Activation and maintenance of peripheral semantic features of unambiguous words after right hemisphere brain damage in adults

Computed tomography findings as early predictors of long-term language impairment in patients with traumatic brain injury

This study aims to assess the relationship between computed tomography (CT) findings, during the acute phase of hospitalization, and long-term language impairment in people with traumatic brain injury (TBI). Another aim was to assess the receptive and expressive abilities of subjects with TBI based on the location of the injury. This is a retrospective observational study including 49 participants with TBI due to war injuries. The Arabic Diagnostic Aphasia Battery (A-DAB-1) was administered to the participants and the Helsinki CT score was computed to quantify brain damage. The results showed that the Helsinki CT score was negatively correlated with the total score of the A-DAB-1 (r = -0.544, p-value < 0.0001). Simple linear regression supported such findings and reflected an inversely proportional relationship between both variables (p-value < 0.0001). When compared with subjects having right hemisphere damage, subjects with left hemisphere and bilateral brain damage performed more poorly on language tasks respectively as follows: A-DAB-1 overall score (92.08-66.08-70.28, p-value = 0.021), Content of descriptive speech (9.57-6.69-7.22, p-value = 0.034), Verbal fluency (6.57-3.54-3.89, p-value = 0.002), Auditory comprehension (9.71-7.54-7.78, p-value = 0.039), Complex auditory commands (9.71-7.65-7.56, p-value = 0.043), Repetition (9.75-7.08-7.61, p-value = 0.036), Naming (9.93-7.15-8.11, p-value = 0.046). Following TBI, CT findings on admission can significantly predict long-term language abilities, with left side lesions inducing poorer outcomes.

Treating limb apraxia via action semantics: a preliminary study

Limb apraxia is evident in approximately 50% of patients after left hemisphere cerebral vascular accident (LCVA) and increases disability and caregiver dependence. Individuals with apraxia exhibit abnormalities in spatio-temporal aspects of gesture production and/or in knowledge of tool-related actions (action semantics). This preliminary study of three LCVA participants aimed to (i) explore the efficacy of a novel Action Network Treatment (ANT) that focused on improving the semantic association between tool actions and other types of tool knowledge, an intervention inspired by successful semantic network treatments in aphasia (e.g., Edmonds et al., 2009), and (ii) explore whether there are individuals with apraxia who benefit from ANT relative to a version of a comparatively well-studied existing apraxia treatment (Smania et al., 2006; Smania et al., 2000) that shapes gesture via focus on practicing the spatio-temporal aspects of gesture production (Tool Use Treatment or TUT). One participant demonstrated treatment benefits from both ANT and TUT, while another only benefited from TUT. These findings indicate that our novel semantic network strengthening approach to gesture training may be efficacious in at least some individuals with apraxia, and provide a foundation for future study of the characteristics of people with apraxia who benefit from each approach.

The role of the right hemisphere in semantic control: A case-series comparison of right and left hemisphere stroke

Semantic control processes guide conceptual retrieval so that we are able to focus on non-dominant associations and features when these are required for the task or context, yet the neural basis of semantic control is not fully understood. Neuroimaging studies have emphasised the role of left inferior frontal gyrus (IFG) in controlled retrieval, while neuropsychological investigations of semantic control deficits have almost exclusively focussed on patients with left-sided damage (e.g., patients with semantic aphasia, SA). Nevertheless, activation in fMRI during demanding semantic tasks typically extends to right IFG. To investigate the role of the right hemisphere (RH) in semantic control, we compared nine RH stroke patients with 21 left-hemisphere SA patients, 11 mild SA cases and 12 healthy, aged-matched controls on semantic and executive tasks, plus experimental tasks that manipulated semantic control in paradigms particularly sensitive to RH damage. RH patients had executive deficits to parallel SA patients but they performed well on standard semantic tests. Nevertheless, multimodal semantic control deficits were found in experimental tasks involving facial emotions and the 'summation' of meaning across multiple items. On these tasks, RH patients showed effects similar to those in SA cases - multimodal deficits that were sensitive to distractor strength and cues and miscues, plus increasingly poor performance in cyclical matching tasks which repeatedly probed the same set of concepts. Thus, despite striking differences in single-item comprehension, evidence presented here suggests semantic control is bilateral, and disruption of this component of semantic cognition can be seen following damage to either hemisphere.

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

PURPOSE

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.

METHOD

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.

RESULTS

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.

CONCLUSION

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.

Contextual Constraint Treatment for coarse coding deficit in adults with right hemisphere brain damage: generalisation to narrative discourse comprehension

Coarse coding is the activation of broad semantic fields that can include multiple word meanings and a variety of features, including those peripheral to a word's core meaning. It is a partially domain-general process related to general discourse comprehension and contributes to both literal and non-literal language processing. Adults with damage to the right cerebral hemisphere (RHD) and a coarse coding deficit are particularly slow to activate features of words that are relatively distant or peripheral. This manuscript reports a pre-efficacy study of Contextual Constraint Treatment (CCT), a novel, implicit treatment designed to increase the efficiency of coarse coding with the goal of improving narrative comprehension and other language performance that relies on coarse coding. Participants were four adults with RHD. The study used a single-subject controlled experimental design across subjects and behaviours. The treatment involved pre-stimulation, using a hierarchy of strong and moderately biased contexts, to prime the intended distantly related features of critical stimulus words. Three of the four participants exhibited gains in auditory narrative discourse comprehension, the primary outcome measure. All participants exhibited generalisation to untreated items. No strong generalisation to processing non-literal language was evident. The results indicate that CCT yields both improved efficiency of the coarse coding process and generalisation to narrative comprehension.

Studies on semantic priming effects in right hemisphere stroke: A systematic review

The role of the right cerebral hemisphere (RH) associated with semantic priming effects (SPEs) must be better understood, since the consequences of RH damage on SPE are not yet well established.

Generalization of a Novel, Implicit Treatment for Coarse Coding Deficit in Right Hemisphere Brain Damage: A Single Subject Experiment

BACKGROUND: This manuscript reports generalization effects of Contextual Constraint Treatment for an adult with right hemisphere brain damage (RHD). Contextual Constraint Treatment is designed to stimulate inefficient language comprehension processes implicitly, by providing linguistic context to prime, or constrain, the intended interpretations of treatment stimuli. The study participant had a coarse coding deficit, defined as delayed mental activation of particularly distant semantic features of words (e.g., rotten as a feature of "apple"). Treatment effects were expected to generalize to auditory comprehension of narrative discourse, and perhaps to figurative language interpretation, because coarse coding has been hypothesized and/or demonstrated to support these abilities. AIMS: This treatment study aimed to induce generalization of Contextual Constraint Treatment in an adult with RHD with inefficient coarse coding. METHODS #ENTITYSTARTX00026; PROCEDURES: The participant in this study was a 75 year old man with RHD and a coarse coding deficit. A single subject experimental design across behaviors (stimulus lists) was used to document performance in baseline, treatment, and follow-up phases. Treatment consisted of providing brief, spoken context sentences to prestimulate, or constrain, intended interpretations of stimulus items. The participant made no explicit associations or metalinguistic judgments about the constraint sentences or stimulus words; rather, these contexts served only as implicit primes. Probe tasks were adapted from prior work on coarse coding in RHD. The dependent measure was the percentage of responses that met predetermined response time criteria. There were two levels of contextual constraint, Strong and Moderate. Treatment for each item began with the provision of the Strong constraint context, to minimize the production or reinforcement of erroneous or exceedingly slow responses. Generalization was assessed to a well-standardized measure of narrative discourse comprehension and to several metalinguistic tasks of figurative language interpretation. OUTCOMES #ENTITYSTARTX00026; RESULTS: Treatment-contingent gains, associated with respectable effect sizes, were evident after a brief period of treatment on one stimulus list. Generalization occurred to untrained items, suggesting that the treatment was facilitating the underlying coarse coding process. Most importantly, generalization was evident to narrative comprehension performance, for both overall accuracy and accuracy answering questions about implied information, and all of these gains maintained through three follow-up sessions. CONCLUSIONS: Though the results are still preliminary, this single-subject experimental design documents the potential for meaningful gains from a novel treatment that implicitly targets an underlying language comprehension process in an adult with RHD.

A novel, implicit treatment for language comprehension processes in right hemisphere brain damage: Phase I data

BACKGROUND: This manuscript reports the initial phase of testing for a novel, "Contextual constraint" treatment, designed to stimulate inefficient language comprehension processes in adults with right hemisphere brain damage (RHD). Two versions of treatment were developed to target two normal comprehension processes that have broad relevance for discourse comprehension and that are often disrupted by RHD: coarse semantic coding and suppression. The development of the treatment was informed by two well-documented strengths of the RHD population. The first is consistently better performance on assessments that are implicit, or nearly so, than on explicit, metalinguistic measures of language and cognitive processing. The second is improved performance when given linguistic context that moderately-to-strongly biases an intended meaning. Treatment consisted of providing brief context sentences to prestimulate, or constrain, intended interpretations. Participants made no explicit associations or judgments about the constraint sentences; rather, these contexts served only as implicit primes. AIMS: This Phase I treatment study aimed to determine the effects of a novel, implicit, Contextual Constraint treatment in adults with RHD whose coarse coding or suppression processes were inefficient. Treatment was hypothesized to speed coarse coding or suppression function in these individuals. METHODS #ENTITYSTARTX00026; PROCEDURES: Three adults with RHD participated in this study, one (P1) with a coarse coding deficit and two (P2, P3) with suppression deficits. Probe tasks were adapted from prior studies of coarse coding and suppression in RHD. The dependent measure was the percentage of responses that met predetermined response time criteria. When pre-treatment baseline performance was stable, treatment was initiated. There were two levels of contextual constraint, Strong and Moderate, and treatment for each item began with the provision of the Strong constraint context. OUTCOMES #ENTITYSTARTX00026; RESULTS: Treatment-contingent gains were evident after brief periods of treatment, for P1 on two treatment lists, and for P2. P3 made slower but still substantial gains. Maintenance of gains was evident for P1, the only participant for whom it was measured. CONCLUSIONS: This Phase I treatment study documents the potential for considerable gains from an implicit, Contextual constraint treatment. If replicated, this approach to treatment may hold promise for individuals who do poorly with effortful, metalinguistic treatment tasks, or for whom it is desirable to minimize errors during treatment. The real test of this treatment's benefit will come from later phase studies of study, which will test broad-based generalization to various aspects of discourse comprehension.

Performance of Individuals with Left-Hemisphere Stroke and Aphasia and Individuals with Right Brain Damage on Forward and Backward Digit Span Tasks

BACKGROUND: Working memory (WM) limitations have been suggested as a significant source of the linguistic processing deficits observed in individuals with aphasia (IWA). Digits forward (DF) and digits backward (DB) span tasks are frequently used to study WM in both healthy and clinical populations. Unfortunately, only a handful of studies have explored digit span in IWA. AIMS: The purpose of the current study is to measure the DF and DB spans of IWA and compare their digit spans to a group with right brain damage, but no aphasia (RBD). Additionally, DF and DB span is compared within each group to determine if there is indeed a performance differential that may support the idea that DB is a more difficult WM task in these populations. METHODS AND PROCEDURES: Seventeen IWA and 14 individuals with RBD participated in a DF and DB span task. Modifications to the span tasks were implemented to accommodate language deficits. A series of two digits were orally presented to each participant continuing to a maximum of eight digits. There were seven trials per digit series. Participants were asked to point to the correct order of digits on a written 1-9 digit list provided on individual note cards or verbally repeat the numbers if the participant was able to do so. OUTCOMES AND RESULTS: IWA demonstrated shorter digit spans than the RBD group. Both groups performed worse on the DB span tasks than the DF span tasks. CONCLUSIONS: The results are consistent with previous studies suggesting that DB span is shorter than DF span in other populations and that there are differences in performance on digit span tasks between the two groups. The differences between RBD group and IWA may be explained by decreased attentional capacity or inefficient resource allocation in IWA, or alternatively, a deficient phonological loop. Future studies should explore these possibilities.

Can high-level inferencing be predicted by Discourse Comprehension Test performance in adults with right hemisphere brain damage?

BACKGROUND: Adults with right hemisphere brain damage (RHD) can have considerable difficulty in drawing high-level inferences from discourse. Standardised tests of language comprehension in RHD do not tap high-level inferences with many items or in much depth, but nonstandardised tasks lack reliability and validity data. It would be of great clinical value if a standardised test could predict performance on high-level inferencing measures. AIMS: This study addressed whether performance of adults with RHD on the Discourse Comprehension Test (DCT; Brookshire & Nicholas, 1993) could predict their performance on a nonstandardised measure of high-level inference in narrative comprehension. METHODS #ENTITYSTARTX00026; PROCEDURES: This study used a within-group correlational design. Participants were 32 adults with damage limited to the right cerebral hemisphere, as a result of cerebrovascular accident. Half of the participants were male and half female. Participants averaged 64.5 years of age and 14.2 years of education. Participants listened to narrative stimuli and to yes/no questions about each narrative. Each DCT narrative was followed by the standard 8 questions about stated or implied main ideas or details. The high-level inferencing task contained 6 narrative scenarios from Winner, Brownell, Happé, Blum, and Pincus (1998). Each scenario describes a character who commits a minor transgression and later denies it. Two versions of each story are designed to induce different interpretations of the character's denial. In one version, the character tells a white lie when he is unaware that he was seen committing the transgression. In the other versions, when aware of being seen, the character makes an ironic joke. The narratives were interrupted periodically by comprehension questions. Four Pearson correlation coefficients were computed, between each of two DCT predictor variables (total accuracy for all comprehension questions; accuracy on questions about implied information) and two indicators of high-level inferencing (total accuracy to answer experimental questions in Joke stories; total accuracy to answer experimental questions in Lie stories). OUTCOMES #ENTITYSTARTX00026; RESULTS: Correlation coefficients were low-to-moderate, and nonsignificant. CONCLUSIONS: Performance on the DCT by adults with RHD did not predict their high-level inferencing performance, as measured in this study. The issue that motivated this study should be pursued further in light of the potential advantages to be gained, for both clinical and research purposes. It may be, however, that specific measures of various types of high-level inferencing will need to be developed and validated.

Discourse Impairments Following Right Hemisphere Brain Damage: A Critical Review

Right hemisphere brain damage (RHD) rarely causes aphasias marked by clear and widespread failures of comprehension or extreme difficulty producing fluent speech. Nonetheless, subtle language comprehension deficits can occur following unilateral RHD. In this article, we review the empirical record on discourse function following right hemisphere damage, as well as relevant work on non-brain damaged individuals that focuses on right hemisphere function. The review is divided into four sections that focus on discourse processing, inferencing, humor, and non-literal language. While the exact role that the right hemisphere plays in language processing, and the exact way that the two cerebral hemispheres coordinate their linguistic processes are still open to debate, our review suggests that the right hemisphere plays a critical role in managing inferred or implied information by maintaining relevant information and/or suppressing irrelevant information. Deficits in one or both of these mechanisms may account for discourse deficits following RHD.

Theoretical Considerations for Understanding "Understanding" by Adults With Right Hemisphere Brain Damage

This article reviews and evaluates leading accounts of narrative comprehension deficits in adults with focal damage to the right cerebral hemisphere (RHD). It begins with a discussion of models of comprehension, which explain how comprehension proceeds through increasingly complex levels of representation. These models include two phases of comprehension processes, broad activation of information as well as pruning and focusing interpretation of meaning based on context. The potential effects of RHD on each processing phase are reviewed, focusing on factors that range from relatively specific (e.g., how the right versus the left hemisphere activate word meanings; how the right hemisphere is involved in inferencing) to more general (the influence of cognitive resource factors; the role of suppression of contextually-irrelevant information). Next, two specific accounts of RHD comprehension difficulties, coarse coding and suppression deficit, are described. These have been construed as opposing processes, but a possible reconciliation is proposed related to the different phases of comprehension and the extent of meaning activation. Finally, the article addresses the influences of contextual constraint on language processing and the continuity of literal and nonliteral language processing, two areas in which future developments may assist our clinical planning.

Coarse coding and discourse comprehension in adults with right hemisphere brain damage

BACKGROUND: Various investigators suggest that some discourse-level comprehension difficulties in adults with right hemisphere brain damage (RHD) have a lexical-semantic basis. As words are processed, the intact right hemisphere arouses and sustains activation of a wide-ranging network of secondary or peripheral meanings and features-a phenomenon dubbed "coarse coding". Coarse coding impairment has been postulated to underpin some prototypical RHD comprehension deficits, such as difficulties with nonliteral language interpretation, discourse integration, some kinds of inference generation, and recovery when a reinterpretation is needed. To date, however, no studies have addressed the hypothesised link between coarse coding deficit and discourse comprehension in RHD. AIMS: The current investigation examined whether coarse coding was related to performance on two measures of narrative comprehension in adults with RHD. METHODS #ENTITYSTARTX00026; PROCEDURES: Participants were 32 adults with unilateral RHD from cerebrovascular accident, and 38 adults without brain damage. Coarse coding was operationalised as poor activation of peripheral/weakly related semantic features of words. For the coarse coding assessment, participants listened to spoken sentences that ended in a concrete noun. Each sentence was followed by a spoken target phoneme string. Targets were subordinate semantic features of the sentence-final nouns that were incompatible with their dominant mental representations (e.g., "rotten" for apple). Targets were presented at two post-noun intervals. A lexical decision task was used to gauge both early activation and maintenance of activation of these weakly related semantic features. One of the narrative tasks assessed comprehension of implied main ideas and details, while the other indexed high-level inferencing and integration. Both comprehension tasks were presented auditorily. For all tasks, accuracy of performance was the dependent measure. Correlations were computed within the RHD group between both the early and late coarse coding measures and the two discourse measures. Additionally, ANCOVA and independent t-tests were used to compare both early and sustained coarse coding in subgroups of good and poor RHD comprehenders. OUTCOMES #ENTITYSTARTX00026; RESULTS: The group with RHD was less accurate than the control group on all measures. The finding of coarse coding impairment (difficulty activating/sustaining activation of a word's peripheral features) may appear to contradict prior evidence of RHD suppression deficit (prolonged activation for context-inappropriate meanings of words). However, the sentence contexts in this study were unbiased and thus did not provide an appropriate test of suppression function. Correlations between coarse coding and the discourse measures were small and nonsignificant. There were no differences in coarse coding between RHD comprehension subgroups on the high-level inferencing task. There was also no distinction in early coarse coding for subgroups based on comprehension of implied main ideas and details. But for these same subgroups, there was a difference in sustained coarse coding. Poorer RHD comprehenders of implied information from discourse were also poorer at maintaining activation for semantically distant features of concrete nouns. CONCLUSIONS: This study provides evidence of a variant of the postulated link between coarse coding and discourse comprehension in RHD. Specifically, adults with RHD who were particularly poor at sustaining activation for peripheral semantic features of nouns were also relatively poor comprehenders of implied information from narratives.