Asymmetry of brain halves
The differences between the left and right hemispheres of the brain are hereditary
Researchers from the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, together with colleagues from Research Center Jülich, Montréal Neurological Institute and Hospital, and University of Cambridge describe to what extend the anatomy of the human cortex is different between left and right, at the finest scale to date. Moreover, they describe that microstructural asymmetry of the brain is heritable and corresponds to asymmetry of brain function at rest. And they demonstrate to what extend individuals show differences in brain structure between the left and right hemispheres related to inter-individual variability in language-related skills such as reading and mental health, such as anxiety.
The human brain has two halves that make our behaviors and thoughts more efficient. This procedure is associated with difference between the two halves in structure and function during evolution and development. “Previous studies have shown a difference in macroscale morphology such as cortical thickness between left and right halves of the brain and that these differences ultimately correspond to behavioral differences between individuals, such as language skills.
However, how brain structural asymmetry and function may relate was unclear. We wanted to gain more evidence from microscale level to understand the neurobiological mechanisms that may underlie more coarse differences in cortical thickness, and link structural asymmetry to function”, explains Bin Wan, first author of the study. “It can help us understand how the anatomy of the brain supports functions that are linked to brain asymmetry such as language and attention, but also various neuropsychiatric disorders show differences in asymmetry”, explains Bin Wan.
Brain halves of monozygotic twins are more similar
He and his colleagues examined an ultra-high-resolution whole-brain post-mortem histological atlas of a 65-year-old male and observed that the cell architecture was different between the two halves, for example in language-related brain regions. They had similar findings when we translated the post-mortem model to different, living participant’s brains using in-vivo MRI. Most of the differences were found to be more similar in monozygotic twins than in unrelated people, indicating microstructural brain asymmetry is heritable.
Moreover, the degree of asymmetry in the brain varied with language skills and mental health traits in the sample. “Overall, it's our first try to map the differences between two halves across the entire brain at a microscale level, which may ultimately understand how subtle differences between the two halves of the human brain link to brain function and behavioral variation in health and disease”, concludes Sofie Valk, last author of the study and research group leader at MPI CBS.
