I can't find any studies that look into the effects on mood specifically, but I found a related paper where they applied a magnetic field to the amygdalae of rats to increase the frequency of seizures. The idea of magnetic stimulation to parts of the brain causing altered states is in the public consciousness thanks to the God Helmet, though that applied a magnetic field to the temporal lobes to induce altered states and failed replication. That is likely why magnetic fields were used as an example.
Yes, I intended to show that a relatively non-invasive technique may be sufficient to drastically distort the mind. The same point could be made with blood clogging, eletric overdrive - seizures - or a small tumor, if history shows that trans-cranial magnetic stimulation was a placebo after all.
We are familiar with the thesis that Value is Fragile. This is why we are researching how to impart values to an AGI.
Embedded Minds are Fragile
Besides values, it may be worth remembering that human minds too are very fragile.
A little magnetic tampering with your amygdalas, and suddenly you are a wannabe serial killer. A small dose of LSD can get you to believe you can fly, or that the world will end in 4 hours. Remove part of your Ventromedial PreFrontal Cortex, and suddenly you are so utilitarian even Joshua Greene would call you a psycho.
It requires very little material change to substantially modify a human being's behavior. Same holds for other animals with embedded brains, crafted by evolution and made of squishy matter modulated by glands and molecular gates.
A Problem for Paul-Boxing and CEV?
One assumption underlying Paul-Boxing and CEV is that:
It is easier to specify and simulate a human-like mind then to impart values to an AGI by means of teaching it values directly via code or human language.
Usually we assume that because, as we know, value is fragile. But so are embedded minds. Very little tampering is required to profoundly transform people's moral intuitions. A large fraction of the inmate population in the US has frontal lobe or amygdala malfunctions.
Finding out the simplest description of a human brain that when simulated continues to act as that human brain would act in the real world may turn out to be as fragile, or even more fragile, than concept learning for AGI's.