CHICAGO (CBS) — It’s not exactly a scene from The Walking Dead, but researchers at the University of Illinois at Chicago have found that, in the hours after death, some brain cells not only remain active, but actually increase activity.

In a new study published in Scientific Reports, the researchers found the so-called “zombie genes” even “grow to gargantuan proportions” after we die, according to UIC.

The researchers analyzed gene expression in fresh brain tissue collected during routine brain surgery to simulate the post-mortem interval and death, and found gene expression in some cells increased after a person dies.

Those “zombie genes” were specific to a single type of cell — inflammatory cells called glial cells, which grow and sprout long arm-like appendages for several hours after death, according to UIC.

“That glial cells enlarge after death isn’t too surprising given that they are inflammatory and their job is to clean things up after brain injuries like oxygen deprivation or stroke,” said Dr. Jeffrey Loeb, professor and head of neurology and rehabilitation at the UIC College of Medicine, who authored the study.

Loeb said most research studies that use postmortem human brain tissue to find treatments and potential cures for disorders such as autism, schizophrenia, and Alzheimer’s disease, don’t account for cell activity after death.

“Most studies assume that everything in the brain stops when the heart stops beating, but this is not so,” Loeb said. “Our findings will be needed to interpret research on human brain tissues. We just haven’t quantified these changes until now.”