The new study, considered among the most ambitious in the field of sports-related brain injury, aims to develop ways to spot the disease in the living and figure out why certain players get it and others do not. A more comprehensive understanding of the disease, the researchers said, may lead to ways to prevent it.

“There are so many critical unanswered questions about C.T.E.,” Dr. Robert Stern, the lead principal investigator and a professor at Boston University School of Medicine, said in a statement. “We are optimistic that this project will lead to many of these answers, by developing accurate methods of detecting and diagnosing C.T.E. during life, and by examining genetic and other risk factors for this disease.”

The grant did not come from a pool of money created in 2012 when the N.F.L. pledged $30 million to the N.I.H. to pay for research on C.T.E. and other issues related to head trauma and said it would not have any veto power over how the money was used.

The N.I.H. had asked to use some of it, but after encountering delays with the Foundation for the National Institutes of Health, which is administering the money, it decided to finance the grant with other funds, said a person familiar with the process but who spoke on condition of anonymity because the researchers’ statement is the official comment.

The foundation said the N.F.L. was willing to contribute to the new study, but it was the N.I.H.’s decision to finance it on its own.