The human brain is an incredibly complex organ: there are about 86 billion neurons and an uncountable number of other cells with an extremely precise position, that make the brain work correctly.
The brain carries out many functions, some of which not yet understood. Sometimes we hear about the discovery of new types of neurons, such as mirror neurons which are involved in the comprehension of someone else’s emotions. This kind of mirror neuron was localized just a few days ago, in april 2019.
The Complexity is also anatomical
The complexity of the human brain is not only functional but also anatomical. Every region of the brain has its own precise function. Certainly, neurons aren’t randomly positioned.
The brain, as well as the spinal cord, has two different substances: grey matter and white matter. The first one is composed of neuron bodies, while the latter by axons.
For more information read also A journey in the Nervous System: the neurons
The grey matter can be found in the cerebral cortex, the most external part of the brain, and in some deep spots, called ganglia, such as basal ganglia or the thalamus.
Neurons need to communicate with each other. This is the primary function of white matter. It is an ensemble of axons, which are nervous fibers covered by myelin. These fibers are able to transport messages very quickly.
The Cerebral Cortex: Lobes and Gyri Division
In Anatomy, the cerebral cortex is divided into lobes and gyri. This division is important because it allows exact descriptions of the different areas of the brain (Brodmann described 52 areas).
The five lobes are: frontal, temporal, parietal, occipital, and insular. Acting as a border among lobes are some fissures. For example, in the middle of the cortex there is the central fissure of Rolando. It is the border between the frontal lobe, placed on the front, and the parietal and temporal one, on the side
During evolution, the human brain has become more complex. For this reason, the brain now has convolutions. They increase the surface of the cerebral cortex without requiring a larger volume. This shape has led to the existence of grooves and giry, that we exploit to identify, with increasing precision the functions of a precise region.
Anteriorly to the central fissure, there is the primary motor cortex, posteriorly, there is the primary somatosensorial one. What does this mean? It means that in the first region, we find neurons that control the planning and execution of movements, whereas, in the second one, we find neurons that receive information from the environment.
As we can see in the picture above, different regions have different functions. The largest part of the occipital lobe, the back part of the brain, is occupied by the visual cortex. Images captured by our eyes are processed by the back part of the brain, we could say that we see thanks to our nape.
Observing Neuron Activation
When our brain receives a stimulus, only some neurons are activated. We can see this activation through devices such as fMRI (functional Magnetic Resonance Imaging), SPECT (Single Photon Emission Computed Tomography) or EEG (Electroencephalography). These technologies allow localizing, for example, the damages of the brain that, depending on their location, will have different consequences on different performances.