Inducing Ignorance in the Brain

Context:

Brains in Vats and Virtual Reality on Steroids

In the (reasonably near) future, humans have developed the field of medicine significantly, and we now have the technology to isolate the brain in a vat of oxygenated fluid. Assume the process of doing so is safe, although irreversible, and that a machine facilitates all body functions - providing nutrients, circulating blood and fluid, and the nasty one - providing stimulus as best it can.

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In most cases, the transfer from body to vat is voluntary. Some people will choose to have their brains placed into new bodies, while others will have supercomputers simulate life for them - providing electrical input as if the situations the isolated brain is encountering are real.

However, sometimes these transfers take place without the knowledge, and thus consent, of the participant. Perhaps the government is particularly evil, and has the money to sedate the person - the next time they wake up, they will assume things are normal, when in fact they may be in a simulation or a new body. Let's focus on the simulation aspect of this scenario.

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The resulting problem

When someone voluntarily chooses to enter a simulation in this way, they will understand that the world is not real. That means it's 'ok' if some things are a little off - if they don't feel quite as tall, or if it's harder to breathe, or if their vision is better - they will know it's a simulation, and that's expected.

When someone is transferred involuntarily, they may realize there's a problem when not everything around them is exact - and that may reveal the true nature of what happened. For example,

Jessica is $f$ feet tall, with shade $s$ skin, weight $h$ hair, and predisposed conditions that change things no one else can tell by looking at her $p$, $r$, and $e$

When Jessica is transferred, she does not feel $f$ feet tall, her skin is shade $q$, her hair is too light, and she doesn't have conditions $p$ and $r$. She knows something's up because she's heard these stories before, and she knows the associated symptoms.

The illusion is broken, and Jessica freaks the **** out.

It is impossible to exactly reproduce the sensations any person receives with a machine in this way!

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My thoughts

One might argue that this scenario is analogous to dreaming - you can proceed through a dream while being ignorant that everything around you isn't real. Perhaps there's a way to make Jessica ignore aspects of herself, while still functioning inside the simulation, so she doesn't realize the problem. I'm thinking something kind of like how in The Sixth Sense,

The psychiatrist has been dead since the opening scene in which he was shot, but he has been ignorant to the signs that he's a ghost and continues to try to interact with the world as normal

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The question

Short of a lobotomy, is there a way to induce ignorance (kind of like a dream) that allows the individual to function without realizing the nature of their reality?

When answering this
hard-science is not expected but acceptable
science-based would be great but may not be possible
science-fiction or pseudoscience is fine, but not ideal