| Right hemisphere brain damage | |
|---|---|
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| Horizontal section of right cerebral hemisphere | |
| Specialty | Psychiatry, Neurology |
Right hemisphere brain damage (RHD) is the result of injury to the right cerebral hemisphere. [1] The right hemisphere of the brain coordinates tasks for functional communication, which include problem solving, memory, and reasoning. [1] Deficits caused by right hemisphere brain damage vary depending on the location of the damage. [2]
Individuals with right hemisphere damage exhibit deficits in visual processing. It appears as though they are only able to recognize the parts of a picture, symbol, etc. rather than seeing the image as a whole. This was shown during an experiment when patients with right hemisphere damage had to draw an M made up of small triangles. When they attempted to recreate the image, they only depicted the small triangles. This countered patients with left hemisphere damage who were able to draw the M, but left out the small triangles that made it up. [3] In addition, those with right hemisphere damage have difficulty changing their perception of a whole pertaining to an image. They focus on one particular whole and have a hard time changing their perception and incorporating another whole when new information is presented. This phenomenon is called inference revising and individuals with right hemisphere damage therefore experience a deficit in this area.[ citation needed ]
Patients with right hemisphere brain damage most commonly have difficulties with attention, perception, learning, memory, recognition and expression of emotion, and neglect. [4] Other frequently occurring, though slightly less common, deficits include reasoning and problem solving, awareness, and orientation. [4] It is also common for patients with right hemisphere damage to have a flat affect, lack of emotional expression, while speaking. Additionally, these patients commonly have difficulty recognizing other people's emotions when expressed through facial expressions and tone of voice. [2] This lack of ability to recognize emotion suggests individuals have an impaired theory of mind, the ability to recognize the thoughts and feelings of others outside of one’s self. Although these deficits alone may complicate therapy, the patient may also exhibit anosognosia, or ignorance of his or her impairments. [5] [6] Due to possible anosognosia, it is common for patients to not become frustrated or upset when they are unable to complete tasks they were previously able to complete. [7]
Unlike those of people with aphasia, the speech patterns of individuals with right hemisphere damage are not typically characterized by “word finding problems, paraphasias, circumlocutions, or impaired phonological processing.” Circumlocution in persons with RHD tends to center around general concepts, not specific words. For example, in describing what brought a RHD-affected individual to the hospital, though the patient would likely remember the word “stroke” and other specific words to describe his situation, the RHD impairment to his discourse level and cognitive processes would likely prevent him from describing the situation in a coherent manner. [8]
The syntax of RHD-affected individuals tends to be “accurate and varied”; unlike people with aphasia, they tend not to have difficulty with word retrieval. In addition, people with right hemisphere damage usually understand the literal meaning of most statements. Linguistically, in cases in which RHD patients seem to have syntactic deficits, they are typically the result of problems with semantic processing. [8]
In a 1962 study, Eisenson observed a “looseness of verbalization” in RHD-affected individuals, noting that right hemisphere damage appears to affect “relatively abstract language formulations.” According to Eisenson, this is evidence that the right hemisphere likely controls “super- or extra-ordinary” language function. In other words, RHD patients have trouble with higher-level language tasks (relating to semantic and lexical processing) less common in day-to-day, average discourse. [9] In describing semantic deficits in persons with right hemisphere damage, a distinction must be drawn between convergent and divergent semantic processing. Tasks involving convergent semantic processing (“relatively straightforward linguistic tasks in which the number of responses is limited”), which involve the most straightforward meanings of words, are not nearly as difficult for RHD patients as tasks involving divergent semantic processing (tasks that “elicit a wide range of meanings which may diverge from a single semantic concept to include non-dominant meanings that are alternate, connotative, and/or less familiar”). [9]
In terms of convergent semantic processing, people with RHD do not demonstrate semantic impairment at the phonemic level, nor do they tend to have difficulty understanding the primary meanings of individual words. Their comprehension of simple, unambiguous sentences also remains intact, as does their basic word retrieval; this evidence suggests that these tasks are functions of the left hemisphere. [10] On the other hand, the right hemisphere is more involved in recognizing multiple and non-primary meanings of words, divergent semantic processing tasks that are impaired in individuals with right hemisphere damage. [11] Along these lines, RHD patients experience difficulty with verbal fluency; in an experiment in which RHD-affected individuals were asked to name items within a category, they tended to suggest objects connected in more ways than one (with many characteristics in common). For example, when asked to name vegetables, people with RHD would name spinach, cabbage, and lettuce, which share the attributes not only of being vegetables but also of being “green and leafy.” Such results “support a model of semantic processing in which the [right hemisphere] is superior in generating multiple, loosely connected meanings with little overlap,” a function clearly affected by right hemisphere damage.[ citation needed ]
As a result of pragmatic deficits, individuals with right hemisphere damage have a hard time understanding the figurative cues in language and tend to simply understand sentences from their literal meanings. For instance if someone were to say, Joey took the lion’s share, they would assume Joey took the portion that belonged to the lion as opposed to the colloquial meaning-the majority. On the same vein, they also do not understand pragmatics and the underlying clues language might have. Because of this, implicit commands or suggestions in sentences are lost on people with right hemisphere damage. In addition, they have a hard time staying on topic during a conversation and therefore show a deficit in topic maintenance. Some however may stick to the main topic, but bury it in their speech with a large amount of detail that is not relevant to the main point. They also tend to show a lack of awareness for the knowledge they share with those they are communicating with and will mention people or things for which others do not have a reference.
Considering the highly contextual and often ambiguous nature of discourse, it tends to be the area of communication most affected by right hemisphere damage. RHD is particularly evident in the inference patterns of affected individuals. Though RHD patients are typically capable of making basic inferences about situations, more subtle inferences key to discourse and conversation are often severely impaired. As Penelope Myers notes, much empirical research has shown that persons with right hemisphere damage are “significantly impaired in generating inferences about individual elements of pictured scenes,” and, most significantly, in compiling information about the individual elements together to understand the situation at-large. [12] This impairment also applies to written or spoken text. For example, Beeman (1993) cites a patient who mentioned his ability to read “straightforward texts” but noted that he had stopped reading novels with multiple characters as, in the patient’s words, “I can’t put it all together.” [13]
As further evidence of this phenomenon, there has been research done with right hemisphere damaged patients using Norman Rockwell pieces. In these experiments, participants are shown a painting, without the title attached, and are asked to describe what is happening in the scene. As can be expected, there are variances between the answers of people with right hemisphere damage and no brain damage. These experiments have provided further evidence for the idea that individuals with right hemisphere damage have a hard time recognizing emotions of others as they do not mention them when asked to describe the paintings. In addition, this process has suggested that they do not pick up relevant cues and have difficulty incorporating the small details they do notice together to form a big picture. When actually describing the paintings, patients either give the experimenter too much description of what is happening, without addressing the overall theme of the piece, or provide them with a very basic one sentence description about what they see. After analyzing and comparing the descriptions of participants with no brain damage and those with right hemisphere damage, the researchers found that those with right hemisphere damage used twice as many words than those without brain damage even after the researchers took out the part of the descriptions that appeared to be tangential. [3]
Furthermore, RHD-affected individuals experience deficits in inference-revision capabilities. As an example [from Brownell et al. (1986)], when presented with the sentence, "Barbara became too bored to finish the history book," both RHD subjects and control subjects assumed Barbara was reading the book. However, when subjects were then presented with a second sentence, "She had already spent five years writing it," control subjects altered their initial inference, whereas RHD subjects demonstrated great difficulty revising their inferences and drawing a broad, revised conclusion about the information at hand. [14] RHD patients' difficulty with understanding non-literal meanings is also a significant cause of discourse impairment. As noted above, right hemisphere damage affects understanding of figurative language such as idioms, as a result of the right hemisphere’s role in activating non-literal and peripheral meanings. As a result of their difficulties understanding alternate meanings and making situational inferences, people with right hemisphere damage face significant challenges in terms of discourse. [15]
Difficulties with communication are likely to be linked to a patient's cognitive deficits. For example, communication breakdown may result because a patient with right hemisphere brain damage fails to observe appropriate social conventions or because the patient may ramble and fail to recognize appropriate times to take conversational turns. [2] The patient may also have difficulty comprehending sarcasm, irony, and other paralinguistic aspects of communication. [16] Although they do not understand irony, it has been found that patients with right hemisphere damage can provide a clear punchline for a joke, but are lost when the punchline has to connect multiple ideas or themes. Along with sticking to the main point of a story, patients may find it difficult to extract the theme of a story, or arrange sentences based on the theme of a story. [17]
Nespoulous, Code, Virbel and Lecours studied speech of those with different kinds of aphasias and coined a term for the speech patterns of those with right hemisphere damage. According to them, these patients engage in modalizing speech which is made up speech about the patient’s perspective on the real world. They found that those with right hemisphere damage contrast those with Wernicke’s Aphasia as those patients use referential speech which Nespoulous et al. identify as speech pertaining to the real world and what is occurring in it. With referential speech, the patients describe what they did, but leave out their attitude towards it. In modalizing speech, a description of the real world is missing, but they include their emotional attitude [18] [ clarification needed ]
A frequently occurring motor deficit is left-sided hemiparesis (in strokes affecting the motor cortex). A less common motor deficit in this population is dysphagia. [4]
Patients with right hemisphere brain damage often display sensory deficits such as left neglect, in which they ignore everything in the left visual field. [5] This neglect can be present throughout many daily activities including reading, writing and self-care activities. [2] For example, individuals with left neglect typically leave out details on the neglected side of drawings or try to draw out all the details on the nonneglected side. [19] Homonymous hemianopsia is another sensory deficit that is sometimes observed in this population. [4]
Stroke is the most common source of damage for a right hemisphere damage. The stroke for this disorder occurs in the right hemisphere of the brain. Other etiologies that cause right hemisphere damage include: trauma (traumatic brain injury), disease, seizures disorders, and infections. Depending on the etiology that causes the right hemisphere damage, different deficits can be accounted for. [20] "The level of deficit or disorder an individual with right hemisphere damage displays depends on the location and extent of the damage. A small focal right hemisphere stroke can produce a very specific deficit and leave most other cognitive and perceptual processes intact, whereas a very large stroke in the right hemisphere more than likely results in multiple profound deficits. [21] " Adults with right hemisphere damage may exhibit behavior that can be characterized by insensitivity to others and preoccupation with self; unawareness of the social context of conversations; and verbose, rambling and tangential speech. [22]
Right hemisphere brain damage is diagnosed by a medical professional. Computerized tomography (CT) scans and magnetic resonance imaging (MRI) are often used to determine where the damage occurred and how severe it is (ASHA). [23]
Standardized assessments are used by speech-language pathologists to determine the presence and severity of right hemisphere brain damage. The three most popular standardized assessments include:
- The Mini Inventory of Right Brain Injury - Second Edition (MIRBI-2) - a standardized test that can be used to identify the presence, severity, and identify the patient's strengths and weaknesses.
- The Right Hemisphere Language Battery - Second Edition, (RHLB-2) -a comprehensive test battery for evaluation of right hemisphere-injured adults.
- The Rehabilitation Institute of Chicago Evaluation of Communicative Problems in Right-Hemisphere Dysfunction Revised (RICE-R) -includes nine subtests which include a patient interview and ratings of facial and written expression and severity ratings for each subtest. [2]
Non-standardized tests can also be useful in determining the communicative deficits of adults with right-hemisphere brain damage. Those procedures include tests of: Visual and Spatial Perception, Attention, and Organization, Component Attentional Processes and Visual Organization. [Do the previously listed “tests” need to be capitalized?] Other non-standardized tests that can be used include:
- The Boston Diagnostic Aphasia Exam (BDAE)-Auditory comprehension, oral expression, and reading subtests
- The Revised Token Test
- The Boston Naming Test
- The Word Fluency Test. [2]
Treatment for right hemisphere damage is given by speech-language pathologists. There is not much research that has been done regarding the efficacy of treatments for right hemisphere damage. The research that has been done has shown that persons with right hemisphere damage benefit from therapy at both the chronic and acute stages of recovery for language. [24] Research has also shown that treatment given by speech-language pathologists to persons with right hemisphere damage results in improvement in the areas of problem solving, attention, memory, and pragmatics. [25]
Different treatment approaches can be used to treat the different symptoms of right hemisphere damage including neglect, visuospatial awareness, prosody, and pragmatics. Therapy for each person is individualized to their symptoms and severity of impairment. Intervention should focus on the needs of the person in both communication and functional aspects.
Data from the American Speech-Language-Hearing Association (ASHA) indicate that treatment for individuals with right hemisphere damage tends to focus on areas other than communication, including swallowing, memory, and problem solving. Deficits in language expression, language comprehension, and pragmatics are addressed much less frequently (in 22%, 23%, and 5% of individuals, respectively). [26] The lack of research focusing on communication treatment is cited as a possible explanation for these low percentages. [24] Small-scale and pilot studies have been conducted in recent years to fill the identified gaps in the treatment literature. Emerging evidence is discussed below.
Right hemisphere damage can lead to aprosodia—the inability to produce or comprehend emotional prosody of language. Emotional prosody is typically conveyed and interpreted through changes in pitch, rhythm, or loudness (Leon et al., 2005). [27] Right hemisphere damaged patients have the most difficulty then with sentence types that revolve around pitch and inflection. These sentence types include: declarative, as there is a fall in pitch at the end; interrogative, as there is a rise in pitch for a yes/no question and a drop when there is an interrogative pronoun; and imperative sentence types where there is even pitch until a rise of intensity is made at the end of the command. Research thus far has focused primarily on motoric-imitative and cognitive-linguistic approaches to prosody treatment. In a motoric-imitative approach, the client imitates clinician-modeled sentences produced with target emotional prosody. Modeling and cueing is gradually reduced following a six-step hierarchy until the client reaches independent production. In the cognitive-linguistic approach, the client is prompted to produce sentences with the support of cue cards. Cues include the name of the target emotion, the vocal characteristics of the emotional tone, and a picture of a corresponding facial expression. Again, cues are gradually removed as the client progresses toward independent production. [28] Clinical studies of small groups of participants (four participants; [27] 14 participants. [28] ) revealed statistically significant gains in the production of emotional prosody following treatment. Additional research is needed to replicate the results of the limited studies that have been conducted thus far, to evaluate the efficacy of additional treatment approaches, and to compare the relative efficacy of different approaches. [24] [29]
It appears as though individuals with right hemisphere damage maintain their real world knowledge and their mental scripts of what the world is like and what to expect from common scenarios, they just can’t translate it when they see it. Despite this, right hemisphere damage can lead to deficits in discourse abilities, including difficulty with interpretation of abstract language, making inferences, and understanding nonverbal cues. [24] [29] In particular, individuals with right hemisphere damage struggle with the skilled use of context to interpret and express ideas. [29] A study of five participants with right hemisphere damage found that participants’ ability to orally interpret metaphors was statistically significantly improved following a five-week structured training intervention. The training program included five phases focused on facilitating the use of word meanings and semantic associations to increase participants’ understanding of metaphors. [30] Another study of three participants found that a contextual stimulation treatment increased participants’ ability to efficiently activate distantly associated meanings and to suppress contextually inappropriate meanings. [31] Again, additional research is needed to replicate and extend results, but the emerging literature represents a small step toward evidence-based treatments for right hemisphere damage. [24]
Research has indicated that women are more likely to be left hemisphere dominant, and men are more likely to be right hemisphere dominant. Because of this, women recover faster from left hemisphere damage, and men are more likely to recover faster from right hemisphere damage. Men who have suffered a right hemisphere stroke also have significantly better rehabilitation outcomes than men who suffer a left hemisphere stroke. Recovery of functional abilities is often greater in male stroke survivors than females, especially in the area of activities of daily living. [32]
Left neglect is common in patients recovering from right hemisphere damage as the right hemisphere controls the left half of the body. The presence and severity of neglect has been shown to influence functional outcomes as well as length of rehabilitation after a stroke.[ citation needed ]
Patients with neglect for peripersonal space (space within reach), are likely to recover most during the first 10 days after a stroke, but further improvements from 6 months to 1 year post onset are unlikely. However, the prognosis for patients with neglect for personal body space or neglect for far space is much better. These types of neglect are more likely to recover completely or almost completely after 6 months post onset. Although there may be some lasting effects of neglect of varying degrees based on the type, many patients with neglect are likely to improve over time (Appelros et al., 2004). [33]
The Functional Independence Measure (FIM) is often used to determine the functional skills a patient has at various times after their brain damage. Research has indicated that patients with more severe neglect are less likely to make functional improvements than patients with less severe neglect based on FIM scores. Additionally, patients with any level of neglect tend to have reduced functional cognitive and communication skills than patients without neglect (Cherney et al., 2001). [34]
Patients with neglect have been shown to need rehabilitation longer than patients who suffered from right hemisphere damage that did not result in neglect. On average, patients with neglect stayed in inpatient rehabilitation facilities one week longer, and this length of stay did not differ for patients with more or less severe neglect (Cherney et al., 2001). [34]
Anosognosia is a lack of awareness or understanding of the loss of function caused by the brain injury and is common in individuals who have suffered a right hemisphere stroke. Because patients with anosognosia may be unaware of their deficits, they may be less likely to seek treatment once they are released from the hospital. The lack of proper treatment could lead to higher levels of dependency later on. In order to make functional recovery gains, right hemisphere stroke survivors should receive rehabilitation services, so patients with anosognosia should be encouraged to seek out additional treatment. However, due to the anosognosia, these patients often report a higher perceived quality of life than other right hemisphere stroke survivors because of the unawareness of the resulting deficits (Daia et al., 2014). [35] Those with right hemisphere damage may confabulate, or make up stories to help explain what is going on in their minds compared to what is actually occurring in the outside world. For example, one patient who had right hemisphere damage was in a wheelchair and kept putting his left hand in the spokes. When the nurse asked him to stop, he looked down and said, “that’s not my hand.” Since the right hemisphere controls motor functioning for the left side of the body, the patient did not recognize the actions of his own hand and made up a story to explain what was going on. This often occurs because what is actually happening to them is deeply disturbing so their minds need a way to cope. Patients with smaller lesions often recover faster from anosognosia than patients with larger lesions resulting in anosognosia (Hier et al., 1983). [36]
Age: Younger patients typically recover faster than older patients, especially with regards to prosopagnosia (difficulty recognizing faces)
Size of lesion: Patients with smaller lesions typically recover faster from neglect and hemiparesis (unilateral body weakness) than patients with larger lesions (Hier et al., 1983). [36]
For the majority of the nineteenth century, the left brain hemisphere was the key focus of clinical research on language disorders (Brookshire, 2007). [2] In the twentieth century, focus gradually shifted to include right hemisphere damage (Brookshire, 2007). [2] It is now well established that language and cognition can be seriously impaired by unilateral right hemisphere brain damage. [37] Specific cognitive tests can help diagnose the existence of right hemisphere brain damage and differentiate symptoms from those of left hemisphere damage. [38] Unlike the aphasias, caused by left hemisphere damage and generally resulting in focused language deficits, right hemisphere brain damage can result in a variety of diffuse deficits which complicate formal testing of this disorder (Brookshire, 2007). [2] These formal tests assess areas such as understanding humor, metaphors, sarcasm, facial expression, and prosody. [20] However, not all individuals with right hemisphere brain damage have problems in language or communication and some may have no discernible symptoms. [37] Indeed, about half of patients with right hemisphere damage have intact communication abilities (Brookshire, 2007). [2] [39]
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 the Global North. Aphasia can also be the result of brain tumors, brain infections, or neurodegenerative diseases.
Expressive aphasia, also known as Broca's aphasia, is a type of aphasia characterized by partial loss of the ability to produce language, although comprehension generally remains intact. A person with expressive aphasia will exhibit effortful speech. Speech generally includes important content words but leaves out function words that have more grammatical significance than physical meaning, such as prepositions and articles. This is known as "telegraphic speech". The person's intended message may still be understood, but their sentence will not be grammatically correct. In very severe forms of expressive aphasia, a person may only speak using single word utterances. Typically, comprehension is mildly to moderately impaired in expressive aphasia due to difficulty understanding complex grammar.
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 speech, which is characterized by typical speech rate, intact syntactic abilities and effortless speech output. Writing often reflects speech in that it tends to lack content or meaning. In most cases, motor deficits do not occur in individuals with Wernicke's aphasia. Therefore, they may produce a large amount of speech without much meaning. Individuals with Wernicke's aphasia are typically unaware of their errors in speech and do not realize their speech may lack meaning. They typically remain unaware of even their most profound language deficits.
Apraxia is a motor disorder caused by damage to the brain, which causes difficulty with motor planning to perform tasks or movements. The nature of the damage determines the disorder's severity, and the absence of sensory loss or paralysis helps to explain the level of difficulty. Children may be born with apraxia; its cause is unknown, and symptoms are usually noticed in the early stages of development. Apraxia occurring later in life, known as acquired apraxia, is typically caused by traumatic brain injury, stroke, dementia, Alzheimer's disease, brain tumor, or other neurodegenerative disorders. The multiple types of apraxia are categorized by the specific ability and/or body part affected.
Agnosia is the inability to process sensory information. Often there is a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss. It is usually associated with brain injury or neurological illness, particularly after damage to the occipitotemporal border, which is part of the ventral stream. Agnosia only affects a single modality, such as vision or hearing. More recently, a top-down interruption is considered to cause the disturbance of handling perceptual information.
Aphasiology is the study of language impairment usually resulting from brain damage, due to neurovascular accident—hemorrhage, stroke—or associated with a variety of neurodegenerative diseases, including different types of dementia. These specific language deficits, termed aphasias, may be defined as impairments of language production or comprehension that cannot be attributed to trivial causes such as deafness or oral paralysis. A number of aphasias have been described, but two are best known: expressive aphasia and receptive aphasia.
Agraphia is an acquired neurological disorder causing a loss in the ability to communicate through writing, either due to some form of motor dysfunction or an inability to spell. The loss of writing ability may present with other language or neurological disorders; disorders appearing commonly with agraphia are alexia, aphasia, dysarthria, agnosia, acalculia and apraxia. The study of individuals with agraphia may provide more information about the pathways involved in writing, both language related and motoric. Agraphia cannot be directly treated, but individuals can learn techniques to help regain and rehabilitate some of their previous writing abilities. These techniques differ depending on the type of agraphia.
Anomic aphasia is a mild, fluent type of aphasia where individuals have word retrieval failures and cannot express the words they want to say. By contrast, anomia is a deficit of expressive language, and a symptom of all forms of aphasia, but patients whose primary deficit is word retrieval are diagnosed with anomic aphasia. Individuals with aphasia who display anomia can often describe an object in detail and maybe even use hand gestures to demonstrate how the object is used, but cannot find the appropriate word to name the object. Patients with anomic aphasia have relatively preserved speech fluency, repetition, comprehension, and grammatical speech.
Anosognosia is a condition in which a person with a disability is cognitively unaware of having it due to an underlying physical or psychological condition. Anosognosia can result from physiological damage to brain structures, typically to the parietal lobe or a diffuse lesion on the fronto-temporal-parietal area in the right hemisphere, and is thus a neuropsychiatric disorder. A deficit of self-awareness, it was first named by the neurologist Joseph Babinski in 1914. Phenomenologically, anosognosia has similarities to denial, which is a psychological defense mechanism; attempts have been made at a unified explanation. Anosognosia is sometimes accompanied by asomatognosia, a form of neglect in which patients deny ownership of body parts such as their limbs. The term is from Ancient Greek ἀ- a-, 'without', νόσος nosos, 'disease' and γνῶσις gnōsis, 'knowledge'. It is also considered a disorder that makes the treatment of the patient more difficult, since it may affect negatively the therapeutic relationship.
Conduction aphasia, also called associative aphasia, is an uncommon form of difficulty in speaking (aphasia). It is caused by damage to the parietal lobe of the brain. An acquired language disorder, it is characterised by intact auditory comprehension, coherent speech production, but poor speech repetition. Affected people are fully capable of understanding what they are hearing, but fail to encode phonological information for production. This deficit is load-sensitive as the person shows significant difficulty repeating phrases, particularly as the phrases increase in length and complexity and as they stumble over words they are attempting to pronounce. People have frequent errors during spontaneous speech, such as substituting or transposing sounds. They are also aware of their errors and will show significant difficulty correcting them.
Global aphasia is a severe form of nonfluent aphasia, caused by damage to the left side of the brain, that affects receptive and expressive language skills as well as auditory and visual comprehension. Acquired impairments of communicative abilities are present across all language modalities, impacting language production, comprehension, and repetition. Patients with global aphasia may be able to verbalize a few short utterances and use non-word neologisms, but their overall production ability is limited. Their ability to repeat words, utterances, or phrases is also affected. Due to the preservation of the right hemisphere, an individual with global aphasia may still be able to express themselves through facial expressions, gestures, and intonation. This type of aphasia often results from a large lesion of the left perisylvian cortex. The lesion is caused by an occlusion of the left middle cerebral artery and is associated with damage to Broca's area, Wernicke's area, and insular regions which are associated with aspects of language.
Transcortical sensory aphasia (TSA) is a kind of aphasia that involves damage to specific areas of the temporal lobe of the brain, resulting in symptoms such as poor auditory comprehension, relatively intact repetition, and fluent speech with semantic paraphasias present. TSA is a fluent aphasia similar to Wernicke's aphasia, with the exception of a strong ability to repeat words and phrases. The person may repeat questions rather than answer them ("echolalia").
The language module or language faculty is a hypothetical structure in the human brain which is thought to contain innate capacities for language, originally posited by Noam Chomsky. There is ongoing research into brain modularity in the fields of cognitive science and neuroscience, although the current idea is much weaker than what was proposed by Chomsky and Jerry Fodor in the 1980s. In today's terminology, 'modularity' refers to specialisation: language processing is specialised in the brain to the extent that it occurs partially in different areas than other types of information processing such as visual input. The current view is, then, that language is neither compartmentalised nor based on general principles of processing. It is modular to the extent that it constitutes a specific cognitive skill or area in cognition.
Transcortical motor aphasia (TMoA), also known as commissural dysphasia or white matter dysphasia, results from damage in the anterior superior frontal lobe of the language-dominant hemisphere. This damage is typically due to cerebrovascular accident (CVA). TMoA is generally characterized by reduced speech output, which is a result of dysfunction of the affected region of the brain. The left hemisphere is usually responsible for performing language functions, although left-handed individuals have been shown to perform language functions using either their left or right hemisphere depending on the individual. The anterior frontal lobes of the language-dominant hemisphere are essential for initiating and maintaining speech. Because of this, individuals with TMoA often present with difficulty in speech maintenance and initiation.
Mixed transcortical aphasia is the least common of the three transcortical aphasias. This type of aphasia can also be referred to as "Isolation Aphasia". This type of aphasia is a result of damage that isolates the language areas from other brain regions. Broca's, Wernicke's, and the arcuate fasiculus are left intact; however, they are isolated from other brain regions.
Semantic dementia (SD), also known as semantic variant primary progressive aphasia (svPPA), is a progressive neurodegenerative disorder characterized by loss of semantic memory in both the verbal and non-verbal domains. However, the most common presenting symptoms are in the verbal domain. Semantic dementia is a disorder of semantic memory that causes patients to lose the ability to match words or images to their meanings. However, it is fairly rare for patients with semantic dementia to develop category specific impairments, though there have been documented cases of it occurring. Typically, a more generalized semantic impairment results from dimmed semantic representations in the brain.
Primary progressive aphasia (PPA) is a type of neurological syndrome in which language capabilities slowly and progressively become impaired. As with other types of aphasia, the symptoms that accompany PPA depend on what parts of the left hemisphere are significantly damaged. However, unlike most other aphasias, PPA results from continuous deterioration in brain tissue, which leads to early symptoms being far less detrimental than later symptoms. Those with PPA slowly lose the ability to speak, write, read, and generally comprehend language. Eventually, almost every patient becomes mute and completely loses the ability to understand both written and spoken language. Although it was first described as solely impairment of language capabilities while other mental functions remain intact, it is now recognized that many, if not most of those with PPA experience impairment of memory, short-term memory formation and loss of executive functions. It was first described as a distinct syndrome by M. Marsel Mesulam in 1982. Primary progressive aphasias have a clinical and pathological overlap with the frontotemporal lobar degeneration (FTLD) spectrum of disorders and Alzheimer's disease. However, PPA is not considered synonymous to Alzheimer's disease due to the fact that, unlike those affected by Alzheimer's disease, those with PPA are generally able to maintain the ability to care for themselves, remain employed, and pursue interests and hobbies. Moreover, in diseases such as Alzheimer's disease, Pick's disease, and Creutzfeldt-Jakob disease, progressive deterioration of comprehension and production of language is just one of the many possible types of mental deterioration, such as the progressive decline of memory, motor skills, reasoning, awareness, and visuospatial skills.
Aprosodia is a neurological condition characterized by the inability of a person to properly convey or interpret emotional prosody. Prosody in language refers to the ranges of rhythm, pitch, stress, intonation, etc. These neurological deficits can be the result of damage of some form to the non-dominant hemisphere areas of language production. The prevalence of aprosodias in individuals is currently unknown, as testing for aprosodia secondary to other brain injury is only a recent occurrence.
Anosodiaphoria is a condition in which a person who has a brain injury seems indifferent to the existence of their impairment. Anosodiaphoria is specifically used in association with indifference to paralysis. It is a somatosensory agnosia, or a sign of neglect syndrome. It might be specifically associated with defective functioning of the frontal lobe of the right hemisphere.
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 like the original one, or has some other connection to it, or they will replace it with random sounds. Accordingly, persons with jargon aphasia often use neologisms, and may perseverate if they try to replace the words they can not find with sounds.
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