A team led by researchers at the University of Oxford used thousands of brain scans and genetic data to look for associations between genes, brains and handedness. They discovered for the first time, gene regions linked to human handedness and structural differences in language areas of the brain.
'Many researchers have studied the biological basis of handedness, but using large datasets from UK BioBank has allowed us to shed considerably more light on the processes leading to left-handedness,' said Dr Akira Wiberg at the University of Oxford. 'We discovered that, in left-handed participants, the language areas of the left and right sides of the brain communicate with each other in a more coordinated way.'
Using around 400,000 sequenced genomes from the UK BioBank, the researchers found four genetic regions associated with handedness, three of which were linked to proteins involved in brain structure and development. They also showed, using brain scans from around 9000 participants, that these genetic variations caused structural changes to the white matter tracts that join language-processing regions. The authors suggested that this may give left-handers an advantage when it comes to language skills and verbal tasks, but said that this needs to verified in large dataset studies using verbal cognition tests.
'This raises the intriguing possibility for future research that left-handers might have an advantage when it comes to performing verbal tasks, but it must be remembered that these differences were only seen as averages over very large numbers of people and not all left-handers will be similar,' Dr Wiberg said.
The researchers also found that left-handers had a slightly higher chance of schizophrenia and a slightly lower chance of Parkinson's disease, but again, they stressed that more research is needed to determine whether this is more than just coincidence.
Professor Dominic Furniss, also at Oxford and joint senior author on the study, added: 'Here we have demonstrated that left-handedness is a consequence of the developmental biology of the brain, in part driven by the complex interplay of many genes. It is part of the rich tapestry of what makes us human.'
The work was published in Brain.