Report from ISMRM: MR brain studies show humans combine nature and nurture

Two functional MRI studies presented this week at the International Society for Magnetic Resonance in Medicine meeting offered innovative views about human mental development.

A brain imaging study from the Institute of Child Health in London suggests that a precultural need to pass on creative problem-solving skills from mother to child is the reason that maternal genomic factors determine prefrontal brain development in the offspring.

Elsewhere in the U.K., University of Liverpool researchers tapped into the brains of members of professional musicians to measure if their lifelong efforts to master an instrument and a classical repertoire have paid off with increased gray matter, a development indicative of enhanced visual memory.

Dr. Jonathan Wells of the Institute of Child Health has had a longstanding research interest in genetics and maternity. The hypothesis behind the London study is that the controlling mechanism for human maternal behavior has shifted through evolution away from instinctive behaviors governed by neuroendocrine regulation to intelligent strategies that favor creative activity.

This change should benefit mothers, the main providers of parental care, more than fathers, according to Wells, and it should be expressed through genomic imprinting. If the hypothesis is true, he reasons that the mother's genome - not the father's - should determine the composition of their offspring's gray matter density in frontal lobe regions associated with intelligent functions.

Volumetric MR imaging performed as a part of a randomized infant feeding trial suggests that Wells is right. The 75 men and women in his study were drawn randomly from 817 mothers and 655 fathers. At the time of a child's birth, the height and head circumference of each parent were measured. Those data were used to create an encephalization quotient (EQ), an experimental accepted proxy for parental brain genomes. The children underwent 3D MR brain imaging to measure their gray matter density.

A comparison of results from parents and children found a highly significant positive correlation between the maternal EQ and the child's frontal lobe gray matter density (p

The data led Wells to conclude that the maternal genome controls the development of the child's frontal lobe regions, a genetic reality that may be associated with increased control over food allocation.

These findings have nothing to do with ability to learn and play classical music, the nuture slant of the second study. Here, the hypothesis involved the effect on brain structure of devotion to a cognitively demanding activity. Performing music at a professional level is among the most complex of human accomplishments, requiring physical skill, improvisation, sight-reading, and memorization of long passages, said Dr. Vanessa Anne Sluming of the University of Liverpool.

Sluming performed a battery of standard neuropsychology tests and volumetric MRI on 38 musician volunteers from the Royal Liverpool Philharmonic Orchestra and an equal number of subjects drawn from the general public to allow a voxel-by voxel regression analysis of gray matter concentration.

A comparison of the male musicians with male nonmusicians found that the musicians had significantly larger bilateral hippocampal volumes and larger clusters of gray matter density within the right posterior hippocampus (p = 0.045), Sluming said. Gray matter density in this region appears to increase as the male musicians grow older until they reach the age of 50.

No significant differences were observed in the amount of hippocampal gray matter measured in the brain of female musicians compared with women in the general public. Musicians of both sexes scored significantly higher than their counterparts from the general public on visual memory tests, but not on verbal memory scores.

Wells suggests his results are food for thought. Sluming cites the need for more research to sort out the meaning of her findings.

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