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Lobes of the human brain (Occipital lobe is shown in yellow)
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Medial surface of left cerebral hemisphere ( Cuneus and Lingual Gyrus are at left)
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The is the
Visual Processing Center of the
Mammal ian
Brain . The
Primary Visual Cortex is
Brodmann Area 17 , located in the interior portion of the occipital lobe at the
Calcarine Sulcus and sometimes continuing onto the surface of the lobe. The lobes'
Peristriate Region s are the sites for center visuospatial processing, for color discrimination and for discrimination of movement.
The occipital lobes are the smallest of four true lobes in the human brain. Located in the rearmost portion of the skull, the occipital lobes are part of the
Forebrain Structure .
The lobes rest on the tentorium cerebelli, a process of dura mater that separates the cerebrum from the
Cerebellum . They are structurally isolated in their respective cerebral hemispheres by the separation of the
Cerebral Fissure . The front edge of the occipital lobe is separated from the
Parietal Lobe by the
Parieto-occipital Sulcus . The sides of the lobe merge with the parietal lobes along a vague boundary defined by 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 , and the area below the sulcus is the
Lingual Gyrus .
Retinal Sensors 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.
Cells on the posterior aspect of the occipital lobes'
Gray Matter are arranged as a spatial map of the retinal field.
Functional Neuroimaging 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 vision loss from similarly positioned "field cuts" in each eye. Occipital lesions can cause visual hallucinations. Lesions in the parietal-temporal-occipital association area are associated with
Color Agnosia ,
Movement Agnosia ,
Agraphia and
Alexia .
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 . It contains a low-level description of the local orientation, spatial-frequency and color properties within small
Receptive Fields .
Primary Visual Cortex projects to the occipital areas of the
Ventral Stream (
Visual Area V2 and
Visual Area V4 ), and the occipital areas of the
Dorsal Stream (
Visual Area V3 ,
Visual Area MT (V5), and
Visual Area DP .)
