual pathway in young adult mice. Histological investigation did not identify demyelination or gliosis in the optic tracts, pretectal nuclei, superior colliculi, lateral geniculate nuclei or visual cortices. However, top-down proteomic assessment of the optic nerve/tract revealed a significant change in the abundance of 34 spots in high-resolution two-dimensional (2D) gels. Subsequent liquid chromatography-tandem mass spectrometry (LC-TMS) analysis identified alterations in 75 proteoforms. Literature mining revealed the relevance of these proteoforms in terms of proteins previously implicated in animal models, eye diseases and human MS. Importantly, 24 proteoforms were not previously described in any animal models of MS, eye diseases or MS itself. Bioinformatic analysis indicated involvement of these proteoforms in cytoskeleton organization, metabolic dysregulation, protein aggregation and axonal support. Collectively, these results indicate that continuous CPZ-feeding, which evokes a slow demyelination, results in proteomic changes that precede any clear histological changes in the visual pathway and that these proteoforms may be potential early markers of degenerative demyelinating conditions.
Topics: Animals; Cuprizone; Disease Models, Animal; Mice; Mice, Inbred C57BL; Multiple Sclerosis; Proteins; Proteomics; Visual Pathways
PubMed: 35644788
DOI: 10.1007/s12031-022-01997-w -
AJNR. American Journal of Neuroradiology May 2016Visual hallucinations are relatively uncommon presentations in medical and psychiatric clinics, where they are generally regarded as a marker of possible underlying... (Review)
Review
Visual hallucinations are relatively uncommon presentations in medical and psychiatric clinics, where they are generally regarded as a marker of possible underlying "organic" brain disease. Thus, patients with visual hallucinations are often referred for imaging of the brain. This article presents a pragmatic approach for the radiologist reviewing such imaging. Because conditions that can present with visual hallucinations are legion, a familiarity with the features of the hallucinations themselves, which can serve as clues to the underlying cause, can be helpful in interpreting such cases. We consider the nature of visual hallucinations and the mechanisms underlying their formation. We then provide a framework to guide the search for their cause, first in terms of focal lesions along the visual pathway and then global conditions affecting >1 region.
Topics: Brain; Brain Diseases; Female; Hallucinations; Humans; Male; Neuroimaging; Visual Pathways
PubMed: 26744445
DOI: 10.3174/ajnr.A4636 -
The Journal of Neuroscience : the... Aug 2019Visual information reaches the cerebral cortex through parallel ON and OFF pathways that signal the presence of light and dark stimuli in visual scenes. We have... (Comparative Study)
Comparative Study
Visual information reaches the cerebral cortex through parallel ON and OFF pathways that signal the presence of light and dark stimuli in visual scenes. We have previously demonstrated that optical blur reduces visual salience more for light than dark stimuli because it removes the high spatial frequencies from the stimulus, and low spatial frequencies drive weaker ON than OFF cortical responses. Therefore, we hypothesized that sustained optical blur during brain development should weaken ON cortical pathways more than OFF, increasing the dominance of darks in visual perception. Here we provide support for this hypothesis in humans with anisometropic amblyopia who suffered sustained optical blur early after birth in one of the eyes. In addition, we show that the dark dominance in visual perception also increases in strabismic amblyopes that have their vision to high spatial frequencies reduced by mechanisms not associated with optical blur. Together, we show that amblyopia increases visual dark dominance by 3-10 times and that the increase in dark dominance is strongly correlated with amblyopia severity. These results can be replicated with a computational model that uses greater luminance/response saturation in ON than OFF pathways and, as a consequence, reduces more ON than OFF cortical responses to stimuli with low spatial frequencies. We conclude that amblyopia affects the ON cortical pathway more than the OFF, a finding that could have implications for future amblyopia treatments. Amblyopia is a loss of vision that affects 2-5% of children across the world and originates from a deficit in visual cortical circuitry. Current models assume that amblyopia affects similarly ON and OFF visual pathways, which signal light and dark features in visual scenes. Against this current belief, here we demonstrate that amblyopia affects the ON visual pathway more than the OFF, a finding that could have implications for new amblyopia treatments targeted at strengthening a weak ON visual pathway.
Topics: Adolescent; Adult; Amblyopia; Brain; Cerebral Cortex; Darkness; Eye; Female; Fixation, Ocular; Humans; Light; Male; Middle Aged; Neuronal Plasticity; Photic Stimulation; Psychophysics; Thalamus; Vision, Monocular; Visual Acuity; Visual Pathways; Young Adult
PubMed: 31189574
DOI: 10.1523/JNEUROSCI.3215-18.2019 -
Neurodegenerative Disease Management Oct 2018In this review, a current overview is provided of how optical coherence tomography and infrared oculography can aid in assessing the visual system and CNS in multiple... (Review)
Review
In this review, a current overview is provided of how optical coherence tomography and infrared oculography can aid in assessing the visual system and CNS in multiple sclerosis (MS). Both afferent and efferent visual disorders are common in MS and visual complaints can have a tremendous impact on daily functioning. Optical coherence tomography and infrared oculography can detect and quantify visual disorders with high accuracy, but could also serve as quantitative markers for inflammation, neurodegeneration and network changes including cognitive decline in MS patients. The assessment of the efferent and afferent visual pathways is relevant for monitoring and predicting the disease course, but is also potentially valuable as an outcome measure in therapeutic trials.
Topics: Eye; Humans; Infrared Rays; Multiple Sclerosis; Tomography, Optical Coherence; Visual Pathways
PubMed: 30226111
DOI: 10.2217/nmt-2018-0011 -
Veterinary Ophthalmology May 2022The visual system is known to be vital for cognition and perception in the feline and canine and much behavioral research for these species has used visual stimuli and...
The visual system is known to be vital for cognition and perception in the feline and canine and much behavioral research for these species has used visual stimuli and focused on visual perception. There has been extensive investigations into the visual pathway in cats and dogs via histological and neurobiological methods, however to date, only one study has mapped the canine optic pathway in vivo. Advanced imaging methods such as diffusion MRI (DTI) have been routinely used in human research to study the visual system in vivo. This study applied DTI imaging methods to assess and characterize the optic pathway of feline and canine subjects in vivo. The optic nerve (ON), optic tract (OT), and optic radiation (OR) were successfully delineated for each species and the average volume and FA for each tract is reported. The application of DTI to map the optic pathway for canine and feline subjects provides a healthy baseline for comparison in future studies.
Topics: Animals; Cat Diseases; Cats; Diffusion Magnetic Resonance Imaging; Diffusion Tensor Imaging; Dog Diseases; Dogs; Humans; Visual Pathways
PubMed: 34784441
DOI: 10.1111/vop.12940