In the world's largest study of the human brain, involving more than 200 scientists worldwide, researchers have found that genes that affect brain size may play a part in intelligence and memory function. The study was put together by combining brain scans and genetic data from 21,000 people worldwide.
Dr Margie Wright from the Queensland Institute of Medical Research, which contributed to the study, said brain size can not only have an effect on thoughts and behaviour, but also intelligence. According to Dr Wright, one gene showed a strong correlation with overall brain size while another influenced the size of the brain's hippocampus, which is involved with memory.
Dr Wright said the gene involved with the hippocampus influences the rate at which this part of the brain shrinks with age. She added that people with dementia often show pronounced shrinkage in the hippocampus so further investigation to see if there are genetic links to dementia will be worthwhile. The hippocampus is also reduced in people with schizophrenia and major depression.
“The effects of the two genes on brain size are very small and the links to cognitive function are subtle,” Dr Wright said. “However, as we can lose up to 10 per cent of our brain volume in later life, these results are quite significant in people with the genetic variant that increases shrinkage.” These individuals could be more vulnerable to factors such as poor diet, excessive alcohol consumption, or little exercise, she said.
A separate study at QIMR showed those with larger brains scored slightly higher on a standardised IQ test. Dr Wright explained this global large scale study could be a stepping stone for more work into the brain's genetics and disorders.
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