The occipital lobe is the visual processing center Visual perception is the ability to interpret information and surroundings from visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision . The various physiological components involved in vision are referred to collectively as the visual system, and are the focus of much research in psychology, cognitive of the mammalian Mammals are a class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by hair and/or fur, three middle ear bones used in hearing, and a neocortex region in the brain. Some mammals have sweat glands, but most do not brain The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all. In vertebrates, the brain is located in the head, protected by the skull and close to the primary containing most of the anatomical region of the visual cortex The term visual cortex refers to the primary visual cortex and extrastriate visual cortical areas such as V2, V3, V4, and V5. The primary visual cortex is anatomically equivalent to Brodmann area 17, or BA17. The extrastriate cortical areas consist of Brodmann area 18 and Brodmann area 19. There is a visual cortex for each hemisphere of the brain.[1] The primary visual cortex The term visual cortex refers to the primary visual cortex and extrastriate visual cortical areas such as V2, V3, V4, and V5. The primary visual cortex is anatomically equivalent to Brodmann area 17, or BA17. The extrastriate cortical areas consist of Brodmann area 18 and Brodmann area 19. There is a visual cortex for each hemisphere of the brain is Brodmann area 17 A Brodmann area is a region of the cortex defined based on its cytoarchitecture, or organization of cells, commonly called V1 (visual one). Human V1 is located on the medial side of the occipital lobe within the calcarine sulcus; the full extent of V1 often continues onto the posterior pole of the occipital lobe. V1 is often also called striate cortex because it can be identified by a large stripe of myelin, the Stria of Gennari. Visually driven regions outside V1 are called extrastriate cortex. There are many extrastriate regions, and these are specialized for different visual tasks, such as visuospatial processing, color discrimination and motion perception. The name derives from the overlying occipital bone The occipital bone, a saucer-shaped membrane bone situated at the back and lower part of the cranium, is trapezoid in shape and curved on itself. It is pierced by a large oval aperture, the foramen magnum, through which the cranial cavity communicates with the vertebral canal, which is named from the Latin oc- + caput, "back of the head".
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Anatomy
Animation. Occipital lobe (red) of left cerebral hemisphere.The occipital lobes are the smallest of four lobes in the human cerebral cortex. Located in the rearmost portion of the skull, the occipital lobes are part of the forebrain A cerebral hemisphere is defined as one of the two regions of the brain that are delineated by the body's median plane, (medial longitudinal fissure). The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres has an outer layer of grey matter called the cerebral cortex that is supported by. It should be noted that the cortical lobes are not defined by any internal structural features, but rather by the bones of the skull that overlie them. Thus, the occipital lobe is defined as the part of the cerebral cortex that lies underneath the occipital bone. (See the human brain The human brain is the center of the human nervous system and is a highly complex organ. Enclosed in the cranium, it has the same general structure as the brains of other mammals, but is over three times as large as the brain of a typical mammal with an equivalent body size. Most of the expansion comes from the cerebral cortex, a convoluted layer article for more information.)
The lobes rest on the tentorium cerebelli, a process of dura mater that separates the cerebrum from the cerebellum The cerebellum is a region of the brain that plays an important role in motor control. It is also involved in some cognitive functions such as attention and language, and probably in some emotional functions such as regulating fear and pleasure responses, but it is its function in movement that is most clearly understood. The cerebellum does not. They are structurally isolated in their respective cerebral hemispheres by the separation of the cerebral fissure. At the front edge of the occipital are several lateral occipital gyri, which are separated by lateral occipital sulcus.
The occipital aspects along the inside face of each hemisphere are divided by the calcarine sulcus. Above the medial, Y-shaped sulcus lies the cuneus The cuneus receives visual information from the contralateral superior retina representing the inferior visual field. It is most known for its involvement in basic visual processing. Pyramidal cells in the cuneus (striate cortex) project to extrastriate cortices (BA 18,19). The mid-level visual processing that occurs in the extrastriate projection, and the area below the sulcus is the lingual gyrus.
Function
The most important functional aspect of the occipital lobe is that it contains the primary visual cortex.
Retinal The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses. These sensors A photoreceptor, or photoreceptor cell, is a specialized type of neuron found in the eye's retina that is capable of phototransduction. The great biological importance of photoreceptors is that as cells they convert light (electromagnetic radiation) into the beginning of a chain of biological processes. More specifically, the photoreceptor absorbs convey stimuli through the optic tracts to the lateral geniculate bodies, where optic radiations continue to the visual cortex. Each visual cortex receives raw sensory information from the outside half of the retina on the same side of the head and from the inside half of the retina on the other side of the head.
The cuneus (Brodmann's area 17) receives visual information from the contralateral superior retina representing the inferior visual field. The lingula receives information from the contralateral inferior retina representing the superior visual field. The retinal inputs pass through a "way station" in the lateral geniculate nucleus The lateral geniculate nucleus is the primary processing center for visual information received from the retina of the eye. The LGN is found inside the thalamus of the brain, and is thus part of the central nervous system of the thalamus The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections. Its function includes relaying sensation, special sense and motor signals to the cerebral cortex, along with the regulation of before projecting to the cortex.
Cells on the posterior aspect of the occipital lobes' gray matter Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil , glial cells (astroglia and oligodendrocytes) and capillaries. Grey matter contains neural cell bodies, in contrast to white matter, which does not and mostly contains myelinated axon tracts. The color difference arises mainly from the are arranged as a spatial map of the retinal field. Functional neuroimaging Functional neuroimaging is the use of neuroimaging technology to measure an aspect of brain function, often with a view to understanding the relationship between activity in certain brain areas and specific mental functions. It is primarily used as a research tool in cognitive neuroscience, cognitive psychology, neuropsychology, and social reveals similar patterns of response in cortical tissue of the lobes when the retinal fields are exposed to a strong pattern.
If one occipital lobe is damaged, the result can be homonomous Homonymous hemianopsia, or homonymous hemianopia, is a medical term for a type of partial blindness resulting in a loss of vision in the same visual field of both eyes vision loss Vision loss or visual loss is the absence of vision where it existed before, which can happen either acutely or chronically (i.e. over a long period of time) from similarly positioned "field cuts" in each eye. Occipital lesions Because the definition of lesion is so broad, the varieties of lesions are virtually endless. They are subsequently classified by their features. If a lesion is caused by a tumor it will be classified as malignant versus benign. Lesions may be classified by the shape they form, as is the case with many ulcers, which can have a bullseye or 'target' can cause visual hallucinations A hallucination, in the broadest sense of the word, is a perception in the absence of a stimulus. In a stricter sense, hallucinations are defined as perceptions in a conscious and awake state in the absence of external stimuli which have qualities of real perception, in that they are vivid, substantial, and located in external objective space. The. Lesions in the parietal-temporal-occipital association area are associated with color agnosia, movement agnosia, and agraphia Dysgraphia is a deficiency in the ability to write, regardless of the ability to read, not due to intellectual impairment.
Functional anatomy
The occipital lobe is divided into several functional visual areas. Each visual area contains a full map of the visual world. Although there are no anatomical markers distinguishing these areas (except for the prominent striations in the striate cortex), physiologists have used electrode recordings to divide the cortex into different functional regions.
The first functional area is the primary visual cortex The term visual cortex refers to the primary visual cortex and extrastriate visual cortical areas such as V2, V3, V4, and V5. The primary visual cortex is anatomically equivalent to Brodmann area 17, or BA17. The extrastriate cortical areas consist of Brodmann area 18 and Brodmann area 19. There is a visual cortex for each hemisphere of the brain. It contains a low-level description of the local orientation, spatial-frequency and color properties within small receptive fields. Primary visual cortex The term visual cortex refers to the primary visual cortex and extrastriate visual cortical areas such as V2, V3, V4, and V5. The primary visual cortex is anatomically equivalent to Brodmann area 17, or BA17. The extrastriate cortical areas consist of Brodmann area 18 and Brodmann area 19. There is a visual cortex for each hemisphere of the brain projects to the occipital areas of the ventral stream The Two-Streams hypothesis is a widely accepted, but still controversial, account of visual processing. As visual information exits the occipital lobe, it follows two main channels, or "streams." The ventral stream travels to the temporal lobe and is involved with object identification. The dorsal stream (or, "where pathway") (visual area V2 and visual area V4), and the occipital areas of the dorsal stream The Two-Streams hypothesis is a widely accepted, but still controversial, account of visual processing. As visual information exits the occipital lobe, it follows two main channels, or "streams". The ventral stream travels to the temporal lobe and is involved with object identification. The dorsal stream (or, "where pathway") - visual area V3, visual area MT (V5), and the dorsomedial area (DM).
Additional images
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Base of brain. |
Drawing to illustrate the relations of the brain to the skull. |
Occipital lobe in blue |
See also
- Lobes of the brain
- Regions of the human brain Anatomical regions of the brain are listed vertically, following hierarchies that are standard in neuroanatomy. Functional, connective, and developmental regions are listed horizontally in parenthesis where appropriate
- Sulcus Lunatus
- Visual evoked potential An evoked potential is an electrical potential recorded from the nervous system of a human or other animal following presentation of a stimulus, as distinct from spontaneous potentials as detected by electroencephalography (EEG) or electromyography (EMG)
References
- ^ "SparkNotes: Brain Anatomy: Parietal and Occipital Lobes". http://www.sparknotes.com/psychology/neuro/brainanatomy/section5.rhtml. Retrieved 2008-02-27.
Categories: Cerebrum
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Fri, 04 Jun 2010 17:54:49 GMT+00:00
Lincoln Journal Star Police reports say she suffered a "severe brain injury with a subdural hematoma to the occipital lobe ." Police reports indicate she was able to tell ...
Q. Trace the usual pathway of a drop of blood from the aorta to the left occipital lobe of the brain?
Asked by Ayumi - Mon Mar 8 17:39:08 2010 - - 1 Answers - 0 Comments
A. Not a cancer question.
Answered by thinkingtime - Mon Mar 8 21:06:29 2010
