Intraparietal sulcus

At a glance

English

Intraparietal sulcus

Latin (TA2)

Sulcus intraparietalis

System

Brain and spinal cord

Region

Head

Side

Paired, left and right

About the intraparietal sulcus

The intraparietal sulcus is a prominent furrow on the outer, convex surface of the parietal lobe. It usually begins near the postcentral sulcus, often joined to its lower part, and runs first upwards and then backwards, roughly parallel to the upper margin of the hemisphere. This gives it a first, oblique part and a second, more horizontal part. At its back end it turns down into the occipital lobe as the occipital ramus, where it meets the transverse occipital sulcus at a T-junction.

Above the sulcus lies the superior parietal lobule, a strip of cortex that continues over the upper border of the hemisphere into the precuneus. Below it lies the inferior parietal lobule, made up of the supramarginal gyrus, which arches round the end of the lateral sulcus, and the angular gyrus, which arches round the end of the superior temporal sulcus. The depth of the sulcus is considerable, and much of the important cortex lies hidden in its banks rather than on the surface.

Recordings in monkeys and functional imaging in humans have divided the cortex of the sulcus into a series of areas, often named by position: lateral, ventral, medial, anterior and caudal. The lateral and ventral areas take part in visual attention and in planning saccadic eye movements; the medial and ventral areas guide reaching and pointing; the anterior area controls grasping and handling objects; and the caudal area uses binocular disparity to judge depth. All of them send fibres forwards to the frontal lobe. The sulcus forms the core of the dorsal attention network, active when attention is turned deliberately to a place or object, and it is involved in learning sequences of finger movements and in visuospatial working memory. It also holds a sense of number: activity here rises when people compare quantities, calculate or even hear words such as 'more' or 'many', and children with developmental dyscalculia tend to have less grey matter in the left sulcus.

Damage to the region, often from strokes in the posterior middle cerebral artery territory, can impair reaching under visual guidance (optic ataxia), grasping, attention to one side of space, and calculation, depending on side and site. Right-sided lesions particularly produce neglect of the left side of space.

Function and supply

Function

Its cortex links vision with action, guiding eye movements, reaching and grasping, directs voluntary attention, and processes number and visuospatial working memory.

Blood supply

Parietal branches of the middle cerebral artery, with the anterior cerebral artery reaching its upper margin.