Here’s some scary news just in time for Halloween. Studies suggest that our brains still function after we die. That means, when we die, we know that we are dead. The research was first published in 2014 and says our consciousness may still function for a period after our physical body is declared dead. Therefore, it is arguable that a person could hear themselves be pronounced dead by a doctor.

This study, which is the most significant scientific studies of its kind, was done by a team of researchers led by Dr. Sam Parnia, the director of critical care and resuscitation research at NYU Langone School of Medicine in New York. Parnia and his team of researchers studied people who had suffered cardiac arrest and had technically been declared dead and then later revived. A large number of participants in the study report being aware of their surroundings during the period in which they were pronounced dead. While most were unable to recall specific memories, 39% of the study’s participants could describe a “perception awareness.” A small percent say they were able to hear full conversations, and even see what was happening around them.

Dr. Parnia tells the Independent, death is scientifically defined by the heart no longer beating and the lack of blood flow to the brain.

“Technically, that’s how you get the time of death – it’s all based on the moment when the heart stops,” Dr. Parnia states. “Once that happens, blood no longer circulates to the brain, which means brain function halts almost instantaneously.”

Moreover, “you lose all your brain stem reflexes – your gag reflex, your pupil reflex, all that is gone,” Dr. Parnia continues. However, this research suggests brain energy that happens after death could indicate that death is more complicated than that.

A 2013 study from the University of Michigan studied brain signals of rats that were anesthetized and experienced a heart attack. Researchers of the study observed brain activity suggesting a “hyper-alerted state” shortly after the rats were pronounced dead.

“This is a very neat demonstration of an idea that’s been around for a long time: that under certain unfamiliar and confusing circumstances – like near-death – the brain becomes overstimulated and hyperexcited… “ Dr. Jason Braithwaite, the professor at the University of Birmingham, told BBC in regards to the rat research. “Like ‘fire raging through the brain,’ activity can surge through brain areas involved in conscious experience, furnishing all resultant perceptions with realer-than-real feelings and emotions.”