The Human Connectome Project: A retrospective

Abstract

The Human Connectome Project (HCP) was launched in 2010 as an ambitious effort to accelerate advances in human neuroimaging, particularly for measures of brain connectivity; apply these advances to study a large number of healthy young adults; and freely share the data and tools with the scientific community. NIH awarded grants to two consortia; this retrospective focuses on the "WU-Minn-Ox" HCP consortium centered at Washington University, the University of Minnesota, and University of Oxford. In just over 6 years, the WU-Minn-Ox consortium succeeded in its core objectives by: 1) improving MR scanner hardware, pulse sequence design, and image reconstruction methods, 2) acquiring and analyzing multimodal MRI and MEG data of unprecedented quality together with behavioral measures from more than 1100 HCP participants, and 3) freely sharing the data (via the ConnectomeDB database) and associated analysis and visualization tools. To date, more than 27 Petabytes of data have been shared, and 1538 papers acknowledging HCP data use have been published. The "HCP-style" neuroimaging paradigm has emerged as a set of best-practice strategies for optimizing data acquisition and analysis. This article reviews the history of the HCP, including comments on key events and decisions associated with major project components. We discuss several scientific advances using HCP data, including improved cortical parcellations, analyses of connectivity based on functional and diffusion MRI, and analyses of brain-behavior relationships. We also touch upon our efforts to develop and share a variety of associated data processing and analysis tools along with detailed documentation, tutorials, and an educational course to train the next generation of neuroimagers. We conclude with a look forward at opportunities and challenges facing the human neuroimaging field from the perspective of the HCP consortium.

Keywords: Behavior; Connectivity; Diffusion imaging; Functional MRI; Magnetoencephalography; Parcellation; informatics.

Figure 1.. Major Milestones for the WU-Minn-Ox HCP.

Milestones over the entire Human Connectome Project timeline, including projects directly sparked by HCP. Releases of HCP data are bolded, Lifespan HCP-Development & HCP-Aging and Connectomes Related to Human Disease (CRHD) Projects are in red, including HCP Early Psychosis (HCP-EP), a CRHD project based at Brigham & Women’s Hospital/Indiana University.

Figure 2.. A. Data downloaded via ConnectomeDB.

Cumulative downloads from the March 2013 Q1 first major release to December 2020 (when database infrastructure changes affected the tracking of downloads) are indicated by the black line in petabytes (PB) of data. Number of individuals downloading by month is represented by the blue bars. HCP data release dates are indicated with red arrows on the X-axis. B. Publications citing HCP since inception. Citations listed in PubMed using the search string: "MH091657"[All Fields] OR "Human Connectome Project"[All Fields]. Publication month is determined by Epublish date/month, if available, or final published date, if not. HCP data release dates are indicated with red arrows on the X-axis.

Figure 4.

Timeline of large-scale imaging projects predating and postdating HCP. Years of project span for several large scale imaging projects. ADNI, Alzheimer’s Disease Neuroimaging Initiative (3 waves of funding, Mueller et al. 2005); 1000 Functional Connectomes (Biswal et al. 2010); ABCD, Adolescent Brain and Cognitive Development Study (Casey et al. 2018); UK Biobank (Miller et al. 2016); Developing HCP (Bastiani et al. 2019a); CRHD, Connectomes Related to Human Disease; Lifespan HCP-Development & HCP-Aging (Bookheimer et al. 2019; Harms et al. 2018; Somerville et al. 2018); Baby Connectome Project (Howell et al. 2019); Brain/MINDS Beyond (Koike et al. 2021). All projects except ADNI 1–3 and 1000 Functional Connectomes involved HCP-style scanning and preprocessing.