The forebrain (prosencephalon) is the front and top of the brain and the largest of its three main divisions: the cerebrum (the cortex of both hemispheres, the hippocampus and the basal ganglia) plus the diencephalon at its core (thalamus, hypothalamus, epithalamus). Its modelled parts are lit together. [1][2][3]
The 3D brain needs JavaScript. The text below still says where the forebrain is and what it does.
All 13 are lit together, on both sides where they are paired; tap a name in the list to focus one. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
The model draws the cerebral cortex as its five lobes (frontal, parietal, temporal, occipital and the insula), so when everything is lit the lobes hide the deep members; tap a name in the list, or use the side slice, to see them. The cerebrum’s white matter (the corpus callosum, internal capsule and other tracts) belongs to the forebrain too but is left dark here, so the lit set shows its grey-matter parts. [2][4]
Not lit: the subthalamus (below the thalamus) and the olfactory bulb (under the front of the frontal lobe). Both belong to the forebrain, but neither is a separate shape in this 3D model, so no marker is placed at a guessed position. [1][2][4]
Also part of it, each lit on its own page: cerebrum.
Part of: the three divisions of the brain, each lit on its own page: the forebrain (this page), the midbrain and the hindbrain. The forebrain is the front and top division; the midbrain lies behind and below it, and the hindbrain behind and below the midbrain. [1][5]
Where it is
It is the rostral (forward-most) of the three divisions: in the adult brain it is the cerebrum and the diencephalon, which sit in front of and above the midbrain. [1][5]
The cerebrum consists of the cerebral cortex, the white matter under it and the basal ganglia; its subcortical structures include the hippocampus and the olfactory bulb. [1][2]
What it does
Wikipedia sums up the whole division: the forebrain controls body temperature, reproductive functions, eating, sleeping and the display of emotions. [1]
The thalamus relays almost every sensory signal on to the cerebral cortex (smell is the main exception), and the hypothalamus is largely involved in regulating homeostasis. [6][7]
Inside it
In the embryo the forebrain vesicle divides into two: the telencephalon, which becomes the cerebrum, and the diencephalon, which gives rise to the thalamus and hypothalamus among other structures. At about 8 weeks the forebrain splits into the left and right cerebral hemispheres. [3][1]
Other names
Prosencephalon is its embryological name, which OpenStax notes can be loosely translated as forebrain. [3][1]
Telencephalon, also called the cerebrum or endbrain: the cortex drawn here as the frontal lobe, parietal lobe, temporal lobe, occipital lobe and insula, with the hippocampus, caudate nucleus, putamen and globus pallidus beneath it. [2][3]
Diencephalon, the core of the forebrain: the thalamus, hypothalamus, pineal gland and habenula (the subthalamus is not drawn). [1][8]
Size
On this model the forebrain together fit in a box about 180 mm front to back, 117 mm top to bottom and 141 mm side to side (the box they fit in, not their volume). [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.