Hearing a recording of one’s own voice can be a cringe-worthy experience. Scientists took advantage of that uncomfortable truth in recent research in the journal Current Biology, turning up the notch with a karaoke experiment. The goal was to ignite feelings of embarrassment and shame — all in the good name of helpful sleep science.
Eus van Someren, Ph.D., a professor at the Netherlands Institute for Neuroscience and corresponding author on the study, tells Inverse that this experiment came to fruition after his team discovered that people with insomnia have a hard time shedding the distress caused by bad emotional experiences.
That suffering can last weeks — even years — and they wanted to find out exactly why. They had two major questions: What is it about sleep that underlies the problem, and what brain circuits are involved?
“The ultimate goal is to find the best handles for a development towards treatment,” van Someren says. “This is much needed, given the enormous prevalence of insomnia.”
So the team set out to cause some embarrassment. To do this, 29 people performed karaoke sessions that were recorded. The catch was that they had to wear headphones that muffled out the sound of their own voice — that way, the scientists could impede pitch correction and promote out-of-tune singing. The participants were not diagnosed with any psychiatric disorders, and they covered a wide range of experiences with insomnia; some had never experienced it, while others were very familiar.
The participants later heard the recordings of their singing while an fMRI machine scanned their brains. They were also exposed to a scent intended to boost their memory of listening to the recordings the next time they smelled it.
When asked to choose which emotions they felt after hearing the recording, the most frequent and intense feelings reported were embarrassment and shame. The initial fMRIs confirmed those emotions: As they listened to their out-of-tune singing, the participants’ amygdalae lit up with higher than normal activity. This almond-shaped structure in the brain is involved in processing emotions and is known to activate during emotionally distressing experiences.
Subsequently, the participants spent the night in the lab hooked up to electroencephalogram monitors. While they slept, the scientists wafted in their trigger smell, curious to see whether it would disrupt their sleep.
When the participants were brain scanned and exposed to the same song recordings the next morning, a trend emerged: The amygdalae of people who experienced fewer interruptions during rapid eye movement (REM) sleep reacted less strongly than they did the first time around. They felt less embarrassed than they did before. Meanwhile, the people who had fragmented REM sleep ended up feeling more embarrassed than they did on the first go.
As for the smells, when compared to the good REM sleepers and control subjects (people in the experiment who were not exposed to a smell), the embarrassment felt by the poor REM sleepers was exacerbated by experiencing the scent.
The team believes that the continuation of embarrassment stems back to the fact that fragmented REM sleep harms the amygdala’s ability to process emotional memories overnight.
Processing emotional memories requires synaptic connections to change — some have to be weakened, others strengthened. A chemical called noradrenaline strongly affects the balance between this weakening and strengthening. REM, van Someren explains, is a “very special state” because it is the “only state we have that provides a ‘time-out’ from noradrenaline.”
“People with very restless REM sleep may never enjoy this state anymore,” van Someren says. “It is likely that this has repercussions for the balance between weakening and strengthening of synapses, and thus affects overnight emotion regulation.”
In other words, for the majority of people, a night of good REM sleep helps alleviate whatever shame or distress was felt the day before. That doesn’t happen as efficiently when REM sleep is fragmented, and it can become a perpetuating issue. If distress doesn’t dissolve overnight, that can lead to another night of bad sleep, creating a cycle of poor sleep and feeling bad.
That state of existence describes the profile of people with insomnia, which van Someren hopes his research can help. He says that instead of focusing on examining sleep-regulating systems in the brain that have been derailed, his team’s study suggests that the better way to help insomniacs is to look for mechanisms in circuits that regulate emotional memory.
“We also hope that people start to realize that sleep is not always ‘the more the better,’ but that a maladaptive kind of sleep [one with bad REM] can exist,” he explains.
Restoring REM sleep through novel treatments could be one way of helping to halt this maladaptive sleep. Healthy sleep is central to overall health — and some distressing memories need help being scooted away from the foremost of your thoughts.
Animal studies show that insufficient silencing of the locus coeruleus (LC) during REM sleep impairs sleep-related brain plasticity. Restless REM sleep, a characteristic of several psychiatric disorders, likely reflects insufficient LC silencing. We investigated whether endogenous REM sleep interruptions interfere with overnight reorganization of limbic circuits in human volunteers with a wide range of insomnia severity, from no insomnia complaints to fulfilling community-sample criteria for insomnia disorder. We induced a self-conscious emotion during two functional MRI sessions and recorded sleep EEG in between. Amygdala reactivity decreased overnight in proportion to the total duration of consolidated REM sleep. Restless REM sleep, in contrast, impeded overnight amygdala adaptation. Using targeted memory reactivation with odors tagged to the self-conscious emotional stimulus, we could experimentally enhance both the favorable effect of consolidated REM sleep and the unfavorable effect of restless REM sleep. The findings reveal a maladaptive type of sleep, providing a target for interventions in mental disorders characterized by restless REM sleep.