The brain and the language

 

he latest discoveries in the field of neuroanatomy, biological development and genetics have radically changed our understanding of brain development. The contributions that have emerged in recent years have questioned not only the classical ideas about size, intelligence and the introduction of new functions, but have also provided tools with which we can prove that the human brain differs from that of other primates in a few aspects.

Although in essence the human brain is not too different from that of other primates, the truth is that there are fundamental differences that explain, to a large extent, the reason for our remarkable capacity and the idiosyncrasy of some of the faculties that allow us to discriminate between us Humans and other species. Among them, language stands out, perhaps the most distinctive element and the one that allows us to excel in the animal kingdom. Moreover, a good part of the other differences that separate us from other species are the result of language evolution.

Theories about the origin

Where do these differences come from? In other words: is language born or made? There are several theories that try to explain how we acquire that capacity.

The formalist school , led by Noam Chomsky, says that in our brain there is a kind of innate template for the structure of language that we have inherited in some way. The formalists believe in the influence of the symbolic capacity in the structure of the language. However, they provide no clue as to how this capability came to our head.

The functionalist alternative has often been raised as opposed to Chomsky’s vision. He affirms that the structure of language is the result of the limitations imposed when communicating. The most radical functionalists, like Elizabeth Bates, consider that in order to execute the language a very powerful device in the head is necessary, a neural network of a certain sophistication.

In the face of theories that consider the language to be internally structured, there is a third option that could be called a systemist . It consists in the idea that language is a complex system in whose structure many inputs participate . The contribution of a template, although minimal, and the ability to process symbolic information are the two aspects that most influence the creation of this system.

Brain evolution

Anyway, there is irrefutable evidence that throughout history the human brain has evolved to some extent linked to the evolution of language.

The formalist view suggests that something similar to a module, a computer program or some type of chip has been literally inserted into the circuits of a normal brain. In other words, we are an ape brain plus a computer language. Regardless of whether or not we accept this comparison, there are reasons to believe that this modularity is soft and not hard. Otherwise it could not evolve.

At the other extreme are those who say that what has made the language possible is that human brains have enlarged in the last 2.5 million years. This argument is based on something similar to adding more computing power, but in my opinion it does not solve the fundamental questions about the structure and characteristics of the language.

The language, engine of change

I think it is more accurate to say that we have an ape brain that has been slightly modified for 2.5 million years, so it works better and better. They have been subtle changes, but they involve anatomical and behavioral qualities. Among them, I would highlight four: 1) the expansion of the domain of prefrontal systems, crucial in the language process; 2) changes in the circuitry of our driving system, which allow us to be able to articulate speech to use combinations of non-innate sounds, manipulate, restructure and produce them quickly; 3) the involvement of the cerebellum, so that the motor system does a mental work of automation, and 4) the involvement of the deep structure of our brain.

Today we know that the anatomical and behavioral adaptations associated with language are located in different parts of the brain and body (for example, changes in the position of the larynx are recorded) and that they are perfectly integrated to carry out a functional optimization. That is why it is difficult to imagine that they could have been due to something other than the evolutionary process.

Its specificity also indicates that these are adaptations subject to a long selection for its contribution to the language. In short, language itself is the main motor of the evolution of the brain since it has directed most of its great changes. However, this does not mean that 2.5 million years ago people did not speak, but that for a long period of time there was a basic form of language (baptized by experts as “protal language”) that was demanding certain functions from brain and that this has been solving.

The term “building a niche” is probably the best way to approach this idea of ​​evolution. Humans have built the symbolic communication niche, which has forced brains to improve and adapt to that niche. In this sense, my thesis is that language and human brains coevolve. They push each other and eventually integrate more and more.

Areas of the brain specialized in language

Each of the brain systems that regulate language acts through the activity of different brain areas. Three of the most important areas are the Broca Area, the Wernicke Area and the Angular Circumvolution .

1. Drill Area

Broca’s area is part of the instrumental system of language. The drill area is related to the ability to order phonemes to create words and then sentences . That is why it is also linked to the use of verbs and other words necessary to interact. When this area is damaged, there is also a syntactic difficulty (relative to the order, the combination and the relationship between the words).

It is called Broca’s area by the person who began his study (Paul Broca) in 1861. What he did was analyze the brain of a person who had had very significant difficulties to express himself verbally, while his understanding of language was apparently functional. He found a tumor in a part of the left cerebral hemisphere, and christened the clinical picture as “epidemic.” Thereafter, this area of ​​the left cerebral hemisphere is known as Broca’s area and is related to disorders in the expressive faculty of verbal language , for example, “Broca’s aphasia.”

Broca’s aphasia: symptoms and causes of this disorder

Since the brain controls or supervises a large part of the functions of our body, damage to different regions of this structure can cause very varied alterations. Aphasias are a type of linguistic disorder that occurs as a result of lesions in brain areas related to language.

In this article we will describe the symptoms and causes of Broca’s aphasia , expressive, motor or production. This neuropsychological disorder consists of the alteration of the expressive language as a result of damage to the frontal lobe, although the auditory understanding is not necessarily affected, as it happens in other types of aphasia.

What is aphasia?

Aphasias are alterations of language that appear because of lesions in certain regions of the brain, mainly due to head injuries and strokes, also called infarcts or strokes. The term is based on classical Greek and translates as “inability to speak.”

There are different types of aphasia that are characterized by idiosyncratic combinations of alterations in four linguistic domains: verbal comprehension, oral expression, functional communication and literacy . Most of them share the presence of anomie, which consists of persistent difficulty in recovering words from memory.

Other common signs and symptoms of aphasias are articulatory and comprehensive deficits, reduced spontaneous language, inability to read and / or write, dysprosodia (changes in tone and rhythm of speech) and the use of neologisms (in psychopathology, words that only have meaning for those who say them).

Therefore aphasias do not only affect spoken language, but also writing and mimicry , including sign language. This is because all these forms of communication depend on the same cognitive functions, related to brain structures and pathways that are damaged in aphasia.

Symptoms and signs of Broca’s aphasia

The basic signs of Broca’s aphasia are related to speech production. People with this syndrome have severe difficulties finding words and articulating sentences fluently, and speech prosody is also affected, which causes speech to be monotonous. The writing is equally affected.

In the context of this disorder , people often speak of “telegraphic speech” to refer to the way they express themselves to those who suffer from it: they pause a lot because they have many difficulties in articulating (or gesturing) words that are not content, that is, they communicate mainly through sequences of nouns and verbs.

The intensity of these symptoms depends on the severity of the injury; while in some cases only mild anomie, moderate reductions in expressive fluency and the phenomenon of “foreign accent” appear, in others the person may be unable to emit any word. In most cases at least the most formulaic expressions are retained.

Since the regions related to Broca’s aphasia are involved in motor skills, it is not surprising that the brain lesions that cause it also cause motor signs. Highlights include hemiparesis (paralysis in one half of the body), apraxia (deficit in propositional movements) and dysarthria, which affects pronunciation .

In a synthetic way we can say that the main characteristics of Broca’s aphasia are the following:

• Lack of fluency in spontaneous language
• Alterations in writing
• Maintenance of listening and reading comprehension
• Word repetition deficit
• Problems remembering words, such as object names (anomie)
• Associated motor disorders (dysarthria, apraxia, hemiparesis)

Causes of this disorder

Broca’s aphasia appears as a result of lesions in the anterior part of the brain, especially in the frontal lobe of the left hemisphere, which plays a more relevant role than the right in the execution of movements, including those that are necessary for speech and writing.

Although the name of the disorder is associated with Brodmann area 44 , known as the “Broca area,” the damage that is limited to this brain region causes only mild linguistic and motor symptoms. The most severe manifestations appear when the lesion extends to surrounding areas, such as the anterior insula, the precentral gyrus and the opercular region.

The most common cause of Broca’s aphasia is ischemic strokes, which consist in the interruption of blood flow, and therefore oxygen, to a certain area of ​​the brain. In this case, the regions affected by oxygen hypoperfusion are those mentioned in the previous paragraph.

With some frequency the brain injuries that cause this type of aphasia are due to other reasons; the most frequent are craniocerebral trauma, cerebral hemorrhages ,  brain tumors located near the language areas and extradural hematomas (accumulations of blood or other fluids between the meninges and the skull).

2. Wernicke area

Wernicke‘s area is also part of the instrumental language system. It helps to evoke and vocalize concepts, and is also responsible for processing the sounds to combine them creating units capable of having meaning .

It is not directly responsible for regulating semantic activity (that of giving meaning to linguistic expressions), but for decoding phonemes. However, when there is damage in this brain area, producing difficulties for discrimination and sound processing, the semantic field is affected.

The regions that make up this area are related to two other brain areas, responsible for regulating motor and premotor activity. The Wernicke area and motor activity zones are connected through a direct corticocortical pathway, and a corticosubcortical pathway. The first way is that which regulates associative learning in a more conscious and voluntary dimension; and the second is linked to automatic behaviors such as habits.

This area is located in the left hemisphere of the brain, around the Silvio fissure and next to the insula cortex . It has been studied since the mid-nineteenth century (with which there are several proposals on where it is located) and was named in honor of the neurologist Carl Wernicke.

Wernicke area: anatomy, functions and disorders

Anatomy and structure of the Wernicke area

 

Wernicke‘s area is a region of the brain that is located at the back of the upper temporal gyrus of the dominant hemisphere , usually the left, with a large number of exceptions among left-handed people. The superior temporal gyrus is located near the primary auditory cortex, as well as the outermost parts of this sensory system.

This area of ​​the brain borders the angular rotation of  the parietal lobe , involved in language, reasoning and memory. The blood supply to the Wernicke region depends on the middle cerebral artery, essential for the transport of nutrients to the cortex as a whole.

There is some disagreement about the exact delimitation of the Wernicke area. Thus, while many experts consider that it is identified with the anterior part of Brodmann’s area 22 of the temporal lobe (involved in the recognition of auditory verbal stimuli according to neurofunctional studies), others place it in the multimodal cortex of the parietal.

Functions of this brain region

This cortical structure was first described by the German neurologist and psychiatrist Carl Wernicke in 1874. This author proposed the existence of a link between the brain region to which its name would be given and the production and imitation of oral language. His hypothesis was based on the analysis of lesions in the superior temporal gyrus and their associated signs.

From this milestone in the field of neuroanatomy, the localizationist vision attributed by the receptive language (that is, the auditory understanding of speech) to the Wernicke area began to consolidate. From this point of view the region is considered the brain center for language comprehension , or at least a very relevant structure in this function.

Among the cognitive functions that were related to the Wernicke area throughout the nineteenth and twentieth centuries are the semantic processing of linguistic information (both in auditory and written format), language recognition and interpretation.

Recent research on language

It is important to mention the relationship between Wernicke and Broca’s area , located in the forebrain and traditionally associated with language production. It has long been believed that the two regions are connected through a set of nerve fibers that are called an “arcuate fascicle.”

However, at present we know that in reality the arched fascicle connects the Wernicke area with the premotor and motor cortex in general, and not only with the  Broca area ; In any case, the uncinate fascicle would be responsible for such interaction. More relevant are the discoveries surrounding the functions of these two regions.

While understanding of language has traditionally been attributed to Wernicke‘s area, recent studies with neuroimaging suggest that this region might be involved rather in speech production . Paradoxically, today it is also believed that Broca’s area can be related mainly to language comprehension and not to its production.

In any case, it is important to note that brain functions are not usually located in a single brain structure. Similarly, language is a very complex function in which large regions and networks that mainly, but not exclusively, play the frontal and temporal lobes play important roles  .

Symptoms of Wernicke’s aphasia

Often lesions in the temporal lobe of the dominant hemisphere of the brain cause a language disorder that has been given the name “Wernicke‘s aphasia” because of its relationship with the area at hand. This alteration has also been called “sensory aphasia”, “receptive”, “understanding” and “fluid” based on its defining characteristics.

People with Wernicke‘s aphasia have difficulty understanding other people’s speech. In addition, and despite being fluent and well articulated, his speech is usually meaningless and full of paraphias , or phoneme substitutions for similar ones. These alterations also occur in written language, which shares brain base with spoken language.

The similarity of Wernicke‘s aphasia symptoms with the language alterations that occur in the context of schizophrenia is striking. Thus, in both disorders we find phenomena such as neologisms (words without shared meaning) and the lack of coherence of the phrases (schizoafasia, paragramatism or word salad) .

3. Angular gyrus

The brain is covered by numerous folds or reliefs that have very important functions and not yet fully known. These folds or reliefs are called convolutions .

One of the convolutions involved in the regulation of language is the angular gyrus, also known as angular gyrus or Broadmann area 39 (AB39). In addition to language, this area participates in the activity of episodic and semantic memory , in mathematical skills, literacy and spatial attention.

Lesions in this area have been related to semantic aphasia. Because of its relationship with the comprehensive activity of language and communication, many scientists believe that this gyrus is an extension or part of the Wernicke Area.