For hours after death, some cells in the human brain are still active. A new study from the University of Chicago, Illinois shows that they are increasing their activity, and it grows to gigantic proportions.

UIC researchers analyzed gene expression in fresh brain tissue that was harvested during routine brain surgery after removal to mimic postmortem interval and death. They found that gene expression in some cells does increase after death.

These “zombie genes” were specific to one type of cell: inflammatory cells called glial cells. The researchers observed that glial cells grow and germinate in the brain within hours of death.

Most of the studies that use post-mortem human brain tissue to find treatments and potential cures for disorders such as autism, schizophrenia, and Alzheimer’s do not take into account post-mortem gene expression or cellular activity.

The authors also note that the global gene expression pattern in fresh human brain tissue does not match any of the published reports of postmortem brain gene expression in people without neurological disorders or in people with a wide range of neurological disorders, such as autism or Alzheimer’s disease.

The authors conducted an experiment with simulated death: they studied the expression of all human genes over 24 hours. They found that about 80% of the genes analyzed remained relatively stable for 24 hours. These are genes that provide basic cellular functions. Another group, which is present in neurons and is closely associated with memory and thinking, rapidly degrades within a few hours after death.

The third group of “zombie genes” increased their activity at the same time that neuronal genes were declining.