Left Hemisphere Lesions Research Articles

Recovering two languages with the right hemisphere

Converging evidence suggests that the right hemisphere (RH) plays an important role in language recovery from aphasia after a left hemisphere (LH) lesion. In this longitudinal study we describe the neurological, cognitive, and linguistic profile of A.C., a bilingual who, after a severe traumatic brain injury, developed a form of fluent aphasia that affected his two languages (i.e., Romanian and Italian). The trauma-induced parenchymal atrophy led to an exceptional ventricular dilation that, gradually, affected the whole left hemisphere. A.C. is now recovering both languages relying only on his right hemisphere. An fMRI experiment employing a bilingual covert verb generation task documented the involvement of the right middle temporal gyrus in processes of lexical selection and access. This case supports the hypothesis that the RH plays a role in language recovery from aphasia when the LH has suffered massive lesions.

Heterogeneity in semantic priming effect with a lexical decision task in patients after left hemisphere stroke.

ABSTRACTInvestigations on the semantic priming effect (SPE) in patients after left hemisphere (LH) lesions have shown disparities that may be explained by the variability in performance found among patients. The aim of the present study was to verify the existence of subgroups of patients after LH stroke by searching for dissociations between performance on the lexical decision task based on the semantic priming paradigm and performance on direct memory, semantic association and language tasks. All 17 patients with LH lesions after stroke (ten non-fluent aphasics and seven non aphasics) were analyzed individually. Results indicated the presence of three groups of patients according to SPE: one exhibiting SPE at both stimulus onset asynchronies (SOAs), one with SPE only at long SOA, and another, larger group with no SPE.

Functional foreign accent syndrome

Foreign accent syndrome (FAS) is a rare disorder where the affected person speaks in an accent that the listener perceives as foreign. Although most cases have left hemisphere lesions, some...

Short-term effect of neck muscle vibration on postural disturbances in stroke patients.

Balance disorders after stroke have a particularly detrimental influence on recovery of autonomy and walking. The present study is aimed at assessing the effect of proprioceptive stimulation by neck muscle vibration (NMV) on the balance of patients with right hemispheric lesion (RHL) and left hemispheric lesion (LHL). Thirty-one (31) patients (15 RHL and 16 LHL), mean age 61.5years (±10.6), mean delay 3.1 (±1.6) months after one hemispheric stroke were included in this prospective study. The mean position in mediolateral and anteroposterior plane of the CoP (center of pressure) and the surface were evaluated using a force platform at rest and immediately after 10min of vibration on the contralesional dorsal neck muscle. NMV decreases the lateral deviation balance induced by the stroke. Twenty patients (64.5%) experienced a visual illusion of light spot moving toward the side opposite stimulus. These patients showed more improvement by vibration than those without visual illusion. There was an interaction between sensitivity and side of stroke on the effect of NMV. Proprioceptive stimulation by NMV reduces postural asymmetry after stroke. This short-term effect of the vibration is more effective in patients susceptible to visual illusion. This result was consistent with a central effect of NMV on the structures involved in the elaboration of perception of body in space.

Processing verbal morphology in patients with congenital left-hemispheric brain lesions

The goal of this study was to test whether children, teenagers and adults with congenital left-hemispheric brain lesions master the regularities of German verbal inflectional morphology. Thirteen patients and 35 controls without brain damage participated in three experiments. A grammaticality judgment task, a participle inflection task and a nonce-verb inflection task revealed significant differences between patients and controls. In addition, a main effect of verb type could be observed as patients and controls made more mistakes with irregular than with regular verbs. The findings indicate that the congenitally damaged brain not only has difficulties with complex syntactic structures during language development, as reported by earlier studies, but also has persistent deficits on the morphological level. These observations suggest that the plasticity of the developing brain cannot fully compensate for congenital brain damage which affects regions associated with language functions.

Universal and language-specific sublexical cues in speech perception: a novel electroencephalography-lesion approach.

SEE CAPPA DOI101093/BRAIN/AWW090 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE : The phonological structure of speech supports the highly automatic mapping of sound to meaning. While it is uncontroversial that phonotactic knowledge acts upon lexical access, it is unclear at what stage these combinatorial rules, governing phonological well-formedness in a given language, shape speech comprehension. Moreover few studies have investigated the neuronal network affording this important step in speech comprehension. Therefore we asked 70 participants-half of whom suffered from a chronic left hemispheric lesion-to listen to 252 different monosyllabic pseudowords. The material models universal preferences of phonotactic well-formedness by including naturally spoken pseudowords and digitally reversed exemplars. The latter partially violate phonological structure of all human speech and are rich in universally dispreferred phoneme sequences while preserving basic auditory parameters. Language-specific constraints were modelled in that half of the naturally spoken pseudowords complied with the phonotactics of the native language of the monolingual participants (German) while the other half did not. To ensure universal well-formedness and naturalness, the latter stimuli comply with Slovak phonotactics and all stimuli were produced by an early bilingual speaker. To maximally attenuate lexico-semantic influences, transparent pseudowords were avoided and participants had to detect immediate repetitions, a task orthogonal to the contrasts of interest. The results show that phonological 'well-formedness' modulates implicit processing of speech at different levels: universally dispreferred phonological structure elicits early, medium and late latency differences in the evoked potential. On the contrary, the language-specific phonotactic contrast selectively modulates a medium latency component of the event-related potentials around 400 ms. Using a novel event-related potential-lesion approach allowed us to furthermore supply first evidence that implicit processing of these different phonotactic levels relies on partially separable brain areas in the left hemisphere: contrasting forward to reversed speech the approach delineated an area comprising supramarginal and angular gyri. Conversely, the contrast between legal versus illegal phonotactics consistently projected to anterior and middle portions of the middle temporal and superior temporal gyri. Our data support the notion that phonological structure acts on different stages of phonologically and lexically driven steps of speech comprehension. In the context of previous work we propose context-dependent sensitivity to different levels of phonotactic well-formedness.

The clinical assessment of apraxia

Neurologists are familiar with the standard definition of apraxia: ‘an inability to perform a motor task that cannot be adequately explained by motor weakness, sensory loss or a lack of...

Brain activity underlying tool-related and imitative skills after major left hemisphere stroke.

Apraxia is a debilitating cognitive motor disorder that frequently occurs after left hemisphere stroke and affects tool-associated and imitative skills. However, the severity of the apraxic deficits varies even across patients with similar lesions. This variability raises the question whether regions outside the left hemisphere network typically associated with cognitive motor tasks in healthy subjects are of additional functional relevance. To investigate this hypothesis, we explored regions where functional magnetic resonance imaging activity is associated with better cognitive motor performance in patients with left hemisphere ischaemic stroke. Thirty-six patients with chronic (>6 months) large left hemisphere infarcts (age ± standard deviation, 60 ± 12 years, 29 male) and 29 control subjects (age ± standard deviation, 72 ± 7, 15 male) were first assessed behaviourally outside the scanner with tests for actual tool use, pantomime and imitation of tool-use gestures, as well as for meaningless gesture imitation. Second, functional magnetic resonance imaging activity was registered during the passive observation of videos showing tool-associated actions. Voxel-wise linear regression analyses were used to identify areas where behavioural performance was correlated with functional magnetic resonance imaging activity. Furthermore, lesions were delineated on the magnetic resonance imaging scans for voxel-based lesion-symptom mapping. The analyses revealed two sets of regions where functional magnetic resonance imaging activity was associated with better performance in the clinical tasks. First, activity in left hemisphere areas thought to mediate cognitive motor functions in healthy individuals (i.e. activity within the putative 'healthy' network) was correlated with better scores. Within this network, tool-associated tasks were mainly related to activity in supramarginal gyrus and ventral premotor cortex, while meaningless gesture imitation depended more on the anterior intraparietal sulcus and superior parietal lobule. Second, repeating the regression analyses with total left hemisphere lesion volume as additional covariate demonstrated that tool-related skills were further supported by right premotor, right inferior frontal and left anterior temporal areas, while meaningless gesture imitation was also driven by the left dorso-lateral prefrontal cortex. In summary, tool-related and imitative skills in left hemisphere stroke patients depend on the activation of spared left hemisphere regions that support these abilities in healthy individuals. In addition, cognitive motor functions rely on the activation of ipsi- and contralesional areas that are situated outside this 'healthy' network. This activity may explain why some patients perform surprisingly well despite large left brain lesions, while others are severely impaired.

Brain Activation During Singing: "Clef de Sol Activation" Is the "Concert" of the Human Brain.

Humans are the most complex singers in nature, and the human voice is thought by many to be the most beautiful musical instrument. Aside from spoken language, singing represents a second mode of acoustic communication in humans. The purpose of this review article is to explore the functional anatomy of the "singing" brain. Methodologically, the existing literature regarding activation of the human brain during singing was carefully reviewed, with emphasis on the anatomic localization of such activation. Relevant human studies are mainly neuroimaging studies, namely functional magnetic resonance imaging and positron emission tomography studies. Singing necessitates activation of several cortical, subcortical, cerebellar, and brainstem areas, served and coordinated by multiple neural networks. Functionally vital cortical areas of the frontal, parietal, and temporal lobes bilaterally participate in the brain's activation process during singing, confirming the latter's role in human communication. Perisylvian cortical activity of the right hemisphere seems to be the most crucial component of this activation. This also explains why aphasic patients due to left hemispheric lesions are able to sing but not speak the same words. The term clef de sol activation is proposed for this crucial perisylvian cortical activation due to the clef de sol shape of the topographical distribution of these cortical areas around the sylvian fissure. Further research is needed to explore the connectivity and sequence of how the human brain activates to sing.

ID 30 – Influence of M1 hand knob ischemic stroke on motor activation: An fMRI study in chronic stage

Objective To evaluate whether stroke lesion focused on the primary motor cortex hand knob re-localizes the hand motor area in the affected hemisphere. Methods The study included 8 right-handed chronic ischemic stroke patients (2 females, age range: 48–68 years) with hand knob localized lesion (2 left hemisphere, 6 right hemisphere, at least 2 years from stroke). Block-design fMRI was performed using a 3T MR scanner during finger tapping task to both hemispheres. For the analysis, images with left hemisphere lesions were flipped. Differences between affected and unaffected hemispheres were tested with a paired t-test using a threshold of p T = 4.79), uncorrected for multiple comparisons. Results Significantly reduced motor activation in the affected hemisphere versus unaffected hemisphere was observed in the posterior part of precentral gyrus (hand-knob), pars opercularis and pars triangularis of the inferior frontal gyrus, inferior parietal cortex, intraparietal sulcus and lobule VI in cerebellum. Conclusions Reduction in the hand motor activation was observed in M1 in the affected hemisphere. Key message fMRI is capable to detect abnormal motor activation after focal stroke on hand knob area.

Abstract WP140: Infarct Location Predicts Quality of Life Outcomes After Minor Stroke

Introduction: Neuro-QOL was developed to provide researchers with a continuous, validated, patient-reported measurement of quality of life. Previous studies suggest that minor ischemic stroke (MIS) can lead to disability and impaired quality of life in a substantial proportion of patients. We hypothesized that infarct location predicts 3-month QOL in patients with MIS. Methods: We identified MIS (NIHSS ≤ 5) with confirmed acute infarcts on DWI, admitted between August 2012 and July 2013, and who underwent Neuro-QOL outcomes assessments at 3 months. Impaired QOL was defined as T-scores >0.5 SD worse than the general population mean of 50 (SD 10) in any of 5 domains: upper extremity, lower extremity, executive functions, general concerns, and social satisfaction. We analyzed the relationship between acute infarct locations and impaired QOL in univariate and multivariate analysis. We further stratified our analysis by any rehabilitation services (RS) received post-discharge. Results: Among 169 patients (mean age 64.3 years, 54.4% male, 24.9% black, median initial NIHSS score 1, 36.7% received RS post-stroke), impaired QOL was noted in 56 (33.1%) patients at 3 months (56.5% in patient with vs. 19.6% in those without RS, p<0.001). Patients with left hemispheric infarcts (45.8 vs. 20.9%, p=0.001) and thalamic-brainstem infarcts were more likely to have impaired QOL (54.1 vs. 27.3%, p=0.002). In multivariable analysis, left hemispheric (adj. OR 3.45, 95% 1.61-7.41) and thalamic-brainstem infarction (adj. OR 4.59, 95% CI 1.91-11.00) were independent predictors of impaired QOL adjusting for age, NIHSS score, and recurrent stroke. Stratifying by RS, left hemispheric (34.0% vs 8.3% p=0.001) and thalamic-brainstem lesion location (52.6% vs 12.5% p<0.001) was significantly associated with QOL only in those who did not receive RS. Discussion: Left hemispheric and thalamic-brainstems infarcts were independently associated with impaired QOL, especially in MIS patients who did not receive rehabilitation services post-stroke. These data imply that specific acute infarct locations predict patient-reported impairments in QOL and may be useful biomarkers for future studies of targeted rehabilitation services in MIS patients.

Difference in Anxiety between Left and Right Hemispheric Lesions of Ischemic among Patients with Stroke at Dr. Moewardi Hospital

Background: The difference of lesion location and anxiety usually manifests into different signs and symptomps based on the patient’s lesion location. This study aimed to determine the difference in anxiety between left and right hemispheric lesions of ischemia among patients with stroke. Subjects and Method: This was an analytic observational study with cross sectional design. A total sample of 30 patients with stroke consisting of 15 patients with left hemisphere lesion and 15 patients with right hemisphere lesion of ischemia was selected by random sampling. Anxiety was assessed using Hamilton Rating Scale for Anxiety (HRSA) questionnaire. The data were analyzed by multiple linear regression. Results: After controlling for family supports as confounding factor, this study showed significantly lower anxiety in patients with left hemispheric lesion ischemia than patients right hemispheric lesion (b= -2.77; p = 0.039). Family support lessened anxiety among patients with stroke (b=-5.21; p=0.003). Conclusion: Anxiety in stroke patients with left hemispheric lesion of ischemia is lower than stroke patients with right hemispheric lesion. Keywords : anxiety, ischemic stroke, left hemispheric lesion, right hemispheric lesion Correspondence: M. Maulana Shofri. Faculty of Medicine, Sebelas Maret University, Surakarta. Indonesian Journal of Medicine (2016), 1(3): 146-151 https://doi.org/10.26911/theijmed.2016.01.03.01

Illness Narrative Complexity in Right and Left-Hemisphere Lesions

Human relations are mainly based upon the exchange of narratives. So, it seems reasonable to study the effects of cerebral injuries upon this essential function of human thinking, and in particualr the differences of the structure of narratives in patients affected by left and right cerebral lesions. In this paper the transcripts of audio-taped illness narratives of six enrolled patients (three with right-hemisphere lesions and three with left ones, matched by age and sex) were analyzed by means of two different methods: Semantic Networks Analysis and Latent Dirichlet Allocation. These methods allowed to calculate several numerical indicators of the complexity of the narratives. Results showed that right hemisphere lesions entail a reduction of the narrative complexity, whereas the opposite occurs in patients with Left Hemisphere Lesion.

Neuropragmatic Speech-Language Deficits Specific To Speech Act Type Following Left-Hemispheric Lesion

Neuropragmatic Speech-Language Deficits Specific To Speech Act Type Following Left-Hemispheric Lesion

Late onset mania secondary to stroke: a case report

A number of emotional and behavioral disorders, particularly mood disorders can be observed secondary to a stroke. Depression is the most common mental disorder after a stroke, although mania can also occur, albeit rarely. Left hemisphere lesions lead to depression and right hemisphere lesions to mania, in general. In this report we present a case who presented with manic symptoms and evaluated as late onset mania secondary to stroke of left hemisphere.

Phonetic basis of phonemic paraphasias in aphasia: Evidence for cascading activation

Phonemic paraphasias are a common presenting symptom in aphasia and are thought to reflect a deficit in which selecting an incorrect phonemic segment results in the clear-cut substitution of one phonemic segment for another. The current study re-examines the basis of these paraphasias. Seven left hemisphere-damaged aphasics with a range of left hemisphere lesions and clinical diagnoses including Broca's, Conduction, and Wernicke's aphasia, were asked to produce syllable-initial voiced and voiceless fricative consonants, [z] and [s], in CV syllables followed by one of five vowels [i e a o u] in isolation and in a carrier phrase. Acoustic analyses were conducted focusing on two acoustic parameters signaling voicing in fricative consonants: duration and amplitude properties of the fricative noise. Results show that for all participants, regardless of clinical diagnosis or lesion site, phonemic paraphasias leave an acoustic trace of the original target in the error production. These findings challenge the view that phonemic paraphasias arise from a mis-selection of phonemic units followed by its correct implementation, as traditionally proposed. Rather, they appear to derive from a common mechanism with speech errors reflecting the co-activation of a target and competitor resulting in speech output that has some phonetic properties of both segments.

Double dissociation of a latent working memory process

ABSTRACTBackground. The study explored the construct validity of a computational model of working memory (WM) by determining whether model parameters manifested double dissociations of lesion laterality with type of material studied. The data set modeled involved psychometrically matched verbal and figural WM tasks on which a double dissociation between test version and lesion laterality failed to emerge when total test scores were used as the laterality marker. Method. This re-analysis of a previously published study involved investigating the WM performance of 15 demographically matched controls with 15 adult patients with left-hemispheric (LH) lesions and 15 adult patients with right-hemispheric (RH) lesions. Each participant was given verbal and figural versions of a continuous paired associates test (CPAT). The two versions had previously been psychometrically matched in a larger sample of healthy individuals. A WM model composed of encoding, displacement, and episodic memory parameters was fit to each individual’s performance profiles for both versions of the CPAT. Results. Replicating the previous results for raw scores, rank transformed values of total score performance failed to reveal a double dissociation. Nonetheless an absolute double dissociation was observed for the model’s displacement parameter: RH patients demonstrated deficits on the figural but not verbal WM displacement parameter, whereas LH patients demonstrated deficits on the verbal but not figural WM displacement parameter. Additionally, both LH and RH patients were impaired on the figural encode parameter, perhaps explaining the absence of a double dissociation in total score performance. Conclusions. By combining different patterns of profile and level data into theoretically motivated model parameters, computational models of neurocognition can enhance the construct validity of interpretations of neuropsychological performance.

Loss of regional accent after damage to the speech production network.

Lesion-symptom mapping studies reveal that selective damage to one or more components of the speech production network can be associated with foreign accent syndrome, changes in regional accent (e.g., from Parisian accent to Alsatian accent), stronger regional accent, or re-emergence of a previously learned and dormant regional accent. Here, we report loss of regional accent after rapidly regressive Broca’s aphasia in three Argentinean patients who had suffered unilateral or bilateral focal lesions in components of the speech production network. All patients were monolingual speakers with three different native Spanish accents (Cordobés or central, Guaranítico or northeast, and Bonaerense). Samples of speech production from the patient with native Córdoba accent were compared with previous recordings of his voice, whereas data from the patient with native Guaranítico accent were compared with speech samples from one healthy control matched for age, gender, and native accent. Speech samples from the patient with native Buenos Aires’s accent were compared with data obtained from four healthy control subjects with the same accent. Analysis of speech production revealed discrete slowing in speech rate, inappropriate long pauses, and monotonous intonation. Phonemic production remained similar to those of healthy Spanish speakers, but phonetic variants peculiar to each accent (e.g., intervocalic aspiration of /s/ in Córdoba accent) were absent. While basic normal prosodic features of Spanish prosody were preserved, features intrinsic to melody of certain geographical areas (e.g., rising end F0 excursion in declarative sentences intoned with Córdoba accent) were absent. All patients were also unable to produce sentences with different emotional prosody. Brain imaging disclosed focal left hemisphere lesions involving the middle part of the motor cortex, the post-central cortex, the posterior inferior and/or middle frontal cortices, insula, anterior putamen and supplementary motor area. Our findings suggest that lesions affecting the middle part of the left motor cortex and other components of the speech production network disrupt neural processes involved in the production of regional accent features.

NIMG-46THE USE OF CLINICAL FUNCTIONAL MAGNETIC RESONANCE IMAGING IN BRAIN TUMOUR PATIENTS FOR SURGICAL PLANNING: A SINGLE-SURGEON RETROSPECTIVE COHORT STUDY AT A CANADIAN CENTER

BACKGROUND: Advanced imaging techniques such as functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) are being increasingly used for the pre-operative evaluation of patients with brain tumors. METHODS: The study is a retrospective chart review investigating the use of fMRI from 2002-2013 in the pre-operative evaluation of brain tumour patients. Baseline demographic and clinical data were collected. The specific fMRI protocols used for each patient were recorded. RESULTS: 60 patients were identified over the twelve-year period. The type of tumours most commonly investigated were low-grade glioma, glioblastoma multiforme and meningioma. Most common presenting concerns were seizures (46%), change on surveillance (15%), language deficits (11%), and headache (10%). There was a predominance of left-hemispheric lesions investigated with fMRI (77.6% versus 22.4% for right). The most commonly involved lobes were frontal (46.5%), temporal (28.8%), parietal (16.4%), then insular (5.5%). The most common fMRI paradigms were language (85.2%), motor (79.6%), sensory (18.5%), and memory (9.3%). Most patients ultimately underwent a craniotomy (73.2%) while smaller groups underwent stereotactic biopsy (10.7%) and non-surgical management (16.1%). Time from request for fMRI to actual fMRI acquisition was 3.2 +/− 2.3 weeks. Time from fMRI acquisition to intervention was 5.2 +/− 5.4 weeks. CONCLUSIONS: We have characterized patient demographics in a retrospective single-surgeon cohort undergoing pre-operative clinical fMRI at a Canadian center. Our experience suggests an acceptable wait time from scan request to scan completion/analysis and from scan to intervention.

Motor strategies of postural control after hemispheric stroke

After stroke, the causes of balance disorders include motor disorders, sensory loss, perceptual deficits and altered spatial cognition. This review focuses on motor strategies for postural control after stroke. Weight-bearing asymmetry, smaller surface of stability, increased sway, body tilting and sometimes pushing syndrome are observed. Weakness and sensory impairments account only for some of these disturbances; altered postural reactions and anticipated postural adjustments as well as abnormal synergistic muscular activation play an important part. These disorders are often linked to cognitive impairments (visuospatial analysis, perception of verticality, use of sensory information, attention, etc.), which explain the preeminent disorders of postural control seen with right rather than left-hemisphere lesions. Most of the motor changes are due to an impaired central nervous system but some could be considered adaptive behaviors. These changes have consequences for rehabilitation and need further studies for building customized programs based on the motor comportment of a given patient.