Parietal Lobe — Function, Anatomy and Damage

Where the parietal lobe sits

The parietal lobe starts behind the central sulcus and ends at the parieto-occipital sulcus, with the lateral fissure below it. It is the lobe of perception and sensation, and it spends most of its effort combining what the body reports with what the eyes report. For the surrounding geography, start with the lobes of the brain overview.

Its front strip is the postcentral gyrus, the ridge on the outer surface between the central sulcus and the postcentral sulcus. Behind that, the intraparietal sulcus divides the rest into the superior parietal lobule above and the inferior parietal lobule below. The inferior lobule contains two gyri worth knowing by name: the supramarginal gyrus, which curls around the end of the lateral fissure, and the angular gyrus behind it.

Blood is split down the middle. The anterior cerebral artery supplies the medial third of the postcentral gyrus, which is the leg region, and the middle cerebral artery supplies the outer two thirds, which covers the arm and face.

Somatosensory cortex and the homunculus

The postcentral gyrus holds primary somatosensory cortex, Brodmann areas 3b, 1 and 2. Its body map is the sensory homunculus, and it is a caricature rather than a portrait: the leg hangs over the top edge onto the medial surface, the arm occupies the upper outer surface, and the face, lips and tongue take the lowest and largest position. Body parts that need fine discrimination get huge amounts of cortex, which is why your fingertips can read braille and your back cannot. The somatosensory cortex page walks through the map.

Signals arrive from the thalamus, sorted by origin before they get here. The ventral posterolateral nucleus (VPL) relays sensation from the body, and the ventral posteromedial nucleus (VPM) relays sensation from the head. Everything crosses on the way up, so the left postcentral gyrus feels the right side of the body.

Damage produces loss on the opposite side, and the deficits are about discrimination rather than raw feeling. Objects become hard to identify by touch alone with the eyes closed, and numbers traced on the palm become unreadable.

Space, attention and reaching

Behind the sensory strip, the posterior parietal cortex stops asking what is touching you and starts asking where things are. It takes visual information arriving along the dorsal stream from the occipital lobe and uses it to aim the hands and the eyes. This is the part of the brain that gets your fingers to the cup rather than to the space beside it.

When both parietal lobes are damaged, that machinery collapses into Balint syndrome, a triad of simultanagnosia, in which only one object can be perceived at a time, optic ataxia, in which reaching under visual guidance goes wrong, and ocular apraxia, in which the eyes cannot be moved to a chosen target on command. Vision itself is intact. What is lost is the ability to use it to act in space.

Hemispatial neglect

Neglect is the strangest thing the parietal lobe does when it breaks. A patient fails to attend to, respond to or perceive anything on the side opposite the lesion, even though the eyes work, the sensory pathways work and the arm is strong. The problem is attention, not equipment.

It comes overwhelmingly from the right hemisphere, most often the posterior parietal cortex, the inferior parietal lobule or the temporoparietal junction, usually after a right middle cerebral artery stroke. It is not rare either. Around 80% of patients with an acute right hemisphere stroke show signs of it, and about half still have it long term.

Three bedside tests catch it. Asked to mark the middle of a horizontal line, the patient marks well to the right. Asked to cross out every target on a page, they leave the left side untouched. Asked to draw a clock, they crowd all twelve numbers onto the right half. Extinction is the milder version: a single touch on the left is felt, but the same touch delivered at the same moment as one on the right disappears. Many patients also have anosognosia and will insist nothing is wrong.

Gerstmann syndrome and the angular gyrus

Josef Gerstmann described a tetrad that follows damage to the dominant parietal lobe, particularly the inferior parietal lobule and the angular gyrus where the parietal, temporal and occipital lobes meet. The four features are agraphia, which is impaired writing, acalculia, which is impaired arithmetic, finger agnosia, which is difficulty naming or identifying the fingers, and left-right disorientation. The parietal cortex page covers the surrounding association areas.

Ischemic stroke is the most common cause, followed by hemorrhage, tumors, multiple sclerosis, neurodegenerative disease and some systemic toxins such as carbon monoxide and lead. Most patients turn up with only two or three of the four features, and the complete tetrad is genuinely rare. Whether it deserves to be called a single syndrome is still argued over, since the exact localization is disputed and no proposed explanation for why these four deficits travel together has been confirmed.

That argument does not stop examiners asking about it. Practice pinning deficits to a location in the lesion localization quiz.

See the parietal lobe in 3D

The border between the sensory strip and the association cortex behind it is much clearer on a model you can turn, so find the postcentral gyrus on the 3D brain model and follow it down to the lateral fissure. Then test yourself in the brain lobes quiz and the label the brain quiz. Both are free and neither needs a login.

Sources and further reading

J. DiGuiseppi and P. Tadi, Neuroanatomy, Postcentral Gyrus, StatPearls, NCBI Bookshelf, updated July 24, 2023: https://www.ncbi.nlm.nih.gov/books/NBK549825/.

R. Benjamin and E. Gillespie, Spatial Neglect, StatPearls, NCBI Bookshelf, updated July 5, 2026: https://www.ncbi.nlm.nih.gov/books/NBK562184/.

I. Altabakhi and C. E. Sun, Gerstmann Syndrome, StatPearls, NCBI Bookshelf, updated June 19, 2026: https://www.ncbi.nlm.nih.gov/books/NBK519528/.

Common questions