From what I understand, the very matrices throughout the quanta of atomics, pretty much proves that the brain already works within "holographic contraints".
Atoms if broken completely down are just a mergence of energies, which only when combined give "solidity" and "form".
It's also possible for charges to be entered into the shells of atoms, the problem is that the charges can have a build up effect. This is why something organic can suffer mutations with particular radioactive effects.
I mention that purely because if you look up at a Light tube (say for neon, or just across the roof of the place you work) you'll notice that it works with the process of exciting it's gaseos content with electrical energy, and the lumonisity giving off through the reactions is down to the radiation mentioned above.
The human brain could undergo a similar effect if it's "Wired" to a system wrongly, and in turn this could cause cellular damage, like light sensativity to cells and even fail memory. (Not to forget that certain radiation levels increase the speed of a cells aging rate).
It is however possible to "Project" holographic images to the brain, especially if you consider the wavelengths that can pentrate our skin and understand that 65-70% of our brain makeup is water.
You would have to visualise having a computer system that could project a 3 dimensional hologram into a cluster of glass beads to get a perception of how that would work.
You however would have to calculation the photogenic reaction that can cause chemical composition changes, which release energy enough to incur a change in brain temperature.
(Calorimetrics)
This too would cause noticible changes in the size of portions of the brain (since some of the chemicals would be released through excretion) and also noticible changes in the chemical compositions.
(A person might increase temperature enough to use up lipid tissue, in doing so releasing Nitrogen that traps there into the system. This in turn could reaction in a chemical reaction with water to give Nitrous Oxide [NO], which can in a pure form be known as "Laughing Gas". It might very well be the cause of Manic Depression, where a person is happy one minute but suicidal the next. [The body reacts with the NO in the system, and builds up a resistance to the amount produce, this causes the depression because the person isn't getting enough])
Admittedly a map of the human brain into a holographic format would be of use for people to explorer how the brain works in Virtual reality, but this can give reason to a whole new type of hacking where our very brains might not be safe from particular hack tricks.
For instance take a region of stimulii and loop the stimulation through the hologram to your "Victim", and suddenly your victim has to fight an "erge" that he can't win. The outcome is either completely destructive acts of the victim trying to escape the torment or what ever it is you "erge" of them.
(This could be anything from a harmless practical joke of scratching a region in public to attacking someone.)
This is the main reason why a majority of scienticist speak out about the usage of such equipment, purely because of the implications of "What could happen" if the wrong people had control and in certain respects I agree with them too.