University of Utah researchers are about to start a $740,000 research project examining precisely how compounds in marijuana affect the human brain.

The two-year study will use brain-imaging technology to track how the psychoactive compounds and other components of the plant interact with our brain networks — and why those substances can have different effects on different people..

Though 29 U.S. states currently allow medical use of marijuana, “critical questions remain unanswered” about the drug, a U. announcement about the study pointed out. The major research project comes as a medical marijuana ballot initiative is set to land on the Utah ballot in November.

State legislators have balked at legalizing access to the drug in recent years, often citing what they view as insufficient medical research. But Utah support for medical legalization has nevertheless stayed around 75 percent.

The biggest medical unknowns about marijuana include which brain receptors its so-called cannabinoids interact with and which mechanisms are at work in how the drug affects anxiety, pain and mood, Jon-Kar Zubieta, a U. psychiatrist and the study’s co-investigator, said in a statement.

The U. study will examine 40 adults, and involve U. researchers from a range of departments, including neuro-imaging, biostatistics and physics. It will use advances in medical imaging to compare how the brain reacts to a placebo versus marijuana’s main active compounds tetrahydrocannabinol (THC) — the psychoactive component in pot — and cannabidiol, or CBD.

“Deciphering the personalized effects of CBD and THC will have a profound impact on how various cannabinoids may best be used for medical treatments,” Zubieta said.

The grant fund the study is from the Ray and Tye Noorda Foundation and the California-based Wholistic Research and Education Foundation.

The state of Utah has embarked on its own push into marijuana research. Lawmakers last year approved a bill allowing research into the risks and benefits of the drug, and earlier this year, they signed off on a measure that allows the state to grow marijuana for such research purposes.

Previous efforts to fully legalize medical marijuana for certain conditions like Alzheimer’s and cancer, have failed on Utah’s Capitol Hill, with lawmakers often citing their desire for more study. Much of that debate could be rendered moot, though, if the ballot initiative passes later this fall.