Cerebral Dominance For Language Research Articles

A Weak Shadow of Early Life Language Processing Persists in the Right Hemisphere of the Mature Brain.

Studies of language organization show a striking change in cerebral dominance for language over development: We begin life with a left hemisphere (LH) bias for language processing, which is weaker than that in adults and which can be overcome if there is a LH injury. Over development this LH bias becomes stronger and can no longer be reversed. Prior work has shown that this change results from a significant reduction in the magnitude of language activation in right hemisphere (RH) regions in adults compared to children. Here we investigate whether the spatial distribution of language activation, albeit weaker in magnitude, still persists in homotopic RH regions of the mature brain. Children aged 4–13 (n = 39) and young adults (n = 14) completed an auditory sentence comprehension fMRI (functional magnetic resonance imaging) task. To equate neural activity across the hemispheres, we applied fixed cutoffs for the number of active voxels that would be included in each hemisphere for each participant. To evaluate homotopicity, we generated left-right flipped versions of each activation map, calculated spatial overlap between the LH and RH activity in frontal and temporal regions, and tested for mean differences in the spatial overlap values between the age groups. We found that, in children as well as in adults, there was indeed a spatially intact shadow of language activity in the right frontal and temporal regions homotopic to the LH language regions. After a LH stroke in adulthood, recovering early-life activation in these regions might assist in enhancing recovery of language abilities.

Magnetoencephalography Language Mapping Using Auditory Memory Retrieval and Silent Repeating Task.

The study aims to (1) examine the spatiotemporal map of magnetoencephalography-evoked responses during an Auditory Memory Retrieval and Silent Repeating (AMRSR) task, and determine the hemispheric dominance for language, and (2) evaluate the accuracy of the AMRSR task in Wernicke and Broca area localization. In 30 patients with brain tumors and/or epilepsies, the AMRSR task was used to evoke magnetoencephalography responses. We applied Fast VEctor-based Spatial-Temporal Analyses with minimum L1-norm source imaging method to the magnetoencephalography responses for localizing the brain areas evoked by the AMRSR task. The Fast-VEctor-based Spatial-Temporal Analysis found consistent activation in the posterior superior temporal gyrus around 300 to 500 ms, and another activation in the frontal cortex (pars opercularis and/or pars triangularis) around 600 to 900 ms, which were localized to the Wernicke area (BA 22) and Broca area (BA 44 and BA 45), respectively. The language-dominant hemispheric laterization elicited by the AMRSR task was comparable with the result from an Auditory Dichotic task result given to the same patient, with the exception that AMRSR is more sensitive on bilateral language laterization cases on finding the Wernicke and Broca areas. For all patients who successfully finished the AMRSR task, Fast-VEctor-based Spatial-Temporal Analysis could establish accurate and robust localizations of Broca and Wernicke area and determine hemispheric dominance. For subjects with normal auditory functionality, the AMRSR paradigm evaluation showed significant promise in providing reliable assessments of cerebral language dominance and language network localization.

Interhemispheric Asymmetry of Lateral Sulcus and its Significance in Adult Human Brains: A Cadaveric Study from Southern India

Introduction: Cerebral hemispheres are the two main parts of human brain. Though, the cerebral hemispheres may appear to be identical, one hemisphere is functionally dominant over the other. They also exhibit physical variations. The dominance may be due to lateralisation of cortical functions. In about 90% of the total population, the left hemisphere is dominant over the right where the speech and language areas are located. These areas are situated within the Pars Opercularis (PO) and Pars Triangularis (PT) in the dominant hemisphere of the Lateral Sulcus (Sylvian Fissure). The interhemispheric asymmetry of the Sylvian Fissure (SF) may be the basis of cerebral dominance for language, which is less studied in human beings. These asymmetries are relative and vary according to the functions concerned. Therefore, knowledge of the interhemispheric asymmetries is helpful in neurological diagnosis and management. Aim: To measure the length of the lateral sulcus and its rami on both hemispheres and to study their interhemispheric asymmetry. Materials and Methods: A cross-sectional pilot study was done on 30 whole brains of embalmed adult human cadavers irrespective of sexes taken from the Institute of Anatomy of Madras Medical College, Tamil Nadu, India, between the months of June to August, 2017. The lateral sulcus was measured on the superolateral surface of the brain. All measurements were taken with the help of a thin copper wire placed on the surface, its ends being held in position with artery forceps. The wire was then placed on a graduated metal scale and the lengths of the anterior ascending, anterior horizontal, posterior rami and total length of the lateral sulcus were noted. A data sheet was made using Microsoft excel software and the mean length of each ramus was calculated. Results: The mean total length of the SF was noted to be 8.4±0.51 cm on the right side and 8.8±0.56 cm on the left. The mean length of stem of lateral sulcus was 2.5±0.4 cm and 2.6±0.3 cm on the right and left side, respectively. The mean length of the anterior ascending ramus was found to be 2.7±0.3 cm on the right side and 3.13±0.3 cm on the left side. The mean length of the anterior horizontal ramus was found to be 2.34±0.37 cm on the right side and 2.55±0.4 cm on the left side. The mean length of the posterior ramus was found to be 5.6±0.65 cm on the right side and 6.1±0.63 cm on the left side. Conclusion: The SF and their rami of the left side were longer than of the right side in most specimens. This signifies the functional asymmetry between right and left cerebral hemispheres which may be related to language lateralisation of human brain. This interhemispheric difference has been implicated in various genetic syndromes and behavioural disorders in children particularly involving language milestone.

Left-handed musicians show a higher probability of atypical cerebral dominance for language.

Music processing and right hemispheric language lateralization share a common network in the right auditory cortex and its frontal connections. Given that the development of hemispheric language dominance takes place over several years, this study tested whether musicianship could increase the probability of observing right language dominance in left‐handers. Using a classic fMRI language paradigm, results showed that atypical lateralization was more predominant in musicians (40%) than in nonmusicians (5%). Comparison of left‐handers with typical left and atypical right lateralization revealed that: (a) atypical cases presented a thicker right pars triangularis and more gyrified left Heschl's gyrus; and (b) the right pars triangularis of atypical cases showed a stronger intra‐hemispheric functional connectivity with the right angular gyrus, but a weaker interhemispheric functional connectivity with part of the left Broca's area. Thus, musicianship is the first known factor related to a higher prevalence of atypical language dominance in healthy left‐handed individuals. We suggest that differences in the frontal and temporal cortex might act as shared predisposing factors to both musicianship and atypical language lateralization.

SCOPE OF SPEECH LANGUAGE THERAPY

The consistent indulgence of the developed world in neurological research, during the post second world war era, led to several discoveries and subsequently the laying down of several theories about socio-communicative behaviors in human beings. The areas of the brain responsible for the functions of speech and language were studied further, providing an insight to the role of the brain in cognitive skills of attention, recall, memory, analytical and inferential skills, as well as judgment, necessary during verbal and nonverbal communication. Information about cerebral dominance for language, which lies in the left hemisphere for a larger majority of people; led to establishing the role of the right hemisphere for the supra-segmental features of language, or the meaning of spoken utterances carried by the rhythm in our speech. Thus ‘aphasiology’ emerged as the ‘study of aphasia’ which is an acquired language disorder that results from an insult to the brain, mostly in adults who have used language in the best possible way through their lives; but may also be seen in children known as ‘childhood aphasia.’ The period and pattern of recovery from aphasia varied greatly in adults and children, which led to establishing the theory of ‘critical period’ for language development, shedding more light on the miraculous development and functioning of the human neurological system since birth, for language. Knowledge about the rapid development of the human brain in the early years of life led to the essential concept of ‘early intervention’ of children having any communicative or physical challenges

Inhibitory or excitatory connections between hemispheres? Evidence from sentence comprehension in patients with aphasia

Inhibitory or excitatory connections between hemispheres? Evidence from sentence comprehension in patients with aphasia

Hemispheric specialization in affective responses, cerebral dominance for language, and handedness: Lateralization of emotion, language, and dexterity

Hemispheric specialization in affective responses has received little attention in the literature. This is a fundamental variable to understand circuit dynamics of networks subserving emotion. In this study we put to test a modified “valence” hypothesis of emotion processing, considering that sadness and happiness are processed by each hemisphere in relation to dominance for language and handedness. Mood induction and language activation during functional magnetic resonance imaging (fMRI) were used in 20 right-handed and 20 nonright-handed subjects, focusing on interconnected regions known to play critical roles in affective responses: subgenual cingulate cortex, amygdala, and anterior insular cortex. We observed a consistent relationship between lateralization of affective processing, motor dexterity, and language in individuals with clear right-handedness. Sadness induces a greater activation of right-hemisphere cortical structures in right-handed, left-dominant individuals, which is not evident in nonright-handed subjects who show no consistent hemispheric dominance for language. In anterior insula, right-handed individuals displayed reciprocal activation of either hemisphere depending upon mood valence, whereas amygdala activation was predominantly left-sided regardless of mood valence. Nonright-handed individuals exhibited less consistent brain lateralization of affective processing regardless of language and motor dexterity lateralization. In contrast with traditional views on emotion processing lateralization, hemispheric specialization in affective responses is not a unitary process but is specific to the brain structure being activated.

Left-hemisphere lateralization for language and interhemispheric fiber tracking in patients with schizophrenia

BackgroundIt has been suggested that the degree of hemispheric specialization (HS) depends on the structural connectivity between the two hemispheres, that is to say the corpus callosum (CC). Studies, performed only on healthy participants, investigated this anatomo-functional relationship. Nevertheless, it has never been studied in schizophrenia. We therefore propose to study the anatomo-functional relationships between the integrity of interhemispheric connectivity and leftward functional lateralization for language in patients with schizophrenia compared with healthy participants, driven by a multimodal approach combining fMRI and DTI-based fiber tractography. We hypothesized that reduced leftward functional lateralization for language in patients with schizophrenia could be related to a callosal hypoconnectivity. Materials and methodsSeventeen patients based on the DSM-IV, and 17 controls were included. The functional laterality index and interhemispheric diffusion values between homologue temporal regions, belonging to the language network, were individually extracted in order to study the anatomo-functional relationships. ResultsIn the patients, higher mean and radial diffusivity (RD) values (thicker myelin sheaths) were associated with less leftward lateralization. In contrast, the controls presented higher RD values and lower fractional anisotropy values (axonal loss) with more leftward lateralization. ConclusionsOur study revealed a relationship between the CC and the HS for language, but did not provide evidence clarifying the direction of the relationship between callosal connectivity and functional lateralization for language. In particular, the present findings showed that the loss of integrity in interhemispheric callosal fibers was associated with reduced leftward cerebral dominance for language in patients with schizophrenia.

Role of the Wada test and functional magnetic resonance imaging in preoperative mapping of language and memory: two atypical cases

The Wada test is an invasive procedure used to determine cerebral memory and language dominance as well as risk of cognitive deficits following neurosurgery. However, the potential risks of Wada testing have led some to consider foregoing Wada testing in candidates for resective epilepsy surgery with right hemispheric seizure onset. We present two atypical cases in which the Wada test showed unexpected memory and language lateralization. These cases underscore the importance of functional magnetic resonance in which imaging and Wada examination in right-handed individuals even when the lesion would not suggest atypical language representation.

LP50: Atypical cerebral language dominance in a right-handed patient: an anatomoclinical study with DES, fMRI and DTI

LP50: Atypical cerebral language dominance in a right-handed patient: an anatomoclinical study with DES, fMRI and DTI

Specific speech and language impairments in children: assessments, diagnostics, classification and outcome

Specific Language Impairment (SLI) is an heterogeneous disorder characterized by an inadequate development that cannot be explained by an auditory sensory defect, a motor-neurological defect, a general cognitive impairment nor an unwillingness to communicate. There are many subtypes of SLI, both in severity and type that may be associated with a different outcome. Although many of these children recover clinically, the majority will maintain minor language impairments leading to a poor school achievement and learning difficulties. A proportion of cases remain severely impaired causing social isolation and an occupations/professional handicap. The origin of these syndromes is probably genetic. Although the are assumed to reflect a dysfunctional of the neuronal networks subserving the comprehension,, elaboration and production of language, they are not due to evident focal brain lesions, but are associated with atypical patterns of cerebral dominance and specialization for language. A variety of language processing impairments have been described in these children, namely a difficulty in analyzing rapidly changing speech sounds, acquiring language morphology and grammar and a poor phonological memory. Therapeutic intervention in these children must be individualized and interdisciplinary (speech therapy, alternative forms of communication, psychological support and special education). This is essential to prevent social isolation, low self-esteem, emotional and behavioral symptoms and educational problems. DOI: http://dx.doi.org/10.17575/rpsicol.v16i1.467

Cerebral lateralization for language in deaf children with cochlear implantation

Functional Transcranial Doppler ultrasonography (fTCD) was used to investigate the effects of early acoustic deprivation and subsequent reafferentation on cerebral dominance for language in deaf children provided with Cochlear Implantation (CI). Twenty children with CI (13 in right ear and 7 in left ear) and 20 controls matched for age, sex and handedness were administered a fTCD animation description task. Left hemisphere dominance for language with comparable mean Laterality Indexes (LIs) was found in children with CI and controls; right-ear implanted subjects showed cerebral activation controlateral to implanted ear more frequently than left-ear implanted ones. Linguistic proficiency of CI recipients was below age expectation in comparison to controls; language scores did not significantly differ between children with left and right LI, whereas both age and side of implantation were significantly related to language outcome. Theoretical implication and potential clinical application of fTCD in CI management are discussed.

Cerebellar language mapping and cerebral language dominance in pediatric epilepsy surgery patients.

ObjectiveChildren with epilepsy often have reorganization of language networks and abnormal brain anatomy, making determination of language lateralization difficult. We characterized the proportion and distribution of language task activation in the cerebellum to determine the relationship to cerebral language lateralization.MethodsForty-six pediatric epilepsy surgery candidates (aged 7–19 years) completed an fMRI auditory semantic decision language task. Distribution of activated voxels and language laterality indices were computed using: (a) Broca's and Wernicke's areas and their right cerebral homologues; and (b) left and right cerebellar hemispheres. Language task activation was anatomically localized in the cerebellum.ResultsLateralized language task activation in either cerebral hemisphere was highly correlated with lateralized language task activation in the contralateral cerebellar hemisphere (Broca vs. cerebellar: ρ = −0.54, p < 0.01). Cerebellar language activation was located within Crus I/II, areas previously implicated in non-motor functional networks.ConclusionsCerebellar language activation occurs in homologous regions of Crus I/II contralateral to cerebral language activation in patients with both right and left cerebral language dominance. Cerebellar language laterality could contribute to comprehensive pre-operative evaluation of language lateralization in pediatric epilepsy surgery patients. Our data suggest that patients with atypical cerebellar language activation are at risk for having atypical cerebral language organization.

Atypical cerebral language dominance in a right-handed patient: An anatomoclinical study

ObjectiveApproximately 97% of the right-handers has left hemisphere language dominance. Within the language dominant hemisphere Broca's area is of crucial importance for a variety of linguistic functions. As a result, tumour resection in and around Broca's area is controversial. However, studies showed that by means of Direct Electrical Stimulation (DES) tumour resection in this region can be safely performed. We report unexpected anatomoclinical findings in a right-handed patient who underwent tumour resection in the left prefrontal lobe. MethodsLanguage functions in this right-handed patient were extensively examined in the pre-, intra-, and postoperative phase by means of a standardised battery of neurolinguistic and neurocognitive tests. Results obtained in the pre- and postoperative phase are compared. In addition, intraoperative DES findings and postoperative functional Magnetic Resonance Imaging (fMRI) and Diffusion Tensor Imaging (DTI) results are reported. ResultsTumour resection near Broca's area was safely performed since no positive language sites were found during intraoperative DES. Since no linguistic deficits occurred in the pre-, intra-, or postoperative phase, atypical language dominance was suspected. Neuropsychological investigations, however, disclosed permanent executive dysfunction. Postoperative fMRI and DTI confirmed right cerebral language dominance as well as a crossed cerebro-cerebellar functional link with the left cerebellar hemisphere. DiscussionAtypical right hemisphere language dominance in this right-handed patient is reflected by: (1) the total absence of language problems in the pre-, intra- and postoperative phase, (2) absence of positive stimulation sites during DES, (3) a clearly more pronounced arcuate fasciculus in the right cerebral hemisphere (DTI), (4) a crossed functional connection between the right cerebrum and the left cerebellum (fMRI). Two hypothetical explanations for the pattern of crossed cerebral language dominance are put forward: (1) preoperative brain plasticity mechanisms inducing a shift of language functions to the right hemisphere or (2) right hemisphere language dominance as a maturational variant. This case with atypical cerebral language dominance shows that although DES is the ‘gold standard’ to identify eloquent language regions and their pathways, fMRI and DTI are important adjuncts to guide surgery, to identify language lateralisation and to study anatomoclinical correlations.

Sensitivity and specificity of Ankara University Cerebral Dominance Inventory in comparison with the Wada test

We aimed to examine the sensitivity and specificity of the Ankara University Cerebral Dominance Inventory (AUCDI) in determining left cerebral dominance compared with the Wada test. The AUCDI and Wada test were applied to 49 patients referred to Ankara University for epilepsy surgery. Hand, foot and 'total' preference scores were specified according to the results of the inventory. Thirty-eight of the patients had left cerebral dominance and 11 had atypical cerebral dominance for language. 86 % of the patients were right-handed and 43 % were right-footed. When compared with the results of the Wada test, the sensitivity of the AUCDI for each 'total preference', and hand and foot preference was 90, 95 and 50 % and specificity was 46, 46 and 82 %, respectively. The percentage of right-footed patients was low when compared with the other studies. This difference might result from the method used for assessing foot preference by the actual demonstration of the task rather than just asking about the performance. The AUCDI was found to be sensitive in terms of 'total preference' and hand preference, and specific in terms of foot preference for determining the left hemisphere dominance in patients preferring the right side. It was a cheap and noninvasive alternative to the Wada test, appropriate for clinical bedside evaluation.

The Corpus Callosum in Monozygotic Twins Concordant and Discordant for Handedness and Language Dominance

We used diffusion tensor imaging to assess callosal morphology in 35 pairs of monozygotic twins, of which 17 pairs were concordant for handedness and 18 pairs were discordant for handedness. Functional hemispheric language dominance was established for each twin member using fMRI, resulting in 26 twin pairs concordant and 9 twin pairs discordant for language dominance. On the basis of genetic models of handedness and language dominance, which assume one "right shift" (RS) gene with two alleles, an RS+ allele biasing toward right-handedness and left cerebral language dominance and an RS- allele leaving both asymmetries to chance, all twins were classified according to their putative genotypes, and the possible effects of the gene on callosal morphology was assessed. Whereas callosal size was under a high genetic control that was independent of handedness and language dominance, twin pairs with a high probability of carrying the putative RS+ allele showed a connectivity pattern characterized by a genetically controlled, low anisotropic diffusion over the whole corpus callosum. In contrast, the high connectivity pattern exhibited by twin pairs more likely to lack the RS+ allele was under significantly less genetic influence. The data suggest that handedness and hemispheric dominance for speech production might be at least partly dependent on genetically controlled processes of axonal pruning in the corpus callosum.

Test de escucha dicótica para niños hispanohablantes: validación de unas nuevas series de pares de palabras y de sílabas en castellano

Dichotic listening test can estimate hemispheric dominance for language. To study the usefulness of a new set of dichotic pairs of Spanish stimuli in middle childhood. The stratified control group comprised 40 healthy, right-handed children, aged 3.5- 7.5 years, of both sexes, with average ability at speaking Spanish. The clinical sample comprised 12 children with right spastic hemi-paretic cerebral palsy, average general intelligence and sentence repetition index over -2z. Each listening series is composed of 20 age-appropriate dichotic pairs: one syllable, word, or number; or trains of two or three syllables or numbers. Voice onset time, duration and stress of stimuli were balanced. Hemispheric dominance index (HDI) for language was calculated using a formula with the scores of stimuli from right or left ears. Statistical analysis evaluated the age-related accuracy and discriminant power of each HDI. In the non-forced attention paradigm, the range of HDI is 0-200. Values of HDI ≥ 112 indicate left hemisphere dominance for language, whereas values of HDI ≤ 88 indicate right hemisphere dominance. All 40 typical subjects showed left HDI for language, without influence of age and sex. In contrast, ten out of twelve (83%) right hemiparetic children had right HDI. The results show that this new set of dichotic pairs is useful in the initial assessment of cerebral dominance for language and valid for use in Spanish speaking children aged 3.5 years or more.

Neuroimaging of Voice Hearing in Non-Psychotic Individuals: A Mini Review

Auditory verbal hallucinations (AVH) or “voices” are a characteristic symptom of schizophrenia, but can also be observed in healthy individuals in the general population. As these non-psychotic individuals experience AVH in the absence of other psychiatric symptoms and medication-use they provide an excellent model to study AVH in isolation. Indeed a number of studies used this approach and investigated brain structure and function in non-psychotic individuals with AVH. These studies showed that increased sensitivity of auditory areas to auditory stimulation and aberrant connectivity of language production and perception areas is associated with AVH. This is in concordance with investigations that observed prominent activation of these areas during the state of AVH. Moreover, while effortful attention appears not to be related to AVH, individuals prone to hallucinate seem to have an enhanced attention bias to auditory stimuli which may stem from aberrant activation of the anterior cingulated regions. Furthermore, it was observed that decreased cerebral dominance for language and dopamine dysfunction, which are consistently found in schizophrenia, are most likely not specifically related to AVH as these abnormalities were absent in healthy voice hearers. Finally, specific aspects of AVH such as voluntary control may be related to the timing of the supplementary motor area and language areas in the experience of AVH.

Opposite cerebral dominance for reading and sign language

We present a case of right hemispheric dominance for sign language but left hemispheric dominance for reading, in a left-handed deaf patient with epilepsy and left mesial temporal sclerosis. Atypical language laterality for ASL was determined by preoperative fMRI, and congruent with ASL modified WADA testing. We conclude that reading and sign language can have crossed dominance and preoperative fMRI evaluation of deaf patients should include both reading and sign language evaluations.

Language dominance, handedness and sex: Recessive X-linkage theory and test

The possibility is investigated that cerebral dominance for language and handedness share a common X-linkage and that the relation between the two is therefore a function of sex. In particular, an X-linked recessive account is shown to predict an overall configuration of language dominance, handedness and sex within which there is a sex effect in the pattern of language dominance among right-handed but not left-handed people. The recent accurate determination of cerebral dominance among relatively large samples of the general population by means of functional transcranial Doppler ultrasonography makes it possible to test this new theory rigorously, and its parameter-free pattern of predictions is found to be supported.