An international team of neuroscientists from the United States and Europe has mapped 180 distinct areas, including 97 that were previously unknown, in human brain cortex, or outer mantle.
The team, led by Washington University in St. Louis researchers Dr. David Van Essen and Dr. Matthew Glasser, has also developed software that automatically detects the ‘fingerprint’ of each of cortex areas in an individual’s brain scans.
“Using multi-modal magnetic resonance images from the Human Connectome Project (HCP) and an objective semi-automated neuroanatomical approach, we delineated 180 areas per hemisphere bounded by sharp changes in cortical architecture, function, connectivity, and/or topography in a precisely aligned group average of 210 healthy young adults,” the scientists said.
“We characterized 97 new areas and 83 areas previously reported using post-mortem microscopy or other specialized study-specific approaches.”
Earlier studies often used just one measure, such as examining postmortem tissue with a microscope. Uncertain delineation of cortex areas has sometimes led to shaky comparability of brain imaging findings.
“The situation is analogous to astronomy where ground-based telescopes produced relatively blurry images of the sky before the advent of adaptive optics and space telescopes,” Dr. Glasser said.
The team set out to banish this blurriness by using multiple, precisely aligned, magnetic resonance imaging (MRI) modalities to measure cortical architecture, activity, connectivity, and topography in a group of 210 healthy participants.
These measures – including cortex thickness, cortex myelin content, task and resting-state functional MRI (fMRI) – cross-validated each other.
The findings were, in turn, confirmed in an additional independent sample of 210 healthy participants.
Even though some cortex areas turned out to be atypically located in a small minority of subjects, the data-derived algorithms incorporated into the software were able to successfully map them.
While the study included fMRI scans of subjects performing tasks, the team determined that resting-state MRI techniques should suffice to map the areas in future studies using the tools they developed.
“Some areas may turn out to have further subdivisions or be subunits of other areas, in light of new data,” Dr. Van Essen said.
“The ability to discriminate individual differences in the location, size, and topology of cortical areas from differences in their activity or connectivity should facilitate understanding of how each property is related to behavior and genetic underpinnings,” Dr. Glasser added.
The team’s results were published online this week in the journal Nature.
Matthew F. Glasser et al. A multi-modal parcellation of human cerebral cortex. Nature, published online July 20, 2016; doi: 10.1038/nature18933