Right Hemisphere Damage Group Research Articles

The continuous performance test aids the diagnosis of post-stroke cognitive impairment in patients with right hemisphere damage.

The purpose of the study was to investigate the time course difference of relative changes in oxygenated hemoglobin (Oxy-Hb) concentration in the prefrontal cortex (PFC) between controls and patients with post-stroke cognitive impairment (PSCI) who had right hemisphere damage (RHD) using the continuous performance test (CPT) and functional near-infrared spectroscopy (fNIRS) technology. The study aimed to evaluate the feasibility of CPT in the diagnosis and evaluation of PSCI with RHD. A total of 16 patients with RHD (RHD group) and 32 normal subjects (control group) were recruited. The Montreal Cognitive Assessment Scale was used to assess post-stroke cognitive impairment. The CPT and fNIRS were employed to investigate task-related changes in Oxy-Hb levels. The RHD group showed significantly lower accuracy and hit rates than the control group; however, the average reaction time was significantly longer in the former. Although the two groups showed no statistically significant difference in terms of left and right PFC integral values, the mean values were greater in the RHD group. The centroid value of the right PFC was significantly higher in the RHD group than in the control group. The time course of Oxy-Hb concentrations in the PFC differed between the two groups. In the RHD group, neural compensation was observed in both prefrontal lobes; however, the rate of compensation was slower on the affected side. The CPT may be helpful in the clinical diagnosis of PSCI with RHD. It may therefore be used to evaluate the effectiveness of cognitive interventions.

Perception of grammatical tone in Akan patients with left and right hemisphere brain damage

ABSTRACT It remains a matter of debate what roles the left and right hemispheres play in processing speech prosody. Brain lesion studies have demonstrated that lexical tone perception among native speakers of tonal languages is more disrupted in left hemisphere damaged (LHD) individuals than right hemisphere damaged (RHD) individuals. This has been taken to suggest that linguistically-relevant prosodic cues are predominantly left-lateralised, whereas non-linguistic stimuli are predominantly right-lateralised. However, this phenomenon has only been examined in lexical tone, leaving grammatical tone perception unexplored. The aim of this study was twofold: Firstly, to examine how individuals with LHD and RHD perceive grammatical tone, and secondly to compare grammatical tone to non-linguistic tone perception. Therefore, native Akan speakers with LHD, RHD and no-brain damage (NBD) controls were tested in two discrimination tasks that examined linguistic and non-linguistic tone perception. The results showed that while both the individuals with LHD and RHD show impairment in grammatical tone perception, there was a trend of a better performance for the RHD group. Nonetheless, for non-linguistic tone perception, individuals with LHD outperformed the RHD individuals, although both had reduced performance compared to the NBD individuals. A further analysis revealed that the reduced perceptual abilities of both the LHD and RHD groups in grammatical tone perception can be attributed to grammatical problems rather than tone per se. We conclude that there is potentially a bilateral involvement of the two hemispheres in grammatical tone processing, with the left being the dominant hemisphere.

Reading and listening comprehension in Cantonese-speaking people with right hemisphere versus left hemisphere brain damage

ABSTRACT The problem in language comprehension in people with right hemisphere damage (RHD) is more equivocal than people with left hemisphere damage. This study explores the reading and listening comprehension of Cantonese-speaking individuals with RHD, left hemisphere damage, and neurotypical healthy controls using the Cantonese Computerized Revised Token Test (CRTT-Cantonese) adapted from the English CRTT. Eighteen native Cantonese-speaking individuals with RHD, 32 individuals with left hemisphere damage and aphasia (PWA), and 42 healthy controls participated in this study. All the participants completed the Cantonese Aphasia Battery, Hong Kong Oxford Cognitive Screen, the listening comprehension version of CRTT-Cantonese (CRTT-L-Cantonese), and the reading comprehension version of CRTT-Cantonese (CRTT-R-WF-Cantonese) across different sessions. Linear mixed-effect analysis revealed significant differences among the groups in CRTT-Cantonese tests. However, there were no significant difference between CRTT-L-Cantonese and CRTT-R-WF-Cantonese within the PWA, RHD and healthy control groups. Tukey post-hoc pairwise comparisons showed that PWA scored significantly lower than RHD and healthy control groups (p < 0.0001) in both CRTT-L-Cantonese and CRTT-R-WF-Cantonese, and the RHD group scored significantly lower than healthy control group only on the CRTT-R-WF-Cantonese. The results demonstrate that the CRTT-L-Cantonese and CRTT-R-WF-Cantonese differentiate language comprehension abilities among PWA, RHD and healthy control groups. Although the current findings did not show any diversion between reading and listening comprehension in RHD group, this group showed poorer performance in reading comprehension when compared to healthy controls. The latter findings may support the view that the right hemisphere contributes to reading comprehension in Chinese.

Pragmatic deficits in patients with schizophrenia and right hemisphere damage: A pilot study.

While pragmatic deficits are well documented in patients with schizophrenia (SCZ) and right hemisphere damage (RHD), there is a paucity of research comparing the pragmatic deficits of these two groups. Do they experience similar cognitive dysfunction or is there a dissociation between the two patient groups? To investigate the nature of pragmatic deficits in these two groups and to gain an understanding of the underlying cognitive mechanisms that might be associated with these deficits to further future investigations. A total of 60 participants (15 patients with SCZ; 15 with RHD; 30 (15 + 15) healthy controls (HC) were administered the Bengali Audio-Visual Test-Battery for Assessment of Pragmatic Skills. Both SCZ and RHD patients were found to have significant pragmatic deficits compared with their matched controls. SCZ patients were found to score significantly better than the RHD group in six out of the 10 pragmatic skills when controlled for age and education. Discriminant function analysis was performed and 86.7% of the cases (HC = 100%, SCZ = 73.3% and RHD = 86.7%) were correctly reclassified into their original categories using the test scores. The study suggests that there is heterogeneity in the nature of the pragmatic breakdown within and across patient groups. Therefore, individualized restorative measures targeting the disrupted cognitive mechanism(s) might help elevate pragmatic competence and enhance the social functioning of patients with pragmatic deficits. What is already known on the subject Pragmatic deficits are common in adults with cognitive impairments of different etiologies. However, few studies have explored pragmatic deficits across clinical populations. Consequently, very little is known about the nature of pragmatic deficits in patients with schizophrenia and right hemisphere damage. What this paper adds to existing knowledge This work offers preliminary data on pragmatic difficulties in patients with schizophrenia and right hemisphere damage. This study overrides the boundaries of traditional classifications and evaluates pragmatic difficulties in these two clinical populations with reference to the underlying cognitive mechanisms, which might be disrupted. What are the potential or actual clinical implications of this work? The study adds a transdiagnostic perspective suggesting that there might be heterogeneity in pragmatic deficits, both within and across patient groups, and stresses the need for individualized therapy.

Left hemisphere damage produces deficits in predictive control of bilateral coordination.

Previous research has demonstrated hemisphere-specific motor deficits in ipsilesional and contralesional unimanual movements in patients with hemiparetic stroke due to MCA infarct. Due to the importance of bilateral motor actions on activities of daily living, we now examine how bilateral coordination may be differentially affected by right or left hemisphere stroke. To avoid the caveat of simply adding unimanual deficits in assessing bimanual coordination, we designed a unique task that requires spatiotemporal coordination features that do not exist in unimanual movements. Participants with unilateral left (LHD) or right hemisphere damage (RHD) and age-matched controls moved a virtual rectangle (bar) from a midline start position to a midline target. Movement along the long axis of the bar was redundant to the task, such that the bar remained in the center of and parallel to an imaginary line connecting each hand. Thus, to maintain midline position of the bar, movements of one hand closer to or further away from the bar midline required simultaneous, but oppositely directed displacements with the other hand. Our findings indicate that left (LHD), but not right (RHD) hemisphere-damaged patients showed poor interlimb coordination, reflected by significantly lower correlations between displacements of each hand along the bar axis. These left hemisphere-specific deficits were only apparent prior to peak velocity, likely reflecting predictive control of interlimb coordination. In contrast, the RHD group bilateral coordination was not significantly different than that of the control group. We conclude that predictive mechanisms that govern bilateral coordination are dependent on left hemisphere mechanisms. These findings indicate that assessment and training in cooperative bimanual tasks should be considered as part of an intervention framework for post-stroke physical rehabilitation.

Asymmetries in force matching are related to side of stroke in right-handed individuals

Asymmetries in grasp force matching extend beyond quantifying a single measure of maximum grip strength and advance our application of side-specific treatment interventions. A cross sectional study design investigated grasp-force matching performance in right-handed individuals with a stroke and age-matched healthy controls. A visual representation of the 20% Maximum Voluntary Contraction (MVC) was matched in three conditions in the absence of visual feedback with the same (Ipsilateral Remembered – IR) or opposite hand (Concurrent – CC and Contralateral Remembered – CR). Greater overall relative error (RE) was found in contralateral compared to ipsilateral matching tasks. In the CR condition, post hoc analysis revealed significant differences between control and right hemisphere damage (RHD) group (95% CI [16.41–88.59]; p < 0.01) as well as left hemisphere damage (LHD) group and RHD (95% CI [23.4–95.09]; p < 0.01). Right hand matching relative error was 2.49 times larger in the RHD compared to the LHD group. Within the RHD group, matching errors were greater for the right than left hand in both contralateral conditions (95% CI [34.25–101.07]; p < 0.001).Individuals with RHD showed greater asymmetries in contralateral matching tasks compared to LHD and controls. More specifically, the RHD group had the greatest difficulty matching tasks with their right (non-paretic) than left (paretic) hand. In order to elucidate this asymmetry in the clinic the use of complementary grasp measures may be considered.

Effects of lesion extent and location on upper limb function following hemispheric stroke

A large proportion of stroke survivors present spastic paresis of the upper limb (UL). Therapeutic interventions result in large variance in the response of patients to the same treatment protocols, possibly stemming from differences in lesion characteristics, among other factors. Here we concentrated on the impact of lesion size and location on UL function following stroke, comparing the effect of right hemisphere damage (RHD) to that of left hemisphere damage (LHD). Clinical and lesion data for the current study were collected as part of a multicenter randomized, controlled trial (ENHANCE project; ClinicalTrials.gov, ID: NCT02725853 ). Two groups of patients with subacute stroke were compared: those with right hemisphere ( n = 8) and left hemisphere damage ( n = 15). Voxel-based lesion symptom mapping (VLSM) was employed to identify voxel clusters in the normalized brain where damage exerts a significant impact on the functioning of the hemiparetic UL, as revealed by the Functional Ability Scale of the short (streamlined) version of the Wolf Motor Function Test. Motor function of the hemiparetic UL was affected in LHD patients by damage to voxel clusters involving (a) cortical areas of the superior temporal regions and the insula, (b) white matter tracts, notably the superior and inferior fronto-occipital fascicles, the corona radiata and the internal capsule, and (c) the basal ganglia and thalamus. In the RHD group, VLSM analysis showed a different pattern where UL function was affected almost exclusively by damage to subcortical structures of the corona radiata, the capsular-putaminal region, the superior longitudinal fasciculus and the external capsule. Motor function of the hemiparetic upper limb in patients with subacute stroke was affected differently by damage to homologous structures in the left and right cerebral hemispheres.

Effects of lesion extent and location on upper limb spasticity following hemispheric stroke

Spasticity of the hemiparetic upper limb (UL) leading to difficulty performing activities of daily living is a major concern in stroke rehabilitation. Spasticity results from impaired control of motoneuronal activation thresholds exerted by descending direct and indirect pathways. This is reflected by pathological alteration of the specific muscle length/joint angle at which the stretch reflex and other proprioceptive reflexes begin to act (tonic stretch reflex threshold, TSRT). The relationship between lesion location and the appearance of spasticity is poorly understood. We investigated the relationship between lesion characteristics and elbow-flexor (biceps) TSRT in the hemiparetic UL, as part of an international multicenter RCT (ENHANCE project; ClinicalTrials.gov, ID: NCT02725853 ). Elbow-flexor TSRT (°) was examined in 8 right-hemisphere damaged (RHD) and 15 left hemisphere damaged (LHD) stroke patients using the Montreal Stretch Reflex Threshold device. Normalized lesion data were used for voxel-based lesion-symptom mapping (VLSM) analyses of lesion impact on biceps spasticity. Application of VLSM using 10 continuous affected voxels as a minimum for consideration, showed in the LHD group, a cluster localized in the superior part of the corona radiata, where damage affected the level of spasticity in the biceps as revealed by its TSRT (smaller clusters were recognized in the external capsule and insula). In the RHD group, VLSM failed to reveal voxel clusters where damage affected the biceps TSRT. The paucity of hemispheric voxels where damage is related to increased spasticity levels may indicate that impaired regulation of motoneuronal activation threshold after stroke is attributed to the sum effect of various brainstem control substrates (which cannot be analyzed using VLSM), rather than to direct corticospinal control.

Predictability effect reflects different contributions from each hemisphere: data from left and right hemisphere damage patients

Predictability effect reflects different contributions from each hemisphere: data from left and right hemisphere damage patients

Lexico-semantic deficits in people with right hemisphere damage: Evidence from convergent naming tasks

Abstract The right hemisphere (RH) continues to attract considerable scientific attention on its word processing skills. Despite extensive research in this direction, consensus on this issue is lacking. In this context, the present study explored the influence of right hemisphere damage (RHD) on word retrieval (i.e., oral naming) tasks. We administered a battery of 10 convergent naming tasks on a group of 22 right-handed persons with RHD as well as on an equal number of neurotypical age-, gender-, handedness-, and literacy-matched (i.e., control) participants. The comparison of accuracy scores and errors obtained from the two groups revealed significantly poorer performance in the RHD group except on one task (i.e., definition-naming). Additionally, analysis of errors revealed a preponderance of semantic errors. These findings support the role of the right hemisphere in word processing.

The ear craves the familiar: Pragmatic repetition in left and right cerebral damage

Background: Repetition occurs plentifully in normal conversation, but empirical studies of the pragmatic use of repetition are rare and pragmatic repetition, defined as verbal repetition in conversational use, in disordered language has not been systematically investigated. Applying a method of analysis that was piloted utilising normal discourse, discourse samples from persons with left and right brain damaged were examined for incidence and charcteristics of repetition.Aims: The purpose of this exploratory study was to examine verbal repetition following cerebral hemispheric damage. From previous studies of hemispheric influences on communicative competence, it was hypothesised that unilateral damage would affect verbal repetition differently. Following earlier results for hemispheric effects on proportion of formulaic expressions, overall more verbal repetition was predicted in persons with left hemisphere damage than those with right hemisphere damage or healthy speakers. Furthermore, previous studies led to a prediction of more repetition of formulaic (than novel, propositional) expressions following left hemisphere damage than the other two study groups. We explored whether characteristics and functions of repetition, developed as part of a new method for quantifying repetition in spontaneous speech, differed systematically between groups.Methods & Procedures: Transcripts of discourse by persons diagnosed with a single cerebral vascular accident and from age- and education-comparable healthy control (HC) participants were analysed. A method was developed for quantifying verbal repetition and identifying five factors, specifically localness (immediate, delayed, or distant), preservation of the original target (identical or altered), source (self or other), grammatical unit of speech (word, phrase, clause, or sentence), and phrase type (formulaic or novel), and three functions (maintaining form, enhancing content, and socialisation).Outcomes & Results: Results revealed significantly higher use of repetition by left hemisphere (28%) than right hemisphere-damaged (RHD) participants (19%) or the HC group (18%). The proportion of formulaic expression repeated by the left hemisphere group was significantly higher (57%) than the right hemisphere group (30%). Fewer repetitions were used by the left hemisphere group (25%) for the function of enhancing the content of talk as compared to the HC group (40%), whereas the RHD group used the least repetition for socialisation (15%).Conclusions: Pragmatic repetition is to be distinguished from rote repetition (on command) in aphasia diagnosis and from pathological repetition behaviours, including perseveration, following brain damage. The method described here allows for the measurement of pragmatic repetition and its characteristics in normal and disordered language. The findings support previous results for pragmatic and formulaic language behaviours in these populations. This study provides new information on the roles of repetition in normal conversation and on the impact of neurological damage on this function. Identification and measurement of repetition will inform perspectives on evaluation and rehabilitation of conversational speech.

Relationship Between Arm Usage and Instrumental Activities of Daily Living After Unilateral Stroke

Haaland KY, Mutha PK, Rinehart JK, Daniels M, Cushnyr B, Adair JC. Relationship between arm usage and instrumental activities of daily living after unilateral stroke. ObjectiveTo determine whether the preferred pattern of arm use after unilateral hemispheric damage was associated with better everyday functioning. Our previous work showed that right-handed stroke patients with right hemisphere damage (RHD) used their right, ipsilesional arm most frequently, while those with left hemisphere damage (LHD) used both arms together most frequently. This effect was explained by right-hand preference, but its relationship to functional performance is not known. DesignObservational cohort. SettingResearch laboratory. ParticipantsStroke patients (n=60; 30 RHD, 30 LHD) and healthy controls (n=52). InterventionsNot applicable. Main Outcome MeasuresThe Functional Impact Assessment was used to assess performance on instrumental activities of daily living (IADLs). ResultsThe preferred patterns of arm use were similar to those in our previous report. However, it was the greater use of both arms together that was associated with better IADL performance in both stroke groups. Ipsilesional arm use alone was not significantly associated with IADL performance in the RHD group and was associated with poorer performance in the LHD group. ConclusionsThe modal arm use pattern did not always optimize IADL functioning. Better IADL functioning in both stroke groups was associated with the use of both arms together, which is the most common arm use pattern of healthy individuals doing these same IADLs. An important practical question that arises from these findings is whether bilateral arm rehabilitation should be emphasized, because using both arms together is the best predictor of better performance on everyday tasks.

Emotion recognition and marital satisfaction in stroke

Deficits in the comprehension of facial and prosodic expressions are commonly associated with right hemisphere stroke. However, little is known regarding the impact of these disorders on social relations. We examined facial and prosodic processing, mood, and marital satisfaction in 12 right hemisphere damaged (RHD) stroke patients and nine controls. Results revealed significant impairments in the comprehension of facial expressions and prosody among RHD stroke patients. Nonparametric correlations in the RHD group showed significant associations between marital satisfaction and facial affect discrimination and matching, and nonaffective prosody discrimination. We conclude that deficits in the recognition of nonverbal expressions are associated with reduced relationship satisfaction.

What's left to learn about right hemisphere damage and pragmatic impairment?

Background: The nature and causes of pragmatic impairments following right hemisphere damage (RHD) continue to pose a challenge to researchers and clinicians. It is widely accepted that impairment in pragmatic and para-linguistic aspects of language can result from unilateral damage to the right hemisphere (RH), but it still uncertain exactly what the RH's special contributions to these areas of language and communication is. Advancing our understanding of the RH's role in pragmatics and communication will require a theoretical framework for pragmatics that is suited to the clinical environment. Aims: I first sketch several theoretical approaches to pragmatics, and suggest that Perkins' (2007) emergentist approach to pragmatics is the best suited to describing and explaining communication difficulties in a clinical setting. I then consider some of the implications of adopting the emergentist approach for research on pragmatic impairment in RHD by describing three relatively unexplored areas of research in the domain of RHD and pragmatics: application of conversation analysis techniques, investigation of the contribution of perceptual impairments to pragmatic impairment, and the comparison of pragmatic impairment across clinical groups. Main Contribution: I propose that the emergentist approach to pragmatics provides a useful framework for investigating issues of pragmatic impairment in RHD and other clinical groups, and show how adopting this approach naturally leads to research in three relatively unexplored areas. Conclusions: I argue that pursuing these lines of investigation will help move forward research in RHD, pragmatic impairment, and the general role of the right hemisphere in pragmatics.

Perceptual discrimination of Shona lexical tones and low-pass filtered speech by left and right hemisphere damaged patients

Background: While the role of the right hemisphere (RH) in prosodic processing is prominent, research on the perception of lexical tones has shown that left hemisphere damaged (LHD) patients are more impaired than right hemisphere damaged (RHD) patients. Dichotic listening and imaging studies with healthy speakers of tone languages demonstrate that at least at the phonemic and lexical level, prosody is processed in the left hemisphere (LH) when the variations in pitch are phonemically distinctive. There is no report available yet on the perceptual discrimination of a Bantu language in patients after unilateral brain damage. Aims: We addressed the question of how well Shona aphasic patients and right hemisphere damaged patients perceive pitch contrasts in Shona lexical words and also in their homologous low-pass filtered counterparts. We also sought to discover the validity of the current hypotheses on hemispheric lateralisation particularly the hypothesis on hemispheric lateralisation based on language function to account for the Shona data. Methods & Procedures: A total of 7 LHD and 7 RHD patients and 14 healthy controls participated in two discrimination tasks that examined perception of lexical tone in (a) bisyllabic Shona words and (b) low-pass filtered stimuli. In both tasks the participants were tasked with judging the pitch as the same or different in 120 bisyllabic words and 120 low-pass filtered stimuli. Outcomes & Results: The results demonstrated that the tonal discrimination of the LHD group was more reduced in comparison to the RHD group and control participants. However, the performance of the RHD patients was not error free relative to the control participants, although significantly better than the LHD patients in both tasks. Conclusions: At least for the phonemic and lexical levels, brain damage to the dominant hemisphere results in lexical tone impairment for LHD patients, and cognitive load processing results in a subdued but good performance for RHD patients. The LH is therefore dominant for processing tone when it is lexically distinctive.

Communication difficulties following right-hemisphere stroke: Applying evidence to clinical management

Following reports in the 1960s that language may be affected by right-hemisphere (RH) lesions, many limitations to effective communication in the population with right-hemisphere damage (RHD) have been described. However, stereotypical portrayals and descriptions of carefully selected cases may be misleading as to the extent of communication deficits. In many of the parameters in which RHD patients are presented as typically impaired (e.g. discourse skills), a less severe picture may emerge when data from the non-brain-damaged (NBD) population are considered, controlling for age and education-level variables. Subsequent to RHD, some people show deficits on some communication measures, but many of these communication behaviours are also present in some NBD adults. Thus, diagnosis of deficit must be made with reference both to the healthy peer population and the individual's pre-lesion behaviour. The authors’ RH-stroke research programme includes studies of incidence of communication deficit, comparisons of RHD and NBD groups in various spoken discourse and comprehension tasks, comparison of RHD groups of different ages, detailed analysis of topic within discourse in RHD and NBD groups, family members’ views of communication behaviour following RHD, and the natural course of communication change in the first year after RH stroke. The findings from several studies are summarised and used as the basis for management recommendations, which may guide future outcome research. There is an urgent need for the evaluation of communication management programmes, to determine whether therapists may, with confidence, offer an effective intervention service to those people whose communication skills are affected by RHD.

Functional implications of ipsilesional motor deficits after unilateral stroke

Wetter S, Poole JL, Haaland KY. Functional implications of ipsilesional motor deficits after unilateral stroke. Arch Phys Med Rehabil 2005;86:776–81. Objective To investigate the functional impact of ipsilesional motor deficits after unilateral stroke and the best predictors of those deficits. Design Observational cohort. Setting Primary care Veterans Affairs and private medical center. Participants Volunteer right-handed sample; stroke patients with left (LHD) or right hemisphere damage (RHD) a mean of 3.9 to 5.2 years poststroke and able-bodied participants who were tested using their left (LAB) or right hand. Interventions Not applicable. Main outcome measure The Jebsen-Taylor Hand Function Test (JHFT). Results Ipsilesional JHFT performance was impaired to the same extent in the LHD and RHD groups. LHD patients with apraxia had poorer scores on the JHFT than LHD patients without apraxia and the LAB group. Regression analyses showed that severity of apraxia was the best predictor of JHFT performance for the LHD group and that right (ipsilesional) motor performance (grip strength, finger tapping) was the best predictor of JHFT performance for the RHD group. Conclusions Ipsilesional deficits are present on simulated activities of daily living after LHD or RHD, suggesting that rehabilitation after stroke should include the ipsilesional arm and that ipsilesional limb apraxia is a better predictor of ipsilesional functional motor skills after LHD than aphasia or simple motor skills (grip strength, finger tapping). These findings suggest that limb apraxia should be assessed more routinely after stroke of the left hemisphere.

The production of linguistic prosodic structures in subjects with right hemisphere damage

This study examined the right hemisphere contribution to the production of linguistic prosody where acoustic features of prosodic structures in different linguistic contexts were examined accompanied by perceptual judgements. When control and right hemisphere damaged (RHD) subjects were asked to produce lexical stress differences (Experiment 1), prosodic boundaries to denote syntactic constituents (Experiment 2), and questions and statements (Experiment 3) conveyed through prosody, both groups were similar in producing the duration, F0 and amplitude acoustic cues within prosodic structures to convey different linguistic meanings. Listeners were able to perceive the meanings of the productions of both groups in Experiments 1 and 3, but had greater difficulty perceiving the productions of the RHD group in Experiment 2. These findings, which suggest that the right hemisphere has a limited role in the production of linguistic prosody, are discussed in relation to perceptual theories of prosody.

Metaphor Comprehension in Right Brain-Damaged Patients with Visuo-Verbal and Verbal Material: A Dissociation (RE)Considered

Metaphor comprehension was investigated in 50 right-hemisphere damaged (RHD) patients and 38 control subjects in two experimental conditions: a visuo-verbal and a verbal test. In the visuo-verbal test, subjects had to match a metaphorical sentence with one of four pictures representing the correct metaphorical meaning, the literal meaning, a control metaphor and a control literal meaning. In the verbal test, a metaphorical sentence had to be matched to a correct written metaphorical interpretation, a literal or a control interpretation. On both tests, the number of correct metaphorical responses in the RHD group was lower than in the control group. However, RHD patients performed more poorly in the visuo-verbal than in the verbal condition. Interestingly, when they selected the wrong response, the RHD patients tended to select the literal one only in the visuo-verbal condition. Context does not seem to be responsible for the dissociation between the two tests. The influence of the RHD patients' major visuo-spatial deficits was also checked, to exclude their role in the tendency to be literal with visuo-verbal material. Results are discussed in the perspective of an integration deficit.

Sensitivity to prosodic structure in left- and right-hemisphere-damaged individuals

An experiment was conducted in order to determine whether left- (LHD) and right-hemisphere-damaged (RHD) patients exhibit sensitivity to prosodic information that is used in syntactic disambiguation. Following the work of Marslen-Wilson, Tyler, Warren, Grenier, and Lee, and Lee (1992)1992, a cross-modal lexical decision task was performed by LHD and RHD subjects, as well as by adults without brain pathology (NC). Subjects listened to sentences with attachment ambiguities with either congruent or incongruent prosody, while performing a visual lexical decision task. Results showed that each of the unilaterally damaged populations differed from each other, as well as from the NCs in terms of sensitivity regarding prosodic cues. Specifically, the RHD group was insensitive to sentence prosody as a whole. This was in contrast to the LHD patients, who responded to the prosodic manipulation, but in the unexpected direction. Results are discussed in terms of current hypotheses regarding the hemispheric lateralization of prosodic cues.