Inner Hemispheric and Interhemispheric Connectivity Balance in the Human Brain

Krupnik, Ronnie; Yovel, Yossi; Assaf, Yaniv

doi:10.1523/jneurosci.1074-21.2021

Cited by 19 publications

(12 citation statements)

References 81 publications

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“…While many anatomical tracing studies focus only on ipsilateral connections within a hemisphere, PMv has many transcallosal connections with heterotopic areas in the other hemisphere 67 , 68 and consistent with this anatomical observation it is established that PMv exerts similar facilitatory and inhibitory influences over the activity of M1 both ipsilaterally and contralaterally 45 , 46 , 66 , 69 , 70 . Therefore, the PMv-to-M1 circuit can also be studied interhemispherically, thus making it possible to probe mechanisms that involve fibres passing through the corpus callosum, and that may be unique to interhemispheric circuits 23 , 71 – 75 . Taken together, these features of PMv-to-M1 projections (the presence of both clear behavioural and clear physiological readouts, the link to a defined interhemispheric white matter tract) make them an ideal test bed for hypotheses about how myelin shapes circuit function and behaviour in humans.…”

Section: Introductionmentioning

confidence: 99%

A macroscopic link between interhemispheric tract myelination and cortico-cortical interactions during action reprogramming

et al. 2022

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Myelination has been increasingly implicated in the function and dysfunction of the adult human brain. Although it is known that axon myelination shapes axon physiology in animal models, it is unclear whether a similar principle applies in the living human brain, and at the level of whole axon bundles in white matter tracts. Here, we hypothesised that in humans, cortico-cortical interactions between two brain areas may be shaped by the amount of myelin in the white matter tract connecting them. As a test bed for this hypothesis, we use a well-defined interhemispheric premotor-to-motor circuit. We combined TMS-derived physiological measures of cortico-cortical interactions during action reprogramming with multimodal myelin markers (MT, R1, R2* and FA), in a large cohort of healthy subjects. We found that physiological metrics of premotor-to-motor interaction are broadly associated with multiple myelin markers, suggesting interindividual differences in tract myelination may play a role in motor network physiology. Moreover, we also demonstrate that myelination metrics link indirectly to action switching by influencing local primary motor cortex dynamics. These findings suggest that myelination levels in white matter tracts may influence millisecond-level cortico-cortical interactions during tasks. They also unveil a link between the physiology of the motor network and the myelination of tracts connecting its components, and provide a putative mechanism mediating the relationship between brain myelination and human behaviour.

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Section: Introductionmentioning

confidence: 99%

A macroscopic link between interhemispheric tract myelination and cortico-cortical interactions during action reprogramming

et al. 2022

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“…It has been reported that tract specificity can be lost through bottlenecks such as the corpus callosum when applying DTI-based tractography (117), although other studies have reported that deterministic tractography can achieve successful reconstruction of interhemispheric connections via the corpus callosum (118,119). In addition, interhemispheric connectivity via the corpus callosum that was reconstructed from conventional diffusion imaging data has been supported by high angular resolution diffusion imaging (HARDI), and also by post mortem examination of white matter anatomy (120)(121)(122).…”

Section: Discussionmentioning

confidence: 99%

Genetic architecture of the white matter connectome of the human brain

Sha

Schijven

Fisher

et al. 2022

Preprint

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White matter tracts form the structural basis of large-scale functional networks in the human brain. We applied brain-wide tractography to diffusion images from 30,810 adult participants (UK Biobank), and found significant heritability for 90 regional connectivity measures and 851 tract-wise connectivity measures. Multivariate genome-wide association analyses identified 355 independently associated lead SNPs across the genome, of which 77% had not been previously associated with human brain metrics. Enrichment analyses implicated neurodevelopmental processes including neurogenesis, neural differentiation, neural migration, neural projection guidance, and axon development, as well as prenatal brain expression especially in stem cells, astrocytes, microglia and neurons. We used the multivariate association profiles of lead SNPs to identify 26 genomic loci implicated in structural connectivity between core regions of the left-hemisphere language network, and also identified 6 loci associated with hemispheric left-right asymmetry of structural connectivity. Polygenic scores for schizophrenia, bipolar disorder, autism spectrum disorder, attention-deficit hyperactivity disorder, left-handedness, Alzheimer’s disease, amyotrophic lateral sclerosis, and epilepsy showed significant multivariate associations with structural connectivity, each implicating distinct sets of brain regions with trait-relevant functional profiles. This large-scale mapping study revealed common genetic contributions to the structural connectome of the human brain in the general adult population, highlighting links with polygenic disposition to brain disorders and behavioural traits.One sentence summaryVariability in white matter fiber tracts of the human brain is associated with hundreds of newly discovered genomic loci that especially implicate stem, neural and glial cells during prenatal development, and is also associated with polygenic dispositions to various brain disorders and behavioural traits.

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“…84 This trade-off between inter-hemispheric and intra-hemispheric connectivity was also observed in a large-scale human study. 85…”

Section: Discussionmentioning

confidence: 99%

“…84 This trade-off between inter-hemispheric and intra-hemispheric connectivity was also observed in a large-scale human study. 85 Since maintaining a normal level of functional connectivity is essential for the brain to function properly, [86][87][88][89] we hypothesize that in birds, the evolution of brain connectivity took an alternative path in contrast with the emergence of corpus callosum in placental mammals; namely, that the left and right hemispheres developed stronger intra-hemispheric connectivity to compensate the lower inter-hemispheric connectivity while maintaining higher levels of hemispheric autonomy. This hypothesis is in agreement with higher telencephalic neuronal density, i.e.…”

Section: Functional Connectivity In Comparison With Human and Mammali...mentioning

confidence: 99%

Multi-channel recordings reveal age-related differences in the sleep of juvenile and adult zebra finches

Yeganegi

Ondracek

2022

Preprint

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Despite their phylogenetic differences and distinct pallial structures, mammals and birds share many features of sleep structure, most prominently, the existence of distinct stages of rapid eye movement (REM) and slow wave sleep (SWS). However, the structure of sleep does not remain constant during lifetime, but undergoes radical changes during development. Our current understanding of these age-related variations in neural signature of sleep is limited to studies in a small number of mammalian species. How does the neural signature of sleep evolve during brain development in an avian brain? To answer this, we recorded multi-channel EEG from developing juvenile and adult zebra finches for several nights. We compared the structure of sleep in adults and juveniles using the ratio of slow oscillations to gamma oscillations ("depth of sleep", DOS). We observed a significantly larger DOS, as well as less-frequent state transitions in juveniles compared to adults. Furthermore, multichannel EEG revealed local slow oscillations, in addition to global (wide-spread) slow waves. The occurrence of these local waves was correlated with DOS and was higher in frontal sites. In addition, we observed that the functional connectivity increased rapidly during development and was significantly higher in adults than in juveniles. Additionally, a graph theory analysis of highly-correlated networks revealed numerous small networks in juveniles compared to adults, underscoring the lower connectivity observed in juveniles. Overall, our results reveal significant changes in the neural signature of sleep during development in an avian brain that are remarkably similar to age-dependent changes that occur in mammals.

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Inner Hemispheric and Interhemispheric Connectivity Balance in the Human Brain

Cited by 19 publications

References 81 publications

A macroscopic link between interhemispheric tract myelination and cortico-cortical interactions during action reprogramming

A macroscopic link between interhemispheric tract myelination and cortico-cortical interactions during action reprogramming

Genetic architecture of the white matter connectome of the human brain

Multi-channel recordings reveal age-related differences in the sleep of juvenile and adult zebra finches

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