Hemispheric Specialization For Language Research Articles

Functional Topography of Auditory Areas Derived From the Combination of Electrophysiological Recordings and Cortical Electrical Stimulation.

The posterior part of the superior temporal gyrus (STG) has long been known to be a crucial hub for auditory and language processing, at the crossroad of the functionally defined ventral and dorsal pathways. Anatomical studies have shown that this “auditory cortex” is composed of several cytoarchitectonic areas whose limits do not consistently match macro-anatomic landmarks like gyral and sulcal borders. The only method to record and accurately distinguish neuronal activity from the different auditory sub-fields of primary auditory cortex, located in the tip of Heschl and deeply buried in the Sylvian fissure, is to use stereotaxically implanted depth electrodes (Stereo-EEG) for pre-surgical evaluation of patients with epilepsy. In this prospective, we focused on how anatomo-functional delineation in Heschl’s gyrus (HG), Planum Temporale (PT), the posterior part of the STG anterior to HG, the posterior superior temporal sulcus (STS), and the region at the parietal-temporal boundary commonly labeled “SPT” can be achieved using data from electrical cortical stimulation combined with electrophysiological recordings during listening to pure tones and syllables. We show the differences in functional roles between the primary and non-primary auditory areas, in the left and the right hemispheres. We discuss how these findings help understanding the auditory semiology of certain epileptic seizures and, more generally, the neural substrate of hemispheric specialization for language.

Typical and atypical language brain organization based on intrinsic connectivity and multitask functional asymmetries.

Based on the joint investigation in 287 healthy volunteers (150 left-Handers (LH)) of language task-induced asymmetries and intrinsic connectivity strength of the sentence-processing supramodal network, we show that individuals with atypical rightward language lateralization (N = 30, 25 LH) do not rely on an organization that simply mirrors that of typical leftward lateralized individuals. Actually, the resting-state organization in the atypicals showed that their sentence processing was underpinned by left and right networks both wired for language processing and highly interacting by strong interhemispheric intrinsic connectivity and larger corpus callosum volume. Such a loose hemispheric specialization for language permits the hosting of language in either the left and/or right hemisphere as assessed by a very high incidence of dissociations across various language task-induced asymmetries in this group.

The depth and breadth of multiple perceptual asymmetries in right handers and non-right handers

ABSTRACTSeveral non-verbal perceptual and attentional processes have been linked with specialization of the right cerebral hemisphere. Given that most people have a left hemispheric specialization for language, it is tempting to assume that functions of these two classes of dominance are related. Unfortunately, such models of complementarity are notoriously hard to test. Here we suggest a method which compares frequency of a particular perceptual asymmetry with known frequencies of left hemispheric language dominance in right-handed and non-right handed groups. We illustrate this idea using the greyscales and colourscales tasks, chimeric faces, emotional dichotic listening, and a consonant–vowel dichotic listening task. Results show a substantial “breadth” of leftward bias on the right hemispheric tasks and rightward bias on verbal dichotic listening. Right handers and non-right handers did not differ in terms of proportions of people who were left biased for greyscales/colourscales. Support for reduced typical biases in non-right handers was found for chimeric faces and for CV dichotic listening. Results are discussed in terms of complementary theories of cerebral asymmetries, and how this type of method could be used to create a taxonomy of lateralized functions, each categorized as related to speech and language dominance, or not.

MEG imaging of recurrent gliomas reveals functional plasticity of hemispheric language specialization.

In patients with gliomas, changes in hemispheric specialization for language determined by magnetoencephalography (MEG) were analyzed to elucidate the impact of treatment and tumor recurrence on language networks. Demonstration of reorganization of language networks in these patients has significant implications on the prevention of postoperative functional loss and recovery. Whole-brain activity during an auditory verb generation task was estimated from MEG recordings in a group of 73 patients with recurrent gliomas. Hemisphere of language dominance was estimated using the language laterality index (LI), a measure derived from the task. The initial scan was performed prior to resection; patients subsequently underwent surgery and adjuvant treatment. A second scan was performed upon recurrence prior to repeat resection. The relationship between the shift in LI between scans and demographics, anatomic location, pathology, and adjuvant treatment was analyzed. Laterality shifts were observed between scans; the median percent change was 29.1% across all patients. Laterality shift magnitude and relative direction were associated with the initial position of language dominance; patients with increased lateralization experienced greater shifts than those presenting more bilateral representation. A change in LI from left or right to bilateral (or vice versa) occurred in 23.3% of patients; complete switch occurred in 5.5% of patients. Patients with tumors within the language-dominant hemisphere experienced significantly greater shifts than those with contralateral tumors. The majority of patients with glioma experience shifts in language network organization over time which correlate with the relative position of language lateralization and tumor location.

The Contribution of the Corpus Callosum to Language Lateralization.

The role that corpus callosum development has on the hemispheric specialization of language is poorly understood. Here, we used magnetoencephalographic imaging during linguistic tests (verb generation, picture naming) to test for hemispheric dominance in patients with agenesis of the corpus callosum (AgCC) and found reduced laterality (i.e., greater likelihood of bilaterality or right hemisphere dominance) in this cohort compared with controls, especially in patients with complete agenesis. Laterality was positively correlated with behavioral measures of verbal intelligence. These findings provide support for the hypothesis that the callosum aids in functional specialization throughout neural development and that the loss of this mechanism correlates with impairments in verbal performance.

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.

Are babies born with left-hemisphere language dominance? An fNIRS study.

Event Abstract Back to Event Are babies born with left-hemisphere language dominance? An fNIRS study. Phetsamone Vannasing1*, Anne Gallagher1, Natacha Paquette1, Julie Tremblay1, Olivia Florea1, Dima Safi1, Renée Béland1, Franco Lepore2 and Maryse Lassonde1 1 CHU Sainte-Justine University Hospital Centre, Research Center, Canada 2 Neuropsychology and Cognition Research Center, Psychology, Canada The age at which babies start showing a left hemisphere functional specialization for language remains a matter of controversy. Do newborns already show a hemispheric specialization for language discrimination? Twenty-seven one-day-old infants from francophone parents in Quebec underwent functional near-infrared spectroscopy (fNIRS) to assess whether the neonate brain shows left hemisphere dominance for native language. Fourteen full-term newborns (7 boys, 7 girls) listened to a story read in the language spoken at home (French) and in a foreign language (Arabic). All readings (forward speech conditions) were done by the same speaker. To determine if hemispheric dominance reflects the use of prosodic cues, a second group of 13 full-term newborns (8 boys, 5 girls) were tested with the same utterances played backwards (backward speech conditions). A nonparametric permutation test was applied to find the time points (0 to 30 s) that would show significant differences between the left and right temporal regions for each of the forward and backward speech conditions. Results revealed significantly higher oxyhemoglobin (HbO2) concentration in the left than in the right temporal region when neonates were hearing the story in the French forward condition (p = 0.001). Both forward Arabic and backward French elicited a significantly higher right hemisphere activation (p = 0.007 and p = 0.025, respectively) whereas the backward Arabic condition elicited a bilateral activation (right hemisphere = .0005 mol/L, left hemisphere = .0004 mol/L). We interpreted that within the first few hours after birth, newborns of French speaking parents showed left hemisphere dominance in processing prosodic cues that are language specific. These results confirmed that hemispheric specialization for language and prosodic processing is present at birth. Keywords: Language, development, newborns, Prosody, Functional Near Infrared Spectroscopy (fNIRS) Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Language Citation: Vannasing P, Gallagher A, Paquette N, Tremblay J, Florea O, Safi D, Béland R, Lepore F and Lassonde M (2015). Are babies born with left-hemisphere language dominance? An fNIRS study.. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00312 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Mrs. Phetsamone Vannasing, CHU Sainte-Justine University Hospital Centre, Research Center, Montreal, Canada, pvannasing@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Phetsamone Vannasing Anne Gallagher Natacha Paquette Julie Tremblay Olivia Florea Dima Safi Renée Béland Franco Lepore Maryse Lassonde Google Phetsamone Vannasing Anne Gallagher Natacha Paquette Julie Tremblay Olivia Florea Dima Safi Renée Béland Franco Lepore Maryse Lassonde Google Scholar Phetsamone Vannasing Anne Gallagher Natacha Paquette Julie Tremblay Olivia Florea Dima Safi Renée Béland Franco Lepore Maryse Lassonde PubMed Phetsamone Vannasing Anne Gallagher Natacha Paquette Julie Tremblay Olivia Florea Dima Safi Renée Béland Franco Lepore Maryse Lassonde Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Resting-state functional connectivity predicts the strength of hemispheric lateralization for language processing in temporal lobe epilepsy and normals.

In temporal lobe epilepsy (TLE), determining the hemispheric specialization for language before surgery is critical to preserving a patient's cognitive abilities post-surgery. To date, the major techniques utilized are limited by the capacity of patients to efficiently realize the task. We determined whether resting-state functional connectivity (rsFC) is a reliable predictor of language hemispheric dominance in right and left TLE patients, relative to controls. We chose three subregions of the inferior frontal cortex (pars orbitalis, pars triangularis, and pars opercularis) as the seed regions. All participants performed both a verb generation task and a resting-state fMRI procedure. Based on the language task, we computed a laterality index (LI) for the resulting network. This revealed that 96% of the participants were left-hemisphere dominant, although there remained a large degree of variability in the strength of left lateralization. We tested whether LI correlated with rsFC values emerging from each seed. We revealed a set of regions that was specific to each group. Unique correlations involving the epileptic mesial temporal lobe were revealed for the right and left TLE patients, but not for the controls. Importantly, for both TLE groups, the rsFC emerging from a contralateral seed was the most predictive of LI. Overall, our data depict the broad patterns of rsFC that support strong versus weak left hemisphere language laterality. This project provides the first evidence that rsFC data may potentially be used on its own to verify the strength of hemispheric dominance for language in impaired or pathologic populations.

On the origins of human handedness and language: A comparative review of hand preferences for bimanual coordinated actions and gestural communication in nonhuman primates

Within the evolutionary framework about the origin of human handedness and hemispheric specialization for language, the question of expression of population-level manual biases in nonhuman primates and their potential continuities with humans remains controversial. Nevertheless, there is a growing body of evidence showing consistent population-level handedness particularly for complex manual behaviors in both monkeys and apes. In the present article, within a large comparative approach among primates, we will review our contribution to the field and the handedness literature related to two particular sophisticated manual behaviors regarding their potential and specific implications for the origins of hemispheric specialization in humans: bimanual coordinated actions and gestural communication. Whereas bimanual coordinated actions seem to elicit predominance of left-handedness in arboreal primates and of right-handedness in terrestrial primates, all handedness studies that have investigated gestural communication in several primate species have reported stronger degree of population-level right-handedness compared to noncommunicative actions. Communicative gestures and bimanual actions seem to affect differently manual asymmetries in both human and nonhuman primates and to be related to different lateralized brain substrates. We will discuss (1) how the data of hand preferences for bimanual coordinated actions highlight the role of ecological factors in the evolution of handedness and provide additional support the postural origin theory of handedness proposed by MacNeilage [MacNeilage [2007]. Present status of the postural origins theory. In W. D. Hopkins (Ed.), The evolution of hemispheric specialization in primates (pp. 59-91). London: Elsevier/Academic Press] and (2) the hypothesis that the emergence of gestural communication might have affected lateralization in our ancestor and may constitute the precursors of the hemispheric specialization for language.

Lateralization, praxis, and communicative gestures: Developmental and comparative perspectives

This special issue is the result of a workshop held in the fall of 2012 at Paris Descartes Universite, Paris, France. The goal of the workshop was to explore the relationships between different aspects of hand-use lateralization, that is, hand preference for praxis and communication through their developments in human infants, and by comparing them with nonhuman primates who also lack language. The workshop brought together an interdisciplinary group of scholars: comparative and developmental psychologists, ethologists, and neuroscientists convened for 1 day of talks and discussions. This special issue gathers the contributions of some of those participants. The first article (MacNeilage) places hand-use lateralization within a larger context by synthesizing evidence of left brain/right side asymmetries in routine whole-body actions in several species of marine mammals. The reported data suggest a commonality of patterns between humans and marine mammals for leading the right side in turning asymmetries. MacNeilage postulates that such asymmetries may be the result of a left-hemisphere intentional control and more generally, a left-hemisphere specialization for movement dynamics (Sainburg, 2005). Three articles are concerned with the lateralization of motor behavior in human fetuses and human infants. Hepper notes the early emergence of lateralized behaviors during the prenatal period (from 10 weeks gestation). He proposes that mediation of these behaviors is most likely genetic and that the pattern of fetal lateralization is the precursor of the laterality observed postnatally. Although it can be tempting to relate the behavioral biases with structural and functional differences between the hemispheres, Hepper cautions against interpreting the former as a casual effect of the latter. In her article, Fagard questions the relationships between hand preference and hemispheric specialization for language. Even as early fetal signs of lateralization become better known, she notes that there is still too little evidence about: (1) how genetic and environmental factors interact to lead to mature handedness and language lateralization; and (2) what exactly is the nature of the relationship between both processes of lateralization. Are handedness and hemispheric specialization for language causally related (and in which direction) or independent in origin? To answer these questions, Fagard calls for considering their codevelopment during early ontogeny. In their article, Michel and colleagues tackle the issue of the relationships of the development of handedness and that of hemispheric specialization for speech processing. They borrow the developmental sequence proposed by Arbib’s (2006) mirror system hypothesis about the linkage of action and language. This view is based on the idea that hand preference must reflect a lateralized difference in neural control of manual actions and speech actions (gestures) that will ultimately lead to speech. Michel and colleagues employ embodiment theory to suggest that Manuscript Received: 21 June 2013 Manuscript Accepted: 21 June 2013 Correspondence to: Jacques Vauclair Article first published online in Wiley Online Library (wileyonlinelibrary.com): 19 July 2013 DOI 10.1002/dev.21152 2013 Wiley Periodicals, Inc. Developmental Psychobiology

Early development of hand preference and language lateralization: Are they linked, and if so, how?

It is often taken for granted that, in a large majority of typical persons, hand preference and hemispheric specialization for language are interrelated. In this article, I argue that there is currently little serious evidence to support this view. I contend that the best way to investigate the true relationship between hand preference and language lateralization would be to look at their codevelopment. Since both hand preference and language asymmetries are expressed very early, even before birth, a systematic comparison of the very early development of both behavioral traits is needed to understand this relationship. At present, such data are clearly lacking. I discuss existing data on the development of hand preference and language asymmetry, and on the relations between the two. I conclude that this evidence favors the view that the two asymmetries develop relatively independently.

Hemispheric asymmetry modulation for language processing in aging: meta-analysis of studies using the dichotic listening test

Growing evidence suggests that age impacts on interhemispheric representation of language. Dichotic listening test allows assessing language lateralization for spoken language and it generally reveals right-ear/left-hemisphere (LH) predominance for language in young adult subjects. According to reported results, elderly would display increasing LH predominance in some studies or stable LH language lateralization for language in others ones. The aim of this study was to depict the main pattern of results in respect with the effect of normal aging on the hemisphere specialization for language by using dichotic listening test. A meta-analysis based on 11 studies has been performed. The inter-hemisphere asymmetry does not seem to increase according to age. A supplementary qualitative analysis suggests that right-ear advantage seems to increase between 40 and 49 y old and becomes stable or decreases after 55 y old, suggesting right-ear/LH decline.

Sex-Linked & Handedness Effects: Do Temporal-Parietal Asymmetry Patterns Diverge in Adults Who Stutter? (P02.053)

Objective: To determine whether sex-linked or handedness factors may be associated with divergent temporal-parietal asymmetry patterns in adults who stutter (AWS) compared to matched controls. Background Developmental stuttering is more common in males than females (5:1 in adults) and in non-right handers. There is evidence that these factors mediate anatomical relationships (PT, planum temporale; PAR, posterior ascending ramus). Therefore, we hypothesized that typical configurations (Leftward PT, Rightward PAR) would be found in male controls, whereas female controls and adults who stutter (AWS) would have atypical configurations. We postulated that these relationships would be modified by degree of handedness (defined by Hand Preference Inventory scores, HPI). Design/Methods: Participants included Controls (n=44, ½ men) and AWS (n=19, 3 females) matched on age (Mean = 31.4) and education (Mean = 16.6); 1/3 non-right handers. Volumetric MRI scans were acquired; neuropsychological assessments were completed. The full extent of the PT and PAR were measured and volumes were computed as % of hemisphere volume. Asymmetry (AQ) was computed: (Left-Right)/[(Left + Right)(.5)]. Results: PT-AQ and PAR-AQ were correlated (r2 = -.424). The association did not vary in male and female Controls, nor did the association vary when AWS were compared to Controls. PT-AQ and PAR-AQ did not predict HPI, but left PT volume was predicted by HPI score (p Conclusions: Although we did not find any differences in AWS, our results support the postulate that left PT size may be an important determinant of the relationship of language and manual preference. Hemispheric specialization for language is associated with handedness in right-handers as the crossed-motor pathways for manual dexterity and skill are left lateralized. A major question is how these functional representations diverge in people who are not strongly right-handed. Supported by: NIH DC04957; Malcolm Fraser Foundation. Disclosure: Dr. Foundas has nothing to disclose. Dr. Corey has nothing to disclose.

The sound of one-hand clapping: handedness and perisylvian neural correlates of a communicative gesture in chimpanzees

Whether lateralization of communicative signalling in non-human primates might constitute prerequisites of hemispheric specialization for language is unclear. In the present study, we examined (i) hand preference for a communicative gesture (clapping in 94 captive chimpanzees from two research facilities) and (ii) the in vivo magnetic resonance imaging brain scans of 40 of these individuals. The preferred hand for clapping was defined as the one in the upper position when the two hands came together. Using computer manual tracing of regions of interest, we measured the neuroanatomical asymmetries for the homologues of key language areas, including the inferior frontal gyrus (IFG) and planum temporale (PT). When considering the entire sample, there was a predominance of right-handedness for clapping and the distribution of right- and left-handed individuals did not differ between the two facilities. The direction of hand preference (right- versus left-handed subjects) for clapping explained a significant portion of variability in asymmetries of the PT and IFG. The results are consistent with the view that gestural communication in the common ancestor may have been a precursor of language and its cerebral substrates in modern humans.

Right-handedness predominance in 162 baboons (Papio anubis) for gestural communication: Consistency across time and groups.

Whether nonhuman primates exhibit population level right manual bias remains a controversial topic. In captive baboons, population-level right-handedness has been reported for both coordinated bimanual actions and communicative gestures. However, some authors remain skeptical of these findings on both methodological and theoretical grounds. Here, we demonstrated the robustness and the consistency across time of the pattern of right-handedness for a species-specific communicative gesture in olive baboons (Papio anubis). First, we showed significant correlations in the 26 retested baboons for the measures of hand preferences between the first and the second session conducted 4 years later (2005-2009) by an observer blind to the previous handedness data. Second, the replication of the study in 96 novel individuals revealed a similar degree of population-level right-handedness than the one expressed in the first group of 66 subjects investigated in 2005. The implications of the findings are discussed within a theoretical framework about the origin of hemispheric specialization for language.

Sex differences in the temporal lobe white matter and the corpus callosum: a diffusion tensor tractography study

We assessed sex differences in fractional anisotropy (FA) and mean diffusion (MD) of temporal lobe white matter (TLWMFA, TLWMMD), TLWM asymmetry, and the relationship between TLWM asymmetry and FA and MD of the corpus callosum (CCFA, CCMD) using diffusion tensor tractography. We found sex differences in the MD of both inferior longitudinal fasciculus (ILF); however, it disappeared after statistical adjustments for intracranial volume and CCMD variability. FA of the superior longitudinal fasciculus (SLFFA) and FA and MD of the ILF (ILFFA, ILFMD) showed leftward asymmetry. In females, the asymmetry indices of SLFFA and the MD of the SLF were significantly correlated with CCFA and CCMD, respectively, which may be related to sex differences in the hemispheric specialization for language.

P03-135 - Delta and gamma EEG bands as markers of left hypofrontality for language in schizophrenia patients

ObjectivesSpectral delta and gamma activity were recorded in 17 schizophrenia patients and 17 matched controls to study brain dysfunction/inhibition and functional linguistic impairment in different phases of written word processing.MethodsMost of patients were suffering from paranoid schizophrenia and obtained relatively high rating in Delusions (P1) and Conceptual disorganization (P2) of the PANSS. Delta and gamma amplitudes were measured while participants performed three linguistic tasks, i.e., visuo-perceptual, rhyming and semantic judgment.ResultsCompared with healthy controls, patients showed no overall delta and gamma differences, revealing a lack of pharmacological-dependent impairment. However, ANOVAs revealed bilateral delta and gamma distributions in patients and, compared with controls, significant greater delta and lower gamma levels in left anterior sites. Healthy participants showed higher delta amplitude in right vs. left anterior sites and a reversed pattern for gamma amplitude: delta and gamma provided complementary results which suggested that controls, but not patients, activated left anterior regions during the linguistic processing. Patients’ hypofrontality was functionally correlated to their lack of left hemispheric specialization for language: the higher delta amplitude in left anterior sites, the higher levels of P1 and P2 positive symptoms; the higher gamma percentage in right anterior sites, the higher levels of N4 (i.e. Passive/apathetic social withdrawal).ConclusionsDelta and gamma rhythms are quantitative indices of the amount of neurons engaged in specific cognitive processes and they represent complementary physiological indices of neural inhibition/activation able to measure both the hypofrontality and the functional deficit of language lateralization in schizophrenia patients.

Delta EEG Band as a Marker of Left Hypofrontality for Language in Schizophrenia Patients

Frontal hypoactivation has consistently been demonstrated in schizophrenia patients. We hypothesized that this well-known deficit is asymmetrical, ie, centered over left frontal locations and, in-line with Crow's theory, associated with both loss of linguistic asymmetry and correlated with positive symptoms. Electroencephalography delta band was used as a quantitative index of cortical inhibition in 17 paranoid schizophrenia patients with prevailing positive symptoms and 17 matched control subjects. Delta amplitude was measured by 38 electrodes, while participants performed 3 linguistic tasks, visuoperceptual, rhyming, and semantic judgment. Compared with control subjects, patients did not show overall delta band differences, revealing no detrimental effects of pharmacological treatment. In healthy participants, analysis of 4 quadrants/regions of interest revealed higher delta amplitude in right vs left anterior sites, indicating significant left anterior disinhibition during linguistic processing. Instead, patients showed bilateral delta band distribution and, compared with control subjects, significant greater delta amplitude (ie, brain inhibition) in linguistic left anterior centers. Patients' left hypofrontality was functionally related to their lack of hemispheric specialization for language and was positively correlated with higher levels of delusions (P1) and conceptual disorganization (P2) Positive and Negative Syndrome Scale subscales. Results suggest, in schizophrenia patients, a functional deficit of Broca's area, a region playing a fundamental hierarchical role between and within hemispheres by integrating many basic processes in linguistic and conceptual organization. The significant correlation between lack of anterior asymmetry and increased positive symptoms is in-line with Crow's hypothesis postulating the etiological role of disrupted linguistic frontal asymmetry on the onset of the key symptoms of schizophrenia.

Paracingulate asymmetry in anterior and midcingulate cortex: sex differences and the effect of measurement technique

Many structural brain asymmetries accompany left hemisphere language dominance. For example, the cingulate sulcus is larger in the medial cortex of the right hemisphere, while the more dorsal paracingulate sulcus is larger on the left. The functional significance of these asymmetries is unknown because fMRI studies rarely attempt to localize activation to specific sulci, possibly due to difficulties in consistent sulcal identification. In medial cortex, for example, there are many regions of partial sulcal overlap where MRI images do not provide sufficient information to unambiguously distinguish a paracingulate sulcus from a displaced anterior cingulate segment. As large samples of postmortem material are rarely available for cytoarchitectural studies of sulcal variation, we have investigated the effect of variation in boundary and sulcal definition on paracingulate asymmetry in the MRI scans of 200 healthy adults (100 men, 100 women). Although women displayed a reliable asymmetry in the size of the paracingulate sulcus, regardless of boundary definition or technique, asymmetry was greatest when (1) the measurement was limited to the midcingulate region between the genu and the anterior commissure; and (2) the more dorsal of two overlapping sulci was always classified as a paracingulate sulcus (rather than as a displaced cingulate segment). The fact that paracingulate asymmetry is maximal in the midcingulate region suggests that this region may play a particular role in hemispheric specialization for language. Future work should investigate the structural and functional correlates of sulcal variation in this region.

Contrast of hand preferences between communicative gestures and non-communicative actions in baboons: Implications for the origins of hemispheric specialization for language

Gestural communication is a modality considered in the literature as a candidate for determining the ancestral prerequisites of the emergence of human language. As reported in captive chimpanzees and human children, a study in captive baboons revealed that a communicative gesture elicits stronger degree of right-hand bias than non-communicative actions. It remains unclear if it is the communicative nature of this manual behavior which induces such patterns of handedness. In the present study, we have measured hand use for two uninvestigated behaviors in a group of captive olive baboons: (1) a non-communicative self-touching behavior (“muzzle wipe” serving as a control behavior), (2) another communicative gesture (a ritualized “food beg”) different from the one previously studied in the literature (a species-specific threat gesture, namely “hand slap”) in the same population of baboons. The hand preferences for the “food beg” gestures revealed a trend toward right-handedness and significantly correlated with the hand preferences previously reported in the hand slap gesture within the same baboons. By contrast, the hand preferences for the self-touching behaviors did not reveal any trend of manual bias at a group-level nor correlation with the hand preferences of any communicative gestures. These findings provide additional support to the hypothesized existence in baboons of a specific communicative system involved in the production of communicative gestures that may tend to a left-hemispheric dominance and that may differ from the system involved in purely motor functions. The hypothetical implications of these collective results are discussed within the theoretical framework about the origins of hemispheric specialization for human language.