Right Hemisphere Brain Damage Research Articles

Bayesian modelling disentangles language versus executive control disruption in stroke.

Stroke is the leading cause of long-term disability worldwide. Incurred brain damage can disrupt cognition, often with persisting deficits in language and executive capacities. Yet, despite their clinical relevance, the commonalities and differences between language versus executive control impairments remain under-specified. To fill this gap, we tailored a Bayesian hierarchical modelling solution in a largest-of-its-kind cohort (1080 patients with stroke) to deconvolve language and executive control with respect to the stroke topology. Cognitive function was assessed with a rich neuropsychological test battery including global cognitive function (tested with the Mini-Mental State Exam), language (assessed with a picture naming task), executive speech function (tested with verbal fluency tasks), executive control functions (Trail Making Test and Digit Symbol Coding Task), visuospatial functioning (Rey Complex Figure), as well as verbal learning and memory function (Soul Verbal Learning). Bayesian modelling predicted interindividual differences in eight cognitive outcome scores three months after stroke based on specific tissue lesion topologies. A multivariate factor analysis extracted four distinct cognitive factors that distinguish left- and right-hemispheric contributions to ischaemic tissue lesions. These factors were labelled according to the neuropsychological tests that had the strongest factor loadings: One factor delineated language and general cognitive performance and was mainly associated with damage to left-hemispheric brain regions in the frontal and temporal cortex. A factor for executive control summarized mental flexibility, task switching and visual-constructional abilities. This factor was strongly related to right-hemispheric brain damage of posterior regions in the occipital cortex. The interplay of language and executive control was reflected in two distinct factors that were labelled as executive speech functions and verbal memory. Impairments on both factors were mainly linked to left-hemispheric lesions. These findings shed light onto the causal implications of hemispheric specialization for cognition; and make steps towards subgroup-specific treatment protocols after stroke.

Differences in kinetic factors affecting gait speed between lesion sides in patients with stroke.

The differences in kinetic mechanisms of decreased gait speed across brain lesion sides have not been elucidated, including the arrangement of motor modules reflected by kinetic interjoint coordination. The purpose of this study was to elucidate the differences in the kinetic factors of slow gait speed in patients with stroke on the lesion sides. A three-dimensional motion analysis system was employed to assess joint moment in the lower limb and representative gait parameters in 32 patients with right hemisphere brain damage (RHD) and 38 patients with left hemisphere brain damage (LHD) following stroke as well as 20 healthy controls. Motor module composition and timing were determined using principal component analysis based on the three joint moments in the lower limb in the stance phase, which were the variances accounted for principal components (PCs) and the peak timing in the time series of PCs. A stepwise multiple linear regression analysis was performed to identify the most significant joint moment and PC-associated parameter in explaining gait speed. A negligible difference was observed in age, weight, height, and gait speed among patients with RHD and LHD and controls. The following factors contributed to gait speed: in patients with RHD, larger ankle plantarflexion moment on the paretic (p = 0.001) and nonparetic (p = 0.002) sides and ankle dorsiflexion moment on the nonparetic side (p = 0.004); in patients with LHD, larger ankle plantarflexion moment (p < 0.001) and delayed peak timing of the first PC (p = 0.012) on the paretic side as well as ankle dorsiflexion moment on the nonparetic side (p < 0.001); in the controls, delayed peak timing of the first PC (p = 0.002) on the right side and larger ankle dorsiflexion moment (p = 0.001) as well as larger hip flexion moment on the left side (p = 0.023). The findings suggest that the kinetic mechanisms of gait speed may differ among patients with RHD following patients with stroke with LHD, and controls.

Identifying Spatial Neglect in Chronic Right Hemisphere Stroke Survivors Using the RHDBank Outcomes.

The chronicity of spatial neglect (SN) and the utility of existing diagnostic measures used by speech-language pathologists remain poorly understood. In this retrospective study, we examined how the RHDBank test battery informs the identification of SN after right hemisphere brain damage (RHD) during the chronic phase of recovery. Data from 29 right hemisphere stroke survivors were extracted from the RHDBank, including SN tests, for which we performed laterality index scoring: a 51-item demographic survey, the Apples Test, the Indented Paragraph Test, and the clock drawing task from the Cognitive Linguistic Quick Test (CLQT). Two groups (SN+ and SN-) were identified using the Apples Test. A hierarchical cluster analysis explored CLQT performance clusters in association with SN, and group comparisons of demographic variables and test scores were conducted. Ten patients were identified as having SN+ (34%) using the Apples Test. The Indented Paragraph Test and the CLQT's clock drawing test identified only two of the 20 stroke survivors with SN+. Cluster analyses showed that domain and task scores on the CLQT carried information to classify participants into SN+ and SN- in concordance with performance on the Apples Test. Participants in the SN+ cluster had moderately impaired attention and executive function skills and mildly impaired visuospatial skills. The Apples Test differentiated SN in a group of chronic right hemisphere stroke survivors. Using multiple measures from the CLQT seemed to capture a greater range of problems than clock drawing and paragraph reading tests alone. Therefore, the RHDBank test battery as a whole-and in part the CLQT, Apples Test, and Indented Paragraph Test-can detect certain subtypes of SN in the chronic deficit profile after RHD and is a starting point for diagnostic integration by speech-language pathologists.

Undetected language deficits in left or right hemisphere post-stroke patients

Previous studies have reported that widely used tests for aphasia identification are unable to detect the subtle language deficits of left hemisphere brain damaged (LHBD) individuals. Similarly, the language disorders of individuals with right hemisphere brain damage (RHBD) usually remain undetected, due to the lack of any specialized test for the evaluation of their language processing skills. The aim of the present study was to evaluate the language deficits of 80 individuals suffering from the effects of either a LHBD or RHBD stroke, who were diagnosed as having no aphasia or language deficits based on the application of Boston Diagnostic Aphasia Examination. Their language abilities were examined with the use of the Adults’ Language Abilities Test, which explores morpho-syntactic and semantic phenomena of the Greek language in both the comprehension and production modalities. Results revealed that both groups of stroke survivors performed significantly worse compared to the group of healthy participants. Thus, it appears that the latent aphasia of LHBD and the language deficits of RHBD patients are likely to remain undetected and that patients are at risk of not receiving appropriate treatment if their language abilities are not evaluated by an effective and efficient battery of language tests.

Intersectionality of Race and Question-Asking in Women After Right Hemisphere Brain Damage.

Atypical pragmatic language can impede quality health care access. Right hemisphere brain damage (RHD) results in changes in pragmatic language use; however, little is known about whether there are racial/ethnic influences. Recent research indicated differences in question-asking when RHD survivors were compared with healthy controls, prompting the current examination of question production in women by race/ethnicity and the presence of RHD. Participants were eight Black and eight White women who sustained a single right hemisphere stroke at least 6 months prior to data collection (2016-2020), and eight Black and eight White control participants from the Right Hemisphere Damage Bank (https://rhd.talkbank.org). Videos of informal, first-encounter conversational discourse tasks were transcribed and coded. Analyses were conducted for frequency of questions and question type. Race/ethnicity had a statistically significant effect on the total number of questions and number of content and polar questions. The mean total of questions, number of content questions, and mean number of polar questions for Black participants was significantly less than White participants. There was less variability in question type for Black participants than White participants, and a tendency for Black participants to ask fewer questions regardless of RHD or control status. Acquisition of health information and ensuing health care might be less fruitful for Black women communicating with someone who may not know to conduct comprehension checks and be proactive in provision of information. To be culturally responsive to Black patients with communication disorders, providers might apply this awareness of reduced question-asking to their strategies to improve patient-provider communication. https://doi.org/10.23641/asha.21809475.

Apragmatism: The renewal of a label for communication disorders associated with right hemisphere brain damage.

Right hemisphere communication disorders are neither consistently labelled nor adequately defined. Labels associated with right hemisphere brain damage (RHD) are broad and fail to capture the essence of communication challenges needed for stroke-related service provisions. Determination of rehabilitation needs and best-practice guidelines for the education, management and functional improvement of communication disorders after RHD are all predicated on an apt diagnostic label and disorder characteristics. In this paper apragmatism is proposed as a potential communication-specific diagnostic label for the impairments in communication that occur after RHD. In particular, the researchers aimed: (1) to establish an operational definition of apragmatism; and (2) to describe the linguistic, paralinguistic and extralinguistic communication deficits under the umbrella term apragmatism. An international collaborative of researchers with expertise in RHD followed a multilevel approach to consider the utility of apragmatism as a diagnostic label. Adopting the relational approach to concept mapping, the researchers engaged in a series of group meetings to complete four levels of mapping: (1) identify and review, (2) define, (3) expert discussion and (4) label determination. Apragmatism was established as a suitable diagnostic label for the impairments in communication associated with RHD. The paper offers an operational definition and description of the linguistic, paralinguistic and extralinguistic features of apragmatism through evidence summaries and examples from people with RHD retrieved from the RHDBank. The adoption of the term apragmatism offers an opportunity to capture the hallmark of RHD communication deficits. The use of the term is recommended when referencing the pragmatic language impairments in this population. Apragmatism, which may co-occur with or be exacerbated by cognitive impairments, can interfere with the ability to interpret and convey intended meaning and impact the lives of right hemisphere stroke survivors and their families. What is already known on the subject RHD results in a heterogeneous group of deficits that range in cognitive-communicative complexity. Many of the deficits are subsumed under pragmatics. For example, adults with RHD may demonstrate tangential or verbose communication, insensitivity to others' needs and feelings, prosodic changes, minimal gesture use and facial expression, and more. While descriptions of pragmatic impairments pervade the literature, there is no consistently used diagnostic label. The clinical consequences of this absence include difficulty with inter- and intra-disciplinary communication about these patients, difficulty consolidating findings across research studies, and challenges in communicating about these pragmatic changes with patients, families and other stakeholders. What this paper adds to existing knowledge The term apragmatism is proposed as a diagnostic label to consistently describe pragmatic communication changes after RHD. Apragmatism is characterized using three components of pragmatics: linguistic, paralinguistic and extralinguistic. Descriptions and examples of these three components are provided with supplemental transcripts retrieved from the RHDBank. What are the potential or actual clinical implications of this work? Adoption of the term apragmatism by speech and language therapists and other medical and rehabilitation professionals has the potential to provide consistency in describing the abilities and challenges experienced by people following a right hemisphere stroke. Such improvements may help drive the development of evidence-based assessments and treatments for this population.

Clinical Guidelines for Eliciting Discourse Using the RHDBank Protocol.

Examining discourse after right hemisphere brain damage (RHD) can provide invaluable clinical data and insight into functional communication capabilities. Yet, clinicians preparing to enter the field may have limited experience eliciting and analyzing discourse for therapeutic purposes. The purpose of this work is to present a practical guide for the clinical use of the RHDBank protocol. Following a brief overview of the RHDBank protocol, elicitation guidelines and protocol administration considerations are offered. Measures that should be considered when analyzing RHDBank-elicited discourse are summarized. The RHDBank protocol is positioned as an accessible resource for discourse elicitation in the clinical setting, and examples for the clinical use of the protocol are provided. Discourse production can be a key source of information regarding communication ability following RHD. The RHDBank provides a structured and scripted approach to the clinical elicitation of language and consideration of discourse production. Its immediate clinical utility will assist developing clinicians with the acquisition of a clinically relevant elicitation approach and more comprehensive view of the RHD communication impairments. Application of the protocol can aid in collective knowledge advancement that will promote a better understanding of RHD language production as a clinical entity with an array of possible characteristics.

The Effects of Right Hemisphere Brain Damage on Question-Asking in Conversation.

Right hemisphere brain damage (RHD) can cause challenges with information gathering. Cognitive processes aid in implicit and explicit information gathering, yet the relationship between these processes and question-asking, the most explicit avenue of information gathering, has not been explored. The purpose of this exploratory descriptive study was to test the hypothesis that adults with RHD differ from controls in the types of questions produced during a conversational discourse task and whether observed differences are associated with cognitive limitations. Adults with RHD (n = 15) and controls (n = 15) participated in a 5-min "first-encounter conversation" and were assessed for attention, memory, executive functioning (EF), visuospatial skills, and language domains using the Cognitive Linguistic Quick Test (CLQT). Questions produced during the conversation were coded and tallied by type: polar (yes/no), content (wh-), or alternative (A or B) using Computerized Language Analysis programs. Groups were compared on total questions used, use of questions by type, and CLQT domain scores; associations were computed between cognitive domain scores and question types. Compared with controls, adults with RHD used half as many questions overall and scored significantly lower on the attention, executive function, and visuospatial domains of the CLQT. For the RHD group, there was a significant correlation between EF scores and the production of content and polar questions. The frequency of question-asking is important to understanding the communication profile in adults with RHD. Executive function, attention, and, to a lesser extent, visuospatial capabilities may contribute to question-asking behaviors in conversation in this population. The RHD Framework for Asking Questions is proposed to illustrate the potential areas of deficit in the question-asking process after RHD.

Aprosodia Subsequent to Right Hemisphere Brain Damage: A Systematic Review and Meta-Analysis.

To identify which aspects of prosody are negatively affected subsequent to right hemisphere brain damage (RHD) and to evaluate the methodological quality of the constituent studies. Twenty-one electronic databases were searched to identify articles from 1970 to February 2020 by entering keywords. Eligibility criteria for articles included a focus on adults with acquired RHD, prosody as the primary research topic, and publication in a peer-reviewed journal. A quality appraisal was conducted using a rubric adapted from Downs and Black (1998). Of the 113 articles appraised as eligible and appropriate for inclusion, 71 articles were selected to undergo data extraction for both meta-analyses of population effect size estimates and qualitative synthesis. Across all domains of prosody, the effect estimate was g = 2.51 [95% CI (1.94, 3.09), t = 8.66, p < 0.0001], based on 129 contrasts between RHD and non-brain-damaged healthy controls (NBD), indicating a significant random effects model. This effect size was driven by findings in emotional prosody, g = 2.48 [95% CI (1.76, 3.20), t = 6.88, p < 0.0001]. Overall, studies of higher quality (rpb = 0.18, p < 0.001) and higher sample size/contrast ratio (rpb = 0.25, p < 0.001) were more likely to report significant differences between RHD and NBD participants. The results confirm consistent evidence for emotional prosody deficits in the RHD population. Inconsistent evidence was observed across linguistic prosody domains and pervasive methodological issues were identified across studies, regardless of their prosody focus. These findings highlight the need for more rigorous and sufficiently high-powered designs to examine prosody subsequent to RHD, particularly within the linguistic prosody domain.

Storytelling in speakers with and without brain damage: A macrolinguistic approach

Narrative discourse is investigated in clinical and healthy populations. This study explored the discourse strategies used to tell stories, comparing the patterns of people with left- and right-hemisphere brain damage, as well as healthy speakers. We analyzed picture-elicited discourses by four people with aphasia, two people with right hemisphere damage, and four healthy speakers. We examined their microlinguistic properties, as well as macrolinguistic features, such as the discourse production type of utterances and patterns of story component usage. We identified two storytelling strategies used by the speakers: a narrative strategy marked by a prevalence of narrative discourse production type utterances and scarce use of evaluation clauses, and a quasi-narrative strategy with the opposite pattern. These strategies were used by both healthy speakers and participants with brain damage.

The Focal Attention Window Size Explains Letter Substitution Errors in Reading.

Acquired Neglect Dyslexia is often associated with right-hemisphere brain damage and is mainly characterized by omissions and substitutions in reading single words. Martelli et al. proposed in 2011 that these two types of error are due to different mechanisms. Omissions should depend on neglect plus an oculomotor deficit, whilst substitutions on the difficulty with which the letters are perceptually segregated from each other (i.e., crowding phenomenon). In this study, we hypothesized that a deficit of focal attention could determine a pathological crowding effect, leading to imprecise letter identification and consequently substitution errors. In Experiment 1, three brain-damaged patients, suffering from peripheral dyslexia, mainly characterized by substitutions, underwent an assessment of error distribution in reading pseudowords and a T detection task as a function of cue size and timing, in order to measure focal attention. Each patient, when compared to a control group, showed a deficit in adjusting the attentional focus. In Experiment 2, a group of 17 right-brain-damaged patients were asked to perform the focal attention task and to read single words and pseudowords as a function of inter-letter spacing. The results allowed us to confirm a more general association between substitution-type reading errors and the performance in the focal attention task.

Making Sense of Right Hemisphere Discourse Using RHDBank.

Right hemisphere brain damage (RHD) commonly causes pragmatic language disorders that are apparent in discourse production. Specific characteristics and approaches to assessment, diagnosis, and treatment of these disorders are not well-defined. RHDBank, a shared database of multimedia interactions for the study of communication using discourse, was created to address these gaps. The database, materials, and related analysis programs are free resources to clinicians, researchers, educators, and students. A standard discourse protocol was developed to elicit multiple types of discourse: free speech, conversation, picture description, storytelling, procedural discourse, and question-asking. Testing included measures of cognition, unilateral neglect, and communicative participation. Language samples were video-recorded and transcribed in CHAT format. Currently, the database includes 24 adults with RHD and 24 controls. Illustrative analyses show how RHDBank can facilitate research using micro- and macrolinguistic discourse analysis techniques both within this population and across populations. Educational resources, such as the Grand Rounds tutorial, were developed using case studies from the database. RHDBank is a shared database of resources that can facilitate educational and research efforts to address the gaps in knowledge about RHD communication and improve the clinical management of individuals with RHD.

Zaburzenia sprawności językowych i komunikacyjnych u chorych po udarze prawej półkuli mózgu. Opisy przypadków.

Right hemisphere brain damage manifests itself in the language at the level of not only expression but also reception. Utterances of people with right hemisphere dysfunctions are often disorderly and illogical. As recipients, patients with right hemisphere brain damage, for instance, interrupt their interlocutor’s utterance, cannot understand jokes, mockeries, or ambiguous messages. The paper describes language and communication defi cits arising from right hemisphere brain damage and cases of patients suffering from right hemisphere disorder. The data obtained in the course of examining people with right hemisphere damage show that the most disturbed aspects of language include: lexical and semantic processing, processing complex language information, discourse, and prosody.

Effects of executive attention on garden path processing in Broca’s aphasia

Effects of executive attention on garden path processing in Broca’s aphasia

Design fluency subsequent to onset of aphasia: a distinct pattern of executive function difficulties?

ABSTRACTBackground: Executive function problems commonly co-occur with aphasia and influence language and communication performance as well as aphasia treatment outcomes and prognosis. Prior research, however, has focused on a restricted set of executive skills.Aims: This study examined further the integrity of executive functioning and its relationship to language performance in individuals with aphasia by utilising a design fluency measure, which assesses executive skills like initiation, planning, and cognitive flexibility. To examine domain-general versus domain-specific executive problems and determine the distinctiveness of the aphasic group’s performance pattern, adults with right hemisphere brain damage (RHD) were included. The hypotheses examined were: (a) compared to adults with no brain damage, the aphasic and RHD groups would display design fluency impairments; (b) the design fluency performances of aphasic and RHD groups would be quantitatively but not qualitatively similar; and (c) the design fluency performances of the aphasic and RHD groups would be related to their language abilities, as well as their performance of other executive and cognitive measures.Methods and Procedures: Participants with aphasia, RHD, or no brain damage completed the Ruff Figural Fluency Test (RFFT; Ruff, 1996), the results of which were quantitatively (i.e., number of unique designs, a perseverative error ratio) and qualitatively analysed (i.e., number and maximum length of orderly patterns, design complexity, number, and types of non-repetition errors), along with a formal cognitive-linguistic test battery and a verbal fluency task.Outcomes and Results: The traditional, quantitative RFFT scores of the aphasia, and RHD groups were significantly lower than those of the control group. Only the RHD group significantly differed from the control group when qualitative RFFT variables were analysed. RFFT performances correlated with language and other cognitive test scores, with some differences in the number and nature of these associations across the aphasic and RHD groups.Conclusions: The current design fluency findings indicated that executive function deficits involving initiation, planning, self-monitoring, and cognitive flexibility commonly co-occur with aphasia. These results supported previous research by identifying executive function impairments in many, however, not all individuals with aphasia, and by confirming influential associations between executive function and language, and communication measures. Inclusion of individuals with RHD indicated that such executive function difficulties and a potent relationship between executive functioning and language skills are not only unique to those with aphasia but also prevalent in other patient populations and consistent with the contribution of domain-general factors in acquired cognitive impairments.

Negative Word Production in Adults With Right Hemisphere Brain Damage: Effects of Implicit Assessment and Contextual Bias.

Both theory and evidence suggest that unilateral right hemisphere brain damage (RHD) should impair the processing of negative emotions. Typical metalinguistic assessments, however, may obscure processing strengths. This study investigated whether adults with RHD would produce proportionately fewer negative emotion words than control participants in an implicit assessment task and whether a negatively toned contextual bias would enhance performance. Eleven participants with RHD and 10 control participants without brain damage watched a video in 2 parts and described each segment. Between segments, participants evaluated the emotion conveyed by sentences designed to induce the negative bias. The primary outcome measure, percentage of negative emotion words in video descriptions, did not differ between groups. After the contextual bias, this measure significantly increased for both groups, whereas production of motion words, a control variable, remained constant. Findings are consistent with a view that attributes some deficient RHD performances to the nature and/or demands of explicit metalinguistic assessment tasks. These results call for modulation of prevailing hypotheses that attribute negative emotion processing as an undifferentiated whole solely to the right cerebral hemisphere. The results also further substantiate the rationale of an experimental treatment that exploits contextual bias and priming for individuals with RHD.

Voxel-Based Lesion Symptom Mapping of Coarse Coding and Suppression Deficits in Patients With Right Hemisphere Damage.

This study examined right hemisphere (RH) neuroanatomical correlates of lexical-semantic deficits that predict narrative comprehension in adults with RH brain damage. Coarse semantic coding and suppression deficits were related to lesions by voxel-based lesion symptom mapping. Participants were 20 adults with RH cerebrovascular accidents. Measures of coarse coding and suppression deficits were computed from lexical decision reaction times at short (175 ms) and long (1000 ms) prime-target intervals. Lesions were drawn on magnetic resonance imaging images and through normalization were registered on an age-matched brain template. Voxel-based lesion symptom mapping analysis was applied to build a general linear model at each voxel. Z score maps were generated for each deficit, and results were interpreted using automated anatomical labeling procedures. A deficit in coarse semantic activation was associated with lesions to the RH posterior middle temporal gyrus, dorsolateral prefrontal cortex, and lenticular nuclei. A maintenance deficit for coarsely coded representations involved the RH temporal pole and dorsolateral prefrontal cortex more medially. Ineffective suppression implicated lesions to the RH inferior frontal gyrus and subcortical regions, as hypothesized, along with the rostral temporal pole. Beyond their scientific implications, these lesion-deficit correspondences may help inform the clinical diagnosis and enhance decisions about candidacy for deficit-focused treatment to improve narrative comprehension in individuals with RH damage.

Depressive signs and cognitive performance in patients with a right hemisphere stroke.

This study investigated the influence of suggestive signs of depression (SSD) in right-hemisphere brain-damaged (RHD) patients following a stroke on their cognitive performance measured by a brief neuropsychological assessment battery. Forty-two adults with RHD after a single episode of stroke and 84 matched controls participated in this study. They were assessed by means of the Geriatric Depression Scale and by Brief Neuropsychological Assessment Battery NEUPSILIN. Almost half of the patients showed SSD. The RHD group with SSD (RHD+) showed poorer performance in at least one task among all evaluated cognitive domains (concentrated attention, visual perception, working memory, episodic verbal memory and semantic memory, auditory and written language, constructional praxia and verbal fluency). The association of depression and RHD seems to enhance the occurrence and the severity of cognitive déficits. A brief neuropsychological assessment can be useful to identify cognitive impairment caused by this neuropsychiatric disorder.

Suppression and Narrative Time Shifts in Adults With Right-Hemisphere Brain Damage

This study examined the functioning of a central comprehension mechanism, suppression, in adults with right-hemisphere damage (RHD) while they processed narratives that cued a shift in time frame. In normal language comprehension, mental activation of concepts from a prior time frame is suppressed. The (re)activation of information following a time frame shift was also assessed. Twenty adults (12 RHD; 8 non brain-damaged) completed a speeded word recognition task while listening to narratives in 2 conditions: shift ("an hour later") and no shift ("a moment later"). There was no group difference in suppression for response time proportion data (shift/no shift), but cluster analyses identified a suppression deficit in 8 of the adults with RHD. There was overlap in suppression function at the narrative and lexical levels. The group with RHD was significantly delayed in mentally (re)activating new information after a time shift cue. Results underscore the generality of suppression functioning in adults with RHD. As such, treatment for a suppression deficit at one level may generalize to another level. An apparent independence of suppression and activation deficits suggests that each may need separate treatment. A better understanding of the nature and boundary conditions of suppression and activation deficits should better inform clinical decisions.

Effects of left and right hemisphere damage on sensitivity to global context during lexical ambiguity resolution

Background: A great deal of research suggests that both the left hemisphere (LH) and right hemisphere (RH) contribute to the resolution of lexically ambiguous words. If this is indeed the case, then patients with left (LHD) or right hemisphere brain damage (RHD) should exhibit deficits in ambiguity resolution. Although several studies have explored this issue, there is still little consensus regarding the exact nature of the patients' deficits. Moreover, the focus of most studies has been on ambiguity resolution in short, single-sentence contexts, so less is known about the impact of LH and RH damage on ambiguity resolution in larger contexts. Aims: The goal of the present study was to investigate sensitivity to a global (i.e., two-sentence) context during lexical ambiguity resolution in LHD and RHD patients relative to a group of control participants with no neurological impairment. Control participants were expected to activate only contextually appropriate meanings. In contrast, LHD patients were expected to have difficulty activating ambiguous word meanings or selecting contextually appropriate meanings. RHD patients were expected to have difficulty using context or suppressing contextually inappropriate meanings. Methods & Procedures: Three groups of participants took part in this study: 10 LHD patients with nonfluent aphasia, 8 RHD patients, and 9 age-matched control participants. A cross-modal sentence priming task was employed where participants first listened to a biased two-sentence passage ending in an ambiguous word. After each passage a visual target word, related to either the first or second meaning of the ambiguous word, was presented for lexical decision. Reaction time data were analysed using a repeated-measures ANOVA. Priming effects were tested by way of planned comparisons. Outcomes & Results: The performance of both patient groups differed markedly from that of the control group, who only showed priming for contextually appropriate meanings. The LHD patients did not exhibit any significant priming of ambiguous word meanings, whereas the RHD patients only showed priming for the most frequent or dominant meaning of ambiguous words (e.g., the “animal” meaning as opposed to the “emblem” meaning of seal) regardless of context. Conclusions: Both LH and RH damage can disrupt the process of ambiguity resolution in a global context. Specifically, LH damage is argued to impair the degree of activation of ambiguous word meanings or the time course of meaning activation, while RH damage seems to impair the use of context, leading to frequency-based meaning activation.