What processes in the brain allow you to remember dreams? — Emma Poltrack, Virginia

Deirdre Barrett, author of The Committee of Sleep, replies:

Dreams are notoriously difficult to recall. In fact, if a dream ends before we wake up, we will not remember it. The processes that allow us to create long-term memories largely lie dormant while we sleep, which is why most dreams are forgotten shortly after waking. For instance, an important neurotransmitter for remembering, norepinephrine, exists at very low levels during dreaming, as does electrical activity in areas key to long-term memory, such as the prefrontal cortex.

As the brain awakens, it starts to turn on processes needed for long-term storage. Thus, if we wake straight out of a dream, we have a greater chance of remembering it. A 2011 study showed that people who have more theta brain-wave activity in their prefrontal cortex after waking from REM sleep have better dream recall. Theta activity indicates a slower-paced, more relaxed brain state, and greater theta activity has been linked to enhanced memory while awake.

The emotional content and logical consistency of a dream also affect how much of our dreams we remember. One study found that less coherent dreams were harder to recall than ones with strongly felt content and organized plot lines. The dreams we are likeliest to retain—nightmares and other vivid, emotional dreams—are accompanied by greater arousal of brain and body and are therefore more likely to wake us up.

Certain techniques can help increase dream recall. Anything that captures our attention immediately after waking interferes with dream recall, so just as you are falling asleep, keep reminding yourself that you want to remember your dreams. Let it be your last thought as you are drifting off. Keep a notepad and pen by the bed. When you first wake up, do not jump up or turn your attention to anything. Even if you do not think you can remember a dream, take just a minute to see if there is any feeling or image you can describe. Following these simple steps may cause an entire dream to come flooding back.