I often heard that in meditation it is possible to achieve a dream like state.
It goes way beyond any dreams. (I can't believe i'm actually using this sentence)
> Now, to stay on topic, does one perform the given unlearning process while deep meditation too?
No. But there is side effect for deep meditation - you meditate - there is nothing much to unlearn, if, for example, a monk meditates 2 times a day, each time for a single sitting of ~5hours. One is not conscious of time then - it means when a monk enters meditation, he decides ' i will expierence this or that state/ level of calmness for 5hours ', then, he goes 'in' and is not conscious of time , body or anything, but only experiences those extreme states of bliss and kind of even travel backwards in time - being able to remember previous lives and even, as Buddha said 'see a thousand worlds'- meaning actual, non-imaginary space exploration. - see,. you can really 'actively' imagine, when the mind is empty, can you? Imagining things is directed *taught*, that is - it is workings of your mind and such thing would very soon diminish what is not imaginary.
It's not unlearning process in REM, those are the wrong things. It is collateral of chemical 'rinse', that maintains inter-neuron space.