What does neuroscience say about the dissociation procedure?

Severancethe series which imagines a surgical operation that literally separates private and professional life, returns for a second season. Although the concept of this captivating work of science fiction may seem completely unrealistic, it addresses interesting neuroscientific aspects.

Can the human mind really be split in two by surgery?

Surprisingly, “split brain” patients have existed since the 1940s. To control the symptoms of epilepsy, these patients underwent surgery to separate the left and right hemispheres. Similar operations are still performed today.

Subsequent research into this type of surgery showed that the separate hemispheres of split-brain patients could process information independently. This raises the uncomfortable possibility that the procedure could create two separate consciousnesses cohabiting in the same brain.

In the first season of Severancethe character of Helly R (played by Britt Lower) experiences a conflict between her “ not in » (the side of his mind that remembers his professional life) and his ” outie » (the side outside of work). Similarly, there is evidence of conflict between the two hemispheres of real split-brain patients.

When speaking with split-brain patients, we are usually communicating with the left hemisphere of the brain, which controls speech. However, some patients can communicate with their right hemisphere by, for example, writing or arranging Scrabble letters.

A young patient was asked what career he would like to pursue when he grows up. His left hemisphere chose an office job making technical drawings. His right hemisphere, on the other hand, arranged the letters to spell “racer.”

Split-brain patients have also reported “alien hand syndrome,” where it feels like one of their hands is moving of its own accord. These observations suggest that two distinct conscious “persons” can coexist in the same brain and have conflicting goals.

In the series Severancehowever, thenot in and theoutie both have access to speech. This is an indicator that this fictional “dissociation procedure” involves a more complex separation of brain networks.

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An example of complex separation of functions was described in Neil's clinical case study in 1994. Neil was a teenager with a number of problems following a pineal gland tumor. One of those difficulties was a rare form of amnesia: Neil couldn't remember what he did during his day or report what he learned at school. He had also become unable to read, although he could write, and to name objects, although he could draw them.

Amazingly, Neil managed to continue his studies. The researchers were interested in how he managed to do his homework when he didn't remember what he was learning.

They asked him about a novel he was studying at school, Rosie or the taste of cider by Laurie Lee. During a spoken conversation, Neil could not remember anything about the book, not even the title. But when one of the researchers asked him to write down everything he remembered about the book, he wrote “Red Geranium cider windows with Rosie Dranium smell of damp pepper [sic] and mushrooms” – words all linked 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 seemed lost, including meeting a man with gangrene in hospital. In each case, he was unconscious of his own memory until he wrote it down and it was read back to him. Neil's case is a stunning example. It suggests that having memories inaccessible to our own consciousness is possible.

In Severancel’outie of Irving (John Turturro) can access memories of his work environment not in through painting. He paints the long corridors of the floor where his not inalthough he has no conscious memory of it. In the series, the dissociation procedure may involve blocking conscious access to memory in the same way that access was blocked in Neil.

The role of the hippocampus

Which brain regions could be central to the TV series' dissociation procedure? The region most associated with remembering the events of the workday is the hippocampus. Interestingly, this same brain region also supports the representation of space.

The fact that the same neural structure can both remember that a new colleague joined your team today and represent the office layout suggests that the hippocampus might be a good target for this mock procedure.

In Severancethe transition from the state of not in to that of outie is done at the edge of the office, that is to say at the elevator doors. This is reminiscent of the “door effect”, the phenomenon where passing through a door makes you forget something.

The hippocampus segments our experience into episodes for later recall. Entering a new space indicates that a new episode has begun, leading to increased forgetting of information spanning those episodes. The effect is, however, subtle. Although you can sometimes walk into the kitchen and forget why you went in there, you don't forget that you have kids, unlike the dramatic effect caused by the show's separation procedure.

Perhaps, in the series, the hippocampus's interest in spatial boundaries triggers the shift between not in et outie.

Unfortunately, the idea that the series dissociation procedure might involve a simple incision of the hippocampus has two crucial flaws.

First, it is not only episodic and spatial memory that is dissociated in Severance. Workers have a large amount of semantic knowledge (e.g., facts about Lumon, the company they work for, and its founder) that is inaccessible to their workers. outies. They also form emotional memories related to the rewards they receive for their work and the punishments they receive in the break room.

These forms of memory rely on much more than the hippocampus, and the hippocampus itself is part of a brain-wide episodic memory network that is activated during episodic memory retrieval.

The second flaw is that memory itself is not an isolated process. It is closely linked to perception, attention, language and many other processes. The human memory system is far too complex to be divided entirely into two, but as shown Severanceit is fascinating to imagine this possibility.