I'd speculate that in an isolated brain dreaming would still be possible. Possibly, without external stimulation it would not be possible to be awake. That sai

I'd speculate that in an isolated brain dreaming would still be possible. Possibly, without external stimulation it would not be possible to be awake. That said, there are emerging technologies which would compliment brain preservation, such as the brain-computer interface. BCI therapies have already been effective in giving blind people sight via invasive electrodes (e.g. the work of William Dobelle). Output has also been demonstrated using BCIs. Such a brain could interact with the world through a robotic surrogate, or have an entirely virtual interaction. Arguably, the brain in a tank may have access to a richer experience than the natural body, with synthetic sensory and motor capabilities.