I wasn't thinking so directly to the "brain in a vat" story. It is perhaps possible to reproduce all incoming "electrical" stimuli with patience and time?
But it will not work if you limit brain, to an electrical "computer" (it is not).
But brain is the first endocrine system of body and hormones/peptides produced are modifying directly the manufacturer.
Consciousness needs a "body state" to create a "reference Self". Brain works with differences comparing a state to a newer one and updating continuously the reference material.
Some medical states as psychosis and phantom limbs problems, for an example show that an impairment/perturbation of incoming stimuli create a distortion and "painful solutions".
It is why I persist to think that a cemi field is an integrated "reflection" of brain activity but it can't directly rely the subtle changes in the brain endocrine system.
Do not forget that a neuron is able to synthetize around... 20,000 peptides.