Why do some dreams remain in our memory for a long time while some vanish from our memory even while waking from sleep and we are not able to recollect however hard we try?
T.N. SAMA RAO
Thiruninravur, Tamil Nadu
Dreams occur during a stage of sleep known as REM (rapid eye movement) sleep, also known as paradoxical sleep. It is paradoxical in the sense that although we are sleeping, the brain is actively involved in creating a visual experience called dream, and its metabolic activity is equivalent to that in the awake state.
Most of the dreams are stored in the brain as a learning experience that we cannot demonstrate or remember. It is for the safety and well being of the person who has a dream that he/she doesn’t remember them since most of the dreams that we usually experience are bizarre and often frightful. That is why during the next stage of sleep ie. slow wave sleep (SWS), these dreams get washed off and the person gets up not remembering anything at all.
But yes, we tend to remember some dreams. It is generally seen that if a person gets awake suddenly while dreaming out of fright or someone else forcefully awakens that person while he/she is in REM sleep stage, that dream gets registered in our memories for short periods. Some very well known painters of the Renaissance period have employed this technique of disrupting their REM sleep suddenly and painting their dreams. These paintings are a presentation of that they were seeing.
In general, when we do not give enough time for our dreams to wash off as un-recallable experiences, we tend to remember them, but as a rule, the brain tries all it can to ensure that we get up remembering nothing at all.
So it will suffice to say that dreams are stored as experiences that you cannot recall or tell someone else, but yes, during special circumstances when you disrupt your dream state suddenly, you do remember your dreams albeit for short durations.
AIIMS, New Delhi