Ana Fernandez-Arcos, neurologist: There are people who give so much importance to dreams that they can change their lives'

"We don't know for sure. But, in part, it depends on the importance we give them. When someone makes a habit of explaining or recalling their dreams, or gives them more meaning, the simple act of doing so trains the brain to remember them better. Q. Is remembering a dream indicative of something? A. If a person who doesn't usually remember their dreams suddenly starts remembering them very frequently, it could be indicative of a problem. Or it could mean that the dream is more fragmented for some reason, even a medical reason."

"Yes, that's possible. During sleep, especially in REM sleep, emotional content is activated. We dream in different sleep phases, but [this happens] particularly in REM sleep, when the brain is very active, almost like when we're awake. In other phases, there's more rest. In REM sleep, areas related to intense emotions are activated, so it's common for memories that have impacted us to surface: significant life events, personal situations."

Dream recall partly depends on the importance assigned and on habitual practice of explaining or recalling dreams, which trains the brain to remember them. Sudden frequent dream recall in someone who rarely remembers dreams can indicate a problem or increased fragmentation, possibly for medical reasons. REM sleep strongly activates emotional brain areas, making emotionally charged memories and nightmares more likely and increasing recall of negative content. Dreaming occurs across sleep phases but REM is the most active for emotional processing. There is no scientific evidence that specific dream content carries hidden meanings.

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