Whats the purpose of dreamsthe experiences we feel while we sleep?
Neuroscience has shown that emotions felt during dreams help us resolve emotional distress and prepare for future affective reactions.
But whether fear in dreams links adaptive responses to threatening signals while we are awake is unclear.
Now, researchers have identified brain regions activated when experiencing fear in dreams. Notably, frightening dreams adjusted the response of these same regions to threatening stimuli during wakefulness.
These findings support that emotions in dreams and wakefulness engage similar brain regions. This physically links emotional processes occurring during sleep and emotional brain functions during wakefulness.
These results lay the groundwork for studying how sleep and dreaming influence therapies for psychological disorders, such as anxiety.
Evidence from human and animal research suggests functional links between sleep and emotional processing. Chronic sleep disruption can lead to increased aggressiveness and negative mood states, whereas affective disorders such as depression and posttraumatic stress disorder (PTSD) are frequently associated with sleep abnormalities, such as insomnia and nightmares.
Together these findings indicate that sleep physiology may offer a permissive condition for affective information to be reprocessed and reorganized. Yet, it remains unsettled whether such emotion regulation processes also happen at the subjective, experiential level during sleep, and maybe expressed in dreams.
Researchers have proposed that memories from a persons affective history are replayed in the virtual and safe environment of the dream so that they can be reorganized.
From a neuroscience perspective, one key principle of these models is that experiencing emotions in dreams implicates the same brain circuits as in wakefulness.
Like during wakefulness, people experience a large variety of emotions in their dreams. For example, rapid eye movement (REM) dreaming being usually more emotionally loaded than nonrapid eye movement (NREM) dreams.
While some studies found negative emotions like fear and anxiety in dreams, other studies reported a balance of positive and negative emotions or found that joy and emotions related to approach behaviors may prevail.
When analyzing large data sets of dream reports, a clear disconnection between dreams containing basic, mostly fearrelated emotions and dreams with other more social emotionssuch as embarrassment, excitement, and frustrationwas found. This highlights the distinct dream modes, with fear in dreams representing a prevalent and biologicallyrelevant emotional category.
So, if fearcontaining dreams serve an emotion regulation function, the stronger the recruitment of fearresponsive brain regionsthe amygdala, cingulate cortex, and insuladuring dreaming, the weaker the response of these same regions to actual feareliciting stimuli during wakefulness should be.
This regulatory mechanism may also be followed by enhanced recruitment of brain regions linked to regulating emotions during wakefulness, like the medial prefrontal cortex implicated in fear extinction.
Researchers had recently reported that specific dream contentssuch as faces, places, movement, speech, and thoughtsengage similar brain networks during wakefulness.
Yet two major questions remained. First, do emotions in dreamsin particular, fearrelated emotionsengage the same neural circuits as during wakefulness? Second, is there a link between emotions experienced in dreams and brain responses to emotional stimuli during wakefulness?
In a recent study, researchers collected dream reports and functional brain measures using imaging technology with sufficient accuracy for the detection of the signal originating from deep brain structures.
Here, for the first time, researchers have shown that fearrelated experiences activated the same brain region during both dreaming and awake consciousness.
This region, the insula, is thought to contribute to the social-emotional experience and linked visceral states, possibly giving rise to conscious feelings. The insula also participates in the emotional response to distressing thoughts or gut feelings.
Insula activation during dreaming could, therefore, reflect the integration of internally generated sensory, affective, and bodily information culminating in a subjective feeling of danger.
REM sleep is characterized by activation across brain regions linked to sensation and movement. Also, REM sleep is characterized by paralysis in muscle preventing movement. So, this sleep stage provides a proper condition for the activation of threatening situations with linked emotional and motor reactions.
During REM sleep, the researchers also found activation of a brain region critically involved in responses to dangers.
After finding the brain regions linking fear in dreams and wakefulness, the researchers then asked whether frequently experiencing fear in dreams might affect sensitivity to fear during wakefulness. They found decreased activity in the insula and amygdala, both associated with fear and the perception of negative emotions during wakefulness.
Conversely, activity was increased in the regions thought to regulate the response to threatening stimuli by modulating the activity of the fear-linked amygdala. Precisely, the medial prefrontal cortex prevents expressing fear by decreasing the amygdala output.
On top of that, the medial prefrontal cortex has been linked with extinction learningwhen a neutral conditioned stimulus that previously predicted an aversive unconditioned stimulus no longer does so and the conditioned response subsequently decreases.
Consistent with the suggestion that dreaming may regulate emotion, participants who frequently but not excessively experienced frightening dreams showed a stronger inhibition of the amygdala. This may be mediated by the medial prefrontal cortex.
This interpretation is further supported by the results showing that participants who frequently reported fear in their dreams had reduced autonomic responses to aversive stimuli during wakefulness. In total, this suggests a better ability to regulate defensive and alerting reactions to threatening signals in those individuals.
Contrasting with this potentially beneficial role of negative but benign dreams, recurrent nightmares could represent a failure of the fear extinction function of dreaming. So, patients with nightmares, like those with PTSD, would be more prone to emotional dysregulation.
Besides, exerting ineffective emotional regulation strategies, like fear suppression, and elevated anxiety during wakefulness may lead to increased excitability of negativelyloaded memories at sleeponset or even during sleep. Such disruption in the regulation of emotions during wakefulness and sleep has been proposed as a major contributing factor to insomnia.
The findings in this study show that, beyond sleeping, experiencing negative emotions during dreaming is linked to betteradapted emotional responses during waking life.
The researchers show opposing neural effects of fear experience in dreams and during wakefulness. These results show that individuals who reported a high prevalence of fearrelated emotions in their dreams had stronger fear inhibition during wakefulness.
These results also support claims that dreaming beyond sleep benefits emotion regulation processes by achieving overnight recalibration to foster adapted emotional responses to dangerous reallife events.
Studying the role of positive emotions like positive social interactions in dreams and their potential links with emotional brain responses during wakefulness may be needed to further refine existing models.
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Fears in dreams prepare you for threats while awake - Science 101