Right hemisphere brain damage

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.

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.

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]

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]

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.

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]