The left cerebral hemisphere constitutes the left region of the brain. Anatomically it is identical to the right hemisphere, but it has a series of differences both in its functioning and in the activities it performs.
The left hemisphere is characterized by presenting a much more analytical, detailed and arithmetic functioning than the right hemisphere . Likewise, there is currently a high consensus in naming it as the linguistic hemisphere of the brain.
The term cerebral hemisphere designates each of the two structures that make up the largest region of the brain .
The brain can be divided into two large regions: the left hemisphere and the right hemisphere. Both structures are connected and work together to provide comprehensive brain function.
Anatomical properties of the left hemisphere
The left hemisphere constitutes the left region of the brain . It is an inverse portion to the right hemisphere, but not inversely symmetrical. As with the rest of the body, the left side of the brain is asymmetrical with respect to the right side.
The left hemisphere is separated from the right hemisphere by a deep sagittal fissure located in the midline of the brain. This fissure known as the interhemispheric or longitudinal cerebral fissure allows to establish the anatomical differentiation between both hemispheres of the brain.
The interhemispheric fissure contains a fold of the dura mater and anterior cerebral arteries. In the deepest region of the fissure is the corpus callosum , a commissure formed by a conglomeration of white nerve fibers.
The function of the corpus callosum is to connect both hemispheres by crossing the midline and transferring information from one side to the other. In this way, the left hemisphere works in conjunction with the right hemisphere, thus providing comprehensive and joint brain activity.
Like the right hemisphere, the left hemisphere can be divided into four large cerebral lobes : the frontal lobe located in the frontal part of the skull, the occipital lobe that is in the posterior region (above the nape), the parietal lobe that It is located in the upper region of the brain, and the temporal lobe found in the medial region.
The two cerebral hemispheres are characterized by being very similar to each other. Anatomically they are not symmetrical but they are very similar. In the following image you can see both hemispheres, the left hemisphere being lilac or purple:
Each of the hemispheres encompasses a proportional part of the brain’s structures. For example, the frontal lobe is divided into two parallel regions (one is located in the right hemisphere and another in the left hemisphere).
When speaking of cerebral hemispheres, we do not refer to different brain structures, since each one of them includes a portion of the same brain regions.
However, the left hemisphere is characterized by presenting a series of unique attributes. That is, it presents a series of characteristics different from those of the right hemisphere.
In this sense, the left hemisphere is interpreted as the linguistic cerebral hemisphere, since it is the portion of the brain that plays a more important role in the development of these types of activities.
The main characteristics of the left cerebral hemisphere are:
The left hemisphere uses words to name, describe, and define interior and exterior elements.
Unlike the right cerebral hemisphere, the left hemisphere takes a leading role in the performance of activities related to language and verbal memory .
The left hemisphere uses, apart from language, symbols to represent external objects.
For example, the + sign represents the process of addition and the symbol – the process of subtraction. The association between these symbols and their meanings are activities carried out by the left cerebral hemisphere.
The left cerebral hemisphere presents an analytical functioning of things. Study the elements step by step and part by part. It uses inductive rational methods, and allows the development of analytical and descriptive thinking of people.
The left hemisphere also takes a leading role in the detailed and objective analysis of the elements. It allows specific observations and develops concrete thinking.
The functioning of the left hemisphere is characterized by taking a small piece of information and using it to represent the whole.
As represented in the rest of the characteristics, it adopts an analytical character that allows to go from the most concrete to the most general.
The left cerebral hemisphere is in charge of following the passage of time. Order things in temporal and situational sequences. Analyze the elements starting at the beginning and adopt an organized and sequential operation.
Above all, the left cerebral hemisphere is characterized by providing rational thinking about things. It allows to abstract conclusions based on the reason and the data specifically examined.
The left brain also uses numbers. For example, take an active role in counting.
The conclusions drawn by the left brain are always based on logic: one thing follows another in a logical order.
For example, mathematical problems or reasoned arguments are activities that define well the functioning of this cerebral hemisphere.
Finally, the left brain is characterized by thinking in terms of linked ideas. The elaboration of one thought follows another, so it usually generates convergent conclusions.
Speech, writing, logic, math
The left cerebral hemisphere forms the motor region that is capable of recognizing groups of letters forming words, as well as groups of words forming sentences.
In this way, it carries out activities related to speech, writing, numbering, mathematics and logic, which is why it is named as a verbal hemisphere.
Faculty of expression and understanding
On the other hand, it is responsible for developing the necessary faculties to transform a set of information into words, gestures and thoughts. In this sense, the neurologist Hughlins Jackson described the left hemisphere as the center of the power of expression.
The left hemisphere is responsible for storing concepts that are later translated into words. That is to say, it does not work as a textual memory, since it allows adding meaning to the elements of expression.
The left hemisphere understands ideas and concepts, stores them in a non-verbal language, and subsequently translates these elements into a specific language or language.
More specifically, the left hemisphere specializes in articulated language, motor control of the articulating fundus apparatus, handling of logical information, proportional thinking, processing of serial information, and handling of mathematical information.
Likewise, it plays a major role in verbal memory, grammatical aspects of language, organization of syntax, phonetic discrimination, focused attention, planning, decision-making, time control, execution and memory. long-term among others.
Evaluation of the left hemisphere
The functioning of the left cerebral hemisphere is evaluated by means of intelligence tests. In fact, intellectual performance tests primarily assess the functioning of this hemisphere and examine less the performance of the right cerebral hemisphere.
Specifically, intelligence tests that investigate vocabulary, verbal comprehension, memory and mental arithmetic calculation allow examining the performance of the left brain.
Relationship with the right cerebral hemisphere
Although the left cerebral hemisphere has a number of specific functions, this does not mean that these activities are performed by this part of the brain alone.
In fact, both hemispheres of the brain can participate jointly in the performance of all brain activities. However, in some the left hemisphere takes on a greater role and in others the right hemisphere does.
In this sense, functional differences between hemispheres are minimal, and only in certain brain areas have it been possible to connote distinctions about functioning.
The differences between hemispheres seem to be an exclusive faculty of human beings. Several authors have pointed out that such differentiation exists since language and logic (left hemisphere) require more orderly and sophisticated thought processes than, for example, spatial orientation (right hemisphere).
The two hemispheres of the brain are complementary in most people. Speech is an activity regulated mainly by the left hemisphere, however, about 15% of left-handed individuals and 2% of those who preferentially use the right hand, have the speech centers in both parts of the brain.
Likewise, during the first years of life, people have the potential to develop the speech center in both hemispheres. Thus, a lesion in the left hemisphere in young people results in the development of the language faculty in the right hemisphere.
Finally, emotional processes and the generation of emotions are activities that are carried out equally in both cerebral hemispheres, since they are produced by the limbic system of the brain.
- Anderson, B .; Rutledge, V. (1996). “Age and hemisphere effects on dendritic structure”. Brain. 119: 1983-1990 .
- Boller, and Grafman, J (2,000). Handbook of Neuropsychology. Ed. Elsevier.
- Goldberg, E (2002). The Executive Brain: Frontal Lobes and the Civilized Mind Critique, cop. 2002.
- Jódar, M (Ed) et al (2013). Neuropsychology. Barcelona, Editorial UOC.
- Snell, Richard S. (2009) .Clinical Neuroanatomy (Clinical Neuroanatomy for Medical Students (Snell)). Hagerstwon, MD: Lippincott Williams & Wilkins. p. 262.