Where it is
- A bundle of white matter (axons) crossing the midline of the brain, placed in front of the columns of the fornix. [1]
- The fornix columns arch down in front of the interventricular foramina and behind it, on their way to the mammillary bodies. [2]
- From the midline it runs out sideways on each side into the temporal lobes, which it connects across the midline. [1]
What it does
- It interconnects cortical regions of the two temporal lobes, the two amygdalae and the two olfactory bulbs. [1]
- It carries fibres from the olfactory tracts that cross to the other side, which serve the sense of smell. [1]
- With the posterior commissure it links the two cerebral hemispheres; by joining the amygdalae and temporal lobes it contributes to memory, emotion, speech and hearing. [1]
- Honest limit: its function is still not completely understood; researchers have linked it to roles ranging from colour perception to attention. [1]
Connections
- In most mammals the great majority of fibres joining the two hemispheres travel through the corpus callosum; the anterior commissure is a smaller route that can be clearly seen in the brains of all mammals. [1]
- In marsupials, which have no corpus callosum, it is the main route between the hemispheres and carries all the crossing fibres from the neocortex; in placental mammals it carries only some of them. [1][3]
Inside it
- White matter: a tract of nerve fibres (axons), with no nerve-cell bodies of its own. [1]
Other names
- Also called the precommissure; Latin commissura anterior. [1]
Size
- In a side (sagittal) cut it is oval, with a long vertical axis of about 5 mm. [1]
- On this model the anterior commissure measures about 5 mm front to back, 3 mm top to bottom and 24 mm side to side (the box it fits in, not its volume). [4]
- Centre of the anterior commissure compared with the centre of the left fornix: 22 mm further forward, 12 mm closer to the midline; 25 mm apart in a straight line. [4]
- Centre of the anterior commissure compared with the centre of the posterior commissure: 29 mm further forward, 8 mm higher; 30 mm apart in a straight line. [4]