Wernicke's Area
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Wernicke's area (; ), also called Wernicke's speech area, is one of the two parts of the
cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting of ...
that are linked to speech, the other being
Broca's area Broca's area, or the Broca area (, also , ), is a region in the frontal lobe of the dominant Cerebral hemisphere, hemisphere, usually the left, of the Human brain, brain with functions linked to speech production. Language processing in the brai ...
. It is involved in the comprehension of written and spoken language, in contrast to Broca's area, which is primarily involved in the production of language. It is traditionally thought to reside in
Brodmann area 22 Brodmann area 22 is a Brodmann's area that is cytoarchitecturally located in the posterior superior temporal gyrus of the brain. In the left cerebral hemisphere, it is one portion of Wernicke's area. The left hemisphere BA22 helps with generat ...
, which is located in the superior temporal gyrus in the dominant cerebral hemisphere, which is the left hemisphere in about 95% of
right-handed In human biology, handedness is an individual's preferential use of one hand, known as the dominant hand, due to it being stronger, faster or more dextrous. The other hand, comparatively often the weaker, less dextrous or simply less subjecti ...
individuals and 70% of left-handed individuals. Damage caused to Wernicke's area results in receptive,
fluent aphasia Wernicke's aphasia, also known as receptive aphasia, sensory aphasia or posterior aphasia, is a type of aphasia in which individuals have difficulty understanding written and spoken language. Patients with Wernicke's aphasia demonstrate fluent s ...
. This means that the person with aphasia will be able to fluently connect words, but the phrases will lack meaning. This is unlike
non-fluent aphasia Expressive aphasia, also known as Broca's aphasia, is a type of aphasia characterized by partial loss of the ability to produce language ( spoken, manual, or written), although comprehension generally remains intact. A person with expressive aphas ...
, in which the person will use meaningful words, but in a non-fluent, telegraphic manner.


Structure

Wernicke's area is traditionally viewed as being located in the posterior section of the superior temporal gyrus (STG), usually in the left cerebral hemisphere. This area encircles the
auditory cortex The auditory cortex is the part of the temporal lobe that processes auditory information in humans and many other vertebrates. It is a part of the auditory system, performing basic and higher functions in hearing, such as possible relations to ...
on the
lateral sulcus In neuroanatomy, the lateral sulcus (also called Sylvian fissure, after Franciscus Sylvius, or lateral fissure) is one of the most prominent features of the human brain. The lateral sulcus is a deep fissure in each hemisphere that separates the ...
, the part of the
brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...
where the
temporal lobe The temporal lobe is one of the four Lobes of the brain, major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe ...
and
parietal lobe The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus. The parietal lobe integrates sensory informa ...
meet. This area is neuroanatomically described as the posterior part of
Brodmann area 22 Brodmann area 22 is a Brodmann's area that is cytoarchitecturally located in the posterior superior temporal gyrus of the brain. In the left cerebral hemisphere, it is one portion of Wernicke's area. The left hemisphere BA22 helps with generat ...
. However, there is an absence of consistent definitions as to the location. Some identify it with the unimodal auditory association in the superior temporal gyrus anterior to the primary auditory cortex (the anterior part of BA 22). This is the site most consistently implicated in auditory
word recognition Word recognition, according to Literacy Information and Communication System (LINCS) is "the ability of a reader to recognize written words correctly and virtually effortlessly". It is sometimes referred to as "isolated word recognition" because i ...
by functional brain imaging experiments. Others include also adjacent parts of the heteromodal cortex in BA 39 and BA40 in the
parietal lobe The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus. The parietal lobe integrates sensory informa ...
. Despite the overwhelming notion of a specifically defined "Wernicke's Area," the most careful current research suggests that it is not a unified concept. While previously thought to connect Wernicke's area and
Broca's area Broca's area, or the Broca area (, also , ), is a region in the frontal lobe of the dominant Cerebral hemisphere, hemisphere, usually the left, of the Human brain, brain with functions linked to speech production. Language processing in the brai ...
, new research demonstrates that the
arcuate fasciculus The arcuate fasciculus (AF) is a bundle of axons that generally connects the Broca's area and the Wernicke's area in the brain. It is an association fiber tract connecting caudal temporal cortex and inferior frontal lobe. ''Fasciculus arcuatus'' i ...
instead connects to posterior receptive areas with premotor/motor areas, and not to Broca's area. Consistent with the word recognition site identified in brain imaging, the
uncinate fasciculus The uncinate fasciculus is a white matter association tract in the human brain that connects parts of the limbic system such as the temporal pole, anterior parahippocampus, and amygdala in the temporal lobe with inferior portions of the frontal l ...
connects anterior superior temporal regions with
Broca's area Broca's area, or the Broca area (, also , ), is a region in the frontal lobe of the dominant Cerebral hemisphere, hemisphere, usually the left, of the Human brain, brain with functions linked to speech production. Language processing in the brai ...
.


Function


Right homologous area

Research using
Transcranial magnetic stimulation Transcranial magnetic stimulation (TMS) is a noninvasive form of brain stimulation in which a changing magnetic field is used to induce an electric current at a specific area of the brain through electromagnetic induction. An electric pulse gener ...
suggests that the area corresponding to the Wernicke's area in the non-dominant cerebral hemisphere has a role in processing and resolution of subordinate meanings of ambiguous words—such as ‘‘river’’ when given the ambiguous word "bank." In contrast, the Wernicke's area in the dominant hemisphere processes dominant word meanings (‘‘teller’’ given ‘‘bank’’).


Modern views

Neuroimaging Neuroimaging is the use of quantitative (computational) techniques to study the structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Incre ...
suggests the functions earlier attributed to Wernicke's area occur more broadly in the
temporal lobe The temporal lobe is one of the four Lobes of the brain, major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe ...
and indeed happen also in Broca's area. Support for a broad range of speech processing areas was furthered by a recent study carried out at the
University of Rochester The University of Rochester (U of R, UR, or U of Rochester) is a private research university in Rochester, New York. The university grants undergraduate and graduate degrees, including doctoral and professional degrees. The University of Roc ...
in which
American Sign Language American Sign Language (ASL) is a natural language that serves as the predominant sign language of Deaf communities in the United States of America and most of Anglophone Canadians, Anglophone Canada. ASL is a complete and organized visual lang ...
native speakers were subject to
MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...
while interpreting sentences that identified a relationship using either syntax (relationship is determined by the word order) or inflection (relationship is determined by physical motion of "moving hands through space or signing on one side of the body"). Distinct areas of the brain were activated with the frontal cortex (associated with ability to put information into sequences) being more active in the syntax condition and the temporal lobes (associated with dividing information into its constituent parts) being more active in the inflection condition. However, these areas are not mutually exclusive and show a large amount of overlap. These findings imply that while speech processing is a very complex process, the brain may be using fairly basic, preexisting computational methods.


Clinical significance


Aphasia

Wernicke's area is named after
Carl Wernicke Carl (or Karl) Wernicke (; ; 15 May 1848 – 15 June 1905) was a German physician, anatomist, psychiatrist and neuropathologist. He is known for his influential research into the pathological effects of specific forms of encephalopathy and also ...
, a
German German(s) may refer to: * Germany (of or related to) ** Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ge ...
neurologist Neurology (from el, νεῦρον (neûron), "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the brain, the spinal c ...
and
psychiatrist A psychiatrist is a physician who specializes in psychiatry, the branch of medicine devoted to the diagnosis, prevention, study, and treatment of mental disorders. Psychiatrists are physicians and evaluate patients to determine whether their sy ...
who, in 1874, hypothesized a link between the left posterior section of the superior temporal gyrus and the reflexive mimicking of words and their syllables that associated the sensory and motor images of spoken words. He did this on the basis of the location of
brain injuries Neurotrauma, brain damage or brain injury (BI) is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors. In general, brain damage refers to significant, undiscriminating t ...
that caused
aphasia Aphasia is an inability to comprehend or formulate language because of damage to specific brain regions. The major causes are stroke and head trauma; prevalence is hard to determine but aphasia due to stroke is estimated to be 0.1–0.4% in t ...
.
Receptive aphasia Wernicke's aphasia, also known as receptive aphasia, sensory aphasia or posterior aphasia, is a type of aphasia in which individuals have difficulty understanding written and spoken language. Patients with Wernicke's aphasia demonstrate fluent ...
in which such abilities are preserved is also known as Wernicke's aphasia. In this condition there is a major impairment of language comprehension, while speech retains a natural-sounding rhythm and a relatively normal
syntax In linguistics, syntax () is the study of how words and morphemes combine to form larger units such as phrases and sentences. Central concerns of syntax include word order, grammatical relations, hierarchical sentence structure ( constituency) ...
. Language as a result is largely meaningless (a condition sometimes called ''fluent'' or ''
jargon aphasia Jargon aphasia is a type of fluent aphasia in which an individual's speech is incomprehensible, but appears to make sense to the individual. Persons experiencing this condition will either replace a desired word with another that sounds or looks l ...
''). Wernicke's area receives information from the auditory cortex, and functions to assign word meanings. This is why damage to this area results in meaningless speech, often with paraphasic errors and newly created words or expressions. Paraphasia can involve substituting one word for another, known as semantic paraphasia, or substituting one sound or syllable for another, defined as phonemic paraphasia. This speech is often referred to as “word salad,” as speech sounds fluent but does not have sensible meaning. Normal sentence structure and prosody are preserved, with normal intonation, inflection, rate, and rhythm. This differs from Broca's aphasia, which is characterized by nonfluency. Patients are typically not aware that their speech is impaired in this way, as they have altered comprehension of their speech. Written language, reading, and repetition are affected as well. Damage to the posterior temporal lobe of the dominant hemisphere is the cause of Wernicke's aphasia. The etiology of this damage can vary greatly, with the most common cause being a cerebrovascular event such as an ischemic stroke. Ischemic stroke is the result of a thrombus occluding a blood vessel, restricting blood supply to a particular area of the brain. Other causes of focal damage potentially leading to Wernicke's aphasia include head trauma, infections affecting the central nervous system, neurodegenerative disease, and neoplasms. A cerebrovascular event is more likely the cause in an acute-onset presentation of aphasia, whereas a degenerative disease should be suspected in aphasia with gradual progression over time. Imaging is often useful in identifying a lesion, with most common initial imaging consisting of computed tomography (CT) scan or magnetic resonance imaging (MRI). Electroencephalography (EEG) can also be useful in patients with transient aphasia, where findings may be due to seizures, although this is a less common cause. Diagnosis of aphasia, as well as characterization of type of aphasia, is done with language testing by the provider. Testing should evaluate fluency of speech, comprehension, repetition, ability to name objects, and writing skills. Fluency is assessed by observing the patient's spontaneous speech. Abnormalities in fluency would include shortened phrases, decreased number of words per minute, increased effort with speech, and agrammatism. Patients with Wernicke's aphasia should have fluent speech, so abnormalities in fluency may indicate a different type of aphasia. Comprehension is assessed by giving the patient commands to follow, beginning with simple commands and progressing to more complex commands. Repetition is evaluated by having the patient repeat phrases, progressing from simple to more complex phrases. Both comprehension and repetition would be abnormal in Wernicke's aphasia. Content should also be assessed, by listening to a patient's spontaneous or instructed speech. Content abnormalities include paraphasic errors and neologisms, both indicative of a diagnosis of Wernicke's aphasia. Neologisms are novel words that may resemble existing words. Patients with severe Wernicke's aphasia may also produce strings of such neologisms with a few connecting words, known as jargon. Errors in the selection of phonemes of patients with Wernicke's aphasia include addition, omission, or change in position. Another symptom of Wernicke's aphasia is use of semantic
paraphasia Paraphasia is a type of language output error commonly associated with aphasia, and characterized by the production of unintended syllables, words, or phrases during the effort to speak. Paraphasic errors are most common in patients with fluent for ...
s or "empty speech" which is the use of generic terms like "stuff" or "things" to stand in for the specific words that the patient cannot think of. Some Wernicke's aphasia patients also talk around missing words, which is called "
circumlocution Circumlocution (also called circumduction, circumvolution, periphrasis, kenning, or ambage) is the use of an unnecessarily large number of words to express an idea. It is sometimes necessary in communication (for example, to work around lexical gap ...
." Patients with Wernicke's aphasia can tend to run on when they talk, due to circumlocution combined with deficient self-monitoring. This overabundance of words or press of speech can be described as logorrhea. If symptoms are present, a full neurologic exam should also be done, which will help differentiate aphasia from other neurologic diagnoses potentially causing altered mental status with abnormal speech and comprehension. As an example, a patient with Wernicke's aphasia was asked what brought him to the hospital. His response was, "Is this some of the work that we work as we did before? ... All right ... From when wine hyI'm here. What’s wrong with me because I ... was myself until the taenz took something about the time between me and my regular time in that time and they took the time in that time here and that’s when the time took around here and saw me around in it’s started with me no time and I bekan
egan Egan may refer to: People * Egan (surname) * Egan (given name) Places in the United States * Egan, Illinois, an unincorporated community * Egan, Louisiana, an unincorporated community and census-designated place * Egan, South Dakota, a city * Eg ...
work of nothing else that's the way the doctor find me that way..." Treatment of Wernicke's aphasia first involves addressing the underlying cause. Speech and language therapy is the first line treatment for the aphasia itself, and has a goal of improving language deficits as well as preserving the patient's remaining language skills. A subsequent critical goal of therapy is to teach the patient how to communicate in alternative ways, so they can successfully communicate in daily life. This may include gestures, pictures, or use of electronic devices. While neuroimaging and lesion evidence generally support the idea that malfunction of or damage to Wernicke's area is common in people with receptive aphasia, this is not always so. Some people may use the right hemisphere for language, and isolated damage of Wernicke's area cortex (sparing white matter and other areas) may not cause severe receptive aphasia. Even when patients with Wernicke's area lesions have comprehension deficits, these are usually not restricted to
language processing Language processing refers to the way humans use words to communicate ideas and feelings, and how such communications are processed and understood. Language processing is considered to be a uniquely human ability that is not produced with the sa ...
alone. For example, one study found that patients with posterior lesions also had trouble understanding nonverbal sounds like animal and machine noises. In fact, for Wernicke's area, the impairments in nonverbal sounds were statistically stronger than for verbal sounds.


References


External links

* {{DEFAULTSORT:Wernicke's Area Cerebral cortex Neurolinguistics Temporal lobe