It is located in Brodmann area 21 and 22, which corresponds to the posterior segment of the upper temporal gyrus of the dominant hemisphere, which for 95% of people is the right hemisphere, and includes the auditory cortex on the lateral groove.
Areas 21 and 22 of Brodmann represent the focal point of the Wernicke area, although other areas are also involved in the language understanding process. In fact, in this case, it is necessary to include also areas 20, 37, 38, 39 and 40, involved in the processes of word composition and other types of additional linguistic information.
The Wernicke area is closely linked to the primary auditory cortex, which plays an important role in the understanding of spoken language. Moreover, at an anatomical level, there are numerous connections between the Wernicke area and the Broca area; the latter is mainly devoted to the understanding of language. These two areas, Wernicke and Broca, are connected by a series of files that in turn merge into the arched file.
Wernicke area: what functions does it have?
The functions performed in the Wernicke area are:
- Understanding of language, both written and spoken;
- Management of language semantics, transforming words into their meaning.
- Planning of speech production.
These functions represent the basis of language understanding and are the basis of communication.
Wernicke area: what happens in case of injuries?
Injuries that can occur in the Wernicke area, due to a stroke, can lead to negative consequences in the use of language.
Wernicke's aphasia, concerning language understanding, is characterized by the presence of a deconstructed and meaningless communication, combined with a deficient understanding of language. However, although the message produced is meaningless, the speech is transmitted fluently because the production of language is not compromised by the disturbance.
Unlike Broca's aphasia, the patient uses a large number of functional words, as well as complex verbal times and subordinate sentences.
Sometimes, however, patients replace words with other words with similar meanings and this effect is called semantic paralepsy, in which instead of saying the word they are looking for, they say a different word with the same meaning.
Wernicke's aphasia, therefore, shows itself with linguistic fluidity. In fact, subjects affected by this disorder have no problem in supporting a speech, even if lacking in meaning. All this happens because the brain structure in charge of the production of speech is the Broca area, and confirms that the Wernicke area is specialized in the understanding and semantics of the language, despite being connected to other areas that are able to continue their functions independently.
Another feature of Wernicke's aphasia is auditory misunderstanding. The patient, therefore, is unable to understand what others are telling him. And patients with this type of aphasia are unaware of their lack of understanding. Thanks to the remarkable scientific developments regarding the Wernicke area, it is now clear that damage to this area is the basis of the aetiology of different disorders.
The understanding of the language can be evaluated, for example, through the token test consisting of a series of commands involving 20 tokens of different shapes, sizes, and colors presented in an order of increasing complexity. A compromise in understanding may be due to the failure of word recognition, auditory memory, syntactic structure formation or speech discrimination.
Wernicke's aphasia: the muscles involved
Although all language production is the result of a series of muscular movements, new research shows that the neurological mechanisms involved in language production are not simply limited to the motor commands that stimulate the muscles. Therefore, before these motor commands are sent, the speaker must create a mental image of the sounds that constitute the words. An example of this might be the knowledge that the word "snow" rhymes with "drink" without the need to say those words out loud. A rupture of this recovery process leads to an improper displacement of the spoken words. This phenomenon is a key point of Wernicke's aphasia, commonly associated with a lack of understanding, although problems in language production also remain a constant component.
Wernicke area: clinical syndromes
The Wernicke area could also be damaged by vitamin B1 (thiamine) deficiency. In the long run, this deficiency could lead to the onset of Wernicke-Korsakoff syndrome. The Wernicke area is, in fact, often associated with chronic alcoholism, although Wernicke's encephalopathy may have other etiological causes: malnutrition, increased metabolic needs or in the context of renal dialysis. Recent statistics have shown that 12.5% of patients with a history of chronic alcoholism have shown encephalopathic lesions in the Werincke area. The lesions in this area could consist of vascular congestion, petechial hemorrhages, and microglial proliferation. Chronic cases may also include gliosis, demyelination, and loss of neuropil with relative preservation of neurons. Although neuronal loss is more predominant in the unmyelinated median thalamus, mammary body atrophy is specifically associated with Wernicke's encephalopathy.
Cardinal symptoms of Wernicke's syndrome also include gait ataxia, horizontal nystagmus and encephalopathy. Encephalopathy could be characterized by distractibility, delirium, and a profound disorientation Spatio-temporal and person-related. Although horizontal nystagmus is the most common ocular discovery, vertical nystagmus may also occur. The ataxia experienced in these patients is a combination of vestibular dysfunction, cerebellar involvement and polyneuropathy. Other common findings could include severe hypotension, hypothermia or coma.
In conclusion, due to the great plasticity of the brain, if the left hemisphere is damaged, it is possible that language may also develop in the right hemisphere. Thanks to this phenomenon of brain plasticity, the impact of brain lesions is reduced, thus allowing the manifestation of normal language development.
