Where is the arcuate fasciculus, and what does it join?
The arcuate fasciculus is a bundle of nerve fibres joining the inferior frontal gyrus, which holds Broca’s area, to the back of the superior temporal gyrus, where Wernicke’s area lies. It arches round the back end of the lateral (Sylvian) sulcus, within one hemisphere. [1][2]
A bundle has no shape of its own in this atlas; lit: the two parts it joins.
The 3D brain needs JavaScript. The legend below still names the two parts the arcuate fasciculus joins.
The brain starts seen from the left, where the bundle arches round the back end of the lateral sulcus between its two lit ends. One end is lit in blue (the inferior frontal gyrus), the other in orange (the superior temporal gyrus); the bundle runs between them. Drag to turn, pinch or scroll to zoom; tap a lit part to name it.
The bundle itself is not drawn: BodyParts3D has no shape for any fasciculus, so each end lights the whole gyrus it ends in, on both sides of the brain, not the exact patch of cortex its fibres reach. The arch of fibres between them, under the parietal lobe, is not lit. [3][2]
The two ends: which colour is which
Front end: the inferior frontal gyrus, lit in blue: the inferior frontal gyrus, on both sides of the brain.
In front, its fibres end mostly in Brodmann area 44, the back part of Broca’s area on the inferior frontal gyrus; tractography finds some reaching the lowest part of the precentral gyrus beside it. [1][2][4]
Back end: the superior temporal gyrus, lit in orange: the superior temporal gyrus, on both sides of the brain.
Behind, its main source is the back of the superior temporal gyrus, where Wernicke’s area (Brodmann area 22) lies, behind the auditory cortex on the same gyrus. [1][5]
The bundle runs between the blue and the orange parts; its fibres are not drawn.
Its name is Latin for “curved bundle”. Karl Friedrich Burdach named it about two centuries ago for a bundle running from the frontal to the temporal lobe by arching round the lateral sulcus; the Dejerines drew it passing through the parietal lobe round the sulcus’s back end. [1][2]
It is a long association bundle: association fibres join cortical areas within the same hemisphere, the long ones joining widely separated gyri, the short U-fibres joining gyri next to each other. [6]
It runs beside the superior longitudinal fasciculus, and the two names are sometimes used for one another; they are told apart by where they end in front, the arcuate fasciculus in Broca’s area (area 44), the superior longitudinal fasciculus in the premotor cortex. [1]
Since Norman Geschwind in the 1960s it has been taught as the link between Broca’s and Wernicke’s areas. That model is now mostly considered an oversimplification: diffusion imaging finds its fibres end more widely than once thought, but no satisfactory replacement has been agreed. [1][2]
It is in both hemispheres but not symmetric: the left one is usually stronger. The left is linked with processing complex syntax, the right with prosody, the melody of speech. [1]
It has no myelin at birth; its myelin builds up through childhood, its density rising between about ages 3 and 10. [1]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); it has no shape for any fibre bundle, so a bundle is shown by the two parts it joins.