Neuroscience
The perfect excuse for a siesta! People who stay awake throughout the day become progressively more sensitive to negative emotions. In contrast, those who take an afternoon nap are desensitised to negative emotions yet more responsive to positive ones. The new finding builds on past research by showing that not only does sleep deprivation cause emotional problems, a sleep boost can bring emotional advantages.
Ninad Gujar and his colleagues tested 36 participants (half were male; average age 21) on a face processing task, once at 12pm and then again at 5pm. Half the participants were given a 90-minute napping opportunity after the first task, whilst the others just went about their day as usual.
The task involved the participants looking at a computer screen that showed a male face pulling fearful, sad, angry and happy expressions at various intensities. The participants' goal quite simply was to rate each presentation of the face for intensity on a scale from 1 (definitely neutral) to 4 (mostly happy/sad etc).
For participants who stayed awake through the afternoon, their performance at 5pm, compared with at 12pm, demonstrated heightened sensitivity to fearful and angry facial expressions. By contrast, the participants who'd had a nap were less sensitive to fearful expressions at 5pm yet more sensitive to happy expressions. These emotional processing changes were also accompanied by mood differences: the no-nap group reported less positive mood later in the afternoon, compared with earlier, whereas the nap-group reported a decrease in negative mood.
The emotional processing changes observed among the nap-group were related to rapid-eye-movement (REM) sleep. EEG recordings taken while the nappers slept showed that those who obtained REM sleep were more likely to show the desensitisation to negative emotions and sensitisation to positive ones.
An alternative interpretation of the results is that napping affects visual processing, not emotional sensitivity. But the researchers don't think this stands up to much scrutiny, since any basic visual processing effects ought to have been uniform across the different emotions.
So, assuming the emotional sensitivity account is true, why might the non-napping participants have become more sensitive to negative emotions? One possibility, which is backed up by sleep deprivation research, is that the prefrontal cortex becomes fatigued through the day and therefore less able to dampen down emotional reactivity in the sub-cortex. Alternatively, perhaps heightened sensitivity to fear and anger is adaptive - as we fatigue through the day, it makes sense that we should become more vigilant towards these danger-based signals. Either way, a brief nap appears to give us an emotional recharge, altering the way we respond to other people's facial expressions. The implications for working practices are obvious.
'These data add to a growing collection of findings indicating a regulatory role for sleep in the optimal homeostasis of emotional brain function,' the researchers said, 'which if disrupted may have detrimental contributions to clinical symptomotology in affective disorders.'
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Gujar, N., McDonald, S., Nishida, M., and Walker, M. (2010). A Role for REM Sleep in Recalibrating the Sensitivity of the Human Brain to Specific Emotions. Cerebral Cortex, 21 (1), 115-123 DOI: 10.1093/cercor/bhq064
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.
Earlier on the Digest: How to nap
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- Violent Video Games Slow Our Processing Of Happy Faces
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Neuroscience
An afternoon nap tunes out negative emotions, tunes in positive ones
Ninad Gujar and his colleagues tested 36 participants (half were male; average age 21) on a face processing task, once at 12pm and then again at 5pm. Half the participants were given a 90-minute napping opportunity after the first task, whilst the others just went about their day as usual.
The task involved the participants looking at a computer screen that showed a male face pulling fearful, sad, angry and happy expressions at various intensities. The participants' goal quite simply was to rate each presentation of the face for intensity on a scale from 1 (definitely neutral) to 4 (mostly happy/sad etc).
For participants who stayed awake through the afternoon, their performance at 5pm, compared with at 12pm, demonstrated heightened sensitivity to fearful and angry facial expressions. By contrast, the participants who'd had a nap were less sensitive to fearful expressions at 5pm yet more sensitive to happy expressions. These emotional processing changes were also accompanied by mood differences: the no-nap group reported less positive mood later in the afternoon, compared with earlier, whereas the nap-group reported a decrease in negative mood.
The emotional processing changes observed among the nap-group were related to rapid-eye-movement (REM) sleep. EEG recordings taken while the nappers slept showed that those who obtained REM sleep were more likely to show the desensitisation to negative emotions and sensitisation to positive ones.
An alternative interpretation of the results is that napping affects visual processing, not emotional sensitivity. But the researchers don't think this stands up to much scrutiny, since any basic visual processing effects ought to have been uniform across the different emotions.
So, assuming the emotional sensitivity account is true, why might the non-napping participants have become more sensitive to negative emotions? One possibility, which is backed up by sleep deprivation research, is that the prefrontal cortex becomes fatigued through the day and therefore less able to dampen down emotional reactivity in the sub-cortex. Alternatively, perhaps heightened sensitivity to fear and anger is adaptive - as we fatigue through the day, it makes sense that we should become more vigilant towards these danger-based signals. Either way, a brief nap appears to give us an emotional recharge, altering the way we respond to other people's facial expressions. The implications for working practices are obvious.
'These data add to a growing collection of findings indicating a regulatory role for sleep in the optimal homeostasis of emotional brain function,' the researchers said, 'which if disrupted may have detrimental contributions to clinical symptomotology in affective disorders.'
_________________________________
Gujar, N., McDonald, S., Nishida, M., and Walker, M. (2010). A Role for REM Sleep in Recalibrating the Sensitivity of the Human Brain to Specific Emotions. Cerebral Cortex, 21 (1), 115-123 DOI: 10.1093/cercor/bhq064Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.
Earlier on the Digest: How to nap
- Extras
Eye-catching studies that didn't make the final cut: Women's brains change in size across the menstrual cycle. Do positive children become positive adults? Reminders of death lead people to want to name their children after themselves. 10- to...
- Violent Video Games Slow Our Processing Of Happy Faces
Just 15 minutes playing a violent video game can lend a negative bias to the way we interpret people's facial expressions. Steven Kirsh and Jeffrey Mounts at SUNY-Guneseo in New York asked 197 students to play either 15 minutes of the violent House...
- Students: It's Time To Ditch The Pre-exam All-nighter
Lack of sleep impairs the human brain's ability to store new information in memory, researchers have found. Past research has already shown that sleep is vital for consolidating recently-learned material but now Matthew Walker and colleagues have...
- Of Cats And Basketball Players - How We're Better At Recognising The Emotions Of Those We Identify With
Just as we’re better at recognising people who share our ethnicity, we are also better at interpreting the emotional facial expressions of people from the same ethnic, national, or regional group as ourselves. Pascal Thibault and colleagues at the University...
- Neuroscience & Real Life
Interesting application of neuroscience to real life over at the Creating Passionate Users blog. Angry/negative people can be bad for your brain. Kathy Sierra posted (almost a year ago; I'm slow sometimes) three reasons why it's good to avoid...