Abstract
Functional lateralisation is a fundamental principle of the human brain. However, a comprehensive taxonomy of functional lateralisation and its organisation in the brain is missing. Here, we report the first complete map of functional hemispheric asymmetries in the human brain, reveal its low dimensional structure, and its relationship with structural inter-hemispheric connectivity. Our results suggest that the lateralisation of brain functions is distributed along four functional axes: symbolic communication, perception/action, emotion, and decision-making. The similarity between this finding and recent work on neurological symptoms give rise to new hypotheses on the mechanisms that support brain recovery after a brain lesion. We also report that cortical regions showing asymmetries in task-evoked activity have reduced connections with the opposite hemisphere. This latter result suggests that during evolution, brain size expansion led to functional lateralisation to avoid excessive conduction delays between the hemispheres.
Highlights
Functional lateralisation is a fundamental principle of the human brain
A functional lateralisation map was computed for each term by calculating the difference between hemispheres for each pair of homologous voxels
Given that selected terms could be either correlated or related in a trivial way, a varimax-rotated principal component analysis was run in order to eliminate redundancy in the data
Summary
Functional lateralisation is a fundamental principle of the human brain. a comprehensive taxonomy of functional lateralisation and its organisation in the brain is missing. We report that cortical regions showing asymmetries in task-evoked activity have reduced connections with the opposite hemisphere This latter result suggests that during evolution, brain size expansion led to functional lateralisation to avoid excessive conduction delays between the hemispheres. Despite the implications of functional lateralisation theories for neurodevelopmental and psychiatric disorders[6,7], as well as for stroke recovery[8,9,10,11], a comprehensive mapping of functional lateralisation in the brain is, to our knowledge, still missing in the literature It is not known whether putatively lateralised cognitive functions share similar or different spatial patterns of functional activation and whether these functional activations can be categorised to a limited number of spatial patterns—have a low-dimensional structure. We took advantage of combining the largest fMRI metaanalytic dataset[18] with the highest quality structural connectivity data[19] to produce, for the first time, a comprehensive map of the functional brain architecture of lateralised cognitive functions, characterise its low-dimensional structure, and examine its relationship to corpus callosum connectivity
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