The ability of the human brain to reproduce and comprehend language lies in its neural part. Previously, scientists could only conduct an observation of this phenomenon. Today, thanks to brain imaging technology, it is possible to study the human language abilities at a new level. Methods of brain imaging have provided invaluable assistance to scientists in understanding the processes of interaction of the human brain with language and enabled them to identify parts of the brain related to auditory perception, understanding, and speech production. Research has made it possible to provide even more precise functional division based on those aspects of linguistic processes that are under the control of this area of the brain. This paper aims at observing the Broca area, which contains the information necessary for the reproduction of speech.
The Anatomy of the Cerebral Cortex
The Broca area is one of the main parts of the cerebral cortex. The cerebral cortex is a thin folded layer of neural tissue, which serves as the highest level of the central nervous system and brain function based on the acquired and congenital features that maintain the most advanced organization of personal behavior. Anatomically, the cerebral cortex is divided into right and left hemispheres of the brain. In addition, there are several parts such as the frontal, temporal, parietal, and occipital lobes of the brain share (Flinkera et al., 2014). Commissures coordinate the activity of the two hemispheres of the brain. In the cerebral cortex, there is the alternation of layers containing predominantly neuronal cell bodies. Each neuron is connected via synapses with thousands of other neurons. Different receptors perceive stimuli and transmit energy to the centers of the cerebral cortex in the form of a nerve impulse from the external and internal environment.
Features of the structural and functional organization of the cerebral cortex are associated with the evolution of functions of the central nervous system, namely the transfer of functions of underlying brain structures (Ardila, Bernal, & Rosselli, 2016). However, this does not mean that the cerebral cortex takes over the functions of other structures. Its role is limited to the correction of possible violations of the functions, signal analysis that takes into account individual experience, and the organization of optimal response to these signals. As it keeps the information about the signal, its characteristics, and response to it, it further enables subcortical structures to react to signals in the future. A special feature of the cerebral cortex is that a receptor projects a signal not on one neuron but on the receptive field that is formed by the neuronal connections (Jarrett, 2014). As a result, the signal does not focus on a single neuron but on the set of them.
The Relationship between the Brain and Speech
Speech and brain are closely connected to each other. The history of studying the violations of various forms of speech activity in local brain lesions began in 1861 with the discoveries of French anatomist and surgeon Paul Broca (Flinkera et al., 2014). He showed that the damage caused to the posterior one-third of the first frontal gyrus of the left hemisphere leads to a kind of disease where people lose the ability to speak but retain the ability to understand speech addressed to them. The area of the cerebral cortex became known as the Broca area, and the type of aphasia associated with the damage caused to it was called motor aphasia. Thirteen years later, in 1874, the German psychiatrist Karl Wernicke described another area of the brain of no less importance, which was called the Wernicke’s area (Hickok, Costanzo, Capasso, & Miceli, 2011). He showed that patients with damage caused to the posterior one-third of the first temporal gyrus of the left hemisphere retained the ability to speak but lacked the ability to understand what was said to them. Aphasia caused by the damage in Wernicke’s area was called sensory aphasia (Rogalsky & Hickok, 2011). These discoveries laid the foundation for the clinical study of the cerebral organization of speech activity.
A speech process is based on the number of co-working areas of the cerebral cortex, each of which has its specific meaning for the organization of speech activity. Hence, there is a need for the further search for new areas responsible for other communication functions. The observation that the Broca area is adjacent to the motor cortex and the Wernicke’s area, which is responsible for hearing, gives birth to the assumption that the speech control area correlates with more general behavioral brain areas (Rogalsky & Hickok, 2011). After the discoveries of Broca and Wernicke, scientists enthusiastically continued to search for new speech zones. Thus, recently, specialists from the New York University and NYU Langone Medical Center have proven that both hemispheres are equally involved in speech production (Hickok et al., 2011). Scientists have also identified that, during the hearing and repetition of syllables, neurons are activated in both hemispheres. They have discovered that a language center differs from a speech one. Moreover, it is the center of a high-level information, which provides an understanding of the meaning of words.
The Functions of the Broca Area
As mentioned earlier, the Broca area is a part of the cerebral cortex involved in performing language functions, which sends signals to the motor field in order to set the tongue, lips, and speech muscles in motion, as well as to pronounce words aloud (Flinkera et al., 2014). This part of the brain controls verbal, writing, and speech processes. However, today, it is generally accepted that it is not a speech center since many different areas of the brain are involved in the regulation of speech behavior, and the Broca area is only one of them. Admittedly, different parts of the brain control a variety of speech processes. Thus, reading aloud or silent reading is controlled by different brain areas.
Until recently, it was considered that the speech center that allows perceiving and pronouncing sounds is located in the left hemisphere of the brain. However, experts from the New York University proved that both hemispheres are equally involved in the production of speech (Jarrett, 2014). The damage caused to the Broca area leads to motor speech disorders. They are commonly observed in children; however, this phenomenon also occurs in adults. Despite the discussion, which this theory arouses in scientific circles, there is a reason to accept the motor mechanism of speech perception (Ardila et al., 2016). It is known that Wernicke’s center is closely related to motor speech in the Broca area, forming a single complex. Consequently, the correlation of auditory reception with speech motor skills is the basis for the child’s speech acquisition, learning foreign languages, art, singing, and other processes. The damage in this center results in Broca’s aphasia, which is characterized by the impossibility of combining separate voice movements in a single speech act.
The Broca area contains the information necessary for the reproduction of speech, and it is responsible for human speech. Thus, the ability of the human brain to reproduce and comprehend language is linked to the Broca area that is located in the left hemisphere. However, there are speculations that both hemispheres are responsible for speech, and this hypothesis needs further investigation. Admittedly, this area is closely connected to the Wernicke’s area. Any damage in these areas leads to speech disorders that result in the violation of speech.