February 18, 2014
Brain Region More Active In People Who Can Remember Their Dreams
April Flowers for redOrbit.com - Your Universe Online
Dreams are elusive things. Some people remember their dreams every morning, while others rarely recall anything.
A research team, led by Perrine Ruby, an Inserm Research Fellow at the Lyon Neuroscience Research Center, examined the brain activity of these two types of dreamers, hoping to understand the differences between them.
The findings, published in Neuropsychopharmacology, reveal that the temporo-parietal junction, an information-processing hub in the brain, is more active in people who are able to recall a high number of dreams. The researchers believe that the increased activity in this brain region might facilitate attention orienting toward external stimuli and promote intrasleep wakefulness, thereby facilitating the encoding of dreams in memory.
For those who study the difference between "high dream recallers" (those who recall dreams regularly) and "low dream recallers" (those who rarely recall their dreams), the reasons behind dreaming are still a mystery.
In January 2013, Ruby and her team made two observations. First, they observed that “high dream recallers” have twice as many times of wakefulness during sleep as “low dream recallers." Second, the team noticed that "high dream recallers" brains are more reactive to auditory stimuli during sleep and wakefulness. The findings, published in Cerebral Cortex, suggest that this increased brain reactivity might promote awakenings during the night, and these brief periods of wakefulness may facilitate memorization of dreams.
In the current study, Ruby's team wanted to identify which regions of the brain react differently between high and low dream recallers. The team recruited 41 volunteers, and then used Positron Emission Tomography (PET) to measure the spontaneous brain activity during wakefulness and sleep. The participants were divided into two groups. The first group consisted of 21 "high dream recallers" who were able to recall 5.2 mornings per week in average. The second group, consisting of 20 "low dream recallers," recalled 2 dreams per month in average.
While both awake and asleep, high dream recallers showed stronger spontaneous brain activity in the medial prefrontal cortex (mPFC), as well as the temporo-parietal junction (TPJ), an area of the brain involved in attention orienting toward external stimuli.
“This may explain why high dream recallers are more reactive to environmental stimuli, awaken more during sleep, and thus better encode dreams in memory than low dream recallers. Indeed the sleeping brain is not capable of memorizing new information; it needs to awaken to be able to do that,” explained Ruby.
Mark Solms, neuropsychologist from the University of Cape Town in South Africa, observed in prior research that lesions in these two brain regions led to a cessation of dream recall. The unique aspect of the new study is in showing brain activity differences between high and low dream recallers during sleep and also during wakefulness.
“Our results suggest that high and low dream recallers differ in dream memorization, but do not exclude that they also differ in dream production. Indeed, it is possible that high dream recallers produce a larger amount of dreaming than low dream recallers,” concluded the research team.