Hemispheric Specialization: What It Is, Characteristics And Operation
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 appears that both hemispheres are symmetrical, the truth is that they are not.
These differences between both hemispheres give name to hemispheric specialization and they will be explained in more detail in the next section, but first a brief review will be made of what has been investigated about hemispheric specialization, with the aim of knowing what this discovery is about.
What is known as hemispheric specialization is the set anatomical and neurochemical differences, in addition to the set of different functions performed by the left hemisphere with respect to the right and vice versa Hemispheric specialization is also known as the concept of lateralization.
Lateralization is made up of the functions and processes that are specific to each hemisphere and, therefore, the abilities that are carried out predominantly through one hemisphere would be said to be lateralized.
The 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 management of the right extremities or, on the contrary, those of the left part of the body. For example, having right laterality is what is colloquially known as “being right-handed” or “being left-handed,” in the case of having 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 that each hemisphere performs laterally, as well as those that are carried out through interhemispheric intervention.
1. Right hemisphere specialization
The right hemisphere is responsible for controlling and receiving sensations from 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 comes to it in a global and unmethodical 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 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., time). painting a painting, 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 too It enables us to have the capacity for intuition, to capture the non-verbal signals that another person transmits to us, to visualize the emotions that others express perform 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 carries out information processing in a gradual, analytical and systematic way This hemisphere emphasizes episodic or temporal relationships. Due to these characteristics, it is known that the left hemisphere makes up the analytical and rational part of the human brain.
The left hemisphere is the part of the brain that allows us to carry out logical reasoning, solve mathematical problems and calculations, carry out linear and sequential thoughts, thoughts through language and remember events from the past, as well as think about the future.
3. Interhemispheric integration
There is scientific research that has discovered that there are also actions that are carried out through both hemispheres. This is carried out through various communication channels that are found in the corpus callosum and 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 be this interaction between specialized regions found in both hemispheres of the brain.
It is known that when carrying out activities, which have normally been attributed to hemispheric specialization, it has subsequently been possible to verify that, although to a lesser extent, the other hemisphere also intervenes
For example, when it comes to understanding a metaphor or a saying, as they are linguistic reasoning tasks, it was known that the left hemisphere intervenes; However, it was later discovered that the right hemisphere also intervenes.
The same is true for visuospatial skills (e.g., differentiating between left and right), which are typically associated with the right hemisphere, although the left hemisphere also participates.
On the other hand, it has been found in research that Some people who suffered a serious injury to one of the hemispheres had certain difficulties when processing information For example, patients who had a lesion in the right hemisphere presented difficulties in attending to the global shape of objects; while those who had a lesion on the left were unable to focus on the details of the objects, but they could identify the complete shape of the object.
In this way, 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 clothing and many other details.
The following section will briefly explain how the current knowledge regarding hemispheric specialization was reached.
Historical review of the discovery of hemispheric specialization
The specialization of each hemisphere It emerged as an idea around the year 1860, following the discovery of the French doctor Paul Broca who found that the left hemisphere was essential for humans to process language.
This happened when I was treating a patient with a lesion in the left hemisphere and, therefore, he had serious difficulties speaking, being able to only say the word “tan”. Despite this she was able to understand the language heard, demonstrating that she could follow simple commands.
Subsequently, after having seen multiple cases similar to the one previously reported, 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 the production of speech. For this reason 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 speech production was confirmed by Karl Wernicke, a psychiatrist and neurologist of German origin, who also discovered another area located in the left hemisphere, more specifically in the temporal lobe that, when injured, It prevented the patient from understanding language, even though he was able to articulate simple sentences. Later, the said area was named Wernicke area. When this area is injured, the patient’s condition is known as Wernicke’s aphasia.
The English neurologist John Hughlings Jackson studied different phenomena in which one hemisphere dominated mental function with respect to the other , calling these cases cerebral dominance. In this way supporting the ideas of Broca and Wernicke, who had shown that the understanding and production of language was based on a dominance of the left hemisphere.
In the 1920s, English neuropsychologist Brenda Milner discovered that a lesion in the temporal area of the right hemisphere caused affected people to be unable to assimilate new memories into memory despite the fact that cognitive abilities such as perception, language and reasoning functioned completely normally.
Roger Sperry carried out the research that was decisive in promulgating the theory of hemispheric specialization. His research began with a World War II veteran who had suffered head injuries from a bomb explosion and, as a result, continually suffered epileptic seizures. Then the surgeons who operated on him decided to cut the corpus callosum from his brain and the epileptic seizures disappeared.
However, despite no longer suffering from epileptic seizures, I cannot get rid of some side effects. His right hemisphere was the one that was badly damaged by the operation and, because of this, the patient was not able to control the limbs on the left side. On the other hand, he could control his right limbs and was also capable of understanding language, since this function is managed by the left hemisphere.
It is after Sperry’s discovery that more emphasis began to be placed on the hypothesis that deduced that each hemisphere and each of its areas are specialized in specific functions , without leaving aside the functions of interhemispheric integrations. This is when the exhaustive work began, which continues to this day, of investigating the functions performed by the areas and hemispheres of the brain, one of the greatest unknowns about the study of human beings.
