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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 -
Clinical & Experimental Optometry May 2014Cerebral visual impairment (CVI) comprises visual malfunction due to retro-chiasmal visual and visual association pathway pathology. This can be isolated or accompany... (Review)
Review
Cerebral visual impairment (CVI) comprises visual malfunction due to retro-chiasmal visual and visual association pathway pathology. This can be isolated or accompany anterior visual pathway dysfunction. It is a major cause of low vision in children in the developed and developing world due to increasing survival in paediatric and neonatal care. CVI can present in many combinations and degrees. There are multiple causes and it is common in children with cerebral palsy. CVI can be identified easily, if a structured approach to history-taking is employed. This review describes the features of CVI and describes practical management strategies aimed at helping affected children. A literature review was undertaken using 'Medline' and 'Pubmed'. Search terms included cerebral visual impairment, cortical visual impairment, dorsal stream dysfunction and visual function in cerebral palsy.
Topics: Blindness, Cortical; Child; Humans; Visual Acuity; Visual Pathways
PubMed: 24766507
DOI: 10.1111/cxo.12155 -
Journal of the Neurological Sciences Jul 2006We examined 19 autopsied cases of dementia with Lewy bodies (DLB) using pathological and alpha-synuclein-immunohistochemical methods, and investigated Lewy pathology in...
We examined 19 autopsied cases of dementia with Lewy bodies (DLB) using pathological and alpha-synuclein-immunohistochemical methods, and investigated Lewy pathology in the primary visual pathway (lateral geniculate body and Brodmann's area 17), secondary visual pathway (pulvinar, Brodmann's areas 18 and 19, and inferior temporal cortex), amygdala and substantia nigra, to clarify the relationship between visual misidentification and Lewy pathology in the visual pathway. Consequently, the secondary visual pathway revealed significantly severer Lewy pathology than the primary visual pathway, suggesting that the degeneration of the secondary visual pathway induces dysfunction in the recognition of objects shape and color. In addition, the amygdala revealed significantly severer Lewy pathology and neuronal loss than the primary and secondary visual pathways, suggesting that the degeneration of the amygdala, which receives the afferent connections from the substantia nigra, fails to modulate the visual processing according to cognition and emotion. These findings suggest that Lewy pathologies in the secondary visual pathway and amygdala may cause the dysfunction of the visuo-amygdaloid pathway and participate in visual misidentification in DLB patients. In addition, we compared Lewy pathology between cases with and without visual hallucinations, and showed no significant differences between the two groups.
Topics: Aged; Aged, 80 and over; Amygdala; Autopsy; Brain; Cell Count; Disease Progression; Female; Hallucinations; Humans; Immunohistochemistry; Lewy Bodies; Lewy Body Disease; Male; Middle Aged; Neurons; Substantia Nigra; Visual Pathways; alpha-Synuclein
PubMed: 16624323
DOI: 10.1016/j.jns.2006.02.016 -
NeuroImage. Clinical 2024Impaired motion perception in schizophrenia has been associated with deficits in social-cognitive processes and with reduced activation of visual sensory regions,...
Impaired motion perception in schizophrenia has been associated with deficits in social-cognitive processes and with reduced activation of visual sensory regions, including the middle temporal area (MT+) and posterior superior temporal sulcus (pSTS). These findings are consistent with the recent proposal of the existence of a specific 'third visual pathway' specialized for social perception in which motion is a fundamental component. The third visual pathway transmits visual information from early sensory visual processing areas to the STS, with MT+ acting as a critical intermediary. We used functional magnetic resonance imaging to investigate functioning of this pathway during processing of naturalistic videos with explicit (real) motion and static images with implied motion cues. These measures were related to face emotion recognition and motion-perception, as measured behaviorally. Participants were 28 individuals with schizophrenia (Sz) and 20 neurotypical controls. Compared to controls, individuals with Sz showed reduced activation of third visual pathway regions (MT+, pSTS) in response to both real- and implied-motion stimuli. Dysfunction of early visual cortex and pulvinar were also associated with aberrant real-motion processing. Implied-motion stimuli additionally engaged a wide network of brain areas including parietal, motor and frontal nodes of the human mirror neuron system. The findings support concepts of MT+ as a mediator between visual sensory areas and higher-order brain and argue for greater focus on MT+ contributions to social-cognitive processing, in addition to its well-documented role in visual motion processing.
Topics: Humans; Schizophrenia; Visual Pathways; Temporal Lobe; Brain; Magnetic Resonance Imaging; Brain Mapping; Motion Perception; Photic Stimulation
PubMed: 38309185
DOI: 10.1016/j.nicl.2024.103570 -
Annual Review of Vision Science Sep 2021Visual processing is dynamically controlled by multiple neuromodulatory molecules that modify the responsiveness of neurons and the strength of the connections between... (Review)
Review
Visual processing is dynamically controlled by multiple neuromodulatory molecules that modify the responsiveness of neurons and the strength of the connections between them. In particular, modulatory control of processing in the lateral geniculate nucleus of the thalamus, V1, and V2 will alter the outcome of all subsequent processing of visual information, including the extent to and manner in which individual inputs contribute to perception and decision making and are stored in memory. This review addresses five small-molecule neuromodulators-acetylcholine, dopamine, serotonin, noradrenaline, and histamine-considering the structural basis for their action, and the effects of their release, in the early visual pathway of the macaque monkey. Traditionally, neuromodulators are studied in isolation and in discrete circuits; this review makes a case for considering the joint action of modulatory molecules and differences in modulatory effects across brain areas as a better means of understanding the diverse roles that these molecules serve.
Topics: Animals; Geniculate Bodies; Macaca; Neurons; Visual Pathways; Visual Perception
PubMed: 34524875
DOI: 10.1146/annurev-vision-100119-125739 -
Multiple Sclerosis (Houndmills,... Aug 2017The injury of visual pathway and abnormalities of visual processing speed (VPS) are frequent in MS, but their association remains unexplored.
BACKGROUND
The injury of visual pathway and abnormalities of visual processing speed (VPS) are frequent in MS, but their association remains unexplored.
OBJECTIVE
To evaluate the impact of posterior visual pathway structural and functional integrity on VPS of MS patients.
METHODS
Cross-sectional study of 30 MS patients and 28 controls, evaluating the association of a VPS tests composite (Salthouse Perceptual Comparison test, Trail Making Test A and Symbol Digit Modalities Test) with 3T MRI visual cortex thickness, optic radiations (OR) diffusion tensor imaging indexes, and medial visual component (MVC) functional connectivity (FC) (MVC-MVC FC (iFC) and MVC-brain FC (eFC)) by linear regression, removing the effect of premorbid IQ, fatigue, and depression.
RESULTS
V2 atrophy, lower OR fractional anisotropy (FA) and MVC FC significantly influenced VPS in MS (at none or lesser extent in controls), even after removing the effect of Expanded Disability Status Scale and previous optic neuritis (V2 ( r = 0.210): β = +0.366, p = 0.046; OR FA ( r = 0.243): β = +0.378, p = 0.034; MVC iFC, for example, left cuneus ( r = 0.450): β = -0.613, p < 0.001; MVC eFC, for example, right precuneus-postcentral gyrus ( r = 0.368): β = -0.466, p = 0.002).
CONCLUSION
Posterior visual pathway integrity, structural (V2 thickness and OR FA) and functional (MVC FC), may explain respectively up to 24% and 45% of VPS variability in MS.
Topics: Adult; Cognitive Dysfunction; Cross-Sectional Studies; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Multiple Sclerosis; Psychomotor Performance; Space Perception; Visual Cortex; Visual Pathways; Visual Perception
PubMed: 28273763
DOI: 10.1177/1352458516676642 -
Asian Journal of Surgery Dec 2023
Topics: Humans; Visual Pathways; Hand; Upper Extremity; Foot; Lower Extremity
PubMed: 37541890
DOI: 10.1016/j.asjsur.2023.07.138 -
Journal Francais D'ophtalmologie 1983This study concerns the development of the human primary visual pathway. The lateral geniculate nucleus (LGN), the principle thalamic relay to the visual cortex (area... (Review)
Review
This study concerns the development of the human primary visual pathway. The lateral geniculate nucleus (LGN), the principle thalamic relay to the visual cortex (area 17), has a population of neurons similar to that of the monkey, as identified by Golgi impregnation. Commonest neuron is the multipolar with a radiate or tufted dendritic tree, followed by the bipolar neuron with two or three diametrically opposed dendritic trunks and, more rarely, neurons with beaded dendrites and those with fine, axon-like dendritic processes, possibly interneurons. The dendritic tree of all neurons remains generally within a lamina, but some dendrites cross interlaminar zones. These zones contain neurons whose dendrites enter adjacent laminae. LGN neurons are identifiable at birth, and even earlier, and differ from their adult form by the presence of immature features (growth cones and numerous dendritic and somatic spines), most frequent at four months but disappearing completely by nine months post-natally, when the LGN has reached its "adult" volume. Two stages in the development of area 17 can be defined. The first is marked by rapid growth to its "adult" volume at about four months, and by intense synaptogenesis beginning in the foetus and reaching a maximum around eight months. The second stage is one of stabilization of volume of area 17 and loss of synapses to reach "adult" synaptic density around 11 years, at about 60 p. cent of maximum values. The formation of transitory morphological features in the first year coincides with a period of visual plasticity in the infant. Our observations can be correlated with clinical evaluations of visual activity during the preverbal stage, a period of great importance in the establishment of visual acuity, of stereopsis, and of oculomotor function, all very sensitive to the numerous forms of visual deprivation.
Topics: Animals; Child; Child, Preschool; Geniculate Bodies; Humans; Infant; Infant, Newborn; Neurons; Synapses; Vision, Ocular; Visual Cortex; Visual Pathways
PubMed: 6345646
DOI: No ID Found -
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 -
Intraoperative subcortico-cortical evoked potentials of the visual pathway under general anesthesia.Clinical Neurophysiology : Official... Jul 2021To assess whether intraoperative subcortical mapping of the visual pathways during brain surgeries was feasible.
OBJECTIVE
To assess whether intraoperative subcortical mapping of the visual pathways during brain surgeries was feasible.
METHODS
Subcortico-cortical evoked potentials (SCEPs: 30 stimulations/site, biphasic single pulse, 1.3 Hz, 0.2 ms/phase, maximum 10 mA; bipolar probe) were measured in 12 patients for stimulation of the optic radiation, Meyer's loop or optic nerve. Recorded sites were bilateral central, parietal, parieto-occipital, occipital (subdermal scalp electrodes, 5-4000 Hz). The minimum distances from the stimulation locations, i.e. the closest border of the resection cavity to the diffusion tensor imaging based visual pathways, were evaluated postoperatively (smallest distance across coronal, sagittal and axial planes).
RESULTS
Stimulation elicited SCEPs when the visual tracts were close (≤4.5 mm). The responses consisted of a short (P1, 3.0-5.6 ms; 8/8 patients) and of a middle (P2, 15-21.6 ms; 3/8 patients) latency waveforms. In agreement with the neuroanatomy, ipsilateral occipital responses were obtained for temporal or parietal stimulations, and bi-occipital responses for optic nerve stimulations.
CONCLUSIONS
For the first time to our knowledge, intraoperative SCEPs were observed for stimulations of the optic radiation and of Meyer's loop. Short latency responses were found in agreement with fast conduction of the visual pathway's connecting myelinated fibers.
SIGNIFICANCE
The mapping of the visual pathways was found feasible for neurosurgeries under general anesthesia.
Topics: Adult; Aged; Anesthesia, General; Electric Stimulation; Electroencephalography; Evoked Potentials, Visual; Female; Humans; Intraoperative Neurophysiological Monitoring; Magnetic Resonance Imaging; Male; Microsurgery; Middle Aged; Optic Nerve; Prospective Studies; Visual Cortex; Visual Pathways
PubMed: 34023622
DOI: 10.1016/j.clinph.2021.02.399