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lobus parietalis
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Cerebrum map
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Principal fissures and lobes of the Cerebrum viewed laterally (Parietal Lobe is shown in yellow)
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Lateral surface of left cerebral hemisphere, viewed from the side (Parietal Lobe is in upper right)
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Cerebrum
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Anterior Cerebral <br/> Middle Cerebral
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Superior Sagittal Sinus
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hier
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The is a lobe in the
Brain . It is positioned above (superior to) the
Occipital Lobe and behind (posterior to) the
Frontal Lobe .
The parietal lobe integrates
Sensory information from different
Modalities , particularly determining spatial sense and navigation. For example, it comprises
Somatosensory Cortex and the
Dorsal Stream of the
Visual System . This enables regions of the parietal cortex to map objects perceived visually into body coordinate positions.
The parietal lobe is defined by four anatomical boundaries: the
Central Sulcus separates the parietal lobe from the
Frontal Lobe ; the
Parieto-occipital Sulcus separates the parietal and
Occipital Lobe ; the
Lateral Sulcus (sylvian fissure) is the most lateral boundary separating it from the
Temporal Lobe ; and the
Medial Longitudinal Fissure divides the two hemispheres.
Immediately posterior to the central sulcus, and the most anterior part of the parietal lobe, is the
Postcentral Gyrus (
Brodmann Area 3), the primary
Somatosensory Cortical Area . Dividing this and the posterior parietal cortex is the
Postcentral Sulcus .
The posterior parietal cortex can be subdivided into the
Superior Parietal Lobule (Brodmann areas
5 +
7 ) and the
Inferior Parietal Lobule (
39 +
40 ), separated by the
Intraparietal Sulcus (IP). The intraparietal sulcus and adjacent
Gyri are essential in guidance of limb and
Eye Movement , and based on cytoarchitectural and functional differences is further divided into medial (MIP), lateral (LIP), ventral (VIP), and anterior (AIP) areas.
The parietal lobe plays important roles in integrating sensory information from various parts of the body, knowledge of numbers and their relationsBlakemore & Frith (2005). ''The Learning Brain''. Blackwell Publishing. ISBN 1-4051-2401-6, and in the manipulation of objects. Portions of the parietal lobe are involved with visuospatial processing. Much less is known about this lobe than the other three in the cerebrum.
Various studies in the 1990s found that different regions of the parietal cortex in
Macaque s represent different parts of space.
- The lateral intraparietal (LIP) contains a 2-dimensional topographic map of retinotopically-coded space representing the saliency of spatial locations. It can be used by the oculomotor system for targeting eye movements, when appropriate.
- The ventral intraparietal (VIP) area receives input from a number of senses (visual, receptive fields represented space in a head-centered reference frame. The cells with visual receptive fields also fire with head-centered reference framesZhang T, Heuer HW, Britten KH. (2004) Parietal area VIP neuronal responses to heading stimuli are encoded in head-centered coordinates. Neuron 42(6):993-1001. but possibly also with eye-centered coordinates
- The medial intraparietal (MIP) area neurons encode the location of a reach target in eye-centered coordinates.Pesaran B, Nelson MJ, Andersen RA. (2006) Dorsal premotor neurons encode the relative position of the hand, eye, and goal during reach planning. Neuron 51(1):125-34.
- The anterior intraparietal (AIP) area contains neurons responsive to shape, size, and orientation of objects to be graspedMurata A, Gallese V, Luppino G, Kaseda M, Sakata H. (2000) Selectivity for the shape, size, and orientation of objects for grasping in neurons of monkey parietal area AIP. J Neurophysiol 83(5):2580. PMID 10805659 as well as for manipulation of hands themselves, both to viewed and remembered stimuli. Murata A, Gallese V, Kaseda M, Sakata H. (1996) Parietal neurons related to memory-guided hand manipulation. J Neurophysiol 75(5):2180-6. PMID 8734616
Gerstmann's Syndrome is associated with lesion to the dominant (usually left) parietal lobe.
Balint's Syndrome is associated with bilateral lesions. The syndrome of
Hemispatial Neglect is usually associated with large deficits of attention of the non-dominant hemisphere.
