Human Connectome Project

MGH/Harvard-UCLA consortium

The MGH/Harvard-UCLA consortium focussed on optimizing MRI technology for imaging the brain's structural connections using diffusion MRI, with a goal of increasing spatial resolution, quality, and speed. Diffusion MRI, employed in both projects, maps the brain's fibrous long-distance connections by tracking the motion of water. Water diffusion patterns in different types of cells allow the detection of different types of tissues. Using this imaging method, the long extensions of neurons, called white matter, can be seen in sharp relief.

The new scanner built at the MGH Martinos Center for this project was "4 to 8 times as powerful as conventional systems, enabling imaging of human neuroanatomy with greater sensitivity than was previously possible." The scanner has a maximum gradient strength of 300 mT/m and a slew rate of 200 T/m/s, with b-values tested up to 20,000 s/mm^2. For comparison, a standard gradient coil is 45 mT/m.

Behavioral testing and measurement

To understand the relationship between brain connectivity and behavior better, the Human Connectome Project used a reliable and well-validated battery of measures that assess a wide range of human functions. The core of its battery is the tools and methods developed by the NIH Toolbox for Assessment of Neurological and Behavioral function.

Research

In August 2025, the HCP-Young Adult 2025 Release updated dataset on a new platform called "ConnectomeDB powered by BALSA". The main highlights are significant advances in data processing applied to all the functional Magnetic Resonance Imaging (fMRI) data, multi-run FIX (FMRIB's ICA-based Xnoiseifier) for the 3 tesla task fMRI data, and improvements in temporal Independent Component Analysis (ICA) pipelines while aligning with earlier processing packages of the HCP Lifespan projects. This contributes to the further exploration of the human brain in a large cohort of healthy young adults.

The Human Connectome Project has grown into a large group of research teams. These teams make use of the style of brain scanning developed by the Project. The studies usually include using large groups of participants, scanning many angles of participants' brains, and carefully documenting the location of the structures in each participant's brain. Studies affiliated with the Human Connectome Project are currently cataloged by the Connectome Coordination Facility. The studies fall into three categories: Healthy Adult Connectomes, Lifespan Connectome Data, and Connectomes Related to Human Disease. Under each of these categories are research groups working on specific questions.

Healthy Adult Connectomes

The Human Connectome Project Young Adult study made data on the brain connections of 1100 healthy young adults available to the scientific community. Scientists have used data from the study to support theories about which areas of the brain communicate with one another. For example, one study used data from the project to show that the amygdala, a part of the brain essential for emotional processing, is connected to the parts of the brain that receive information from the senses and plan movement. Another study showed that healthy individuals who had a high tendency to experience anxious or depressed mood had fewer connections between the amygdala and a number of brain areas related to attention.

Lifespan Connectome Data

There are currently four research groups collecting data on connections in the brains of populations other than young adults. The purpose of these groups is to determine ordinary brain connectivity during infancy, childhood, adolescence, and aging. Scientists will use the data from these research groups in the same manner in which they have used data from the Human Connectome Project Young Adult study.

Connectomes Related to Human Disease

Fourteen research groups investigate how connections in the brain change during the course of a particular disease. Four of the groups focus on Alzheimer's disease or dementia. Alzheimer's disease and dementia are diseases that begin during aging. Memory loss and cognitive impairment mark the progression of these diseases. While scientists consider Alzheimer's disease to be a disease with a specific cause, dementia actually describes symptoms which could be attributed to a number of causes. Two other research groups investigate how diseases that disrupt vision change connectivity in the brain. Another four of the research groups focus on anxiety disorders and major depressive disorder, psychological disorders that result in abnormal emotional regulation. Two more of the research groups focus on the effects of psychosis, a symptom of some psychological disorders in which an individual perceives reality differently than others do. One of the teams researches epilepsy, a disease characterized by seizures. Finally, one research team is documenting the brain connections of the Amish people, a religious and ethnic group that has high rates of some psychological disorders.

Although theories have been put forth about the way brain connections change in the diseases under investigation, many of these theories have been supported by data from healthy populations. For example, an analysis of the brains of healthy individuals supported the theory that individuals with anxiety disorders and depression have less connectivity between their emotional centers and the areas that govern attention. By collecting data specifically from individuals with these diseases, researchers hope to have a more certain idea of how brain connections in these individuals change over time.

Status

The project was completed in 2021, and a retrospective analysis is available. A number of new projects have started based on the results.

Useful links

• HCP wiki - Human Connectome Project wiki
• ICA-FIX - Documentation on ICA-FIX algorithm used on resting state fMRI data