The collateral sulcus is a long groove on the underside (tentorial surface) of each cerebral hemisphere, running from near the occipital pole to within a short distance of the temporal pole. In front it separates the parahippocampal gyrus on the inner side from the fusiform gyrus on the outer side; further back it runs below and outside the calcarine sulcus, with the lingual gyrus between the two. [1][2]
The 3D brain needs JavaScript. The text below still says where the collateral sulcus is and what it does.
Opens cut down the midline and seen from the left, so you look at the inner face of the right hemisphere: along its underside the parahippocampal gyrus is lit in blue, the fusiform gyrus in orange; turn it to look from below to see the groove between them. The groove runs where blue meets orange; the side (sagittal) slice button cuts across it. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
A groove has no shape of its own; lit: the parts on either side of it. Lit: on the inner side, the parahippocampal gyrus in blue; on the outer side, the fusiform gyrus in orange. In front, the collateral sulcus lies between the parahippocampal gyrus on the inner (medial) side and the front part of the fusiform gyrus on the outer side. Further back its inner bank is the lingual gyrus, which this atlas draws inside the one occipital lobe shape, so only the front stretch’s two banks are lit. It runs on the underside of the brain, so this page opens cut down the midline. [1][2]
Where it is
It is a large groove on the tentorial surface, the underside of the hemisphere, stretching from near the occipital pole to within a short distance of the temporal pole. [1]
Further out, the occipitotemporal sulcus separates the fusiform gyrus from the inferior temporal gyrus, which is why the collateral sulcus is also called the medial occipitotemporal sulcus. [2][1]
What it does
It is a landmark rather than a working part. On its inner bank, the front of the parahippocampal gyrus holds the entorhinal and perirhinal cortices; the entorhinal cortex is a hub for memory, navigation and the sense of time. [3][4]
Named areas straddle it: “parahippocampal cortex” covers the back of the parahippocampal gyrus and the medial part of the fusiform gyrus, on both sides of the groove. [3]
On its outer bank, the fusiform gyrus has parts critical for recognising faces and bodies; the fusiform face area itself lies on the gyrus’s lateral side, away from this groove, at the shallow mid-fusiform sulcus. [2][5]
Other names
Also called the collateral fissure or the medial occipitotemporal sulcus. [1]
Size
The model has no shape for the collateral sulcus, so the groove itself is not measured here. Measured from the model instead: on the left hemisphere, the stretch where the parahippocampal gyrus and the fusiform gyrus come within 3 mm of each other fits in a box about 51 mm front to back, 22 mm top to bottom and 20 mm side to side (the box that stretch fits in, not the groove’s length along its bends or its depth). [6]
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.