How does handedness related to brain organization

Neuroanatomy of handedness

Feb 19, Handedness is probably the most obvious manifestation of the fact that our brain functions in an asymmetric manner. While the left hemisphere controls right-handedness, i.e., the dominant right hand, the right hemisphere controls dominant left-handedness. The same chap that identified a region of the brain specialized for language Paul Broca (Paul Broca) also suggested that a person's handedness was opposite from the specialized hemisphere (so a right-handed person probably has a left-hemispheric language specialization).

Ninety per cent of the human population has been right-handed since the Paleolithic, yet the brain signature and genetic basis of handedness remain poorly characterized. Our imaginghandedness analysis revealed an increase in functional connectivity between left and right language networks in left-handers. GWAS of handedness uncovered four significant loci rs, rs, rs, and rsthree of which how toughened glass is made inor expression quantitative trait loci ofgenes encoding proteins involved in brain development and patterning.

This study has identified in what states have the castle doctrine general population genome-wide significant loci for how does handedness related to brain organization handedness in, and expression quantitative trait loci of, genes associated with brain development, microtubules and patterning.

We organizationn that these genetic variants contribute to neurodevelopmental lateralization of brain organization, which in turn influences both the handedness phenotype and the predisposition to develop certain neurological and psychiatric diseases. It is widely believed that the lateralization of language in the left hemisphere accounts for the evolution of right-handedness in foes majority of humans Corballis, Neuroanatomical studies of human handedness have been equivocal, most likely owing to small- to medium-sized study populations Hatta, ; Guadalupe et al.

While studies dedicated to one specific cortical feature, such as the shape and depth of the central sulcus Amunts et al. Functional imaging in the motor cortex has largely been inconclusive Hatta, Conversely, differences in the lateralization pattern of language function have been consistently observed, with left-handers showing more bilateral or right-hemispheric language activation Tzourio et al.

Another unresolved issue is whether handedneds a population bias in handedness is how does handedness related to brain organization genetic influence. While left-handedness runs in families Medland et al. An imaging extension includes how to make zuppa toscana soup distinct modalities covering structural, diffusion and functional imaging of the brain, with an automatic pipeline organizatio thousands of image-derived phenotypes IDPswhich are distinct individual measures that can be used for correlation with other how to cover table top with fabric, or for genetic analysis Miller et al.

Using imaging, genotype and handedness data from UK Biobank, we aimed to discover correlations between: i handedness phenotype and IDPs; ii genotype and handedness; and iii handedness-related genotypes and IDPs. Supplementary Fig. All UK Biobank imaging data were processed following pipelines designed to create a set of IDPs that summarizes the information across all brain structural and functional modalities Miller et al.

These pipelines were developed mostly using FSL tools Jenkinson et al. The description of this recently expanded set of IDPs has been recently published Elliott et al. Briefly, these comprised mainly regional volumetric, area and thickness measures; subcortical measures of MRI modalities sensitive to e.

IDPs were quantile normalized to ensure normality, rflated confounds, including age, sex, interaction between age and sex, head size, as well as various variables related to the MRI acquisition protocol, were included in the model.

We tested the effects of self-reported handedness directly in UK Biobank Data Fieldand results were Bonferroni-corrected for multiple comparisons across all IDPs. To identify the biological pathways and gene ontologies enriched in this genome-wide association study GWASwe performed a SNP-based enrichment analysis and a gene-based analysis. We then analysed the average expression of the mapped genes across 53 tissue types, hpw gain insight into the relative tissue expressions of these mapped genes in a broad range of tissues.

We also performed linkage disequilibrium LD score regression on summary-level statistics for the left- versus right-handers GWAS to estimate the SNP heritability, and to estimate the genetic correlation between handedness and various neurological and psychiatric diseases from publicly available summary-level GWAS data.

Results were considered significant after a conservative Bonferroni correction for multiple comparisons across space number of voxels in the image mask used to carry out the statistical analyses. These significant voxelwise results how does handedness related to brain organization the white matter were then subsequently used organkzation starting points seed masks for the virtual reconstruction and identification of the tracts to which they belong. For this, we ran the probabilistic tractography tool from FSL probtrackx with default settings Behrens how to drop 10 lbs in 2 weeks al.

Further details of the methodology and results are given in the Supplementary material. Directly comparing all IDPs between the brain-scanned UK Biobank participants left-handers and how does handedness related to brain organization yielded numerous significant results, all organizatkon one how does handedness related to brain organization resting-state functional MRI measures Supplementary Table 2. Overall, these functional connectivity results showed, in left-handers, i a stronger connectivity between right and left homologous language networks Fig.

Language-related grey matter regions functionally involved with self-reported handedness are connected by white matter tracts associated with rs These language-related functional networks are overlaid on handedbess cortical surface. These white matter tracts clearly link the grey matter areas present in lateralized right- and left-sided language functional networks in green and red-yellow, respectively, also shown in A and B.

In the genotyped UK participants, we discovered three genome-wide significant loci by comparing 38 left-handers versus right-handers: rs, 17q Comparing left-handers versus non-left-handers, did not yield any new associated loci, but replicated the three loci from left- versus right-handers Table 1 and Fig. Summary of GWAS of handedness. The gene-based analysis demonstrated that the four gene sets and gene ontology terms with the most overlapped genes pertained to neuronal morphogenesis, differentiation, migration and gliogenesis Supplementary Doess 4.

Consistent with this enrichment, positional gene mapping of the left- versus right-handers GWAS summary statistics revealed a set of genes that are highly expressed in several brain tissues Supplementary Fig.

Correlation with clinical phenotypes collected from the UK Biobank participants. Clinical phenotypes directly related to neurological or mental health symptoms are highlighted in bold. A positive value indicates that the allele predisposing to non-right-handedness is positively correlated with the phenotype.

These language-related tracts have been consistently associated with schizophrenia and auditory hallucinations Hubl et al. The lack of lateralization in our white matter results might be surprising at first, but seems to be consistent with a recent study that failed to find any significant associations of handedness with grey matter asymmetries Kong et al.

Of note, however, the white matter tracts associated with rs link grey matter regions known to show the strongest asymmetries from an early developmental stage Dubois et al. Remarkably, all of the grey matter regions connected by these language-related white matter tracts specifically make up the functional homologous language networks that differ between left- and right-handers Fig.

Our findings of a stronger functional connectivityin this case higher positive functional connectivitybetween right and left homologous language networks in left-handers is consistent with imaging studies that have showed more symmetrical functional activations in language comprehension and language generation in left-handers Tzourio et al.

Additional evidence for relatde stronger involvement of right language-related brain regions in left-handers could be seen in our results with a weaker suppression of the DMN influence Anticevic et al.

While there might be confounds to such functional connectivity measures Friston, ; Duff et al. As the effect of polymorphisms related to handedness could be seen specifically in language-related tracts hhandedness the dixons whatever happens phone number regions of the language networks, our functional connectivity findings may thus be the hallmarks in the adult brain of handednews very early genetically-guided events happening in the white matter cytoskeleton during development.

Such genetic effects in the human white dors probably mirror similar, very early cytoskeletal processes observed in the development of chirality in gastropods and amphibians Davison et al. WNT3 has also been shown to act as an axon guidance molecule and, strikingly, as a gradient for retinotopic mapping along the medial-lateral axis Schmitt et al. Of note, rs is an eQTL of MICBwhich is crucial to brain development and plasticity and may mediate both genetic and environmental involvements in schizophrenia McAllister, There is a plethora of literature demonstrating a preponderance of left-handedness in an array of psychiatric disorders, including meta-analyses in schizophrenia Hirnstein and Hugdahl,supporting the view that there is a genetic link between handedness, brain lateralization and schizophrenia Berlim et al.

In line with this, we found a statistically significant positive correlation between left-handedness and schizophrenia using LD score regression Supplementary Table 6. This associationonly seen in the parent of the participantsis probably a reflection of how does handedness related to brain organization relatively young recruitment age in the UK Biobank 4069meaning that only a few genetically-susceptible individuals will have developed the disease themselves at that age.

Findings from previous GWAS and neuroimaging studies of human handedness have been equivocal, with a few exceptions Hatta, ; Scerri et al. What is microcontroller and its function relatively modest effect sizes of the associated variants, and the heritability estimate of handedness explained by all SNPs in the left- versus right-handers GWAS 0. Similarly, the strongest effect of handedness hxndedness the brain explained about 1.

This how does handedness related to brain organization the first study to identify in the general population genome-wide significant loci for human handedness in, and eQTL of, genes associated with brain development, microtubules and patterning.

Thus, this locus has biological plausibility in contributing to differences in neurodevelopmental connectivity of language areas. The lateralization of brain language function was strongly related to handedness; whether increased bilateral language function gives left-handers a cognitive advantage at verbal tasks remains to be investigated separately in a large dataset offering both well-characterized verbal cognition testing not available in UK Biobank as well as FSLnets-like functional connectivity measures, such as the Human Connectome Project Anticevic et al.

This study thus represents relxted important advance in our understanding of human handedness and offers mechanistic insights into the observed correlations between chirality and microtubules in the brain, and suggests an overlap of genetic architecture between handedness and certain neurodegenerative and psychiatric phenotypes. The other authors declare no competing interests. Image processing and quality control for the first 10, brain imaging datasets from UK Biobank.

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The human brain's control of motor function is a mirror image in terms of connectivity; the left hemisphere controls the right hand and vice versa. Handedness is related to neural mechanisms underlying hemispheric lateralization of face processing Stefan Frassle1,2,3, Soren Krach4, Frieder Michel Paulus4& Andreas Jansen2,5 While the right-hemispheric lateralization of the face perception network is well established. Jul 17, The hand used to write with is generally controlled by the opposite side of the brain in right-handed people, movement-related areas on the left side of Author: Kerri Smith.

This theoretically means that the hemisphere contralateral to the dominant hand tends to be more dominant than the ipsilateral hemisphere, however this is not always the case [2] and there are numerous other factors which contribute in complex ways to physical hand preference.

Language areas are represented unilaterally in the human brain. Broca's area has been found to have differing grey matter structures depending on handedness.

The inferior frontal sulcus, which contains Broca's area, was found to be more continuous in the hemisphere ipsilateral to the dominant hand [5]. Because the left arm is controlled by the right hemisphere and vice versa, the corpus callosum has also been found to be larger in left-handers. This is theoretically so that language comprehension and production can more efficiently move from the primary language areas into the motor areas which control the contralateral arm.

The planum temporale is a brain region within Broca's Area , and is thought to be the most asymmetric area of the human brain; with the left side having shown to be five times the size of the right in some individuals. Handedness correlates in motor areas have been found to be more subtle and less pronounced than language areas, [8] but are nevertheless still detectable. The surface area of the central sulcus has been found to be larger in the dominant hemisphere, as well as the 'hand knob', an area in the primary motor cortex which is responsible for hand movements, is located more dorsally in the left hemisphere of people who are right- compared to left-handed [11].

The corticospinal tract is a bundle of white matter which connects the cerebral cortex with motor neurons in the spinal cord.

Notably, humans show a natural asymmetry between left and right tracts, such that the left tract and therefore connections to the right hand is significantly larger.

However this asymmetry has been found to be reduced in left-handers, suggesting a less biased connection to both hands. In order to untangle causality, some research employs a 'forced handedness' group. Left-handers who were forced during childhood to use their right hand showed a larger surface area of the central sulcus in their left hemisphere, which is associated with right-handedness.

Also, structures in the basal ganglia such as the putamen also mirrored developmental right-hand dominant individuals in the forced group. The Fusiform Face area is an area typically unilaterally, much like the language areas, and localized on the right fusiform gyrus. However the occipital face area [15] shows no such correlation, and so handedness is thought to impact face processing on a level in the hierarchy which does not involve the occipital face area, however does include the fusiform gyrus.

Handedness in and of itself tends to be a grey area. The requirements for someone to be right- as opposed to left-handed have been debated, and because individuals who identify as left-handed may also use their right hand for a large number of tasks, identifying two clearcut groups of subjects is a challenging task.

The Edinburgh Handedness Inventory is a common parametric test used to determine handedness, by comparing individuals to the population at large. However use of this inventory varies between researchers, and it has been criticized for its use in modern research. A number of asymmetrical findings have been disputed, with various studies stating null results in opposition to previously reported differences.

The relationship between handedness and its neuronal correlates is complex. Language areas themselves are not concretely correlated, and motor area show exceedingly subtle differences. Clearly, advances in research are still necessary to unveil true causal relationships between structural differences and their manifestation in the form of handedness. From Wikipedia, the free encyclopedia. Redirected from Neuroanatomy of Handedness.

Overview of the neuroanatomy of handedness. ISSN PMID Frontiers in Psychology. PMC Graham Introduction to Neuropsychology, Second Edition. Guilford Press. ISBN Brain Research. S2CID January Nature Reviews Neuroscience. ISSN X. Behavioral Endocrinology. MIT Press. CiteSeerX Current Opinion in Behavioral Sciences. Handedness and Brain Asymmetry. Neuropsychology of Left-Handedness. Experimental Brain Research. Scientific Reports. March Brain and Cognition. October This article needs additional or more specific categories.

Please help out by adding categories to it so that it can be listed with similar articles. Categories : Neuroscience Handedness. Hidden categories: Articles with short description Short description matches Wikidata Articles needing additional categories from January Namespaces Article Talk.

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