Hemispheric specialization: what is it, characteristics and functioning?

Let us look at the characteristics of hemispheric specialization and how it affects the brain.

The human brain is divided by the sagittal fissure into two halves that can be clearly differentiated and are known as cerebral hemispheres.

These hemispheres are interconnected through bundles of neuronal fibers that belong to the corpus callosum and, although at first glance it seems that both hemispheres are symmetrical, the truth is that they are not.

These differences between the two hemispheres give name to hemispheric specialization.and will be explained in more detail in the following section, but first we will make a brief review of what has been researched on hemispheric specialization, in order to know what this discovery is about.

What is hemispheric specialization?

What is known as hemispheric specialization is the set of anatomical and neurochemical differences, as well as the set of different functions that the left hemisphere anatomical and neurochemical differences, as well as the set of different functions performed by the left hemisphere with respect to the right hemisphere and vice versa.. Hemispheric specialization is also known as lateralization.

Lateralization is composed of the functions and processes that are specific to each hemisphere and, therefore, the capacities that are performed predominantly through one hemisphere would be said to be lateralized.

Hemispheric specialization, or lateralization, of some brain functions, is based on the idea that there are specific regions in the brain that are responsible for carrying out specialized actions..

Another relevant concept in the field of hemispheric specialization is laterality, which should not be confused with lateralization. Laterality is the predominance in the handling of the right extremities or, on the contrary, those of the left side of the body. For example, having a right laterality is what is colloquially known as "being right-handed" or, "being left-handed", in the case of having a left laterality; there being a majority of right-handed people.

Differences between both hemispheres of the brain.

In this section we will see some of the actions performed laterally by each hemisphere, as well as those performed by interhemispheric intervention.

1. Right hemisphere specialization

The right hemisphere is in charge of controlling and receiving the sensations of the left side of the person's body.. According to the most accepted theories on hemispheric specialization, the right hemisphere is capable of processing the information that reaches it in a global and not very methodical way, emphasizing spatial and visual relationships. Therefore, the right hemisphere is considered the creative and intuitive part of the brain.

This hemisphere allows us to perform skills such as having a holistic or global thinking in our mind, which is based on having abstract ideas and also being able to see globally a set of elements that are related to each other (e.g., when painting a picture, we have the ability to imagine an image as a whole and then proceed to paint, step by step, each of the parts that compose it).

The right hemisphere also The right hemisphere also gives us the capacity for intuition, to pick up the non-verbal signals that another person transmits to us, to visualize the emotions that others express, to understand the emotions that others express, and to understand what they are saying.We can also develop our artistic and musical creativity and fantasize.

2. Left hemisphere specialization

The left hemisphere controls and perceives the sensations of the right body part.

The left hemisphere processes information gradually, analytically and systematically.. This hemisphere emphasizes episodic or temporal relationships. Because of these characteristics, the left hemisphere is known to be the analytical and rational part of the human brain.

The left hemisphere is the part of the brain that allows logical reasoning, problem solving and mathematical calculations, linear and sequential thinking, thinking through language and remembering events of the past, as well as thinking about the future.

3. Interhemispheric integration

There is scientific research that has discovered that there are also actions that are performed by mediation of both hemispheres. This is carried out by means of various communication channels found in the corpus callosum that allow them to be interconnected.. These types of operations, which involve both hemispheres, are known as hemispheric integrations.

Interhemispheric integration comes into operation when performing certain tasks, for which it is necessary that there is this interaction between specialized regions found in both hemispheres of the brain.

It is known that when performing activities, which have normally been attributed to hemispheric specialization, it has subsequently been shown that, although to a lesser extent, the other hemisphere is also involved..

For example, when it comes to understanding a metaphor or a saying, being linguistic reasoning tasks, it was known that the left hemisphere was involved; however, it was later discovered that the right hemisphere is also involved.

The same occurs with visuospatial skills (e.g., differentiating between left and right), which are typically associated with the right hemisphere, although the left hemisphere is also involved.

On the other hand, it has been found in research that some people who suffered a severe lesion in one of the hemispheres had certain difficulties in processing information.. For example, patients with a lesion in the right hemisphere have difficulties in attending to the overall shape of objects, while those with a lesion in the left hemisphere were unable to focus on the details of objects, but could identify the complete shape of the object.

Thus, when we analyze an image, such as an artistic painting, we need the coordinated work of both hemispheres. The right hemisphere would allow us to visualize the image represented in the painting in a global and harmonious way, while thanks to the left hemisphere, we could appreciate the nuances of the image, such as the gestures of the characters represented, the clothes and many other details.

In the following section we will briefly explain how we arrived at the knowledge we have today regarding hemispheric specialization.

Historical review of the discovery of hemispheric specialization.

The specialization of each hemisphere emerged as an idea around the year 1860, following the discovery of the French physician Paul Brocawho found that the left hemisphere was essential for the human being to be able to process language.

This occurred when he was treating a patient with a lesion in the left hemisphere and, as a result, he had serious difficulties in speaking, being able to say only the word "tan". Despite this he was able to understand the language heard, demonstrating that he could follow simple commands.

Later, after having seen multiple cases similar to the one reported above, he was able to observe that in all of them there was a lesion in the inferior prefrontal cortex of the left hemisphere, the area that was later known to involve speech production. This is why it was named Broca's area. Thus, a condition in this part of the brain is called Broca's aphasia.

The discovery of the area of the brain that allows the production of speech was confirmed by Karl Wernicke, a German psychiatrist and neurologist, who also discovered another area located in the left hemisphere, more specifically in the temporal lobe, which, being damaged, prevented the patient from understanding language, although he was able to articulate simple sentences. Later, this area was named Wernicke's area. When this area is damaged, the patient's condition is known as Wernicke's aphasia.

The English neurologist John Hughlings Jackson studied different phenomena in which one hemisphere dominated the mental function with respect to the other, calling these cases as Wernicke's aphasia.calling these cases as cerebral dominance. Thus supporting the ideas of Broca and Wernicke, who had demonstrated that language comprehension and production was based on left hemisphere dominance.

In the 1920s, the English neuropsychologist Brenda Milner discovered that a lesion in the temporal area of the right hemisphere led to the inability of affected persons to assimilate new memories into memory, despite the fact that the cognitive abilities of the left hemisphere were not affected.The lesion was found to have been caused by a lesion in the right temporal area of the right hemisphere, although cognitive abilities such as perception, language and reasoning functioned normally.

Roger Sperry conducted the research that was instrumental in promulgating the theory of hemispheric specialization. His research began with a World War II veteran who had been hit in the head by a bomb blast and, as a result, suffered continual epileptic seizures. Then the surgeons who operated on him decided to cut the corpus callosum of his brain and the epileptic seizures disappeared.

However, although he did not suffer any more epileptic seizures, he could not get rid of some side effects. His right hemisphere was the one that was damaged by the operation and, as a result, the patient was not able to control the limbs on the left side. On the other hand, he was able to control the right limbs and he was also able to understand language, since this function is handled by the left hemisphere.

It was after Sperry's discovery that more emphasis began to be placed on the hypothesis that each hemisphere of the left hemisphere had the ability to understand language. the hypothesis that deduced that each hemisphere and each of its areas are specialized in specific functions, without neglecting the functions of the left hemisphere.without neglecting the functions of interhemispheric integrations. This is when the exhaustive work began, which continues to this day, to investigate the functions performed by the areas and hemispheres of the brain, one of the greatest unknowns in the study of the human being.