As Julia said in the previous queston you asked it is thought that dreams help us to process our thoughts – but it is still fairly unclear. The two possible theories are called the “psychoanalytic theory” and the “activation-synthesis model of dreaming”.
There is evidence for sleep helping commit things to memory (as I mentioned before) but I don’t know if there is specific evidence for dreams helping in this. I would suggest that you are right and they do because dreams occur in light REM sleep and as sleeping for only 6mins aids in learning it can’t be deep sleep that is helping the processing! 🙂
But as for your question about memory loss I would suggest that even if people with severe memory loss do dream then they are unlikely to remember them right? so they couldn’t tell you about their dreams…
Also you would expect their dreams to be different from yours (or them not to dream at all) because they can’t remember much stuff to process…but this is not the case according to some research! Apparently amnesiacs do dream but they don’t recgnise what they dream about …pretty weird.
The scientist talked about in that article has done some cool research since. A lot of his research shows that sleep is important in some forms of memory but not in others. In particular he thinks that sleep does a lot of “post processing” of the things we experience during the day. People with amnesia can do the post-processing even though they don’t remember what it is they are processing!