Visual Cortex: Area of the OCCIPITAL LOBE concerned with the processing of visual information relayed via VISUAL PATHWAYS.Visual Pathways: Set of cell bodies and nerve fibers conducting impulses from the eyes to the cerebral cortex. It includes the RETINA; OPTIC NERVE; optic tract; and geniculocalcarine tract.Evoked Potentials, Visual: The electric response evoked in the cerebral cortex by visual stimulation or stimulation of the visual pathways.Visual Perception: The selecting and organizing of visual stimuli based on the individual's past experience.Photic Stimulation: Investigative technique commonly used during ELECTROENCEPHALOGRAPHY in which a series of bright light flashes or visual patterns are used to elicit brain activity.Visual Fields: The total area or space visible in a person's peripheral vision with the eye looking straightforward.Cerebral Cortex: The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulchi. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions.Brain Mapping: Imaging techniques used to colocalize sites of brain functions or physiological activity with brain structures.Visual Acuity: Clarity or sharpness of OCULAR VISION or the ability of the eye to see fine details. Visual acuity depends on the functions of RETINA, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast.Cats: The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)Sensory Deprivation: The absence or restriction of the usual external sensory stimuli to which the individual responds.Dominance, Ocular: The functional superiority and preferential use of one eye over the other. The term is usually applied to superiority in sighting (VISUAL PERCEPTION) or motor task but not difference in VISUAL ACUITY or dysfunction of one of the eyes. Ocular dominance can be modified by visual input and NEUROTROPHIC FACTORS.Prefrontal Cortex: The rostral part of the frontal lobe, bounded by the inferior precentral fissure in humans, which receives projection fibers from the MEDIODORSAL NUCLEUS OF THE THALAMUS. The prefrontal cortex receives afferent fibers from numerous structures of the DIENCEPHALON; MESENCEPHALON; and LIMBIC SYSTEM as well as cortical afferents of visual, auditory, and somatic origin.Pattern Recognition, Visual: Mental process to visually perceive a critical number of facts (the pattern), such as characters, shapes, displays, or designs.Geniculate Bodies: Part of the DIENCEPHALON inferior to the caudal end of the dorsal THALAMUS. Includes the lateral geniculate body which relays visual impulses from the OPTIC TRACT to the calcarine cortex, and the medial geniculate body which relays auditory impulses from the lateral lemniscus to the AUDITORY CORTEX.Vision, Monocular: Images seen by one eye.Neurons: The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.Magnetic Resonance Imaging: Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.Orientation: Awareness of oneself in relation to time, place and person.Models, Neurological: Theoretical representations that simulate the behavior or activity of the neurological system, processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.Auditory Cortex: The region of the cerebral cortex that receives the auditory radiation from the MEDIAL GENICULATE BODY.Vision, Ocular: The process in which light signals are transformed by the PHOTORECEPTOR CELLS into electrical signals which can then be transmitted to the brain.Motor Cortex: Area of the FRONTAL LOBE concerned with primary motor control located in the dorsal PRECENTRAL GYRUS immediately anterior to the central sulcus. It is comprised of three areas: the primary motor cortex located on the anterior paracentral lobule on the medial surface of the brain; the premotor cortex located anterior to the primary motor cortex; and the supplementary motor area located on the midline surface of the hemisphere anterior to the primary motor cortex.Somatosensory Cortex: Area of the parietal lobe concerned with receiving sensations such as movement, pain, pressure, position, temperature, touch, and vibration. It lies posterior to the central sulcus.Neuronal Plasticity: The capacity of the NERVOUS SYSTEM to change its reactivity as the result of successive activations.Reaction Time: The time from the onset of a stimulus until a response is observed.Contrast Sensitivity: The ability to detect sharp boundaries (stimuli) and to detect slight changes in luminance at regions without distinct contours. Psychophysical measurements of this visual function are used to evaluate visual acuity and to detect eye disease.Macaca: A genus of the subfamily CERCOPITHECINAE, family CERCOPITHECIDAE, consisting of 16 species inhabiting forests of Africa, Asia, and the islands of Borneo, Philippines, and Celebes.Functional Laterality: Behavioral manifestations of cerebral dominance in which there is preferential use and superior functioning of either the left or the right side, as in the preferred use of the right hand or right foot.Space Perception: The awareness of the spatial properties of objects; includes physical space.Attention: Focusing on certain aspects of current experience to the exclusion of others. It is the act of heeding or taking notice or concentrating.Motion Perception: The real or apparent movement of objects through the visual field.Phosphenes: A subjective visual sensation with the eyes closed and in the absence of light. Phosphenes can be spontaneous, or induced by chemical, electrical, or mechanical (pressure) stimuli which cause the visual field to light up without optical inputs.Vision, Binocular: The blending of separate images seen by each eye into one composite image.Action Potentials: Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.Image Processing, Computer-Assisted: A technique of inputting two-dimensional images into a computer and then enhancing or analyzing the imagery into a form that is more useful to the human observer.Ferrets: Semidomesticated variety of European polecat much used for hunting RODENTS and/or RABBITS and as a laboratory animal. It is in the subfamily Mustelinae, family MUSTELIDAE.Psychomotor Performance: The coordination of a sensory or ideational (cognitive) process and a motor activity.Nerve Net: A meshlike structure composed of interconnecting nerve cells that are separated at the synaptic junction or joined to one another by cytoplasmic processes. In invertebrates, for example, the nerve net allows nerve impulses to spread over a wide area of the net because synapses can pass information in any direction.Neural Pathways: Neural tracts connecting one part of the nervous system with another.Psychophysics: The science dealing with the correlation of the physical characteristics of a stimulus, e.g., frequency or intensity, with the response to the stimulus, in order to assess the psychologic factors involved in the relationship.Macaca mulatta: A species of the genus MACACA inhabiting India, China, and other parts of Asia. The species is used extensively in biomedical research and adapts very well to living with humans.Macaca fascicularis: A species of the genus MACACA which typically lives near the coast in tidal creeks and mangrove swamps primarily on the islands of the Malay peninsula.Fixation, Ocular: The positioning and accommodation of eyes that allows the image to be brought into place on the FOVEA CENTRALIS of each eye.Ocular Physiological Phenomena: Processes and properties of the EYE as a whole or of any of its parts.Occipital Lobe: Posterior portion of the CEREBRAL HEMISPHERES responsible for processing visual sensory information. It is located posterior to the parieto-occipital sulcus and extends to the preoccipital notch.Neural Inhibition: The function of opposing or restraining the excitation of neurons or their target excitable cells.Form Perception: The sensory discrimination of a pattern shape or outline.Blindness: The inability to see or the loss or absence of perception of visual stimuli. This condition may be the result of EYE DISEASES; OPTIC NERVE DISEASES; OPTIC CHIASM diseases; or BRAIN DISEASES affecting the VISUAL PATHWAYS or OCCIPITAL LOBE.Retina: The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.Parietal Lobe: Upper central part of the cerebral hemisphere. It is located posterior to central sulcus, anterior to the OCCIPITAL LOBE, and superior to the TEMPORAL LOBES.Darkness: The absence of light.Eye Movements: Voluntary or reflex-controlled movements of the eye.Discrimination (Psychology): Differential response to different stimuli.Dominance, Cerebral: Dominance of one cerebral hemisphere over the other in cerebral functions.Visual Field Tests: Method of measuring and mapping the scope of vision, from central to peripheral of each eye.Rats, Long-Evans: An outbred strain of rats developed in 1915 by crossing several Wistar Institute white females with a wild gray male. Inbred strains have been derived from this original outbred strain, including Long-Evans cinnamon rats (RATS, INBRED LEC) and Otsuka-Long-Evans-Tokushima Fatty rats (RATS, INBRED OLETF), which are models for Wilson's disease and non-insulin dependent diabetes mellitus, respectively.Temporal Lobe: Lower lateral part of the cerebral hemisphere responsible for auditory, olfactory, and semantic processing. It is located inferior to the lateral fissure and anterior to the OCCIPITAL LOBE.Vision Disorders: Visual impairments limiting one or more of the basic functions of the eye: visual acuity, dark adaptation, color vision, or peripheral vision. These may result from EYE DISEASES; OPTIC NERVE DISEASES; VISUAL PATHWAY diseases; OCCIPITAL LOBE diseases; OCULAR MOTILITY DISORDERS; and other conditions (From Newell, Ophthalmology: Principles and Concepts, 7th ed, p132).Cues: Signals for an action; that specific portion of a perceptual field or pattern of stimuli to which a subject has learned to respond.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Electroencephalography: Recording of electric currents developed in the brain by means of electrodes applied to the scalp, to the surface of the brain, or placed within the substance of the brain.Synapses: Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.Entorhinal Cortex: Cerebral cortex region on the medial aspect of the PARAHIPPOCAMPAL GYRUS, immediately caudal to the OLFACTORY CORTEX of the uncus. The entorhinal cortex is the origin of the major neural fiber system afferent to the HIPPOCAMPAL FORMATION, the so-called PERFORANT PATHWAY.Pulvinar: Large mass of nuclei forming the most caudal portion of the THALAMUS and overhanging the GENICULATE BODIES and the dorsolateral surface of the MIDBRAIN. It is divided into four parts: the lateral, medial, inferior, and oral pulvinar nuclei.Electrophysiology: The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.Sensory Thresholds: The minimum amount of stimulus energy necessary to elicit a sensory response.Depth Perception: Perception of three-dimensionality.Electric Stimulation: Use of electric potential or currents to elicit biological responses.Galago: A genus of the family Lorisidae having four species which inhabit the forests and bush regions of Africa south of the Sahara and some nearby islands. The four species are G. alleni, G. crassicaudatus, G. demidovii, and G. senegalensis. There is another genus, Euoticus, containing two species which some authors have included in the Galago genus.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Superior Colliculi: The anterior pair of the quadrigeminal bodies which coordinate the general behavioral orienting responses to visual stimuli, such as whole-body turning, and reaching.Acoustic Stimulation: Use of sound to elicit a response in the nervous system.Frontal Lobe: The part of the cerebral hemisphere anterior to the central sulcus, and anterior and superior to the lateral sulcus.Illusions: The misinterpretation of a real external, sensory experience.Microelectrodes: Electrodes with an extremely small tip, used in a voltage clamp or other apparatus to stimulate or record bioelectric potentials of single cells intracellularly or extracellularly. (Dorland, 28th ed)Kidney Cortex: The outer zone of the KIDNEY, beneath the capsule, consisting of KIDNEY GLOMERULUS; KIDNEY TUBULES, DISTAL; and KIDNEY TUBULES, PROXIMAL.Transcranial Magnetic Stimulation: A technique that involves the use of electrical coils on the head to generate a brief magnetic field which reaches the CEREBRAL CORTEX. It is coupled with ELECTROMYOGRAPHY response detection to assess cortical excitability by the threshold required to induce MOTOR EVOKED POTENTIALS. This method is also used for BRAIN MAPPING, to study NEUROPHYSIOLOGY, and as a substitute for ELECTROCONVULSIVE THERAPY for treating DEPRESSION. Induction of SEIZURES limits its clinical usage.Eye Enucleation: The surgical removal of the eyeball leaving the eye muscles and remaining orbital contents intact.Amblyopia: A nonspecific term referring to impaired vision. Major subcategories include stimulus deprivation-induced amblyopia and toxic amblyopia. Stimulus deprivation-induced amblyopia is a developmental disorder of the visual cortex. A discrepancy between visual information received by the visual cortex from each eye results in abnormal cortical development. STRABISMUS and REFRACTIVE ERRORS may cause this condition. Toxic amblyopia is a disorder of the OPTIC NERVE which is associated with ALCOHOLISM, tobacco SMOKING, and other toxins and as an adverse effect of the use of some medications.Parvalbumins: Low molecular weight, calcium binding muscle proteins. Their physiological function is possibly related to the contractile process.Oxygen: An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.Vision Disparity: The difference between two images on the retina when looking at a visual stimulus. This occurs since the two retinas do not have the same view of the stimulus because of the location of our eyes. Thus the left eye does not get exactly the same view as the right eye.Scotoma: A localized defect in the visual field bordered by an area of normal vision. This occurs with a variety of EYE DISEASES (e.g., RETINAL DISEASES and GLAUCOMA); OPTIC NERVE DISEASES, and other conditions.Magnetoencephalography: The measurement of magnetic fields over the head generated by electric currents in the brain. As in any electrical conductor, electric fields in the brain are accompanied by orthogonal magnetic fields. The measurement of these fields provides information about the localization of brain activity which is complementary to that provided by ELECTROENCEPHALOGRAPHY. Magnetoencephalography may be used alone or together with electroencephalography, for measurement of spontaneous or evoked activity, and for research or clinical purposes.Pyramidal Cells: Projection neurons in the CEREBRAL CORTEX and the HIPPOCAMPUS. Pyramidal cells have a pyramid-shaped soma with the apex and an apical dendrite pointed toward the pial surface and other dendrites and an axon emerging from the base. The axons may have local collaterals but also project outside their cortical region.Evoked Potentials: Electrical responses recorded from nerve, muscle, SENSORY RECEPTOR, or area of the CENTRAL NERVOUS SYSTEM following stimulation. They range from less than a microvolt to several microvolts. The evoked potential can be auditory (EVOKED POTENTIALS, AUDITORY), somatosensory (EVOKED POTENTIALS, SOMATOSENSORY), visual (EVOKED POTENTIALS, VISUAL), or motor (EVOKED POTENTIALS, MOTOR), or other modalities that have been reported.Hemianopsia: Partial or complete loss of vision in one half of the visual field(s) of one or both eyes. Subtypes include altitudinal hemianopsia, characterized by a visual defect above or below the horizontal meridian of the visual field. Homonymous hemianopsia refers to a visual defect that affects both eyes equally, and occurs either to the left or right of the midline of the visual field. Binasal hemianopsia consists of loss of vision in the nasal hemifields of both eyes. Bitemporal hemianopsia is the bilateral loss of vision in the temporal fields. Quadrantanopsia refers to loss of vision in one quarter of the visual field in one or both eyes.Optical Illusions: An illusion of vision usually affecting spatial relations.Auditory Perception: The process whereby auditory stimuli are selected, organized, and interpreted by the organism.Cerebellar Cortex: The superficial GRAY MATTER of the CEREBELLUM. It consists of two main layers, the stratum moleculare and the stratum granulosum.Saccades: An abrupt voluntary shift in ocular fixation from one point to another, as occurs in reading.Nonlinear Dynamics: The study of systems which respond disproportionately (nonlinearly) to initial conditions or perturbing stimuli. Nonlinear systems may exhibit "chaos" which is classically characterized as sensitive dependence on initial conditions. Chaotic systems, while distinguished from more ordered periodic systems, are not random. When their behavior over time is appropriately displayed (in "phase space"), constraints are evident which are described by "strange attractors". Phase space representations of chaotic systems, or strange attractors, usually reveal fractal (FRACTALS) self-similarity across time scales. Natural, including biological, systems often display nonlinear dynamics and chaos.Animals, Newborn: Refers to animals in the period of time just after birth.Electrodes, Implanted: Surgically placed electric conductors through which ELECTRIC STIMULATION is delivered to or electrical activity is recorded from a specific point inside the body.Adaptation, Physiological: The non-genetic biological changes of an organism in response to challenges in its ENVIRONMENT.Color Perception: Mental processing of chromatic signals (COLOR VISION) from the eye by the VISUAL CORTEX where they are converted into symbolic representations. Color perception involves numerous neurons, and is influenced not only by the distribution of wavelengths from the viewed object, but also by its background color and brightness contrast at its boundary.Thalamus: Paired bodies containing mostly GRAY MATTER and forming part of the lateral wall of the THIRD VENTRICLE of the brain.Synaptic Transmission: The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.Face: The anterior portion of the head that includes the skin, muscles, and structures of the forehead, eyes, nose, mouth, cheeks, and jaw.Tupaiidae: The only family of the order SCANDENTIA, variously included in the order Insectivora or in the order Primates, and often in the order Microscelidea, consisting of five genera. They are TUPAIA, Ananthana (Indian tree shrew), Dendrogale (small smooth-tailed tree shrew), Urogale (Mindanao tree shrew), and Ptilocercus (pen-tailed tree shrew). The tree shrews inhabit the forest areas of eastern Asia from India and southwestern China to Borneo and the Philippines.Strabismus: Misalignment of the visual axes of the eyes. In comitant strabismus the degree of ocular misalignment does not vary with the direction of gaze. In noncomitant strabismus the degree of misalignment varies depending on direction of gaze or which eye is fixating on the target. (Miller, Walsh & Hoyt's Clinical Neuro-Ophthalmology, 4th ed, p641)Haplorhini: A suborder of PRIMATES consisting of six families: CEBIDAE (some New World monkeys), ATELIDAE (some New World monkeys), CERCOPITHECIDAE (Old World monkeys), HYLOBATIDAE (gibbons and siamangs), CALLITRICHINAE (marmosets and tamarins), and HOMINIDAE (humans and great apes).Cortical Synchronization: EEG phase synchronization of the cortical brain region (CEREBRAL CORTEX).gamma-Aminobutyric Acid: The most common inhibitory neurotransmitter in the central nervous system.Touch: Sensation of making physical contact with objects, animate or inanimate. Tactile stimuli are detected by MECHANORECEPTORS in the skin and mucous membranes.Aging: The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.Discrimination Learning: Learning that is manifested in the ability to respond differentially to various stimuli.Memory: Complex mental function having four distinct phases: (1) memorizing or learning, (2) retention, (3) recall, and (4) recognition. Clinically, it is usually subdivided into immediate, recent, and remote memory.Dendrites: Extensions of the nerve cell body. They are short and branched and receive stimuli from other NEURONS.Voltage-Sensitive Dye Imaging: Optical imaging techniques used for recording patterns of electrical activity in tissues by monitoring transmembrane potentials via FLUORESCENCE imaging with voltage-sensitive fluorescent dyes.Learning: Relatively permanent change in behavior that is the result of past experience or practice. The concept includes the acquisition of knowledge.Excitatory Postsynaptic Potentials: Depolarization of membrane potentials at the SYNAPTIC MEMBRANES of target neurons during neurotransmission. Excitatory postsynaptic potentials can singly or in summation reach the trigger threshold for ACTION POTENTIALS.Blindness, Cortical: Total loss of vision in all or part of the visual field due to bilateral OCCIPITAL LOBE (i.e., VISUAL CORTEX) damage or dysfunction. Anton syndrome is characterized by the psychic denial of true, organic cortical blindness. (Adams et al., Principles of Neurology, 6th ed, p460)Adrenal Cortex: The outer layer of the adrenal gland. It is derived from MESODERM and comprised of three zones (outer ZONA GLOMERULOSA, middle ZONA FASCICULATA, and inner ZONA RETICULARIS) with each producing various steroids preferentially, such as ALDOSTERONE; HYDROCORTISONE; DEHYDROEPIANDROSTERONE; and ANDROSTENEDIONE. Adrenal cortex function is regulated by pituitary ADRENOCORTICOTROPIN.Fovea Centralis: An area approximately 1.5 millimeters in diameter within the macula lutea where the retina thins out greatly because of the oblique shifting of all layers except the pigment epithelium layer. It includes the sloping walls of the fovea (clivus) and contains a few rods in its periphery. In its center (foveola) are the cones most adapted to yield high visual acuity, each cone being connected to only one ganglion cell. (Cline et al., Dictionary of Visual Science, 4th ed)Brain Waves: Wave-like oscillations of electric potential between parts of the brain recorded by EEG.Calbindin 2: A calbindin protein that is differentially expressed in distinct populations of NEURONS throughout the vertebrate and invertebrate NERVOUS SYSTEM, and modulates intrinsic neuronal excitability and influences LONG-TERM POTENTIATION. It is also found in LUNG, TESTIS, OVARY, KIDNEY, and BREAST, and is expressed in many tumor types found in these tissues. It is often used as an immunohistochemical marker for MESOTHELIOMA.Adaptation, Ocular: The adjustment of the eye to variations in the intensity of light. Light adaptation is the adjustment of the eye when the light threshold is increased; DARK ADAPTATION when the light is greatly reduced. (From Cline et al., Dictionary of Visual Science, 4th ed)Gyrus Cinguli: One of the convolutions on the medial surface of the CEREBRAL HEMISPHERES. It surrounds the rostral part of the brain and CORPUS CALLOSUM and forms part of the LIMBIC SYSTEM.Recognition (Psychology): The knowledge or perception that someone or something present has been previously encountered.Feedback: A mechanism of communication within a system in that the input signal generates an output response which returns to influence the continued activity or productivity of that system.Memory, Short-Term: Remembrance of information for a few seconds to hours.Callithrix: A genus of the subfamily CALLITRICHINAE occurring in forests of Brazil and Bolivia and containing seventeen species.Perceptual Masking: The interference of one perceptual stimulus with another causing a decrease or lessening in perceptual effectiveness.Signal Processing, Computer-Assisted: Computer-assisted processing of electric, ultrasonic, or electronic signals to interpret function and activity.Size Perception: The sensory interpretation of the dimensions of objects.Perceptual Disorders: Cognitive disorders characterized by an impaired ability to perceive the nature of objects or concepts through use of the sense organs. These include spatial neglect syndromes, where an individual does not attend to visual, auditory, or sensory stimuli presented from one side of the body.Axons: Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.Neuropsychological Tests: Tests designed to assess neurological function associated with certain behaviors. They are used in diagnosing brain dysfunction or damage and central nervous system disorders or injury.Interneurons: Most generally any NEURONS which are not motor or sensory. Interneurons may also refer to neurons whose AXONS remain within a particular brain region in contrast to projection neurons, which have axons projecting to other brain regions.Wakefulness: A state in which there is an enhanced potential for sensitivity and an efficient responsiveness to external stimuli.Lighting: The illumination of an environment and the arrangement of lights to achieve an effect or optimal visibility. Its application is in domestic or in public settings and in medical and non-medical environments.Color Vision: Function of the human eye that is used in bright illumination or in daylight (at photopic intensities). Photopic vision is performed by the three types of RETINAL CONE PHOTORECEPTORS with varied peak absorption wavelengths in the color spectrum (from violet to red, 400 - 700 nm).Color: The visually perceived property of objects created by absorption or reflection of specific wavelengths of light.Light: That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.Cerebrovascular Circulation: The circulation of blood through the BLOOD VESSELS of the BRAIN.Long-Term Synaptic Depression: A persistent activity-dependent decrease in synaptic efficacy between NEURONS. It typically occurs following repeated low-frequency afferent stimulation, but it can be induced by other methods. Long-term depression appears to play a role in MEMORY.Vibrissae: Stiff hairs projecting from the face around the nose of most mammals, acting as touch receptors.Vision Tests: A series of tests used to assess various functions of the eyes.Optic Chiasm: The X-shaped structure formed by the meeting of the two optic nerves. At the optic chiasm the fibers from the medial part of each retina cross to project to the other side of the brain while the lateral retinal fibers continue on the same side. As a result each half of the brain receives information about the contralateral visual field from both eyes.Awareness: The act of "taking account" of an object or state of affairs. It does not imply assessment of, nor attention to the qualities or nature of the object.Signal Detection, Psychological: Psychophysical technique that permits the estimation of the bias of the observer as well as detectability of the signal (i.e., stimulus) in any sensory modality. (From APA, Thesaurus of Psychological Index Terms, 8th ed.)Receptors, N-Methyl-D-Aspartate: A class of ionotropic glutamate receptors characterized by affinity for N-methyl-D-aspartate. NMDA receptors have an allosteric binding site for glycine which must be occupied for the channel to open efficiently and a site within the channel itself to which magnesium ions bind in a voltage-dependent manner. The positive voltage dependence of channel conductance and the high permeability of the conducting channel to calcium ions (as well as to monovalent cations) are important in excitotoxicity and neuronal plasticity.Physical Stimulation: Act of eliciting a response from a person or organism through physical contact.Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate: The lectin wheatgerm agglutinin conjugated to the enzyme HORSERADISH PEROXIDASE. It is widely used for tracing neural pathways.Movement: The act, process, or result of passing from one place or position to another. It differs from LOCOMOTION in that locomotion is restricted to the passing of the whole body from one place to another, while movement encompasses both locomotion but also a change of the position of the whole body or any of its parts. Movement may be used with reference to humans, vertebrate and invertebrate animals, and microorganisms. Differentiate also from MOTOR ACTIVITY, movement associated with behavior.Mice, Inbred C57BLTask Performance and Analysis: The detailed examination of observable activity or behavior associated with the execution or completion of a required function or unit of work.Sensory Aids: Devices that help people with impaired sensory responses.Electrophysiological Phenomena: The electrical properties, characteristics of living organisms, and the processes of organisms or their parts that are involved in generating and responding to electrical charges.Saimiri: A genus of the family CEBIDAE consisting of four species: S. boliviensis, S. orstedii (red-backed squirrel monkey), S. sciureus (common squirrel monkey), and S. ustus. They inhabit tropical rain forests in Central and South America. S. sciureus is used extensively in research studies.Thalamic Nuclei: Several groups of nuclei in the thalamus that serve as the major relay centers for sensory impulses in the brain.Neurophysiology: The scientific discipline concerned with the physiology of the nervous system.Parahippocampal Gyrus: A convolution on the inferior surface of each cerebral hemisphere, lying between the hippocampal and collateral sulci.Glutamate Decarboxylase: A pyridoxal-phosphate protein that catalyzes the alpha-decarboxylation of L-glutamic acid to form gamma-aminobutyric acid and carbon dioxide. The enzyme is found in bacteria and in invertebrate and vertebrate nervous systems. It is the rate-limiting enzyme in determining GAMMA-AMINOBUTYRIC ACID levels in normal nervous tissues. The brain enzyme also acts on L-cysteate, L-cysteine sulfinate, and L-aspartate. EC Decortication: Partial or total removal, ablation, or destruction of the cerebral cortex; may be chemical. It is not used with animals that do not possess a cortex, i.e., it is used only with mammals.Cognition: Intellectual or mental process whereby an organism obtains knowledge.Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.Afferent Pathways: Nerve structures through which impulses are conducted from a peripheral part toward a nerve center.Axonal Transport: The directed transport of ORGANELLES and molecules along nerve cell AXONS. Transport can be anterograde (from the cell body) or retrograde (toward the cell body). (Alberts et al., Molecular Biology of the Cell, 3d ed, pG3)Dark Adaptation: Adjustment of the eyes under conditions of low light. The sensitivity of the eye to light is increased during dark adaptation.S100 Calcium Binding Protein G: A calbindin protein found in many mammalian tissues, including the UTERUS, PLACENTA, BONE, PITUITARY GLAND, and KIDNEYS. In intestinal ENTEROCYTES it mediates intracellular calcium transport from apical to basolateral membranes via calcium binding at two EF-HAND MOTIFS. Expression is regulated in some tissues by VITAMIN D.Algorithms: A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.Patch-Clamp Techniques: An electrophysiologic technique for studying cells, cell membranes, and occasionally isolated organelles. All patch-clamp methods rely on a very high-resistance seal between a micropipette and a membrane; the seal is usually attained by gentle suction. The four most common variants include on-cell patch, inside-out patch, outside-out patch, and whole-cell clamp. Patch-clamp methods are commonly used to voltage clamp, that is control the voltage across the membrane and measure current flow, but current-clamp methods, in which the current is controlled and the voltage is measured, are also used.Macaca radiata: A species of macaque monkey that mainly inhabits the forest of southern India. They are also called bonnet macaques or bonnet monkeys.Autoradiography: The making of a radiograph of an object or tissue by recording on a photographic plate the radiation emitted by radioactive material within the object. (Dorland, 27th ed)Consciousness: Sense of awareness of self and of the environment.Retinal Ganglion Cells: Neurons of the innermost layer of the retina, the internal plexiform layer. They are of variable sizes and shapes, and their axons project via the OPTIC NERVE to the brain. A small subset of these cells act as photoreceptors with projections to the SUPRACHIASMATIC NUCLEUS, the center for regulating CIRCADIAN RHYTHM.Corpus Callosum: Broad plate of dense myelinated fibers that reciprocally interconnect regions of the cortex in all lobes with corresponding regions of the opposite hemisphere. The corpus callosum is located deep in the longitudinal fissure.ReadingLong-Term Potentiation: A persistent increase in synaptic efficacy, usually induced by appropriate activation of the same synapses. The phenomenological properties of long-term potentiation suggest that it may be a cellular mechanism of learning and memory.PrimatesNeocortex: The largest portion of the CEREBRAL CORTEX in which the NEURONS are arranged in six layers in the mammalian brain: molecular, external granular, external pyramidal, internal granular, internal pyramidal and multiform layers.Imagination: A new pattern of perceptual or ideational material derived from past experience.Feedback, Sensory: A mechanism of communicating one's own sensory system information about a task, movement or skill.Electron Transport Complex IV: A multisubunit enzyme complex containing CYTOCHROME A GROUP; CYTOCHROME A3; two copper atoms; and 13 different protein subunits. It is the terminal oxidase complex of the RESPIRATORY CHAIN and collects electrons that are transferred from the reduced CYTOCHROME C GROUP and donates them to molecular OXYGEN, which is then reduced to water. The redox reaction is simultaneously coupled to the transport of PROTONS across the inner mitochondrial membrane.Computer Simulation: Computer-based representation of physical systems and phenomena such as chemical processes.Neurons, Afferent: Neurons which conduct NERVE IMPULSES to the CENTRAL NERVOUS SYSTEM.Calbindins: Calcium-binding proteins that are found in DISTAL KIDNEY TUBULES, INTESTINES, BRAIN, and other tissues where they bind, buffer and transport cytoplasmic calcium. Calbindins possess a variable number of EF-HAND MOTIFS which contain calcium-binding sites. Some isoforms are regulated by VITAMIN D.Optic Nerve: The 2nd cranial nerve which conveys visual information from the RETINA to the brain. The nerve carries the axons of the RETINAL GANGLION CELLS which sort at the OPTIC CHIASM and continue via the OPTIC TRACTS to the brain. The largest projection is to the lateral geniculate nuclei; other targets include the SUPERIOR COLLICULI and the SUPRACHIASMATIC NUCLEI. Though known as the second cranial nerve, it is considered part of the CENTRAL NERVOUS SYSTEM.Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Motion: Physical motion, i.e., a change in position of a body or subject as a result of an external force. It is distinguished from MOVEMENT, a process resulting from biological activity.Flicker Fusion: The point or frequency at which all flicker of an intermittent light stimulus disappears.Data Interpretation, Statistical: Application of statistical procedures to analyze specific observed or assumed facts from a particular study.Muscimol: A neurotoxic isoxazole isolated from species of AMANITA. It is obtained by decarboxylation of IBOTENIC ACID. Muscimol is a potent agonist of GABA-A RECEPTORS and is used mainly as an experimental tool in animal and tissue studies.Macaca nemestrina: A species of the genus MACACA which inhabits Malaya, Sumatra, and Borneo. It is one of the most arboreal species of Macaca. The tail is short and untwisted.Normal Distribution: Continuous frequency distribution of infinite range. Its properties are as follows: 1, continuous, symmetrical distribution with both tails extending to infinity; 2, arithmetic mean, mode, and median identical; and 3, shape completely determined by the mean and standard deviation.Electrooculography: Recording of the average amplitude of the resting potential arising between the cornea and the retina in light and dark adaptation as the eyes turn a standard distance to the right and the left. The increase in potential with light adaptation is used to evaluate the condition of the retinal pigment epithelium.Field Dependence-Independence: The ability to respond to segments of the perceptual experience rather than to the whole.Touch Perception: The process by which the nature and meaning of tactile stimuli are recognized and interpreted by the brain, such as realizing the characteristics or name of an object being touched.Alpha Rhythm: Brain waves characterized by a relatively high voltage or amplitude and a frequency of 8-13 Hz. They constitute the majority of waves recorded by EEG registering the activity of the parietal and occipital lobes when the individual is awake, but relaxed with the eyes closed.Time Perception: The ability to estimate periods of time lapsed or duration of time.Emotions: Those affective states which can be experienced and have arousing and motivational properties.Behavior: The observable response of a man or animal to a situation.Agnosia: Loss of the ability to comprehend the meaning or recognize the importance of various forms of stimulation that cannot be attributed to impairment of a primary sensory modality. Tactile agnosia is characterized by an inability to perceive the shape and nature of an object by touch alone, despite unimpaired sensation to light touch, position, and other primary sensory modalities.Albinism: General term for a number of inherited defects of amino acid metabolism in which there is a deficiency or absence of pigment in the eyes, skin, or hair.Eye: The organ of sight constituting a pair of globular organs made up of a three-layered roughly spherical structure specialized for receiving and responding to light.Iontophoresis: Therapeutic introduction of ions of soluble salts into tissues by means of electric current. In medical literature it is commonly used to indicate the process of increasing the penetration of drugs into surface tissues by the application of electric current. It has nothing to do with ION EXCHANGE; AIR IONIZATION nor PHONOPHORESIS, none of which requires current.Visual Prosthesis: Artificial device such as an externally-worn camera attached to a stimulator on the RETINA, OPTIC NERVE, or VISUAL CORTEX, intended to restore or amplify vision.

Vision: modular analysis--or not? (1/5702)

It has commonly been assumed that the many separate areas of the visual system perform modular analyses, each restricted to a single attribute of the image. A recent paper advocates a radically different approach, where all areas in the hierarchy analyse all attributes of the image to extract perceptually relevant decisions.  (+info)

On the neural correlates of visual perception. (2/5702)

Neurological findings suggest that the human striate cortex (V1) is an indispensable component of a neural substratum subserving static achromatic form perception in its own right and not simply as a central distributor of retinally derived information to extrastriate visual areas. This view is further supported by physiological evidence in primates that the finest-grained conjoined representation of spatial detail and retinotopic localization that underlies phenomenal visual experience for local brightness discriminations is selectively represented at cortical levels by the activity of certain neurons in V1. However, at first glance, support for these ideas would appear to be undermined by incontrovertible neurological evidence (visual hemineglect and the simultanagnosias) and recent psychophysical results on 'crowding' that confirm that activation of neurons in V1 may, at times, be insufficient to generate a percept. Moreover, a recent proposal suggests that neural correlates of visual awareness must project directly to those in executive space, thus automatically excluding V1 from a related perceptual space because V1 lacks such direct projections. Both sets of concerns are, however, resolved within the context of adaptive resonance theories. Recursive loops, linking the dorsal lateral geniculate nucleus (LGN) through successive cortical visual areas to the temporal lobe by means of a series of ascending and descending pathways, provide a neuronal substratum at each level within a modular framework for mutually consistent descriptions of sensory data. At steady state, such networks obviate the necessity that neural correlates of visual experience project directly to those in executive space because a neural phenomenal perceptual space subserving form vision is continuously updated by information from an object recognition space equivalent to that destined to reach executive space. Within this framework, activity in V1 may engender percepts that accompany figure-ground segregations only when dynamic incongruities are resolved both within and between ascending and descending streams. Synchronous neuronal activity on a short timescale within and across cortical areas, proposed and sometimes observed as perceptual correlates, may also serve as a marker that a steady state has been achieved, which, in turn, may be a requirement for the longer time constants that accompany the emergence and stability of perceptual states compared to the faster dynamics of adapting networks and the still faster dynamics of individual action potentials. Finally, the same consensus of neuronal activity across ascending and descending pathways linking multiple cortical areas that in anatomic sequence subserve phenomenal visual experiences and object recognition may underlie the normal unity of conscious experience.  (+info)

Transient and permanent deficits in motion perception after lesions of cortical areas MT and MST in the macaque monkey. (3/5702)

We examined the nature and the selectivity of the motion deficits produced by lesions of extrastriate areas MT and MST. Lesions were made by injecting ibotenic acid into the representation of the left visual field in two macaque monkeys. The monkeys discriminated two stimuli that differed either in stimulus direction or orientation. Direction and orientation discrimination were assessed by measuring thresholds with gratings and random-dots placed in the intact or lesioned visual fields. At the start of behavioral testing, we found pronounced, motion-specific deficits in thresholds for all types of moving stimuli, including pronounced elevations in contrast thresholds and in signal-to-noise thresholds measured with moving gratings, as well as deficits in direction range thresholds and motion coherence measured with random-dot stimuli. In addition, the accuracy of direction discrimination was reduced at smaller spatial displacements (i.e. step sizes), suggesting an increase in spatial scale of the residual directional mechanism. Subsequent improvements in thresholds were seen with all motion stimuli, as behavioral training progressed, and these improvements occurred only with extensive behavioral testing in the lesioned visual field. These improvements were particularly pronounced for stimuli not masked by noise. On the other hand, deficits in the ability to extract motion from noisy stimuli and in the accuracy of direction discrimination persisted despite extensive behavioral training. These results demonstrate the importance of areas MT and MST for the perception of motion direction, particularly in the presence of noise. In addition, they provide evidence for the importance of behavioral training for functional recovery after cortical lesions. The data also strongly support the idea of functional specialization of areas MT and MST for motion processing.  (+info)

Modulation of long-term synaptic depression in visual cortex by acetylcholine and norepinephrine. (4/5702)

In a slice preparation of rat visual cortex, we discovered that paired-pulse stimulation (PPS) elicits a form of homosynaptic long-term depression (LTD) in the superficial layers when carbachol (CCh) or norepinephrine (NE) is applied concurrently. PPS by itself, or CCh and NE in the absence of synaptic stimulation, produced no lasting change. The LTD induced by PPS in the presence of NE or CCh is of comparable magnitude with that obtained with prolonged low-frequency stimulation (LFS) but requires far fewer stimulation pulses (40 vs 900). The cholinergic facilitation of LTD was blocked by atropine and pirenzepine, suggesting involvement of M1 receptors. The noradrenergic facilitation of LTD was blocked by urapidil and was mimicked by methoxamine, suggesting involvement of alpha1 receptors. beta receptor agonists and antagonists were without effect. Induction of LTD by PPS was inhibited by NMDA receptor blockers (completely in the case of NE; partially in the case of CCh), suggesting that one action of the modulators is to control the gain of NMDA receptor-dependent homosynaptic LTD in visual cortex. We propose that this is a mechanism by which cholinergic and noradrenergic inputs to the neocortex modulate naturally occurring receptive field plasticity.  (+info)

Competitive mechanisms subserve attention in macaque areas V2 and V4. (5/5702)

It is well established that attention modulates visual processing in extrastriate cortex. However, the underlying neural mechanisms are unknown. A consistent observation is that attention has its greatest impact on neuronal responses when multiple stimuli appear together within a cell's receptive field. One way to explain this is to assume that multiple stimuli activate competing populations of neurons and that attention biases this competition in favor of the attended stimulus. In the absence of competing stimuli, there is no competition to be resolved. Accordingly, attention has a more limited effect on the neuronal response to a single stimulus. To test this interpretation, we measured the responses of neurons in macaque areas V2 and V4 using a behavioral paradigm that allowed us to isolate automatic sensory processing mechanisms from attentional effects. First, we measured each cell's response to a single stimulus presented alone inside the receptive field or paired with a second receptive field stimulus, while the monkey attended to a location outside the receptive field. Adding the second stimulus typically caused the neuron's response to move toward the response that was elicited by the second stimulus alone. Then, we directed the monkey's attention to one element of the pair. This drove the neuron's response toward the response elicited when the attended stimulus appeared alone. These findings are consistent with the idea that attention biases competitive interactions among neurons, causing them to respond primarily to the attended stimulus. A quantitative neural model of attention is proposed to account for these results.  (+info)

CRE-mediated gene transcription in neocortical neuronal plasticity during the developmental critical period. (6/5702)

Neuronal activity-dependent processes are believed to mediate the formation of synaptic connections during neocortical development, but the underlying intracellular mechanisms are not known. In the visual system, altering the pattern of visually driven neuronal activity by monocular deprivation induces cortical synaptic rearrangement during a postnatal developmental window, the critical period. Here, using transgenic mice carrying a CRE-lacZ reporter, we demonstrate that a calcium- and cAMP-regulated signaling pathway is activated following monocular deprivation. We find that monocular deprivation leads to an induction of CRE-mediated lacZ expression in the visual cortex preceding the onset of physiologic plasticity, and this induction is dramatically downregulated following the end of the critical period. These results suggest that CRE-dependent coordinate regulation of a network of genes may control physiologic plasticity during postnatal neocortical development.  (+info)

MST neuronal responses to heading direction during pursuit eye movements. (7/5702)

As you move through the environment, you see a radial pattern of visual motion with a focus of expansion (FOE) that indicates your heading direction. When self-movement is combined with smooth pursuit eye movements, the turning of the eye distorts the retinal image of the FOE but somehow you still can perceive heading. We studied neurons in the medial superior temporal area (MST) of monkey visual cortex, recording responses to FOE stimuli presented during fixation and smooth pursuit eye movements. Almost all neurons showed significant changes in their FOE selective responses during pursuit eye movements. However, the vector average of all the neuronal responses indicated the direction of the FOE during both fixation and pursuit. Furthermore, the amplitude of the net vector increased with increasing FOE eccentricity. We conclude that neuronal population encoding in MST might contribute to pursuit-tolerant heading perception.  (+info)

Retinotopic mapping of lateral geniculate nucleus in humans using functional magnetic resonance imaging. (8/5702)

Subcortical nuclei in the thalamus, which play an important role in many functions of the human brain, provide challenging targets for functional mapping with neuroimaging techniques because of their small sizes and deep locations. In this study, we explore the capability of high-resolution functional magnetic resonance imaging at 4 Tesla for mapping the retinotopic organization in the lateral geniculate nucleus (LGN). Our results show that the hemifield visual stimulation only activates LGN in the contralateral hemisphere, and the lower-field and upper-field visual stimulations activate the superior and inferior portion of LGN, respectively. These results reveal a similar retinotopic organization between the human and nonhuman primate LGN and between LGN and the primary visual cortex. We conclude that high-resolution functional magnetic resonance imaging is capable of functional mapping of suborganizations in small nuclei together with cortical activation. This will have an impact for studying the thalamocortical networks in the human brain.  (+info)

  • Little is known, however, about how neural representations of objects, typically defined by visual features, are influenced by spatiotemporal continuity. (
  • These results indicate that spatiotemporal continuity modulates neural representations of object identity, influencing judgments of object persistence even in the most staunchly "featural" areas of ventral visual cortex. (
  • Moreover, visual similarity produces "repetition attenuation" in neural responses: a weaker neural response is typically observed to a repeated stimulus compared with a novel stimulus ( 11 - 14 ). (
  • Thus, in the present study, we test whether neural structures become dedifferentiated with age, by examining the degree of category-specificity that is present in ventral visual cortex in young and old adults. (
  • It has also recently been demonstrated that a variety of other object categories elicit distinct neural signatures in ventral visual cortex ( 22 ). (
  • Visual experience (light) can activate ERK and its downstream neural targets, MSK and CREB. (
  • Aging often results in reduced visual acuity from changes in both the eye and neural circuits [1- (
  • An international collaboration of neuroscientists have today published a paper in Nature demonstrating the breadth of neural communication in visual cortex using a combination of methods for tracing the projections of individual neurons across the brain. (
  • A neural circuit for spatial summation in visual cortex. (
  • In this project, we develop and simulate a spiking neural network model of multiple interacting areas of macaque visual cortex, connected in a layer-specific fashion. (
  • A deeper understanding of how neural circuits develop and work together to process and transmit information is crucial for addressing numerous visual, neurological, and psychiatric disorders resulting from the dysfunction of these circuits in the brain. (
  • In visual cortex, neural responses to a sustained stimulus adapt over the course of a few seconds. (
  • Mammalian visual perception is enabled not only by neural processing but also by precise eye movements, which allow for efficient scanning of the environment. (
  • We propose that these contextual influences serve pre-attentive visual segmentation by causing relatively higher neural responses to important or conspicuous image locations, making them more salient for perceptual pop-out. (
  • The neural basis of visual perception can be understood only when the sequence of cortical activity underlying successful recognition is known. (
  • Advanced recording techniques to monitor neural activity in the awake-behaving cat (project 4) while cortex was both active and deactivated were developed for this thesis to compliment thesis projects 1-3 involving classical recording techniques in animals passively viewing a square-wave visual stimulus. (
  • Our results suggest that neural connection among SF domains sharing similar SF preference is one of the basis of the contextual modulation of responses in the visual cortex. (
  • Neural Mechanisms of Visual Space Perception in the Parietal Association Cortex. (
  • A day by day log of cortical electric activity in the mouse visual cortex was published in the Journal of Neuroscience by George Washington University (GW) researcher Matthew Colonnese, Ph.D. This research is the first to establish a mouse model for human fetal electrographic development. (
  • Development of Activity in the Mouse Visual Cortex, Journal of Neuroscience (2016). (
  • Unexpectedly, for the centermost 0.75°, the cortical representations for both V2 and V3 are larger than that of V1, indicating that more neuronal processing power is dedicated to second-level analysis in this small but important part of the visual field. (
  • The pRF method is non-invasive and can be applied to a wide range of conditions when it is useful to link fMRI signals in the visual pathways to neuronal receptive fields. (
  • In the visual system, prolonged exposure to a high contrast stimulus leads to a decrease in neuronal responsiveness, referred to as contrast adaptation. (
  • These experiments demonstrate that visual discrimination learning might involve stimulus-selective facilitation of neuronal responses at early stages of visual processing (LGN, V1). (
  • Correspondingly, neuronal response magnitudes in visual cortex are often reduced during divided compared with focused spatial attention. (
  • Visual information coming from the eye goes through the lateral geniculate nucleus in the thalamus and then reaches the visual cortex. (
  • Each hemisphere's V1 receives information directly from its ipsilateral lateral geniculate nucleus that receives signals from the contralateral visual hemifield. (
  • Visual information coming from the eyes passes through the lateral geniculate nucleus in the thalamus and then reaches the visual cortex. (
  • Layer 4, which receives most visual input from the lateral geniculate nucleus (LGN), is further divided into 4 layers, labelled 4A, 4B, 4Cα, and 4Cβ. (
  • After intracardial perfusion, sections of the lateral geniculate nucleus (LGN) and visual cortex (V1) were examined by immunohistochemistry for glial fibrillary acidic protein (GFAP) and CD11b, a subunit of the complement 3 receptor and marker of macrophage and microglia cells (MAC-1). (
  • This loss has been shown to cause neurochemical changes in the lateral geniculate nucleus (LGN) and visual cortex of adult primates. (
  • Monocular deprivation effects in the rat visual cortex and lateral geniculate nucleus are prevented by nerve growth factor (NGF). (
  • Importantly, object-selective cortical regions such as the lateral occipital cortex show such attenuation even though the repeated objects may differ in their sizes, orientations, or perceived depths, revealing cue-independent object representations ( 15 , 16 ). (
  • During the early postnatal development of the neocortex in rats there is an axonal projection from the occipital cortex (which includes the visual cortex) to the spinal cord which is subsequently completely removed through a process of selective collateral elimination. (
  • no labeled cells are seen in the occipital cortex. (
  • However, a similar FB injection made during the first postnatal week results after a 4-day survival in a continuous band of FB-labeled layer V neurons spread throughout the tangential extent of the neocortex, including the occipital cortex. (
  • Injections of the anterograde tracer wheat germ agglutinin conjugated to horseradish peroxidase made into the occipital cortex, or for comparison, into more rostral cortical regions in hamsters ranging in age from neonates to adults, reveal that the extension of pyramidal tract axons is staggered along the anterioposterior axis of the cortex such that axons originating from the posterior regions lag behind those arising from more rostral areas. (
  • Injections into the occipital cortex on P16 label only a few fibers in the medullary pyramidal tract, and none is labeled in hamsters injected as adults. (
  • The dorsal stream begins with V1, goes through Visual area V2, then to the dorsomedial area (DM/ V6) and Visual area MT (middle temporal/ V5) and to the posterior parietal cortex . (
  • In mammals, it is located in the posterior pole of the occipital lobe and is the simplest, earliest cortical visual area. (
  • Decreases were more pronounced in the posterior cingulate/precuneous (BAS 31/7) and right inferior parietal cortex (BA 40) during language-related tasks and more pronounced in left inferior frontal cortex (BA 10/47) during nonlanguage tasks. (
  • Blood flow decreases did not generally show significant differences across the active task states within an experiment, but a verb-generation task produced larger decreases than a read task in right and left inferior parietal lobe (BA 40) and the posterior cingulate/precuneous (BA 31/7), while the read task produced larger decreases in left lateral inferior frontal cortex (BA 10/47). (
  • The results demonstrated two spatially and temporally distinct stages of processing: The first, emerging 70 ms after stimulus onset around the calcarine sulcus, was sensitive to local features only, whereas the second, starting at 130 ms across the occipital and posterior parietal cortices, reflected the global configuration. (
  • In the cat, the superior colliculus (SC) and cortical areas on the medial bank of posterior middle suprasylvian sulcus (pMS) are regions that when unilaterally damaged result in contralateral visual hemineglect. (
  • Seeds in the vestibular [parietal operculum (OP2)], the parietal [posterior parietal cortex (PPC);7A, hIP and the visual cortex (VC) were used for the analysis. (
  • The posterior parietal association cortex (area PG or 7a) is known to be concerned with space vision. (
  • In conclusion we found three groups of neurons in the different part of the posterior parietal association area that were discriminating direction of movement, rotation from translation or orientation of the axis of the visual objects in 3D space. (
  • Spectral and temporal processing in rat posterior auditory cortex. (
  • This undermines the whole concept of the visual system in mammalian cortex as a perfect hierarchy with V1 as the gatekeeper and raises a multitude of questions, including how these two parallel visual systems evolved and how they cooperate to produce a unified visual experience. (
  • Humans have the best of all possible visual worlds because our full stereo vision combines with primitive visual pathways to quickly spot danger, a study led by the University of Sydney has discovered. (
  • The two parallel visual pathways are routed through distinct relay stations in a brain structure called the thalamus: dLGN for V1 and the Pulvinar for POR. (
  • Behavioral, anatomical, and neuroimaging measurements have demonstrated several changes in healthy aging visual pathways that may contribute to reduced visual acuity in aging. (
  • Using gas chromatography mass spectrometry techniques, 6 out of 7 oxysterols analysed from both non-enzymatic and enzymatic pathways were also selectively increased in the Parkinson's disease visual cortex. (
  • Additional visual detection experiments established a clear tradeoff between the amount of information maintained in VSTM and detection sensitivity, while ruling out alternative accounts for the effects of VSTM load in terms of differential spatial allocation strategies or task difficulty. (
  • These findings indicate the dependence of foveal pRF parameters on the spatial extent of the stimulated visual field and are likely associated with methodological biases and/or physiological mechanisms. (
  • Addressing this type of question requires simultaneous measurements at known spatial intervals in the cortex. (
  • Performance in many visual tasks is impaired when observers attempt to divide spatial attention across multiple visual field locations. (
  • Swindale, N.V.: Spatial pattern of response magnitude and selectivity for orientation and direction in cat visual cortex. (
  • More recently, Goodale and Milner extended these ideas and suggested that the ventral stream is critical for visual perception whereas the dorsal stream mediates the visual control of skilled actions. (
  • Visual perception critically depends on orientation-specific signals that arise early in visual processing. (
  • The next piece of the puzzle will be to understand what each of these projection motifs does for visual processing and perception and how these long-range connectivity patterns are established during development," Professor Mrsic-Flogel concluded. (
  • The new study - published online Jan. 4, 2019, in Science - shows for the first time that one of these supposedly higher-order visual areas, which is involved in the perception of moving objects, does not depend on information from V1 at all. (
  • Orientation selectivity of neurons in V1 is believed to be central to visual form perception. (
  • 2003 ) and changes in visual perception (Betts et al. (
  • Given its high-level function, it may seem unlikely that PFC would contribute to low-level visual representations and mediate the perception and recognition of occluded objects. (
  • In addition, women with Turner syndrome, who are deficient in E2, exhibit profound deficits in visual function, including abnormal spatiotemporal processing and deficits in object perception tasks , . (
  • Furthermore, markers of central sensory function (e.g., corrected visual and auditory acuity) account for virtually all age-related variance on a broad array of higher-order cognitive tasks, including speed of processing, memory, verbal fluency, and reasoning ( 4 , 6 ). (
  • In this chapter, discussion will be restricted (or broadened, depending upon one's viewpoint) to consideration of cortical zones shown to have at least some visual sensory responsiveness and direct connectivity with other, unimodal visual areas. (
  • Instead, this region, known as the post-rhinal cortex (POR), appears to obtain visual data directly from an evolutionarily ancient sensory processing center at the base of the brain called the superior colliculus. (
  • The ancestral superior colliculus (called optic tectum in non-mammals) is the main sensory processing center in creatures with little or no cortex, such as fish, amphibians, lizards and birds. (
  • Consideration of the findings that visual STM (VSTM) involves sensory recruitment [e.g. (
  • The numerous interactions between excitatory and inhibitory cells at each stage of visual processing result in cortical maps which depart in several ways from being precise point-to-point replicates of the sensory receptor surface. (
  • We focus on primate visual cortex as a model sensory system with well described anatomy that has been the subject of a large body of neurophysiological studies. (
  • Cortical sensory processing is widely studied in the visual cortex. (
  • When an object is partially occluded, relevant sensory evidence available to the visual system is diminished, making the process of object recognition challenging. (
  • Interaction of sensory responses with spontaneous depolarization in layer 2/3 barrel cortex. (
  • Florian Beissner and Christian Henke, "Methodological Problems in fMRI Studies on Acupuncture: A Critical Review with Special Emphasis on Visual and Auditory Cortex Activations," Evidence-Based Complementary and Alternative Medicine , vol. 2011, Article ID 607637, 7 pages, 2011. (
  • We measured perceptual sensitivity before, during, and after tDCS application over either visual cortex or auditory cortex. (
  • Second, we hypothesized that similar self-organizing mechanisms continue operating in the adult cortex, maintaining it in a continuously-adapting dynamic equilibrium with the input, and tested this hypothesis on the self-organized model. (
  • A developmental model based on these physiological observations, and on comparative studies of cortical organisation, is then proposed, in order to explain how a combination of molecular specification steps and activity-driven processes can generate the variety of visuotopic organisations observed in adult cortex. (
  • For example, presenting two identical objects in rapid succession results in an attenuated fMRI signal in several regions of visual cortex, relative to the rapid presentation of two different objects. (
  • We tested this hypothesis with fMRI and behavioral measures of visual detection sensitivity. (
  • The aim of this study was to assess the effect of propofol/remifentanil anaesthesia on visual-evoked activation of the visual cortex using fMRI-technique. (
  • We applied fMRI-based visual field mapping of the central visual field at 3 T in eight controls to compare the pRF properties of the central visual field of a reference condition (stimulus radius: 14°) and two conditions with simulated peripheral visual field defect, i.e., with a peripheral gray mask, stimulating only the central 7° or 4° radius. (
  • used fMRI with traveling wave visual field mapping methods to show that V1 in healthy aging subjects has lower blood-oxygen-level-dependent (BOLD) activity compared to healthy young adults, but found no change in the overall size of V1. (
  • Also, we quantify the amount of input from ipsi- and contralateral visual fields. (
  • This orderly relationship creates a visuotopic map, whereby V1 neurones on one side of the brain collectively represent the entire contralateral half of the visual field in a gradual and predictable fashion (2,3). (
  • After a resting baseline period of 50 s, the subjects were exposed to a visual stimulus for 20 s, followed by a 50 s resting period in a dimly lit, sound attenuating room. (
  • The visual stimulus was a circular, black and white, alternating checkerboard. (
  • Nine previous positron emission tomography (PET) studies of human visual information processing were reanalyzed to determine the consistency across experiments of blood flow decreases during active tasks relative to passive viewing of the same stimulus array. (
  • Thus, even the smallest stimulus in the visual field will evoke a response from an intricately shaped cluster of thousands of cortical cells distributed over a mean position. (
  • The ability to measure visual field maps in vivo, along with the receptive field properties and stimulus selectivity of the various classes of neurons within these maps, is essential for understanding visual computations. (
  • Experiments have been done to obtain a depth resolved stimulus-specific profile of activation in cat visual cortex. (
  • However, behavioral research demonstrates that not all visual tasks suffer such capacity limits: The costs of divided attention are minimal when the task and stimulus are simple, such as when searching for a target defined by orientation or contrast. (
  • 1979 ascertained the neuroplasticity of kittens' brains, with respect to control of visual stimulus correlated with changes in RNA structures. (
  • Here, we report the consequences of spatiotemporally continuous vs. discontinuous motion on perceptual representations in human ventral visual cortex. (
  • We studied ventral visual cortex, an area of the brain that responds selectively to visual categories (faces, places, and words) in young adults, and that shows little atrophy with age. (
  • In the present study, we focus our attention on ventral visual cortex. (
  • Our understanding of the visual system has reached new heights over the last decade, with new techniques based on brain metabolism, enzyme histochemistry, immunohistochemistry, voltage-sensitive dyes, and brain imaging having been applied rigorously to the study of the visual cortex (e.g. (
  • Bender, D. B., 1983, Visual activation of neurons in the primate pulvinar depends on cortex but not colliculus, Brain Res . (
  • Firstly, they used whole-brain fluorescence-based axonal tracing by labelling neurons in the right visual cortex of each mouse with GFP and then imaging axonal projections by whole-brain serial two-photon tomography. (
  • The visual system is probably the best understood part of the brain. (
  • These findings demonstrate that a brain prosthetic can produce coherent percepts of visual forms. (
  • In the brain, egomotion is processed from multisensory inputs, particularly vestibular and visual ones whose integration remains poorly understood (e.g. (
  • In humans, neuroimaging studies revealed several brain regions involved in visual egomotion processing. (
  • Scientists studying brain process involved in sight have found the visual cortex also uses information gleaned from the ears as well as the eyes when viewing the world. (
  • The researchers targeted inhibitory neurons in the visual cortex to turn them "on," thus silencing that region of the brain. (
  • The adoption of the Latin "cortex" to describe the outer gray matter covering of the brain paints this structure as a thin bark or rind enveloping the remainder of the brain. (
  • To study how miR-132 could impact the ability of this brain region to adapt to changing conditions, the scientists temporarily stitched closed one eyelid in mice, to stop the nerve signals from that eye from reaching neurons in the visual cortex. (
  • Structural brain changes have been reported in the insular cortices using quantitative magnetic resonance imaging (MRI) procedures commonly used in research, but rarely applied in clinical practice. (
  • Although gonadal E2 has often been thought to influence these processes, the possibility that central visual processing may be modulated by brain-generated hormone has not been explored. (
  • Recent data show that glaucoma affects extra-retinal vision-related brain structures (including visual cortex) but dynamics and mechanisms of this degeneration remain unclear. (
  • While a wide range of technologies and therapies are being developed to restore vision, a fundamental question still remains unanswered: would the adult visual brain retain a sufficient plastic potential to learn how to see after a prolonged period of abnormal visual experience? (
  • Leopold, David A. 2018-01-08 00:00:00 Human area Prostriata is a small, unstudied portion of the visual brain set deep in the calcarine sulcus, next to V1. (
  • Publications] M.Taira et al: 'Parietal cortex neurons of the monkey related to the visual guidance of hand movement' Exp.Brain Res.83. (
  • Based on straightforward, carefully described anatomy in humans and primates, and informed by advances in cortical physiology over recent years, Miyawaki offers an accessible approach to understanding the multiple visual cortices. (
  • It is a major benefit to have a developmental mouse model, since there are so many other mouse models of disease and there is such a large gap in our understanding of the normal progression of the developing cortex," said Colonnese, assistant professor of pharmacology and physiology at the GW School of Medicine and Health Sciences. (
  • The results are sensitive to the detailed specification of the lateral connectivity and suggest that the cortical mechanisms that generate geometric visual hallucinations are closely related to those used to process edges, contours, surfaces, and textures. (
  • As part of the federal government's National Institutes of Health (NIH), the National Eye Institute's mission is to "conduct and support research, training, health information dissemination, and other programs with respect to blinding eye diseases, visual disorders, mechanisms of visual function, preservation of sight, and the special health problems and requirements of the blind. (
  • This suggests that the mechanisms mediating adaptation-induced alterations in contrast and response gain are different, and possibly occur at different loci within the visual pathway. (
  • Animal studies have shown that there is developmental regulation of GABAergic mechanisms in visual cortex. (
  • In this study, we show for the first time how these mechanisms develop in the human visual cortex across the lifespan. (
  • The exact roles and mechanisms of the vestibular and visual systems for the recovery of neglect are not yet known. (
  • Although maintaining visual acuity during self-motion is effected by minimizing retinal slip via the brainstem vestibular-ocular reflex, higher order visuovestibular mechanisms also contribute. (
  • Additionally, CO histochemistry revealed sub-compartments of "thick stripes," "thin stripes," and "pale stripes" in the middle layer of the secondary visual cortex (V2), which have been shown to possess distinct connections with V1 and other cortical areas ( Sincich and Horton, 2002 ). (
  • First, adjacent radial columns in the cortex represent partially overlapping regions of the visual field, irrespective of whether these columns are part of the same or different cortical areas. (
  • This rule is not as rigid as the first, as many cortical areas form discontinuous, second-order representations of the visual field. (
  • 19 used for most analyses) of the tracer biocytin in visual area V4 of six macaque monkeys. (
  • This thesis describes the requirements for a robot that can orient cameras with the same dynamics as macaque monkey eyes as well as a camera system that reproduces macaque visual acuity. (
Visual-Gustatory Interaction: Orbitofrontal and Insular Cortices Mediate the Effect of High-Calorie Visual Food Cues on Taste...
Visual-Gustatory Interaction: Orbitofrontal and Insular Cortices Mediate the Effect of High-Calorie Visual Food Cues on Taste... (
Visual cortex - Wikipedia
Visual cortex - Wikipedia (
Category:Visual cortex - Wikimedia Commons
Category:Visual cortex - Wikimedia Commons (
Representation of visual uncertainty through neural gain variability | Nature Communications
Representation of visual uncertainty through neural gain variability | Nature Communications (
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Plus it (
Parts of the Brain That Control Sight |
Parts of the Brain That Control Sight | (
Frontiers | Extracellular Sortilin Proteopathy Relative to β-Amyloid and Tau in Aged and Alzheimer's Disease Human Brains |...
Frontiers | Extracellular Sortilin Proteopathy Relative to β-Amyloid and Tau in Aged and Alzheimer's Disease Human Brains |... (
Spatiotemporal object continuity in human ventral visual cortex | PNAS
Spatiotemporal object continuity in human ventral visual cortex | PNAS (
Aging reduces neural specialization in ventral visual cortex | PNAS
Aging reduces neural specialization in ventral visual cortex | PNAS (
MPI for Brain Research | Max Planck Society
MPI for Brain Research | Max Planck Society (
Visual cortex development in the ferret. I. Genesis and migration of visual cortical neurons | Journal of Neuroscience
Visual cortex development in the ferret. I. Genesis and migration of visual cortical neurons | Journal of Neuroscience (
Stimulus complexity shapes response correlations in primary visual cortex | PNAS
Stimulus complexity shapes response correlations in primary visual cortex | PNAS (
Hold the Fries: Foods Linked to Prostate Cancer Risk
Hold the Fries: Foods Linked to Prostate Cancer Risk (
The Foveal Confluence in Human Visual Cortex | Journal of Neuroscience
The Foveal Confluence in Human Visual Cortex | Journal of Neuroscience (
Nicotinic Receptors: Neurons on Nicotine - BioTechniques
Nicotinic Receptors: Neurons on Nicotine - BioTechniques (
Plus it
Plus it (
Homosynaptic long-term depression in the visual cortex | Journal of Neuroscience
Homosynaptic long-term depression in the visual cortex | Journal of Neuroscience (
Table of Contents - September 22, 2006, 313 (5794) | Science
Table of Contents - September 22, 2006, 313 (5794) | Science (
Prior Expectations Bias Sensory Representations in Visual Cortex | Journal of Neuroscience
Prior Expectations Bias Sensory Representations in Visual Cortex | Journal of Neuroscience (
Mechanisms of contour perception in monkey visual cortex. I. Lines of pattern discontinuity | Journal of Neuroscience
Mechanisms of contour perception in monkey visual cortex. I. Lines of pattern discontinuity | Journal of Neuroscience (