| Brain: Parietal lobes | ||
|---|---|---|
| Principal fissures and lobes of the cerebrum viewed laterally. (Parietal Lobe is shown in yellow) | ||
| Lateral surface of left cerebral hemisphere, viewed from the side. (Parietal Lobe is shown in orange.) | ||
| Latin | lobus parietalis | |
| Gray's | subject #189 822 | |
| Part of | Cerebrum | |
| Artery | Anterior cerebral Middle cerebral |
|
| Vein | Superior sagittal sinus | |
| NeuroNames | hier-77 | |
| MeSH | Parietal+Lobe | |
| NeuroLex ID | birnlex_1148 | |
The parietal lobe is a part of the Brain 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 name derives from the overlying parietal bone, which is named from the Latin paries-, wall.
Contents |
The parietal lobe is defined by three anatomical boundaries: the central sulcus separates the parietal lobe from the frontal lobe; the parieto-occipital sulcus separates the parietal and occipital lobes; 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 secondary 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 (IPS). 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 relations,[1] and in the manipulation of objects. Portions of the parietal lobe are involved with visuospatial processing. Although multisensory in nature, the posterior parietal cortex is often referred to by vision scientists as the dorsal stream of vision (as opposed to the ventral stream in the temporal lobe). This dorsal stream has been called both the 'where' stream (as in spatial vision)[2] and the 'how' stream (as in vision for action).[3] The posterior parietal cortex (PPC) receives somatosensory and/or visual input which then, through motor signals, controls movement of the arm, hand, as well as eye movements.[4]
Various studies in the 1990s found that different regions of the posterior parietal cortex in Macaques represent different parts of space.
More recent fMRI studies have shown that humans have similar functional regions in and around the intraparietal sulcus and parietal-occipital junction.[13] The human 'parietal eye fields' and 'parietal reach region', equivalent to LIP and MIP in the monkey, also appear to be organized in gaze-centered coordinates so that their goal-related activity is 'remapped' when the eyes move.[14] Both the left and right parietal systems play a determining role in self transcendence, the personality trait measuring predisposition to spirituality [1]
This lobe is divided into two hemispheres- left and right. The left hemisphere plays a more prominent role for right handers and is involved in symbolic functions in language and mathematics. Meanwhile, the right hemisphere plays a more prominent role for most left handers and is specialised to carry out images and understanding of maps i.e.spatial relationships. Damage to the right hemisphere of this lobe results in the loss of imagery, visualization of spacial relationships and neglect of left side space and left side of the body. Even drawings may be neglected on the left side. Damage to the left hemisphere of this lobe will result in problems in mathematics, long reading, writing and understanding symbols. The parietal association cortex enables individuals to read, write, and solve mathematical problems.The sensory inputs from the right side of the body go to the left side of the brain and vice-versa.
Gerstmann's syndrome is associated with lesion to the dominant (usually left) parietal lobe.[15] 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. Optic ataxia is associated with difficulties reaching toward objects in the visual field opposite to the side of the parietal damage. Some aspects of optic ataxia have been explained in terms of the functional organization described above.[16]
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||