Paint by numbers: Three-dimensional representations map the volume of distinct regions as rat brains develop from birth (left) to adulthood (right).

Researchers have divided the rat brain into 26 structures that are visible using brain imaging and are present from birth to adulthood, according to a study published 15 February in Neuroimage¹.

This rodent map may allow researchers to track developmental changes in brain volume. Many children with autism have abnormally large heads until age 2, after which their head size begins to normalize. Researchers rely on techniques that can gauge brain volume to measure more subtle alterations in volume.

These studies require both an understanding of typical brain development and a standard set of brain regions that are easily distinguishable using imaging techniques.

In the new study, the researchers set out to build the latter, a ‘brain ontology’ that traces a hierarchical set of brain regions that originate during embryonic development and remain distinct into adulthood.

They photographed the brains of five newborn rats, whose brains are developmentally equivalent to those of third-trimester human fetuses, and five 80-day-old rats, an advanced age for rodents. Maps of the rodent brain at intermittent ages might prove even more useful for autism research.

The researchers then segmented these brains into 26 different structures. They measured the volume of each segment at both ages and created three-dimensional reconstructions of the brain at each age.

By comparing the volume at day 0 and day 80, the researchers created a graphic that shows how much each brain region changes during development. For example, the cerebellum, which plays a role in motor control, is about 40 times bigger in the adult rats than it is in newborns.

The same ontology probably exists in people and other mammals, the researchers say, making the rodent map useful for studying autism and other disorders.

References:

1: Calabrese E. et al. NeuroImage 67, 375-384 (2013) PubMed