Parietal Lobe Anatomy: 4 Functions of the Parietal Lobe

The parietal lobe is one of four major lobes found in the cerebrum, or the uppermost part of the human brain. There is a parietal lobe in each cerebral hemisphere. The parietal lobe in the left hemisphere relates to physical function in the right side of the body; the parietal lobe in the right hemisphere relates to physical function in the left side of the body.

The parietal lobe sits within the cerebrum and extends backwards from a boundary along the frontal lobe called the central sulcus, which is located in the top mid-section of the brain. The parietal lobe is located above the temporal lobe, which is responsible for housing long-term memories, and the occipital lobe, which processes visual information. The Sylvian fissure, also called the lateral sulcus or lateral fissure, marks the boundary between the parietal and and temporal lobes.

The outer surface of the parietal lobe is part of the cerebral cortex, which contains the gray matter neurons the body uses for conscious thought. Beneath the cerebral cortex is a thick layer of white matter, which gets its color from bundles of neurons with white myelin sheaths. White matter provides connectivity between the parietal lobe and other parts of the central nervous system such as the brainstem.

The parietal lobe itself is made up of the postcentral gyrus (also known as Brodmann area 3), the supramarginal gyrus, the angular gyrus, and the cingulate gyrus. These gyri are separated from the superior parietal lobule (also known as Brodmann areas 5 and 7) by the intraparietal sulcus. The intraparietal sulcus, for its own part, is divided into medial, ventral, lateral, and anterior regions. Beneath the parietal cortex in each hemisphere is the central sulcus and the precuneus.

The parietal lobes of the brain control many aspects of stimulus reception and computation.

1. 1. Spatial awareness: The superior parietal lobule and inferior parietal lobule largely control the body’s sense of spatial awareness. (The cerebellum also governs spatial awareness, and it’s connected to the parietal cortex via neural pathways).
2. 2. Navigation: Closely related to spatial awareness is the ability known as proprioception, which includes the modalities of navigation and spatial sense. These abilities are linked to the parietal lobe's somatosensory cortex, located behind the central sulcus in the postcentral gyrus.
3. 3. Language processing: The parietal lobe's somatosensory cortex provides cortical support to the understanding of language. The parietal association cortex works in concert with areas of the temporal lobe and frontal lobe to enable this.
4. 4. Sense perception: Sensory inputs on the skin, including pain receptors, communicate with the anterior parietal lobe via the thalamus. Although most of the body's visual stimuli are processed by the occipital lobe, the parietal lobe also plays a role thanks to the dorsal visuofugal pathway. The posterior superior parietal lobe also handles some auditory stimuli.

Damage to the neurons in the parietal lobe can lead to numerous setbacks related to motor skills, visual attention, and cognition.

1. 1. Hemineglect: The effects of hemineglect include attentional deficiencies and a compromised visual field that does not align with normal eye movements. Neuroscience links this condition to lesions in the right superior parietal lobule or right inferior parietal lobule. It can also link to optic ataxia, where individuals cannot fully process visual cues in the absence of other stimuli.
2. 2. Aphasia and dyslexia: Damage to a person's dominant parietal lobe can lead to language impairment, which may take the form of dyslexia or, when the damage is acute, aphasia. Dyslexia can make reading difficult, while aphasia can affect both verbal and written communication.
3. 3. Agnosia: Parietal lesions can cause agnosia, which in neurology is the dysfunctional recognition of symbols and stimuli.
4. 4. Agraphia and alexia: These disorders respectively cause an inability to write and an inability to recognize words spoken or written by others. Such forms of linguistic disorientation often accompany parietal lobe damage.
5. 5. Gerstmann syndrome: This syndrome causes poor differentiation between left and right, as well as agraphia (an inability to write).
6. 6. Hemispheric dysfunction: Damage to the right parietal lobe can impair the body's ability to process spatial relationships and can limit function on the left side of the body. Damage to the left parietal lobe can impair mathematical thinking, structured writing, and response to symbols, as well as function on the right side of the body. The motor dysfunction is called apraxia and it also tends to involve the motor cortex in the brain's frontal lobe.

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