One of the first things to strike you when studying neuroanatomy is the dizzying amount of jargon. Our brain’s incredible complexity has seen generations of neuroscientists build up an exhaustive list of terminology for different brain regions and cell types. Whilst at the most basic level, our nervous system is divided up into a central nervous system (CNS), comprising the brain and spinal cord, and a peripheral nervous system (PNS), made up of the nerves that relay information from our body to the CNS.
Before we can get to identifying all these brain regions, it makes sense to get a grip on the terms that neuroscientists use to denote directions in the brain. As it turns out, “up”, “down”, “left” and “right” aren’t quite up to the task.
A broader term often used here is neuraxis or neuroaxis, which refers to the overall direction in which a nervous system is arranged. The neuraxis is shaped during neurodevelopment.
A simple life with a fish brain
If we all had fish brains, things would be easier. Not just because issues like socioeconomic policy would be less pressing if eating plankton was our number one goal in life, but because in the straight, smooth fish brain, there are only four basic directions you need to get around:
- Rostral – towards the fish’s mouth
- Caudal – towards the fish’s tail
- Ventral – towards the fish’s belly
- Dorsal - towards the fish’s back
This is because the fish brain lines up quite nicely with the body it is housed in – they have a linear nervous system. The human brain, however, is positioned at a 90° angle to the rest of our body, so things are a bit more complicated.
Directions in the brain
We retain the terminology used in the fish brain for our human one:
- Rostral – towards the mouth and eyes
- Caudal – towards the back of the head
- Ventral – towards the neck
- Dorsal - towards the top of the head
But we add a few more layers of directionality:
- Anterior – from Latin ante, meaning before – is equivalent to rostral
- Posterior – from Latin post, meaning after – is equivalent to caudal
- Inferior – from the Latin inferus, meaning lower – is equivalent to ventral
- Superior – from Latin super, meaning higher – is equivalent to dorsal
But wait, there’s more!
Looking at the brain from the front – sorry, anterior – end, structures towards the middle of the brain (in line with your nose) are called medial, whilst structures at the sides, towards the ears, are called lateral.
If you are in the spinal cord, below the brain, things are now flipped, to be in line with the rest of the body
- Rostral, which in the spinal cord is now equivalent to superior – towards the head
- Caudal/inferior – towards the towards the feet
- Ventral/anterior – towards the abdomen
- Dorsal/posterior – towards the back or vertebra
Spinal cord directionality is also used for certain brain structures in the brainstem, including the midbrain, pons and medulla.
Still with us? Let’s look at ways we can cut the brain up based on planes:
Planes of the brain
Coronal/frontal plane: Divides the brain into front and back sections. A cut in this center of this plane chops the brain in half between the nose and the back of the head.
Axial/horizontal plane: Divides the brain into top and bottom sections. A cut through the center of this plane chops the brain in half between the top of the head and the neck. Imagine your brain is a double decker bus going through a tunnel that has a low roof and you’ll get the right idea.
Sagittal plane: Divides the brain into left and right sections. A cut through the center of this plane would chop the brain into two hemispheres, between your ears. A cut that does not go through the center of this plane is termed parasagittal.