For many years psychobiology has tried to establish the biological basis of human behaviour.

Today we know that the nervous system of any person is a control and integration mechanism that regulates and supervises all activities performed by the body. It is divided into two: the central nervous system (CNS) and the peripheral nervous system.

In turn, the CNS is divided into two more substructures: the brain and the spinal cord. Within the brain, there are three substructures: cerebrum, cerebellum and brainstem. Today we will talk about one of them, a very important structure that differentiates us from other species: the human brain .

Human brain and cerebral cortex

The human brain is a complex organ formed by the cortex (lobes) and by different subcortical structures (white substance and grey nuclei). The cortex would be the surface of the brain, which is divided into two: left hemisphere and right hemisphere.

An adult brain weighs approximately 1,500 grams. Although its weight represents only 2% of the body weight, it consumes the same amount of energy as the skeletal muscles at rest.

As for the two hemispheres that divide it, it is known that the right one is more related to visoperception and to a more global perception; the left one would be more related to language, and would be more analytical. However, this distinction is relative, and generally, with few exceptions, both hemispheres of the human brain do everything.

The cerebral cortex is responsible for learning, thinking and decision making , and sends signals to other parts of the brain to allow us to move and communicate. It also uses information from the senses and allows us to interact with and adapt to the world.

The cortex is made up of six cellular layers that allow it to organize the afferences (receiving information) and efferences (sending information) of its neurons (approximately 60 billion).

Your organization in brain lobes

The human brain is made up of 5 lobes (parts of the cerebral cortex with specific functions):

  • Occipital lobe: related to vision.
  • Parietal lobe: related to somatosthetic interpretation.
  • Temporal lobe – related to hearing and memory
  • Frontal lobe: related to higher mental processes, verbal communication and voluntary motor control.
  • Insula: related to memory and sensory (pain) and visceral integration.

Injuries and associated pathologies

The injury of the different cerebral lobes causes diverse pathological consequences, studied by neurology and neuropsychology . Let us look at the most important ones.

Occipital lobe injury

Visual agnosias (failure to recognize objects or people by sight), Anton’s syndrome and Balint’s syndrome.

Parietal Lobe Injury

Constructive apraxia, Gerstmann syndrome, asterognosia (inability to recognize objects by touch).

Temporal Lobe Injury

Impaired hearing and understanding, Klüver-Bucy syndrome.

Frontal Lobe Injury

Impairment of executive functions (dysexecutive syndrome), movement disorders, pseudo-suppression and pseudo-psychopathy.

Ontogenetic development: divisions and structures

The human brain is divided into various structures that arise from three main divisions during gestation and the development of the nervous system.

Prosencephalon (anterior brain, towards the face)

Formed by the telencephalon and the diencephalon . The telencephalon is formed by the cerebral cortex, the basal ganglia and the limbic system (“the center of emotions”); and the diencephalon is formed by the thalamus, hypothalamus, subthalamus, epithalamus, retina and optic nerves.

Midbrain

Formed by a subdivision with the same name, midbrain. This in turn is made up of the tectum, tegméntum and the substantia nigra.

Rhombic brain (rear brain, all the way to the back)

Formed by the midbrain and the myelinebrain. The midbrain is formed by the cerebellum and the bump, and the myelin by the spinal cord .

Differences and similarities between humans and animals

The first difference we find between the human brain and the primate brain, for example, is its size (larger in humans). It is known that the closer the species is to evolutionary humans, the larger their brains are. In addition, the cerebral cortex of the human brain is larger and rougher than that of other animals of the same size.

On the other hand, the human brain has many more cells than those of the brain of other primates, and in addition these show more interconnections, that is to say, they have greater processing capacity.

As for similarities, both in animals and in humans, it is known that within the limbic system already mentioned there is a subcortical structure, the amygdala, which has been consistently related to emotions and aggressive behaviors.

In addition, recent studies reveal that in both animals and humans aggressive behaviour is often associated with a decrease in the activity of serotoninergic neurons.

Bibliographic references:

  • Netter, F. (1989). Nervous system. Anatomy and physiology. Barcelona: Salvat.
  • Carlson, N.R. (2005). Behavioral physiology. Madrid: Pearson Educación.
  • Parra, L., García, A.A., Ortiz, S., Pérez, D., Nájera, J., Basurto, N.E., Espinoza, V. and Rivas, I. (2009). Brain anatomical differences involving functional differences. Rev Fac Med UNAM, 52(4), 177-181.