The nucleus basalis (of Meynert) is a group of large acetylcholine-making neurons in the basal forebrain. Its main body lies under the anterior commissure and the globus pallidus and to the side of the front of the hypothalamus, in an area called the substantia innominata; one on each side. [1]
The 3D brain needs JavaScript. The text below still says where the nucleus basalis is and what it does.
The globus pallidus and hypothalamus are lit together; the nucleus basalis is not drawn on its own. The front (coronal) slice button cuts through them. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
Not a separate shape in this atlas; lit: the part that holds it. Lit: the whole globus pallidus and hypothalamus, on both sides. The nucleus basalis lies between these two lit parts: below the globus pallidus and beside the front of the hypothalamus. It is a loose cluster of cells and has no shape of its own in the BodyParts3D model (nor does the substantia innominata that holds it), so nothing is drawn at a guessed point. [1][2]
Lit here: the globus pallidus and the hypothalamus, the parts the nucleus basalis lies between — see each on its own page.
It sits in the substantia innominata, a layered strip of grey and white matter under the front of the thalamus and the lentiform nucleus (the putamen and globus pallidus together), part of the anterior perforated substance on the underside of the brain. [2][1]
It is one of the basal forebrain structures, which lie in front of and below the striatum and also include the nucleus accumbens, the ventral pallidum, the diagonal band of Broca and the medial septal nucleus. Towards the front it runs on into the cholinergic cells of the nucleus of the diagonal band. [3][1]
It is diffuse rather than sharply bounded: stray neurons of it lie in the inner layers of the globus pallidus and in the bend (genu) of the internal capsule. [1]
What it does
Acetylcholine for the cortex: most of its neurons make acetylcholine and project widely to the neocortex, and the basal forebrain is the main source of the acetylcholine that reaches the neocortex, the hippocampus and the amygdala. [1][3]
Attention: the acetylcholine of the basal forebrain modulates the overall activity of the cortex, possibly leading to greater attention to sensory stimuli; its neurons fire to arousing events, both rewarding and unpleasant, and help sustain attention. [4][1]
Learning and memory: the basal forebrain contains nuclei that are important in learning and memory, and the nucleus basalis is seen as a key node in the memory circuit. [4][3]
Wake and sleep: activating the basal forebrain’s cholinergic, GABA-releasing or glutamate-releasing neurons promotes wakefulness. [3]
Connections
Its axons spread to the whole neocortex; in the visual cortex they boost the input arriving from the eyes while damping signals passed between cortical areas, so a new stimulus gets full attention. [1]
Other names
Named after Theodor Meynert, who described it; also called the nucleus basalis magnocellularis, for its large (magnocellular) cells. It is a different thing from the “basal nuclei”, the textbook name for the basal ganglia. [1][4]
Size
The model has no shape for the nucleus basalis itself, so it is not measured here. The left globus pallidus that holds it measures about 29 mm front to back, 17 mm top to bottom and 17 mm side to side on this model (the box it fits in, not its volume). [5]
The model has no shape for the nucleus basalis itself, so it is not measured here. The hypothalamus that holds it measures about 18 mm front to back, 20 mm top to bottom and 17 mm side to side on this model (the box it fits in, not its volume). [5]
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.