How Did Kaneki Lose His Memories? [Kaneki's Lobotomy]

[Agent Phrank]

This is to refresh your memory just in case you forget.

1.Arima's Lobotomy:​

Long term memories are primarily stored in the hippocampus:

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Which is located here:

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Notice that there are two on each side and they're directly posterior (behind) the eyes.

Damage (indicated by white):

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Chapter 140:
Look at both his hollow eyes:

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On Lobotomies:

Spoiler

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Lobotomies have always been controversial, but were widely performed for more than two decades as treatment for schizophrenia, manic depression and bipolar disorder, among other mental illnesses.

Procedure:

The first procedures involved cutting a hole in the skull and injecting ethanol into the brain to destroy the fibers that connected the frontal lobe to other parts of the brain. Later, Moniz introduced a surgical instrument called a leucotome, which contains a loop of wire that, when rotated, creates a circular lesion in the brain.

The technique involved using an instrument called an orbitoclast, a modified ice pick, which the physician would insert through the patient's eye socket using a hammer. They would then move the instrument side-to-side to separate the frontal lobes from the thalamus, the part of the brain that receives and relays sensory input.

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While a small percentage of people supposedly got better or stayed the same, for many people, lobotomy had negative effects on a patient's personality, initiative, inhibitions, empathy and ability to function on their own.

From Tokyo Ghoul Jack:

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You understand the post-event treatment, don't you?

2. Repressed memories​

Haise's response to how he feels about his amnesia:
Chapter 8 :re

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Haise has several other several breakdowns throughout :re as well.

First breakdown/Haise's subconscious:

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Second time was during Takizawa vs Haise:

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Haise contemplating his sanity again:

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3. Brainwash/Conditioning:​

This is the least evident but the partnership between Akira and Haise can be considered a coping mechanism to prevent the Centipede from emerging.

Recall how Arima requested Akira to occupy a maternal role:

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Other readers are speculating that she might be acting this all out.

Akira also has permission to take lethal action if necessary.

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Haise: I am... I am a ghoul investigator under the Mado Squad... investigating Torso as the mentor of the Quinckes.
Akira: Who are you?
Haise: I am... I am Haise Sasaki.
Akiira: That's right, you're Haise Sasaki.

They obviously want to condition him as a near-perfect CCG investigator who may potentially take Arima's place.

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Become strong, Haise, become strong and kill ghouls.

Bonus:

Spoiler

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credits to whoever made this