Immature Blood Vessels May Confound Baby Brain Images

It’s one of the hottest areas in autism research: scanning the brains of baby sibs, or the infant siblings of children with autism, in hopes of finding early predictive brain signatures of the disorder.A new rat study, published 12 March in theProceedings of the National Academy of Sciences, suggests that these brain scans should be interpreted with caution. Unlike scans of adult brains, the study says, baby brain scans may show changes in blood flow that do not necessarily reflect the activity of neurons in the region.The issue is specific to imaging techniques that measure blood flow in response to an external stimulus, such as a sound or video. These include functional magnetic resonance imaging (fMRI), which detects magnetic field changes across the brain, and functional near-infrared spectroscopy (fNIRS), which uses beams of light to measure activity only in the brain’s outer layers.The new study found that 12-day-old rats (roughly equivalent to human infancy) show a drop in oxygenated, or red, blood flow when responding to a stimulus — the opposite of what happens in the brains of 80-day-old adult rats. The juvenile rat brain shows an adult-like response by about 23 days of age (the human equivalent of this age is difficult to pin down).“In the infant, the whole brain is still developing,” says lead investigator Elizabeth Hillman, associate professor of biomedical engineering and radiology at Columbia University in New York. “The [brain] response isn’t necessarily going to be faithfully reporting neuronal activity in the same way as in the adult brain.”Read more at...SFARI.org, May 2013.