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This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (June 2009) |
| Brain: occipital lobe |
Frontal lobe
Temporal lobe
Parietal lobe
Occipital
lobe
|
| Lobes of the human brain (the occipital lobe is shown in red) |
|
| Medial surface of left cerebral hemisphere. (cuneus and lingual gyrus are at left.) |
| Latin |
lobus occipitalis |
| Gray's |
subject #189 823 |
| Part of |
cerebrum |
| Artery |
posterior cerebral artery |
| NeuroNames |
hier-122 |
| MeSH |
Occipital+Lobe |
| NeuroLex ID |
birnlex_1136 |
The occipital lobe is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex.[1] The primary visual cortex is Brodmann area 17, 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, which is named from the Latin ob, behind, and caput, the head.
Contents
- 1 Anatomy
- 2 Function
- 3 Functional anatomy
- 4 Epilepsy and the occipital lobe
- 5 Additional images
- 6 See also
- 7 References
Anatomy[edit source | edit]
Animation. Occipital lobe (red) of left cerebral hemisphere.
The two occipital lobes are the smallest of four paired lobes in the human cerebral cortex. Located in the rearmost portion of the skull, the occipital lobes are part of the forebrain. 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 article for more information.)
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. 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, and the area below the sulcus is the lingual gyrus.
Damage to the primary visual areas of the occipital lobe can leave a person with partial or complete blindness.[2]
Function[edit source | edit]
A significant functional aspect of the occipital lobe is that it contains the primary visual cortex.
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. 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 of the thalamus before projecting to the cortex. 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 homonymous hemianopsia 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, and agraphia. Damage to the primary visual cortex, which is located on the surface of the posterior occipital lobe, can cause blindness due to the holes in the visual map on the surface of the visual cortex that resulted from the lesions.[3]
Functional anatomy[edit source | edit]
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 the dorsomedial area (DM).
Epilepsy and the occipital lobe[edit source | edit]
Recent studies have shown that specific neurological findings have had an impact on idiopathic occipital lobe epilepsies[4] Occipital lobe seizures are triggered by a flash, or a visual image that contains multiple colors. These are called flicker stimulation (usually through TV) these seizures are referred to as photo-sensitivity seizures. Patients having experienced occipital seizures described their seizure as seeing bright colors, and having severe blurred vision (vomiting was also apparent in some patients). Occipital seizure are triggered mainly during the day, through television, video games or any flicker stimulatory system.[5] Occipital seizures originate from an epileptic focus confined within the occipital lobes. They may be spontaneous or triggered by external visual stimuli. Occipital lobe epilepsies are etiologically idiopathic, symptomatic, or cryptogenic.[6] Symptomatic occipital seizures can start at any age, as well as any stage after or during the course of the underlying causative disorder. Idiopathic occipital epilepsy usually starts in childhood.[7] Occipital epilepsies account for approximately 5% to 10% of all epilepsies.[8]
Additional images[edit source | edit]
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Drawing to illustrate the relations of the brain to the skull.
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See also[edit source | edit]
- Lobes of the brain
- Regions of the human brain
- Sulcus Lunatus
- Visual evoked potential
References[edit source | edit]
- ^ "SparkNotes: Brain Anatomy: Parietal and Occipital Lobes". Archived from the original on 2007-12-31. Retrieved 2008-02-27.
- ^ Schacter, D. L., Gilbert, D. L. & Wegner, D. M. (2009). Psychology. (2nd ed.). New Work (NY): Worth Publishers.
- ^ Carlson, Neil R. (2007). Psychology : the science of behaviour. New Jersey, USA: Pearson Education. p. 115. ISBN 978-0-205-64524-4.
- ^ Chilosi, Anna Maria; Brovedani (November 2006). "Neuropsychological Findings in Idiopathic Occipital Lobe Epilepsies". Epilepsia 47: 76–78. doi:10.1111/j.1528-1167.2006.00696.x. PMID 17105468.
- ^ Destina Yalçin, A., Kaymaz, A., & Forta, H. (2000). Reflex occipital lobe epilepsy. Seizure, 9(6), 436-441.
- ^ Adcock, Jane E; Panayiotopoulos, Chrysostomos P (31). "Journal of Clinical Neurophysiology". Occipital Lobe Seizures and Epilepsies 29 (5): 397–407. Retrieved November 25, 2012.
- ^ Adcock, Jane E. Journal of Clinical Neurophysiology Volume 29 (2012). 'Occipital Lobe Seizures and Epilepsies. DOI: 10.1097/WNP.0b013e31826c98fe
- ^ Adcock, J. E.; Panayiotopoulos, C. P. (2012). Occipital Lobe Seizures and Epilepsies. Journal of Clinical NeuroPhysiology. 29(5), 397-407. doi: 10.1097/WNP.0b013e31826c98fe
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Human brain: forebrain (cerebrum, cerebral cortex, cerebral hemispheres, grey matter) (TA A14.1.09.002–240, 301–320, GA 9.818–826)
|
|
| Frontal lobe |
| Superolateral |
| Prefrontal |
- Superior frontal gyrus
- Middle frontal gyrus
- Inferior frontal gyrus: 11l
- 47-Pars orbitalis
- Broca's area
- 44-Pars opercularis
- 45-Pars triangularis
- Superior frontal sulcus
- Inferior frontal sulcus
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| Precentral |
- Precentral gyrus
- Precentral sulcus
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|
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| Medial/inferior |
| Prefrontal |
- Superior frontal gyrus
- Medial frontal gyrus
- Paraterminal gyrus/Paraolfactory area
- Straight gyrus
- Orbital gyri/Orbitofrontal cortex
- Ventromedial prefrontal cortex
- Subcallosal area
- Olfactory sulcus
- Orbital sulci
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| Precentral |
- Paracentral lobule
- Paracentral sulcus
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|
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| Both |
- Primary motor cortex
- Premotor cortex
- Supplementary motor area
- Frontal eye fields
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|
|
| Parietal lobe |
| Superolateral |
- Superior parietal lobule
- Inferior parietal lobule
- 40-Supramarginal gyrus
- 39-Angular gyrus
- Parietal operculum
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| Medial/inferior |
- Paracentral lobule
- Precuneus
Marginal sulcus
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| Both |
- Postcentral gyrus/primary somatosensory cortex
- Secondary somatosensory cortex
- Posterior parietal cortex
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|
|
| Occipital lobe |
| Superolateral |
- Occipital pole of cerebrum
- Lateral occipital gyrus
- Lunate sulcus
- Transverse occipital sulcus
|
|
| Medial/inferior |
- Primary visual cortex
- Cuneus
- Lingual gyrus
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|
|
| Temporal lobe |
| Superolateral |
- Transverse temporal gyrus/Primary auditory cortex
- Superior temporal gyrus
- Middle temporal gyrus
- Inferior temporal gyrus
- Superior temporal sulcus
- Inferior temporal sulcus
|
|
| Medial/inferior |
- Fusiform gyrus
- Medial temporal lobe
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|
|
Interlobar
sulci/fissures |
| Superolateral |
- Central (frontal+parietal)
- Lateral (frontal+parietal+temporal)
- Parieto-occipital
- Preoccipital notch
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| Medial/inferior |
- Medial longitudinal
- Cingulate (frontal+cingulate)
- Collateral (temporal+occipital)
- Callosal sulcus
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|
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| Limbic lobe |
| Parahippocampal gyrus |
- anterior
- Entorhinal cortex
- Perirhinal cortex
- Posterior parahippocampal gyrus
- Prepyriform area
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| Cingulate cortex/gyrus |
- Subgenual area
- Anterior cingulate
- Posterior cingulate
- Isthmus of cingulate gyrus: Retrosplenial cortex
|
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| Hippocampal formation |
- Hippocampal sulcus
- Fimbria of hippocampus
- Dentate gyrus
- Rhinal sulcus
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| Other |
- Supracallosal gyrus
- Uncus
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|
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| Insular lobe |
- Long gyrus of insula
- Short gyri of insula
- Circular sulcus of insula
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| General |
- Operculum
- Poles of cerebral hemispheres
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Some categorizations are approximations, and some Brodmann areas span gyri.
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anat (n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp
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noco (m/d/e/h/v/s)/cong/tumr, sysi/epon, injr
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proc, drug (N1A/2AB/C/3/4/7A/B/C/D)
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