Have you ever seen the movie The Princess Bride? If so, there’s a line in it that has been getting some attention again lately. It goes, “There’s a big difference between mostly dead and all dead. Mostly dead is slightly alive.”

Yale from Pixabay.

This has been getting widely quoted in a lot of papers regarding a new study called BrainEx that just came out from Yale School of Medicine. In this study, scientists were able to restore some function in the brains of pigs that were killed hours before in a slaughterhouse.

Although none of the brains restored the kind of electrical activity associated with consciousness or awareness, there was a shocking amount of cellular function that was either preserved or even restored (3). The scientists decided to conduct this study in order to study brain cells in an intact organ; this meant the scientists had to supply the brains with oxygen, nutrients, and other cell-protective chemicals.

Now, as a quick side note, what happens if a brain does not get enough oxygen? A lot of bad things. A brain needs oxygen to function, and this is why the researchers continued to supply the brains with oxygen. Reduced oxygen levels are called hypoxia, and brain cells can begin to rapidly die without an oxygen supply since they are extremely sensitive to oxygen deprivation (4). Before death occurs, hypoxia can also cause a person to go into a coma or have a seizure (1).

Courtesy of Public Domain Pictures.

Let’s go back to the study. The team acquired 32 brains from a slaughterhouse. Four hours after the pigs were killed, they were infused with the nutrients and protective chemicals. Pumps were used that mimicked the beats of the heart, which all preserved the brain from degrading (3).

These brains that received the nutrients were very different than the brains that did not have this system set up. Cell death was reduced, while tissue and cellular structure was preserved. There were even some neuronal, glial, and vascular cells that were functional (5).

I want to stress one thing. Although some cellular and molecular functions were restored, this brain was NOT a living brain – it was just cellularly active. There were no signs of brain-wide electrical activity indicating consciousness or life. This is important, because the researchers were ethically worried about seeing signals associated with consciousness (6). If this happened, they would have used anesthesia and shut this all down immediately.

This study brings up the important question. What does it mean to be brain dead? Should this study change how we view brain death? If only the brain is cellularly active, what are the implications of that? Currently, a summary of brain death certification includes the following: (2)

Brain and brainstem, courtesy of
  1. Findings that provide clear etiology of brain dysfunction
  2. Exclusion of confounding conditions that would affect subsequent examinations of cortical or brain stem function
  3. Neurological examination including sleep apnea test and ten minute apnea test
  4. Brainstem reflex assessment
  5. Clinical observations compatible with diagnosis of brain death
  6. Repeat clinical assessment of brain stem reflexes

Also, life support is needed for breathing is a person is brain dead.

I also wanted to pose a couple potential ethical / discussion questions to consider regarding this study.

  • When can an animal / human no longer feel pain? Can we tell from brain death?
  • How do we separate the living from the dead?
  • When is there irreversible loss of brain function (due to hypoxia)?
  • What if consciousness had been brought back in this study? What would be the implications of this?
  • How can this be used to protect animal welfare? Is it even applicable?
  • How might this affect organ donation from people declared brain-dead?
  • Could this be used to help stroke patients?
  • And again, since the brains were only cellularly active, should this change how we view brain death?


  1. Cerebral Hypoxia Information Page. U.S. Department of Health and Human Services.
  2. Goila, A., Pawar, M. The Diagnosis of Brain Death. (2009). Indian Journal of Critical Care Medicine. doi: 10.4103/0972-5229.53108
  3. Greenfieldboyce, N. Scientists Restore Some Function In The Brains Of Dead Pigs. (2019) NPR.
  4. Nikinmaa, M. What is hypoxia? (2013). Acta Physiologica, 209(1).
  5. Sandoiu, A. Some Brain Functions May Be Restored after Death, Pig Study Suggests. (2019). Medical News Today.
  6. Yong, E. Scientists Partly Restore Activity in Dead-Pig Brains. (2019) The Atlantic.

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