Language
" By limiting oneself to the purely physiological study of language, one risks never penetrating to that internal faculty of which language is the manifestation or the external sign" Müller, 1861.
Language [3, 4, 57] is the function that allows us to communicate with others. Whether spoken, written, or signed, communication plays a vital role in our lives. Indeed, through language, we can express our thoughts, needs, and desires; we can inform others and inform ourselves about potential threats or dangers. Without language, there would be no history or progress... In short, language is at the heart, if not at the pinnacle, of the cognitive functions most important to humans [5].
Language and languages :
Language is our faculty to encode and decode abstract or concrete elements through a sequence of signs and symbols understood by others. These signs are structured in a precise way to form meaningful expressions. The set of these signs and the rules of their structure constitute a language. Today, there are more than 6,000 languages across the planet [173] - 1,000 languages in New Guinea alone [174].
The number of symbols and words in a any language is not infinite. However, through their various combinations into sentences, one can form an infinite number of expressions. This shows just how powerful language really is.
The brain's ability to recognize particular words in someone's verbal stream is remarkable. One only needs to listen to a foreign language to realize the difficulty of isolating its constituent elements. A person speaking their native language does not isolate words with silences, like the spaces separating written words, and yet our brain recognizes them individually and assigns them meaning.
Phonatory apparatus :
To be able to speak, we possess a highly sophisticated phonatory apparatus [175]. The human vocal apparatus can be compared to a wind and string musical instrument [175]. It includes a wind source: the lungs (the generator); a vibrating structure: the vocal cords in the larynx (the vibrator); and a series of resonance chambers formed by the pharynx, the mouth, and the nasal cavities (resonator or amplifier). The transformation of laryngeal sound into speech is then completed by the position of the soft palate, tongue, lips, and teeth, which act as modulators of the emitted sound.
Cerebral language areas :
There are two brain regions strongly involved in language: Wernicke's area and Broca's area [41, 74].
Wernicke's area :
This area is located in the temporal lobe, just beside the primary and secondary auditory cortex. It ensures the comprehension of language elements. Wernicke's area receives information from the auditory area for spoken language, analyzes it, and sends impulses to Broca's area via the arcuate fasciculus.
The arcuate fasciculus :
Recent studies have shown that the arcuate fasciculus actually connects Wernicke's area to the region of the primary motor cortex [198] located behind Broca's area, rather than terminating directly on it. It is the lateral portion of the superior longitudinal fasciculus that communicates between Wernicke's area and Broca's area via the supramarginal gyrus [198].
Broca's area :
Located in the frontal lobe, Broca's area is responsible for language expression. It is connected to the primary motor area that controls the contractions of various body muscles, particularly those of the larynx involved in speech.
Cerebral lateralization :
Language is most often under the control of only one of the two brain hemispheres [41], referred to as the dominant hemisphere [50]. This phenomenon is one aspect of the general asymmetry of brain function known as cerebral lateralization [166].
The dominant hemisphere is almost always the left (in 90% of cases [96]) in right-handed people. In left-handed people, brain physiology is both more variable and less understood; the dominant hemisphere is often the left, but sometimes the right. In other cases, lateralization seems less distinct, and the two hemispheres appear more balanced [4].
However, this categorical view of a dominant hemisphere for language is far from absolute. Recent studies have demonstrated the important role of the right hemisphere in intonation (prosody) [41] - the faculty by which one can formulate the same sentence in various ways to convey completely different meanings. It allows for the transformation of a statement into an order, a wish, or a question.