I was doing some research on Mind Flayers and read/heard that Mind Flayers will occasionally extract a brain and use it to research the effects of Psionics, and that they enjoyed the mad thoughts they produced (Though I cannot for the life of me find the source of where I read/heard it). I presume that due to the Elder Brain surviving in a brine pool that they would put some of that brine in a jar and preserve a brain alive in it...
...As an extension to this; would someone who can communicate telepathically then be able to actually speak with the brain in a jar (i.e. GOO warlock ability). I assume if they can, that the brain cannot respond as it cannot 'see' the one speaking to it.
My scenario being that my PC's will soon be fighting Mind Flayers, and if one of them gets their brain extracted, I would rather the Flayer choose to preserve it so that the party GOO warlock could potentially still speak to them but the party member could not respond. Mainly just to mess with them even more - nothing wrong with a little DM Schadenfreude.
My main concern with doing it is that it almost denies 'closure' of a character death. If, as a general rule, Mind Flayers don't/wouldn't 'farm' brains in any particular way then I'd prefer to keep it out of my game. If it's something well within their power and makes sense that they would be doing it; then it's on the players carelessness rather than me just being cruel for the sake of it