European scientists have built the first atlas of white-matter microstructure in the human brain in a project called CONNECT (Consortium of neuroimagers for the non-invasive exploration of brain connectivity and tracts).

The new atlas combines 3D images from the MRI scans of 100 brains of volunteers. To achieve this, the scientists developed advanced diffusion magnetic resonance imaging (MRI) methods providing unprecedented detail and accuracy.

Currently, biomedical research teams around the world studying brain science rely on a brain atlas produced by painstaking and destructive histological (tissue examination) methods on the brains of a few individuals who donated their bodies to science.

The new atlas simulates the impossible process of painstakingly examining every square millimeter of brain tissue (of which there are around 100 million per brain) with a microscope, while leaving the brain intact.

The key novelty in the atlas is the mapping of microscopic features (such as average cell size and packing density) within the white matter, which contains the neuronal fibers that transmit information around the living brain. The results of the project provide new depth and accuracy in our understanding of the human brain in health and disease.

The atlas describes the brain’s microstructure in standardized space, which enables non-expert users, such as physicians or medical researchers, to exploit the wealth of knowledge it contains. The atlas contains a variety of new images that represent different microscopic tissue characteristics, such as the fiber diameter and fiber density across the brain, all estimated using MRI. These images will serve as the reference standard of future brain studies in both medicine and basic neuroscience.

The project will dramatically facilitate and promote future research into white matter structure and function. Historically in neuroscience, the vast majority of research effort has been invested in understanding and studying gray matter and neurons, while white matter has received relatively little attention.

This owes largely to the lack of effective research tools to study white matter, even though it comprises about half the volume of the brain. The new MRI methods that were developed in CONNECT allow researchers, for the first time, to visualize the micro-structure of the living brain over the whole brain.

This opens new realms in our understanding of our most complex organ. In the future, the project members intend to use the technology they have developed to study the dynamics and time dependence of the micro-structure in white matter. For example they will search for a trace that a cognitive task imprints on white matter microstructure, encoding new experiences in the wiring of the brain.

Another future direction is to characterize and understand micro-structural changes caused by different neurodegenerative diseases, such as Alzheimer’s or schizophrenia, to develop better diagnostic procedures for these and other devastating conditions.

The work relied on groundbreaking MRI technology and was funded by the EU’s future and emerging technologies program with a grant of 2.4 million Euros. The participants of the project, were drawn from leading research centers in countries across Europe including Israel, United Kingdom, Germany, France, Denmark, Switzerland and Italy.

The project investigators met in Paris, after 3 years of research, to announce the conclusion of the project and present a report (open access PDF) of their findings.