Neurobiology of loss and recovery of metacognitive function during REM sleep
Unlike cognitive processes during wakefulness, REM sleep is not generally accessible to explicit monitoring of thought. Indeed, during REM sleep we are typically unaware that we are asleep, unaware that our body is lying in bed and, even when dreams occur, oblivious to the fact that we are dreaming. Interestingly, research has documented a rare but physiologically validated state of REM sleep (so-called “lucid” REM sleep), in which it is possible to regain metacognitive function while continuing to remain in physiologically defined REM sleep. Individuals in this state become explicitly aware that they are asleep and cognizant of the fact that they are dreaming. This state can be objectively verified on a sleep polysomnogram from patients in a sleep laboratory by asking patients to execute volitional eye-movements as shown in the figure above. As discussed in a recent review article (Baird et al., 2019), this unusual neuropsychological state therefore presents a unique opportunity to examine the neurophysiological and neurochemical changes associated with global loss and recovery of monitoring function in the human brain.
In a recent innovative line of research, we have undertaken some of the first cognitive neuroscience studies on this state. In one study, we examined the relationship between the functional connectivity of frontopolar cortex and the frequency of metacognitive monitoring during REM sleep using functional connectivity MRI coupled with graph theoretic analysis (Baird et al., 2018). Frequent REM sleep metacognition was found to be associated with increased connectivity between the lateral frontal pole and bilateral angular and middle temporal gyri, a network that is typically deactivated during REM sleep. In another line of research, we have tested whether metacognitive function during REM sleep can be induced pharmacologically. In a recent double blind, placebo-controlled study, we found that cholinergic enhancement with acetylcholinesterease inhibition (AChEI) substantially increased metacognitive monitoring in REM sleep in a dose-related manner (LaBerge, LaMarca & Baird, 2018). These findings provide novel insights into the neurobiological mechanisms underlying the human brain’s capacity for monitoring and control of thought.
Baird, B., Mota-Rolim, S., & Dresler, M. (2019). The cognitive neuroscience of lucid dreaming. Neuroscience and Biobehavioral Reviews, 100, 305-323.
Baird, B., Castelnovo, A., Gosseries, O., Tononi, G. (2018). Frequent lucid dreaming associated with increased functional connectivity between frontopolar cortex and temporoparietal association areas. Scientific Reports, 8(1), 17798.
Laberge, S.*, Baird, B.*, Zimbardo, P. G. (2018). Smooth tracking of visual targets distinguish lucid REM sleep dreaming and perception from imagination. Nature Communications, 9, 3298.
LaBerge, S., LaMarca, K., Baird, B. (2018). Pre-sleep treatment with galantamine stimulates lucid dreaming: A double-blind, placebo-controlled, crossover study. PLoS ONE, 13(8), e0201246.