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NeuroImage May 2022Despite decades of research, our understanding of the relationship between color and form processing in the primate ventral visual pathway remains incomplete. Using fMRI...
Despite decades of research, our understanding of the relationship between color and form processing in the primate ventral visual pathway remains incomplete. Using fMRI multivoxel pattern analysis, we examined coding of color and form, using a simple form feature (orientation) and a mid-level form feature (curvature), in human ventral visual processing regions. We found that both color and form could be decoded from activity in early visual areas V1 to V4, as well as in the posterior color-selective region and shape-selective regions in ventral and lateral occipitotemporal cortex defined based on their univariate selectivity to color or shape, respectively (the central color region only showed color but not form decoding). Meanwhile, decoding biases towards one feature or the other existed in the color- and shape-selective regions, consistent with their univariate feature selectivity reported in past studies. Additional extensive analyses show that while all these regions contain independent (linearly additive) coding for both features, several early visual regions also encode the conjunction of color and the simple, but not the complex, form feature in a nonlinear, interactive manner. Taken together, the results show that color and form are encoded in a biased distributed and largely independent manner across ventral visual regions in the human brain.
Topics: Animals; Brain Mapping; Humans; Magnetic Resonance Imaging; Pattern Recognition, Visual; Photic Stimulation; Visual Cortex; Visual Pathways
PubMed: 35122966
DOI: 10.1016/j.neuroimage.2022.118941 -
The Journal of Comparative Neurology Feb 2019The dorsal lateral geniculate nucleus of the thalamus (LGN) receives the main outputs of both eyes and relays those signals to the visual cortex. Each retina projects to... (Review)
Review
The dorsal lateral geniculate nucleus of the thalamus (LGN) receives the main outputs of both eyes and relays those signals to the visual cortex. Each retina projects to separate layers of the LGN so that each LGN neuron is innervated by a single eye. In line with this anatomical separation, visual responses of almost all of LGN neurons are driven by one eye only. Nonetheless, many LGN neurons are sensitive to what is shown to the other eye as their visual responses differ when both eyes are stimulated compared to when the driving eye is stimulated in isolation. This, predominantly suppressive, binocular modulation of LGN responses might suggest that the LGN is the first location in the primary visual pathway where the outputs from the two eyes interact. Indeed, the LGN features several anatomical structures that would allow for LGN neurons responding to one eye to modulate neurons that respond to the other eye. However, it is also possible that binocular response modulation in the LGN arises indirectly as the LGN also receives input from binocular visual structures. Here we review the extant literature on the effects of binocular stimulation on LGN spiking responses, highlighting findings from cats and primates, and evaluate the neural circuits that might mediate binocular response modulation in the LGN.
Topics: Action Potentials; Animals; Geniculate Bodies; Humans; Photic Stimulation; Retina; Vision, Binocular; Visual Cortex; Visual Fields; Visual Pathways
PubMed: 29473163
DOI: 10.1002/cne.24417 -
Cortex; a Journal Devoted To the Study... Jul 2023Researchers have identified category-specific brain regions, such as the fusiform face area (FFA) and parahippocampal place area (PPA) in the ventral visual pathway,...
Researchers have identified category-specific brain regions, such as the fusiform face area (FFA) and parahippocampal place area (PPA) in the ventral visual pathway, which respond preferentially to one particular category of visual objects. In addition to their category-specific role in visual object identification and categorization, regions in the ventral visual pathway play critical roles in recognition memory. Nevertheless, it is not clear whether the contributions of those brain regions to recognition memory are category-specific or category-general. To address this question, the present study adopted a subsequent memory paradigm and multivariate pattern analysis (MVPA) to explore category-specific and category-general neural codes of recognition memory in the visual pathway. The results revealed that the right FFA and the bilateral PPA showed category-specific neural patterns supporting recognition memory of faces and scenes, respectively. In contrast, the lateral occipital cortex seemed to carry category-general neural codes of recognition memory. These results provide neuroimaging evidence for category-specific and category-general neural mechanisms of recognition memory in the ventral visual pathway.
Topics: Humans; Pattern Recognition, Visual; Visual Pathways; Occipital Lobe; Recognition, Psychology; Brain; Magnetic Resonance Imaging; Brain Mapping; Photic Stimulation
PubMed: 37207411
DOI: 10.1016/j.cortex.2023.04.004 -
Journal of Magnetic Resonance Imaging :... Dec 2021The visual system, consisting of the eyes and the visual pathways of the brain, receives and interprets light from the environment so that we can perceive the world... (Review)
Review
The visual system, consisting of the eyes and the visual pathways of the brain, receives and interprets light from the environment so that we can perceive the world around us. A wide variety of disorders can affect human vision, ranging from ocular to neurologic to systemic in nature. While other noninvasive imaging techniques such as optical coherence tomography and ultrasound can image particular sections of the visual system, magnetic resonance imaging (MRI) offers high resolution without depth limitations. MRI also gives superior soft-tissue contrast throughout the entire pathway compared to computed tomography. By leveraging different imaging sequences, MRI is uniquely capable of unveiling the intricate processes of ocular anatomy, tissue physiology, and neurological function in the human visual system from the microscopic to macroscopic levels. In this review we discuss how structural, metabolic, and functional MRI can be used in the clinical assessment of normal and pathologic states in the anatomic structures of the visual system, including the eyes, optic nerves, optic chiasm, optic tracts, visual brain nuclei, optic radiations, and visual cortical areas. We detail a selection of recent clinical applications of MRI at each position along the visual pathways, including the evaluation of pathology, plasticity, and the potential for restoration, as well as its limitations and key areas of ongoing exploration. Our discussion of the current and future developments in MR ocular and neuroimaging highlights its potential impact on our ability to understand visual function in new detail and to improve our protection and treatment of anatomic structures that are integral to this fundamental sensory system. LEVEL OF EVIDENCE 3: TECHNICAL EFFICACY STAGE 3: .
Topics: Humans; Magnetic Resonance Imaging; Neuroimaging; Optic Nerve; Sense Organs; Visual Pathways
PubMed: 33009710
DOI: 10.1002/jmri.27367 -
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 -
Seminars in Radiation Oncology Apr 2016Patients with tumors adjacent to the optic nerves and chiasm are frequently not candidates for single-fraction stereotactic radiosurgery (SRS) due to concern for... (Review)
Review
Patients with tumors adjacent to the optic nerves and chiasm are frequently not candidates for single-fraction stereotactic radiosurgery (SRS) due to concern for radiation-induced optic neuropathy. However, these patients have been successfully treated with hypofractionated SRS over 2-5 days, though dose constraints have not yet been well defined. We reviewed the literature on optic tolerance to radiation and constructed a dose-response model for visual pathway tolerance to SRS delivered in 1-5 fractions. We analyzed optic nerve and chiasm dose-volume histogram (DVH) data from perioptic tumors, defined as those within 3mm of the optic nerves or chiasm, treated with SRS from 2000-2013 at our institution. Tumors with subsequent local progression were excluded from the primary analysis of vision outcome. A total of 262 evaluable cases (26 with malignant and 236 with benign tumors) with visual field and clinical outcomes were analyzed. Median patient follow-up was 37 months (range: 2-142 months). The median number of fractions was 3 (1 fraction n = 47, 2 fraction n = 28, 3 fraction n = 111, 4 fraction n = 10, and 5 fraction n = 66); doses were converted to 3-fraction equivalent doses with the linear quadratic model using α/β = 2Gy prior to modeling. Optic structure dose parameters analyzed included Dmin, Dmedian, Dmean, Dmax, V30Gy, V25Gy, V20Gy, V15Gy, V10Gy, V5Gy, D50%, D10%, D5%, D1%, D1cc, D0.50cc, D0.25cc, D0.20cc, D0.10cc, D0.05cc, D0.03cc. From the plan DVHs, a maximum-likelihood parameter fitting of the probit dose-response model was performed using DVH Evaluator software. The 68% CIs, corresponding to one standard deviation, were calculated using the profile likelihood method. Of the 262 analyzed, 2 (0.8%) patients experienced common terminology criteria for adverse events grade 4 vision loss in one eye, defined as vision of 20/200 or worse in the affected eye. One of these patients had received 2 previous courses of radiotherapy to the optic structures. Both cases were meningiomas treated with 25Gy in 5 fractions, with a 3-fraction equivalent optic nerve Dmax of 19.2 and 22.2Gy. Fitting these data to a probit dose-response model enabled risk estimates to be made for these previously unvalidated optic pathway constraints: the Dmax limits of 12Gy in 1 fraction from QUANTEC, 19.5Gy in 3 fractions from Timmerman 2008, and 25Gy in 5 fractions from AAPM Task Group 101 all had less than 1% risk. In 262 patients with perioptic tumors treated with SRS, we found a risk of optic complications of less than 1%. These data support previously unvalidated estimates as safe guidelines, which may in fact underestimate the tolerance of the optic structures, particularly in patients without prior radiation. Further investigation would refine the estimated normal tissue complication probability for SRS near the optic apparatus.
Topics: Dose Fractionation, Radiation; Humans; Models, Theoretical; Radiation Dose Hypofractionation; Radiation Injuries; Radiation Tolerance; Radiosurgery; Radiotherapy Dosage; Visual Pathways
PubMed: 27000505
DOI: 10.1016/j.semradonc.2015.11.008 -
Current Opinion in Neurology Feb 2020The incidence of Alzheimer's disease is increasing. Premortem diagnosis of Alzheimer's disease is now possible but require invasive and expensive testing such as PET... (Review)
Review
PURPOSE OF REVIEW
The incidence of Alzheimer's disease is increasing. Premortem diagnosis of Alzheimer's disease is now possible but require invasive and expensive testing such as PET amyloid beta binding and/or spinal fluid amyloid beta levels. There is a great need for minimally invasive and inexpensive biomarkers to allow for early diagnosis and intervention.
RECENT FINDINGS
There has been a large volume of literature assessing ocular biomarkers for Alzheimer's disease. Much of the research to date has significant limitations, including sample size, variable diagnostic criteria for Alzheimer's disease, lack of biomarker assessment, and focus on patients with well established dementia. Work that is more recent has included individuals with early and preclinical Alzheimer's disease with biomarkers included in the design. These studies have shown consistent features of visual pathway involvement in Alzheimer's disease, even in the earliest and preclinical stages.
SUMMARY
It is possible that in the future, ocular biomarkers (particularly retinal imaging techniques) may be part of a multimodality alogorithm screening for preclinical Alzheimer's disease, perhaps combined with other methods, such as blood-based biomarkers.
Topics: Alzheimer Disease; Biomarkers; Early Diagnosis; Humans; Pupil; Retina; Tomography, Optical Coherence; Visual Pathways
PubMed: 31809334
DOI: 10.1097/WCO.0000000000000788 -
Brain and Nerve = Shinkei Kenkyu No... Nov 2016The temporal lobe of the cerebrum consists of several spatially segregated functional regions. There are discrete regions of the temporal lobe where auditory (primary,... (Review)
Review
The temporal lobe of the cerebrum consists of several spatially segregated functional regions. There are discrete regions of the temporal lobe where auditory (primary, secondary and tertiary), visual (motion detection and object recognition) and meta-cognitive (memory and social communication) functions are processed. The subcortical amygdala and hippocampal-complex can also be considered temporal structures. Several nomenclature systems have been promoted over the years resulting in multiple names for most individual gyri and sulci. Herein we review the historical naming systems for cerebral temporal structures and describe their relationship to the functional regions in the temporal lobe. Neuronal populations that process auditory information are located primarily in the medial region of the temporal lobe (the belt and parabelt). The object-recognition prefrontal cortical stream (the "What" pathway) projects through the rostral superior temporal gyrus while the place-related prefrontal cortical stream (the "Where" Pathway) projects through the caudal superior temporal gyrus. The dorsal part of the superior temporal sulcus receives projections from both auditory regions (superior temporal gyrus) and visual processing areas including the motion-recognition related midtemporal area (MT), the fundus of the superior temporal sulcus (FST), and the caudal inferotemporal cortex (TEO). This convergence could be related to dynamic integration of audio-visual information. The ventral part of the superior temporal sulcus also receives projections from motion-detection regions as well as object recognition areas (TE, TEO). This area could be involved in interpretation of dynamic moving objects, especially biological motion.
Topics: Animals; Brain Mapping; Cerebral Cortex; Hippocampus; Humans; Memory; Visual Cortex; Visual Pathways
PubMed: 27852025
DOI: 10.11477/mf.1416200598 -
Current Medical Science Dec 2018With an increasing incidence, diabetic retinopathy is one of the most important complications of diabetes mellitus (DM) and is also known as one of the major reasons of... (Review)
Review
With an increasing incidence, diabetic retinopathy is one of the most important complications of diabetes mellitus (DM) and is also known as one of the major reasons of adult acquired blindness. It is widely accepted that the visual impairment of diabetic patients results from retinal microvascular changes. However, recent clinical experimental and neuroimaging studies suggest that the visual impairment of diabetic patients is also related to the pathophysiological changes of different parts of the visual pathway in diabetic retinopathy. Therefore, the magnetic resonance imaging (MRI) techniques have been widely used for evaluating the microstructural changes, white matter integrity, metabolite changes, and the whole or partial functional and anatomic changes in the diabetic retinopathy patients' brains in order to fully understand the mechanism of vision loss of the diabetic retinopathy patients. This review focuses on the research progress in application of MRI of the visual pathway in diabetic retinopathy.
Topics: Animals; Blindness; Diabetic Retinopathy; Humans; Magnetic Resonance Imaging; Visual Pathways
PubMed: 30536057
DOI: 10.1007/s11596-018-1971-5 -
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