The supramarginal gyrus is the front part of the inferior parietal lobule in each hemisphere, arching over the upturned back end of the lateral (Sylvian) fissure. It corresponds to Brodmann area 40. [1][2]
The 3D brain needs JavaScript. The text below still says where the supramarginal gyrus is and what it does.
Slice
Opens cut by a front (coronal) slice through the supramarginal gyrus. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
Takes part in: speech, reading — see every part of each lit together.
Where it is
The inferior parietal lobule, below the intraparietal sulcus, is made of two gyri: the supramarginal gyrus in front and the angular gyrus behind it. [2]
It is continuous in front with the postcentral gyrus and, around the end of the lateral fissure, behind and below with the superior temporal gyrus. [2]
Above it, the intraparietal sulcus separates it from the superior parietal lobule. [2][3]
Paired: there is one supramarginal gyrus in each hemisphere; this model lights both. [1][4]
What it does
It is part of the somatosensory association cortex, which interprets touch and is involved in perceiving space and where the limbs are. [1]
It helps identify the postures and gestures of other people, and so is counted as part of the mirror neuron system. [1]
It takes part in language perception and processing; both sides are active when people make choices about the sounds of words. [1][5]
The right supramarginal gyrus appears to help people set their own feelings aside when judging someone else’s (overcoming emotional egocentricity), a part of empathy. [1]
Connections
A branch of the superior longitudinal fasciculus (SLF III) runs from the supramarginal gyrus forward to the ventral premotor and prefrontal cortex. [6]
Touch information reaches the parietal lobe through the thalamus and the primary somatosensory cortex on the postcentral gyrus, directly in front of it. [7]
Other names
SMG; Brodmann area 40 (BA40). With the angular gyrus it forms the inferior parietal lobule. [8][2]
Size
On this model the left supramarginal gyrus measures about 38 mm front to back, 42 mm top to bottom and 46 mm side to side (the box it fits in, not its volume); the right one is its mirror image. [4]
Centre of the left supramarginal gyrus compared with the centre of the left angular gyrus: 30 mm further forward, 10 mm higher, 7 mm further from the midline; 32 mm apart in a straight line. [4]
Centre of the left supramarginal gyrus compared with the centre of the left postcentral gyrus: 4 mm further back, 15 mm lower, 15 mm further from the midline; 22 mm apart in a straight line. [4]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); real brains vary in size and shape, so its measurements describe one model, not anyone’s brain.