What’s your favourite brain region?

The human brain, stripped away from the skull, can be held in the palm of one hand. Weighing 1.3 kg on average, it contains approx. 86 billion neurons. These neurons are connected and organised into brain regions that carry out different functions. Structures at the base of the brain are evolutionarily ancient and control vital bodily functions that you don’t need to think about, such as breathing and heart rate and body temperature control. In this course, we are especially interested in the brain regions that are responsible for higher functions, such as learning and memory. My favourite brain region is the cerebellum, which means little brain in Latin.

It sits at the base of the brain at the back of your head, and incredibly, it contains over half the neurons of the brain! So why does the cerebellum have so many neurons? It is in fact a powerful and complex computer that coordinates movement, and is responsible for learning motor skills, such as riding a bike. Like the processor of a computer, the cerebellum is able to perform millions of parallel calculations to coordinate complex muscle movements. Those parallel calculations are performed by neurons that are arranged in repeating tree-like patterns. In this cross section of a rodent cerebellum, you can see this organisation. Look at the beautiful structure revealed by the stained neuronal cell bodies!

But the cerebellum is very old, whereas the hippocampus is one of the evolutionarily recent structures that acts as a processor for a different kind of learning; the learning of facts. The hippocampus is a structure located deep in the brain. In fact, the word hippocampus means seahorse in Greek which reflects its shape. The neurons of the hippocampus are arranged in an organised circuit. The hippocampus receives sensory information and processes it to encode memories. Continuing the computer analogy, the memories formed in the hippocampus are stored in the cortex, which is equivalent to the hard drive. The folds of the cortex maximise surface area and therefore storage capacity.

It has been estimated that the storage capacity of the human brain is equivalent to 10-100 Tb. The cortex is the most evolutionarily recent part of the brain, and its relative size reflects the ability to perform higher functions. In humans it occupies 80 % of the volume of the brain and is responsible for our cognitive abilities being far more advanced than those of other species.