The parietal lobe is one of the four major lobes of the cerebral cortex in the mammalian brain. The parietal lobe is positioned above the temporal lobes and behind the frontal lobe and central sulcus.
The parietal lobe integrates sensory information among various modalities, including spatial and proprioception, the main sensory receptor region for the sense of touch (mechanoreception) in the somatosensory cortex that is only posterior to the central sulcus in the postcentral gyrus, and the dorsal flow of the visual system. The main sensory input of the skin (touch, temperature, and pain receptors), is passed through the thalamus to the parietal lobe.
Some areas of the parietal lobes are important in language processing. The somatosensory cortex can be described as a distorted figure - homunculus (Latin: "little man"), in which parts of the body are given according to how much somatosensory cortex is devoted to them. The superior parietal lobes and inferior parietal lobules are the major areas of body or spacial awareness. Lesions in the superior or superior inferior parietal lobe lead to hemineglect.
The name comes from parietal bone, named after Latin paries -, which means "wall".
Video Parietal lobe
Structure
The parietal lobe is defined by three anatomic boundaries: The central ulcer separates the parietal lobes from the frontal lobes; the parieto-occipital sulcus separates the parietal and occipital lobes; lateral sulcus (fissura sylvian) is the most lateral boundary, separating it from the temporal lobes; and medial longitudinal fissures divide the two hemispheres. In each hemisphere, the somatosensory cortex represents the skin area on the contralateral surface of the body.
Immediately posterior to the central sulcus, and the most anterior portion of the parietal lobe, is the postcentral gyrus (Brodmann 3 area), the primary somatosensory cortical area. This separates from the posterior parietal cortex is the poscentral sulcus.
The posterior parietal cortex can be divided into superior parietal lobe (Brodmann area 7 7) and inferior parietal lobule (39 40), separated by intraparietal sulcus (IPS). The adjacent intraparietal and adjacent sacs are important in the guidance of limb and eye movement, and - based on cytoarchitectural and functional differences - subdivided into medial (MIP), lateral (LIP), ventral (VIP), and anterior (AIP). ) area.
Maps Parietal lobe
Function
The cortical function of the parietal lobe is:
- Two-point discrimination
through touch alone without any other sensory input (ie, visual)
- Graphesthesia - recognize writing on the skin with just a touch of
- Touch localization (bilateral simultaneous stimulation)
The parietal lobe plays an important role in integrating sensory information from different parts of the body, knowledge of numbers and their relationships, and in the manipulation of objects. Its function also includes processing information relating to the sense of touch. Part of the parietal lobe is involved with visuospatial processing. Although multisensor, the posterior parietal cortex is often referred by vision scientists as the dorsal flow of vision (as opposed to the ventral flow in the temporal lobes). This dorsal flow is called the "where" flow (as in spatial vision) and the "how" flow (as in the vision for action). The posterior parietal cortex (PPC) receives somatosensory and/or visual input, which then, through motor signals, controls the movement of the arms, hands, and eye movements.
Various studies in the 1990s found that the various regions of the posterior parietal cortex on apes represent different parts of the space.
- The intraparietal lateral (LIP) containing the neuron map (retinotopically-coded when the eye is corrected) represents the meaning of the spatial location, and attention to this spatial location. This can be used by the oculomotor system to target eye movements, where appropriate.
- The ventral intralarial area (VIP) receives input from a number of senses (visual, somatosensory, auditory, and vestibular). Neurons with receptive fields receive represent the space in a head-centered frame of reference. Cells with visual receptive fields are also illuminated with reference frames of centers but may also be with eye-centered coordinates
- The intraparietal area neuron (MIP) encodes the target location of the range in the nose-centered coordinates.
- The intraparietal anterior region (AIP) contains neurons that are responsive to the shape, size, and orientation of objects to be grasped and to the manipulation of the hand itself, both to be seen and to remember its stimuli. AIP has neurons responsible for grasping and manipulating objects through motor and visual input. The AIP and ventral ventotor work together, responsible for visuomotor transformation for hand action.
More recent fMRI studies have shown that humans have similar functional areas in and around the intrathoretal and parietal-occipital interspector intersections. The "parietal plane of the eyes" of man and the "parietal range", equivalent to LIP and MIP in monkeys, also appear to be arranged in coordinates centered on the gaze so that activity related to their purpose is "mapped back" when the eye moves. Both the left and right parietal systems play a decisive role in self-transcendence, the personality trait that measures the tendency for spirituality.
Clinical interests
The features of parietal lobe lesions are as follows:
- Unilateral parietal lobes
- Loss of contralateral hemisphere
- Astereognosis - the inability to determine 3-D shape by touch.
- Agraphaesthesia - the inability to read numbers or letters drawn by hand, with eyes closed.
- Contralateral homonym Quadrantanopia below
- Nistagmus optokinetic asymmetry (OKN)
- Sensory Seizures
- The phenomenon of extinction (contralateral)
- Hemisphere dominant
- Dysphasia/Afasia
- Dyscalculia
- Dyslexia - a general term for disorders that may involve difficulty in learning to read or interpret words, letters, and other symbols.
- Apraxia - inability to perform complex movements in the presence of normal motor, sensory and cerebellum functions.
- Agnosia (touch of agnosia) - the inability to recognize or differentiate.
- Gerstmann's syndrome - Characterized by acalculia, agraphia, finger anomia and difficulty in right and left differentiation.
- The non-dominant hemisphere
- Spatial Disorientation
- constructive Aprilaksia
- Dressing apraxia
- Anosognosia - a condition in which a person with a disability seems unaware of the existence of his or her disability.
Damage to this lobe in the right hemisphere leads to loss of imagery, visualization of spatial relationships and neglecting the left side and left side of the body. Even images can be ignored on the left side. Damage to this lobe in the left hemisphere will lead to problems in math, long reading, writing, and understanding of symbols. The parietal association cortex allows the individual to read, write, and solve mathematical problems. Sensory input from the right side of the body to the left side of the brain and vice versa.
Hemisalal waiver syndrome is usually associated with a large deficit of non-dominant hemisphere attention. Optical ataxia is associated with the difficulty of reaching objects in the visual field opposite to the side of parietal damage. Some aspects of optic ataxia have been described in terms of the functional organization described above.
Apraxia is a motor control disorder that can be called both for "elemental" motor deficits as well as general cognitive impairment. The concept of apraxia was formed by Hugo Liepmann about a hundred years ago. Apraxia is largely a symptom of left brain damage, but some apraxia symptoms may also occur after right cerebral damage.
Amorphosynthesis is a loss of perception on one side of the body caused by lesions in the parietal lobe. Typically, left-sided lesions cause agnosia, loss of the whole body of perception, while right-sided lesions lead to a lack of recognition of the left side of the person and the extrapersonal space. The term amorphosynthesis was coined by D. Denny-Brown to describe the patient he studied in the 1950s.
It can also cause sensory disturbances in which one of the senses of a person affected (sight, hearing, smell, touch, sense and spatial awareness) is no longer normal..
See also
- Brain Lobes
References
Source of the article : Wikipedia
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