Differences In Language Lateralization Research Articles

Reduced lateralization of multiple functional brain networks in autistic males

BackgroundAutism spectrum disorder has been linked to a variety of organizational and developmental deviations in the brain. One such organizational difference involves hemispheric lateralization, which may be localized to language-relevant regions of the brain or distributed more broadly.Methods In the present study, we estimated brain hemispheric lateralization in autism based on each participant’s unique functional neuroanatomy rather than relying on group-averaged data. Additionally, we explored potential relationships between the lateralization of the language network and behavioral phenotypes including verbal ability, language delay, and autism symptom severity. We hypothesized that differences in hemispheric asymmetries in autism would be limited to the language network, with the alternative hypothesis of pervasive differences in lateralization. We tested this and other hypotheses by employing a cross-sectional dataset of 118 individuals (48 autistic, 70 neurotypical). Using resting-state fMRI, we generated individual network parcellations and estimated network asymmetries using a surface area-based approach. A series of multiple regressions were then used to compare network asymmetries for eight significantly lateralized networks between groups.ResultsWe found significant group differences in lateralization for the left-lateralized Language (d = -0.89), right-lateralized Salience/Ventral Attention-A (d = 0.55), and right-lateralized Control-B (d = 0.51) networks, with the direction of these group differences indicating less asymmetry in autistic males. These differences were robust across different datasets from the same participants. Furthermore, we found that language delay stratified language lateralization, with the greatest group differences in language lateralization occurring between autistic males with language delay and neurotypical individuals.ConclusionsThese findings evidence a complex pattern of functional lateralization differences in autism, extending beyond the Language network to the Salience/Ventral Attention-A and Control-B networks, yet not encompassing all networks, indicating a selective divergence rather than a pervasive one. Moreover, we observed an association between Language network lateralization and language delay in autistic males.

Language lateralization differences between left and right temporal lobe epilepsy as measured by overt word reading fMRI activation and DTI structural connectivity

In cases of brain disease such as temporal lobe epilepsy (TLE), damage may lead to functional reorganization and a shift in language dominance to homolog regions in the other hemisphere. If the effects of TLE on language dominance are hemisphere-focused, then brain regions and connections involved in word reading should be less left-lateralized in left temporal lobe epilepsy (lTLE) than right temporal lobe epilepsy (rTLE) or healthy controls, and the opposite effect should be observed in patients with rTLE. In our study, functional magnetic resonance imaging (fMRI) showed that patients with rTLE had more strongly lateralized left hemisphere (LH) activation than patients with lTLE and healthy controls in language-related brain regions (pars opercularis and fusiform gyrus (FuG)). Corresponding with this difference, diffusion tensor imaging (DTI) found differences in connectivity indicative of patients with lTLE having greater tract integrity than patients with rTLE in the right hemisphere (RH) uncinate fasciculus (UF), inferior longitudinal fasciculus (ILF), and inferior fronto-occipital fasciculus (IFOF) using the network-based statistic analysis method. The UF, ILF, and IFOF tract integrity have previously been associated with lexical (whole-word) processing abilities. Multivariate distance matrix regression provided converging evidence for regions of the IFOF having different connectivity patterns between groups with lTLE and rTLE. This research demonstrates language lateralization differences between patient groups with lTLE and rTLE, and corresponding differences in the connectivity strength of the ILF, IFOF, and UF. This research provides a novel approach to measuring lateralization of language in general, and the fMRI and DTI findings were integral for guiding the neurosurgeons performing the TLE resections. This approach should inform future studies of language lateralization and language reorganization in patients such as those with TLE.

Negligible heritability of language laterality assessed by functional transcranial Doppler ultrasound: a twin study

Background: It is widely assumed that individual differences in language lateralisation have a strong genetic basis, yet prior studies show low heritability (around 0.25) for the related trait of handedness, and two twin studies of structural brain asymmetry obtained similarly low estimates. This report describes heritability estimates from a twin study of language laterality and handedness phenotypes. Methods: The total sample consisted of 194 twin pairs (49% monozygotic) aged from 6 to 11 years. A language laterality index was obtained for 141 twin pairs, who completed a protocol where relative blood flow through left and right middle cerebral arteries was measured using functional transcranial Doppler ultrasound (fTCD) while the child described animation sequences. Handedness data was available from the Edinburgh Handedness Inventory (EHI) and Quantification of Hand Preference (QHP) for all 194 pairs. Heritability was assessed using conventional structural equation modeling, assuming no effect of shared environment (AE model). Results: For the two handedness measures, heritability estimates were consistent with prior research: 0.23 and 0.22 respectively for the EHI and QHP. For the language laterality index, however, the twin-cotwin correlations were very close to zero for both MZ and DZ twins, and the heritability estimate was zero. Conclusions: A single study showing negligible heritability for language laterality cannot rule out a genetic effect on language lateralisation. It is possible that the low twin-cotwin correlations were affected by noisy data: although the split-half reliability of the fTCD-based laterality index was high (0.85), we did not have information on test-retest reliability in children, which is likely to be lower. We cannot rule out the possibility that true heritability of differences in language lateralization is non-zero, but results indicate that the heritability of this trait is low at best. Stochastic variation in neurodevelopment appears to play a major role in determining cerebral lateralisation.

Language Lateralization and Auditory Attention Impairment in Young Adults at Ultra-High Risk for Psychosis: A Dichotic Listening Study

Objectives: Impaired attention and language functions are common in psychosis, but have been less explored in subjects with ultra-high risk for psychosis (UHR). The aim of the study was to investigate differences in language lateralization and auditory attention in UHR subjects compared to healthy controls with a dichotic listening paradigm. In addition, symptoms from The Structural Interview for Prodromal Syndromes (SIPS) were explored in relation to performance on dichotic listening.Methods: The UHR subjects (n = 46, female = 28, mean age = 17.9) were compared to a group of healthy controls (n = 40, female = 20, mean age = 16.8). A split-plot repeated measures analysis of covariance was conducted with group as between-subjects factor and attention conditions (non-forced, forced-right, forced-left) and side (right ear, left ear) as repeated measures factors (2×3×2 design) using gender, age and handedness as covariates. SIPS symptoms were subjected to Spearman’s r correlations with laterality indexes and attentional gain in each ear.Results: There was a statistically significant three-way interaction of group (UHR, healthy controls) × forced condition (non-forced, forced-right, forced-left) × side (right ear, left ear), p = 0.048. The effect was due to an interaction between group × side in the forced-left condition. There were no significant differences between UHR subjects and healthy controls in the non-forced condition. Right ear gain correlated with “Perceptual abnormalities/Hallucinations” (P4), r = 0.486, p = 0.001.Conclusion: UHR subjects demonstrated impairment in top-down attentional mechanisms, but showed no language lateralization abnormalities. Impairment in top-down attentional mechanisms are frequently reported from dichotic listening studies in patients with schizophrenia. Higher levels of perceptual abnormalities and hallucinatory experiences were associated with enhanced report from the right ear in the forced-right condition.

Variation in homotopic areas' activity and inter-hemispheric intrinsic connectivity with type of language lateralization: an FMRI study of covert sentence generation in 297 healthy volunteers.

We investigated the regional correlates of differences in hemispheric lateralization in 297 healthy volunteers [including 153 left-handers (LH)] previously classified into three types of language lateralization according to their hemispheric functional lateralization index measured with fMRI during covert sentence production versus word list production (PRODSENT-LIST): 250 leftward asymmetrical Typicals, 10 rightward asymmetrical Strong-atypicals (only LH), and 37 Ambilaterals with weak lateralization. Using a functionally driven homotopic atlas (AICHA), we compared patterns of regional asymmetry during PRODSENT-LIST in these three groups. Among the 192 homotopic regions of interest (hROIs) of the AICHA atlas, 58 exhibited a significant effect of the type of lateralization on their BOLD signal variation during PRODSENT-LIST. The analyses of patterns of asymmetry of these 58 hROIs showed that (1) hROIs asymmetries in Strong-atypicals were significantly negatively correlated with those observed in Typicals, which indicates that their regional pattern of rightward asymmetries was comparable to the regional pattern of leftward language asymmetries of Typicals; (2) right- and left-handed Typicals had identical profiles, whereas left-handed Ambilaterals exhibited reduced leftward asymmetry as compared eitherto right-handed Ambilaterals or to Typicals. Moreover, left-handed Ambilaterals pattern of hROIs asymmetries significantly positively correlated with those of both Typicals and Strong-atypicals. In 291 of the participants, we tested the hypothesis that differences in language lateralization were associated with differences in inter-hemispheric connectivity during resting state by measuring their regional homotopic inter-hemispheric intrinsic connectivity coefficient (rHIICC) in 36 of the 58 hROIs known to be connected via the corpus callosum. Mean rHIICCs were negatively correlated with task-induced functional asymmetries, suggesting that enhanced inter-hemispheric cooperation at rest translates into increased inter-hemispheric cooperation during language production. In addition, the left-handed Ambilaterals exhibited a significantly larger rHIICC compared with right-handed Ambilaterals and Typicals, confirming a difference in inter-hemispheric organization in this group.

Age-related sex differences in language lateralization: A magnetoencephalography study in children.

It is well supported by behavioral and neuroimaging studies that typical language function is lateralized to the left hemisphere in the adult brain and this laterality is less well defined in children. The behavioral literature suggests there maybe be sex differences in language development, but this has not been examined systematically with neuroimaging. In this study, magnetoencephalography was used to investigate the spatiotemporal patterns of language lateralization as a function of age and sex. Eighty typically developing children (46 female, 34 male; 4-18 years) participated in an overt visual verb generation task. An analysis method called differential beamforming was used to analyze language-related changes in oscillatory activity referred to as low-gamma event-related desynchrony (ERD). The proportion of ERD over language areas relative to total ERD was calculated. We found different patterns of laterality between boys and girls. Boys showed left-hemisphere lateralization in the frontal and temporal language-related areas across age groups, whereas girls showed a more bilateral pattern, particularly in frontal language-related areas. Differences in patterns of ERD were most striking between boys and girls in the younger age groups, and these patterns became more similar with increasing age, specifically in the preteen years. Our findings show sex differences in language lateralization during childhood; however, these differences do not seem to persist into adulthood. We present possible explanations for these differences. We also discuss the implications of these findings for presurgical language mapping in children and highlight the importance of examining the question of sex-related language differences across development.

Sex differences in language asymmetry are age-dependent and small: A large-scale, consonant–vowel dichotic listening study with behavioral and fMRI data

Men are often believed to have a functionally more asymmetrical brain organization than women, but the empirical evidence for sex differences in lateralization is unclear to date. Over the years we have collected data from a vast number of participants using the same consonant–vowel dichotic listening task, a reliable marker for language lateralization. One dataset comprised behavioral data from 1782 participants (885 females, 125 non-right-handers), who were divided in four age groups (children <10 yrs, adolescents = 10–15 yrs, younger adults = 16–49 yrs, and older adults >50 yrs). In addition, we had behavioral and functional imaging (fMRI) data from another 104 younger adults (49 females, aged 18–45 yrs), who completed the same dichotic listening task in a 3T scanner. This database allowed us to comprehensively test whether there is a sex difference in functional language lateralization. Across all participants and in both datasets a right ear advantage (REA) emerged, reflecting left-hemispheric language lateralization. Accordingly, the fMRI data revealed a leftward asymmetry in superior temporal lobe language processing areas. In the N = 1782 dataset no main effect of sex but a significant sex by age interaction emerged: the REA increased with age in both sexes but as a result of an earlier onset in females the REA was stronger in female than male adolescents. In turn, male younger adults showed greater asymmetry than female younger adults (accounting for <1% of variance). There were no sex differences in children and older adults. The males in the fMRI dataset (N = 104) also had a greater REA than females (accounting for 4% of variance), but no sex difference emerged in the neuroimaging data. Handedness did not affect these findings. Taken together, our findings suggest that sex differences in language lateralization as assessed with dichotic listening exist, but they are (a) not necessarily reflected in fMRI data, (b) age-dependent and (c) relatively small.

Second language research using magnetoencephalography: a review

In this review we show how magnetoencephalography (MEG) is a constructive tool for language research and review MEG findings in second language (L2) research. MEG is the magnetic analog of electroencephalography (EEG), and its primary advantage over other cross-sectional (e.g. magnetic resonance imaging, or positron emission tomography) functional imaging methods is the superior temporal resolution it affords. After an overview of MEG technology, research exploring visual language processing in L2, nonnative phonemic contrasts and syntactic processing in L2 are reviewed. We also review MEG investigations of the advantages of bilingualism and of language lateralization differences across languages with different characteristics.

Sex differences in handedness, asymmetry of the Planum Temporale and functional language lateralization

Many studies have investigated sex differences in language lateralization. Despite the large number of investigations, controversy about the presence of sex differences in lateralization remains. This study aims to provide a complete overview of sex differences in several reflections of language lateralization: handedness, asymmetry of the Planum Temporale (PT) and functional lateralization of language, measured by asymmetric performance on dichotic listening tests (Right Ear Advantage) and asymmetry of language activation as measured with functional imaging techniques. Meta-analysis of studies that assessed handedness in males and females yielded more left-handedness in males (mean weighted odds ratio: 1.25, p < 0.001). Meta-analysis of studies on PT asymmetry yielded no sex difference (Hedges g = − 0.11, p = 0.68). Results of the meta-analysis on dichotic listening studies also retrieved no sex difference in lateralization (Hedges g = 0.09, p = 0.18). When the studies were subdivided according to the paradigm they applied, studies that used the consonant–vowel task yielded a sex difference favouring males, while studies that applied other paradigms yielded no sex difference. The subdivision into applied paradigm largely overlapped with the subdivision into studies that did or did not focus on sex differences as their main topic. The observed sex effect may therefore be caused by publication bias. Meta-analysis of functional imaging studies yielded no sex difference (Hedges g = 0.01, p = 0.73) in language lateralization. Sub-analyses of studies that applied different paradigms all yielded no sex difference. In conclusion, males are more frequently non-right handed than females, but there is no sex difference in asymmetries of the Planum Temporale, dichotic listening or functional imaging findings during language tasks.

Sex difference in language lateralization may be task-dependent

Sir, It has been proposed that language is more strongly lateralized in males than in females. Recent imaging studies, however, have yielded a variety of apparently contradictory observations. A meta-analysis by Sommer et al . (2004) has provided us with an up-to-date collection of 24 studies in which language-related activity was assessed with functional imaging techniques in healthy subjects. By combining 14 studies with sufficient data, which employed a variety of language tasks, Sommer and colleagues concluded that ‘sex difference in language lateralization may be absent at the population level’. They further suggested that ‘sex difference in language lateralization may be observed only with some, as yet not defined, language tasks’, because they ‘found no support for’ the hypothesis that ‘sex differences in language lateralization may be task-dependent’. In our previous review of this topic (Kansaku and Kitazawa, 2001), we suggested, on the contrary, that sex differences in language lateralization are task-dependent, and drew attention to the fact that studies that employed passive listening to stories found clear sex-based differences (Kansaku et al ., 2000; Phillips et al ., 2001). Although Sommer and colleagues referred to our study (Kansaku and Kitazawa, 2001), we believe that the authors were not entirely accurate in their interpretation of our paper. Sommer et al . (2004) stated that ‘Kansaku and Kitazawa (2001) suggested that only tasks …

Reply to ‘Time-resolved sex differences in language lateralization’

In response to our meta-analysis on sex differences in language lateralization (Sommer et al ., 2004), Ortigue and colleagues point out the limited time resolution of functional MRI (fMRI), PET and echo Doppler as a possible cause for failing to find a significant sex difference in the meta-analysis. The activation pattern of fMRI and PET studies, they argue, is composed of language components, but also of non-specific cerebral activity, especially when the control task consists of passive rest. Ortigue and colleagues explain that the functionally relevant time for language is between 170 …

Size does count: a reply to Kitazawa and Kansaku

Sir, In their Letter to the Editor, Kitazawa and Kansaku responded to our meta-analysis on sex differences in language lateralization measured with functional imaging techniques (Sommer et al ., 2004). Though Kitazawa and Kansaku gave an interesting interpretation of the data, we do not agree with the alternative calculation of the effect sizes of two studies they suggested. Kitazawa and Kansaku hypothesized that sex differences in language lateralization may be present only when subjects listen to stories, since two studies (Kansaku et al ., 2000; Philips et al …

Time-resolved sex differences in language lateralization

Many clinical, behavioural and brain imaging studies have suggested that language functions are less asymmetrical in women than in men. Sommer and colleagues challenge this view in a recent review on the outcome of 24 functional brain imaging studies (PET, functional MRI or functional transcranial Doppler ultrasound) that looked at possible sex differences in language lateralization. A vote count analysis over all studies revealed a much higher score for those studies that reported no sex differences. In addition, a meta-analysis of the lateralization index in 13 of these studies revealed no statistically significant difference between men and women. The authors concluded that the hypothesis of sex differences in cortical language representation probably has to be rejected at the population level (Sommer et al ., 2004). We believe that the hypothesis of subtle, but crucial sex differences in language representation should not be rejected on these grounds, considering the selective sample of studies included in the review. There is one important limiting factor of functional imaging with PET, fMRI or Doppler, namely their weak temporal resolution. Consequently, the studies reviewed by Sommer and colleagues (Sommer et al ., 2004) might have identified not only regions that are critical for language processing but also other areas that are activated while subjects solve the task, in particular when the control (subtraction) condition consists of ‘passive’ rest. This issue was discussed in detail in an earlier publication of the same group (Ramsey et al ., 2001), in which they propose a combined analysis of several ‘active’ language conditions using so-called conjunction analysis to overcome the problem. In that study, the authors convincingly showed that the latter approach is more reliable for the study of language lateralization and yields a small amount of variance across subjects. Unfortunately, with the exception of one study (Sommer et …

Do women really have more bilateral language representation than men? A meta-analysis of functional imaging studies.

Sex differences in cognition are consistently reported, men excelling in most visuospatial tasks and women in certain verbal tasks. It has been hypothesized that these sex differences in cognition results from a more bilateral pattern of language representation in women than in men. This bilateral pattern of language representation in women is thought to interfere with visuospatial functions in the right hemisphere. To test whether language representation is indeed more bilateral in the female than in the male brain, a meta-analysis was performed on studies that assessed language activity with functional imaging in healthy men and women. Effect sizes were weighted for sample size and the meta-analytic method was applied to obtain a combined effect size. Fourteen studies were included, providing data on 377 men and 442 women. Meta-analysis yielded a mean weighted effect d of 0.21 with a 95% confidence interval of -0.05 to 0.48, indicating no significant difference in language lateralization between men and women. This implies that the putative sex difference in language lateralization may be absent at the population level, or may be observed only with some, as yet not defined, language tasks. It is therefore not likely that differences in language lateralization underlie the general sex differences in cognitive performance, and the neuronal basis for these cognitive sex differences remains elusive.

Handedness, hemispheric asymmetries, and joke comprehension

To address the impact of differences in language lateralization on joke comprehension, event-related brain potentials (ERPs) were recorded as 16 left- and 16 right-handed adults read one-line jokes and non-funny control stimuli (“A replacement player hit a home run with my girl/ball,”). In right-handers, jokes elicited a late positivity 500–900 ms post-stimulus onset that was largest over right hemisphere (RH) centro-parietal electrode sites, and a slow sustained negativity over anterior left lateral sites. In left-handers, jokes elicited a late positivity 500–900 ms post-onset that was larger and more broadly distributed than in the right-handers' ERPs. In right-handed women, the late positivity was larger over RH electrode sites. In left-handed women, the late positivity was bilaterally symmetric. The highly asymmetric slow sustained negativity over left anterior electrode sites was absent from left-handers' ERPs to jokes. Differences may reflect more efficient inter-hemispheric communication in the left-handers, as they are reputed to have relatively larger corpus callosal areas than right-handers. Results support the portrait of more bilateral language representation among left-handers, and suggest language lateralization affects high-level language comprehension tasks such as joke comprehension.

Language lateralization in female patients with schizophrenia: an fMRI study

Gender differences in schizophrenia are among the most consistently reported findings in schizophrenia research. However, the biological substrate underlying these gender differences is still largely unknown. Differences in language lateralization between men and women may underlie some gender differences in schizophrenia. In previous functional imaging studies, language lateralization was found to be decreased in male schizophrenia patients as compared to healthy males, which was due to enhanced language activation of the right hemisphere as compared to the healthy males. It could be hypothesized that decreased language lateralization in schizophrenia is gender specific, i.e. decreased lateralization in male patients and normal lateralization in female patients. To test this hypothesis, language activation was measured in 12 right-handed female patients with schizophrenia and 12 healthy females, and compared to findings in 12 male patients and 12 male controls of an earlier study. Language lateralization was significantly lower in the female patients (0.44) as compared to the female controls (0.75), which was due to increased activation of the right-sided language areas (patients: 19 voxels; controls: 8 voxels), while left hemisphere activation was similar in patients and controls. When these data are compared to the male patients and controls, both patient groups had lower lateralization than their healthy counterparts, but there was no difference between male and female patients. In both sexes, decreased lateralization resulted from increased right hemispheric language activation, which suggests a failure to inhibit nondominant language areas in schizophrenia. These findings indicate that lower language lateralization in women is not likely to underlie gender differences in schizophrenia.

Language Lateralization by Functional MRI: A Comparison with Wada Test-preliminary Results

Purpose: To evaluate the usefulness of functional MR imaging (fMRI) for the determination of languagedomi-nance and to assess differences in language lateralization according to activation task or activated area.Materials and Methods: Functional maps of the language area were obtained during word generation tasks (noun andverb) and a reading task in ten patients (9 right handed, 1 left handed) who had undergone the Wada test. MRexaminations were performed using a 1.5T scanner and the EPI BOLD technique. The SPM program was employed for thepostprocessing of images and the threshold for significance was set at p

Are Subjects' Perceptual Asymmetries on Auditory and Visual Language Tasks Correlated?: A Meta-Analysis

A number of studies have investigated the correlation between subjects' perceptual asymmetries on auditory and visual language tasks. With few exceptions, these studies have found low, nonsignificant correlations between the two types of perceptual asymmetries. However, variations in subjects' perceptual asymmetries on these tasks reflect not only individual differences in language lateralization but also several extraneous variables (e.g., random errors, individual differences in left–right attentional biases). Thus, low correlations between the two types of asymmetries may reflect “masking” by these extraneous variables rather than a “true” cross-modal dissociation. Consistent with this view, a meta-analysis of prior studies revealed a small, but significant correlation between the two types of asymmetries for left-handers. The correlation was nonsignificant for right-handers, presumably reflecting stronger attenuation caused by limited variability in language lateralization in this group. Possible factors mediating significant correlations between the two types of perceptual asymmetries include certain language processes shared by the two types of tasks, cross-modal consistency in individual differences in lateralization of certain modality-specific language processes, and cross-modal consistency in individual differences in left–right attentional biases.

Cued dichotic listening with right-handed, left-handed, bilingual and learning-disabled children

This study used cued dichotic listening to investigate differences in language lateralization among right-handed (control), left-handed, bilingual, and learning-disabled children. A sample of 60 subjects ranging in age from 7–13 yr were administered a CVC dichotic paradigm with three experimental conditions (free recall, directed left, directed right). A three-factor ANOVA design conducted on the data revealed that control, bilingual, and learning-disabled children produced the expected REA suggestive of left hemisphere dominance for language processing whereas left-handed children produced an LEA suggestive of right hemisphere superiority for language processing. The cued attention data derived from groups as well as from individual subjects suggested that in comparison with control children, left-handed children were greatly susceptible to attentional manipulation similar to learning-disabled children only in the opposite hemisphere. Bilingual children were found to have a REA much like control children although recall accuracy was depressed. Further, lambda (λ) analyses conducted on individual subjects indicated that the magnitude and degree of perceptual asymmetry varied widely among individuals of various anomaly groups. These findings lend support to the hypothesis that attentional factors play a larger role in unilateral processing for some anomalous groups of children (i.e. left-handers and learning-disabled) while not affecting others (i.e. controls and bilinguals).