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Science fiction series «Severance», which debuts its second season on Apple TV+ tomorrow, shows a world where people use a surgical procedure to split the human brain — into working and personal parts. One has no idea what’s going on at home, and the other has no idea what the worker is doing in the office, and, as neuropsychologists note, such a procedure «brain split» was tested in real life back in 1940.
Initially, the operation to separate the left and right hemispheres was used to control the symptoms of epilepsy in patients (similar events are being held nowknown as «callosotomy»), and later studies have shown that separated hemispheres can process information independently. This creates a certain probability of what happened in the series — when two different minds live in one brain and even conflict.
In conversation, split-brain patients typically use the left hemisphere, which controls language, but some have used the right hemisphere to express thoughts — for example, when writing or making letters in Scrabble. One subject when asked about a dream job chose an office job in the conversation, but in the game his right hemisphere made the word «racing driver».
Patients with split brains also reported «second-hand syndrome»when one of their arms seemed to move of its own accord. These observations suggest that two separate conscious «people» can coexist in the same brain and have conflicting goals — as in the case of Hallie in «The Gap», when her outer side refused to release her inner side.
However, in the «Severance», both the extra and intro (as the outer and inner sides were called, respectively) have access to speech — this is one indicator that the fictional «Gap» procedure must include a somewhat more complex division of brain networks. One example of such a separation of functions was described in the 1994 report about a teenager named Neil who had a number of complications after a pineal gland tumor — including a rare form of amnesia. The boy could not remember the events of his day or what he had learned at school, and he could not read, write or name objects, but he could draw them quite well.
The researchers were interested in this case because he still successfully completed schoolwork, even though he forgot it. For example, Neil could not recall the novel by Laurie Lee «Cider with Rosie» during a conversation, but when asked to write down everything he remembered about the book, he produced a few legible words related to it. Since Neil could not read, he had to ask the researcher: «What did I write?».
In «The Severance», Irving’s extra constantly draws what looks like the long corridors of the office where his intro works, despite the fact that he remembers nothing about them. Perhaps in the series, the separation procedure involves blocking conscious access to memory — just as this access was blocked for Neil.
What areas can be key to the series break procedure? The one responsible for memorizing the events of the working day — hippocampus (also responsible for the representation of space). The fact that the same neural structure supports both the memory of new colleagues and the representation of the office layout suggests that the hippocampus might be a good target for this fictional procedure.
In the series, the switch between intro and extra takes place in the office elevator — and it resembles «doorway effect» (the phenomenon when, for example, you were on your way to the kitchen and forgot what you wanted to do as soon as you entered it). It is the hippocampus that segments our experience into episodes for further recall, and entering a new space is an indicator that a new episode has started and the previous one is partially forgotten.
Of course, «Gap» has some fantastic elements in this case, which involve the division of memory into more than just spatial or episodic memory. Lumon employees have a large amount of semantic knowledge (for example, facts about the company they work for and its founder), and form emotional memories related to rewards and punishments in the break room. These forms of memory rely on something more than the hippocampus.
The second flaw in the series is that memory itself is not an isolated process. It is closely connected to perception, attention, language, and many other processes. The human memory system is too complex to be completely divided into two parts, but as «The Gap» shows, such possibilities look very interesting.
Based on the article The Conversation co-authored by Rachel Elward, Senior Lecturer in Neuroscience and Neuropsychology, and Lauren Ford, PhD in Cognitive Neuroscience (South Bank University, London).