The following essay is reproduced with permission. 
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Severance, which imagines a world where one’s work and personal lives are surgically separated, will soon return to Apple TV+ for a second season. Although the concept of this fascinating piece of science fiction is far-fetched, it touches on some interesting neuroscience. Can a person’s heart really be surgically divided into two?
Remarkably, “split brain” patients have existed since the 1940s. To control epilepsy symptoms, these patients underwent surgery to separate the left and right hemispheres. Similar surgeries are still performed today.
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Subsequent studies of this type of surgery showed that the separate hemispheres of split-brain patients can process information independently. This raises the unpleasant possibility that this procedure could result in two separate minds within one brain.
In Season 1 of Severance, Helly R. (Britt Lower) experienced a conflict between her “innie” (the side of her mind that recalls her work life) and her “outie” (the side outside of work). Similarly, there is evidence of discrepancies between the two hemispheres in actual split brain patients.
When you talk to a split-brain patient, you are communicating with the left hemisphere, which usually controls language. However, some patients are able to communicate from the right hemisphere, for example by writing or arranging Scrabble letters.
We asked young patients what kind of work they would like to do in the future. His left brain chose an office job creating technical drawings. But his right hemisphere lined up the letters to spell out “car racer.”
Split brain patients also report “alien hand syndrome,” where one hand is perceived to be moving of its own volition. These observations suggest that two separate conscious “people” can coexist in one brain and have conflicting goals.
But with Severance, both innies and outties have access to speech. This is one indication that the hypothetical “amputation procedure” must involve a more complex separation of brain networks.
An example of a complex separation of functions is described in Neal’s 1994 case report. Neil was a teenage boy who had many problems after a pineal gland tumor. One of these difficulties was a rare form of amnesia. That meant Neil couldn’t remember the day’s events or report on what he learned at school. Also, although I can write, I can no longer read, and although I can draw, I can no longer name things.
Amazingly, Neil was able to continue his education. Researchers were interested in how he was able to complete his school work despite having no memory of what he was learning.
They quizzed him on the novel he had been studying in school, The Cider with Rosie by Laurie Lee. During our conversation, Neil couldn’t remember anything about the book. I couldn’t even remember the title. But when a researcher asked Neil to write down everything he remembered about the book, he said, “The smell of bloodshot geranium window cider and rosy dranium wet pepper (sic) and mushroom growth. ” I wrote. Every word was related to the novel. Since Neil couldn’t read, he had to ask the researcher, “What did I write?”
Neil was also able to write down other memories that were thought to be lost, such as meeting a man with gangrene in the hospital. In each case, he was unaware of his memory until he wrote it down and had it read to him. Neil’s case is a surprising example. It suggests that it is possible to have rich memories that are inaccessible to our conscious minds.
At Severance, Irving’s (John Turturro) associates are able to access their associates’ memories of their work environment by drawing pictures. He depicts a long hallway of severed floors (where his innie works), despite having no conscious memory. Presumably, on the show, the amputation procedure will involve blocking conscious access to memories in the same way that memory access was blocked in Neil.
Role of the hippocampus
Which brain region is central to the TV program retirement process? The hippocampus is the one most involved in remembering the events of the workday. And interestingly, this same brain region also supports the representation of space.
The fact that the same neural structures support both remembering that a new colleague joined the team today and representing the layout of the office suggests that the hippocampus may be a good target for this hypothetical procedure. It suggests something.
At Severance, the transition between inside and outside occurs at the boundary between offices, at the elevator door. This is reminiscent of the “doorway effect,” a phenomenon in which people forget something when they walk through the front door.
The hippocampus divides our experiences into episodes that can be recalled later. Entering a new space signals the beginning of a new episode, thus increasing the forgetting of information across these episodes. However, the effect is subtle. Sometimes you may walk into the kitchen and forget why you came in, but unlike the dramatic effects caused by the show’s exit process, you never forget that you have children.
Perhaps, in the play, the hippocampus’ interest in spatial boundaries causes the switch between innie and outie.
Unfortunately, the idea that the show’s cancellation procedure could involve a simple amputation of the hippocampus has two significant flaws.
First, it’s not just episodic and spatial memory that is divided in Severance. Employees have a large amount of semantic knowledge that is not accessible outside (e.g., facts about Lumon, the company they work for, and its founders). They also form emotional memories tied to rewards received for hard work and punishments received in the break room. These forms of memory rely on much more than the hippocampus, which itself is part of the brain-wide episodic memory network that is activated during episodic memory retrieval.
The second flaw is that memory itself is not an independent process. It is closely related to perception, attention, language, and many other processes. The human memory system is far too complex to be completely split into two, and as Severance shows, it’s fun to think about the possibilities.
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