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Why men and women behave differently

- Former IIT Delhi computer science student discovers gender differences in the human brain
Ragini Verma

New Delhi, Dec. 2: An Indian-American computer scientist has discovered novel sex differences in the human brain, fundamentally different hard-wiring patterns that could explain decades of observations that men and women are dissimilar in certain behaviour and capabilities.

A study led by Ragini Verma, an associate professor of radiology at the University of Pennsylvania School of Medicine, has revealed significant differences between men and women in the structural connections linking different regions of their brains.

Verma and her colleagues are among the first to demonstrate differences in the brain’s hard-wiring to support long-standing observations of gender differences in functional tasks. Their findings appeared today in the US journal Proceedings of the National Academy of Sciences.

Their study of structural connections within and across the right and left hemispheres of the brain has suggested that the brain’s communication networks are optimised for intra-hemispheric communication in men and inter-hemispheric communication in women. These differences indicate that women faced with a task are likely to engage several parts of the brain to solve a problem, while men tend to engage one part of the brain intensely.

They also found that male brains are structured to facilitate communication between perception and co-ordinated action, while female brains are designed to facilitate communication between analytical and intuitive processing zones in the brain.

“Functionally, this hard-wiring could manifest in several ways,” Verma told The Telegraph. “Women appear better in social skills perhaps because logical thinking and intuitive parts of the brain are well connected, while men are good at activities that require concerted action and motor skills.”

Scientists have documented sex differences in specific structures in the human brain and in the proportion of white matter for over two decades. Men have greater proportion of white matter that contains fibres and cerebrospinal fluid while women have greater levels of grey matter.

Brain networks showing conspicuous increased intra-hemispheric connectivity in males (upper figure)
and inter-hemispheric connectivity in females (lower figure). The intra-hemispheric connections are shown in blue and inter-hemispheric connections are shown in orange.
Picture credit: Proceedings of the National Academy of Sciences/Ragini Verma/Penn Medicine

The new study used a technique called diffusion magnetic resonance imaging (MRI) to map the fibre bundles that make up the pathways, or roads, in the brains of 949 children and young people aged between eight years and 22 years — 428 males and 521 females.

The scientists used computational methods to build these fibre pathways. “By tracking fibres from every region of the brain to every other region, we get a connectivity network of the brain that we call the structural connectome,” said Verma, who had graduated with mathematics from Lady Shri Ram College, New Delhi, and studied computer science at IIT Delhi before pursuing post-doctoral research first in France then in the US.

The analysis revealed relatively small differences between male and female brains in the age group of eight to 13 years, slightly larger differences in the age group 13 to 17, and the most pronounced differences in those above 17.

A behavioural study by Verma’s colleagues Raquel Gur and Ruben Gur at the university’s department of neuropsychiatry showed six pronounced differences, with girls outperforming boys on attention, word and face memory and social cognition tasks, while the boys performed better in tasks involving spatial processing, motor and sensorimotor speeds. These differences were primarily seen among mid-adolescents aged between 12 and 14 years.

“We’ve always suspected there will be a structural basis for observed functional or behavioural gender differences,” said Shashi Wadhwa, a senior neuroanatomist in India, formerly with the All India Institute of Medical Sciences, New Delhi, who was not associated with the US study.

“The diffusion imaging technology allows us to see fibre bundles in a way we could not see before,” Wadhwa told this newspaper. “It will allow us to understand better the how-and-why of the functional differences between men and women.”

Verma spent two years at a French research laboratory on face-detection software, but moved to the University of Pennsylvania about a decade ago to work on biomedical imaging. “I thought it would be fascinating to apply computer skills to make a difference in someone’s life,” she said.

She is currently using diffusion imaging to develop maps of fibre bundles affected by brain tumours. Surgeons use such maps to remove just the right amount of the tumour tissue and leave critical fibre bundles that might be involved in language or movement untouched.