Significance This study alters our fundamental understanding of the functional interactions between the cerebral hemispheres of the human brain by establishing that the left and right hemispheres have qualitatively different biases in how they dynamically interact with one another. Left-hemisphere regions are biased to interact more strongly within the same hemisphere, whereas right-hemisphere regions interact more strongly with both hemispheres. These two different patterns of interaction are associated with left-lateralized functions, such as language and motor abilities, and right-lateralized functions, such as visuospatial attention. Importantly, the magnitude of lateralization measured for individual participants in these regions predicted the level of cognitive ability for the respective function, demonstrating that lateralization of function is associated with improved cognitive ability.

Two distinct forms of functional lateralization in the human brain