All parts of the brain › Septum (septum of telencephalon)

Where is the septum (septum of telencephalon)?

The septum is on the midline of the brain between the two cerebral hemispheres, under the front of the corpus callosum and in front of the lamina terminalis: the septal area, which holds the septal nuclei. The 3D atlas names this shape the septum of telencephalon. [1][2]

The 3D brain needs JavaScript. The text below still says where the septum (septum of telencephalon) is and what it does.

Slice

Opens cut by a side (sagittal) slice through the septum (septum of telencephalon). Drag to turn, pinch or scroll to zoom, tap any part to name it; .

Cells inside it make acetylcholine: where it is made and where it is sent.

Part of the limbic system — see the whole of it lit.

Next to it, each lit on its own page: corpus callosum, fornix, lateral ventricles.

Where it is

The septal area lies in the lower, back part of the inner (medial) surface of the frontal lobe, underneath the corpus callosum and in front of the lamina terminalis. [1]
The lateral ventricles sit on either side of it, and the thin sheet of the septum pellucidum runs from the corpus callosum down to the fornix, between the front horns of the two lateral ventricles. [3]
How the septum pellucidum relates to what is lit: the septum pellucidum is located in the septal area, and the atlas draws that region as one shape it names only “septum of telencephalon”, so this page names the lit shape the atlas’s way rather than calling it the septum pellucidum. [3][2]

What it does

The septal nuclei here are essential in generating the theta rhythm of the hippocampus. [1]
The septal nuclei play a role in reward and reinforcement along with the nucleus accumbens; the lateral septum is involved in emotional, motivational and spatial behaviour. [1]
The septum pellucidum separates the front horns of the left and right lateral ventricles. [3]
Despite its other name, the medial olfactory area, the septal area has no relation to the sense of smell. [1]

Connections

The septal nuclei have two-way connections with the olfactory bulb, hippocampus, amygdala, hypothalamus, midbrain, habenula, cingulate gyrus and thalamus. [1]
The dorsal septum projects to the lateral preoptic area, the lateral and periventricular hypothalamus and the midline thalamus; fibres from the ventral half reach the hippocampal formation, thalamus, hypothalamus and midbrain. [1]
Acetylcholine, crucial for encoding memories, reaches the hippocampus from the medial septum through the fornix, and so do the theta rhythms generated in the septal nuclei. [4]
The stria medullaris carries fibres from the septal nuclei to the habenula. [5]

Inside it

It consists of the lateral septum and the medial septum; the septal nuclei fall into dorsal, ventral, medial and caudal groups. [1]
The septum pellucidum is a thin, triangular, vertical double sheet of two layers of white and grey matter; in most people the small space between the layers (the cave of the septum pellucidum) disappears in infancy. [3]

Other names

The atlas names this shape “septum of telencephalon” (Latin septum telencephali); the region is the septal area, also called the medial olfactory area. [2][1]
Septum pellucidum is Latin for “translucent wall”; its sheet is also called the lamina septi pellucidi. [3]

Size

On this model the septum (septum of telencephalon) measures about 62 mm front to back, 23 mm top to bottom and 20 mm side to side (the box it fits in, not its volume). [2]
Centre of the septum (septum of telencephalon) compared with the centre of the corpus callosum: 12 mm further forward; 12 mm apart in a straight line. [2]
Centre of the septum (septum of telencephalon) compared with the centre of the left fornix: 16 mm further forward, 14 mm higher, 12 mm closer to the midline; 24 mm apart in a straight line. [2]

Sources

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.