Could sleepless nights of terror be good for you?

Lying awake and listening for demonic footsteps after Paranormal Activity 4 may turn out to be more helpful to your mental health than trying to fall asleep. A study published earlier this month in PLOS ONE shows that losing sleep can prevent frightening memories from taking hold in the brain, at least in rats.

A good night’s sleep has many advantages, including improving our ability to recollect facts or learned motor skills. Losing sleep impairs these kinds of memory, but the impact of sleep deprivation on other kinds of memory, such as that of traumatic events, is still poorly understood.

In this study the authors Tankesh Kumar and Sushil Jha, found that when rats were trained to develop a conditioned fear response to a sound they heard, this response was twice as strong in rats that slept for six hours after the training than in those that stayed awake for this period of time. According to the authors, this result suggests that the rats that stayed awake hadn’t learned to be afraid of the sound as well as the better-rested animals had.

Despite the ill effects of sleep deprivation and associated poor memory under other circumstances, the authors suggest that losing sleep after a traumatic event can actually help prevent fearful memories from taking hold in the brain, potentially providing long-term benefits like reducing the risk of post-traumatic stress disorder (PTSD) or anxiety disorders.

Related PLOS ONE research published last year studied the effects of a similar, odor-induced fear conditioning exercise in rats, and observed changes in brain activity during sleep following the exercise. The researchers also found that these changes correlated with the strength of the fear response observed in rats the next day.

If that scary movie is still keeping you awake, read more PLOS ONE research about how dolphins can go 15 days sleeping with only half of their brain, how ostriches sleep like platypus, or the sleep behavior of the most mysterious creature of them all, the human teenager.


Citations: Kumar T, Jha SK (2012) Sleep Deprivation Impairs Consolidation of Cued Fear Memory in Rats. PLoS ONE 7(10): e47042. doi:10.1371/journal.pone.0047042

Barnes DC, Chapuis J, Chaudhury D, Wilson DA (2011) Odor Fear Conditioning Modifies Piriform Cortex Local Field Potentials Both during Conditioning and during Post-Conditioning Sleep. PLoS ONE 6(3): e18130. doi:10.1371/journal.pone.0018130

Image: another rat by asplosh on Flickr, CC-by license 

Factoring in fear: what scares us most?

Maybe you’ve seen a ghost, or been told the house in this picture is haunted, or watched enough scary movies to associate houses like this with spooks.

But which of these three is the most likely to scare you away? A study published early this week in PLOS ONE suggests any of the three could keep you from stepping in.

Fear is a conditioned response, meaning that we learn to be afraid through a variety of mechanisms, including past experiences, direct instruction, and learned associations. There’s little evidence, though, to show whether one kind of conditioning is stronger than the other.

The authors of this study addressed this question by investigating whether people avoided threats differently depending on how they had learned about them: by direct exposure to the threat, verbal instruction about the threat, or a ‘derived generalization’ that they learned to associate with the threat.

In the first case, participants were trained to associate circles of specific colors with mild electric shocks, a direct exposure to the “threat”. A second group of participants was told verbally that when circles of specific colors appeared on a screen, they would receive a mild shock. A third group of participants were first trained to associate nonsense words with circles of specific colors, and then tested for how strongly they associated the words with the possibility of a shock. Participants were then informed that if they pressed a certain button in response to seeing a color associated with shock, they could avert the unpleasant experience. The study found that, regardless of how the participants had learned to associate the colors or words with the shock, all three groups avoided the unpleasant experience to the same extent.

However, the researchers found differences in the avoidance behavior of groups during the learning period. For example, they found that people who received a verbal warning that certain colors would cause shocks rated the probability of a shock higher in the last phase than the group that had made ‘derived associations’ between words, circles and the possibility of a shock. Why these differences occurred wasn’t clear from this study, the researchers say, but their observations do imply that verbal warning can have a powerful effect on behavior.  Their results may also point to ways that unpleasantness and fear can be associated with certain activities more strongly (or weakly).

Fear conditioning is useful when making decisions about, say, whether to enter a spooky building, but extreme forms of avoidance can lead to severe clinical conditions like anxiety disorders that can hinder day-to-day activities. Previous research shows that anxiety disorders tend to be associated with stronger fear conditioning, and direct contact with an unpleasant event isn’t necessarily required for this conditioning to grow stronger. For example, people with social anxiety disorder tend to avoid large gatherings even though their experience of these may be fairly limited. Studies such as this one could help understand how we learn to avoid stimuli that are perceived as unpleasant even in the absence of repeated exposure, and perhaps eventually point to ways that we could overcome some fears.

Citation: Dymond S, Schlund MW, Roche B, De Houwer J, Freegard GP (2012) Safe From Harm: Learned, Instructed, and Symbolic Generalization Pathways of Human Threat-Avoidance. PLoS ONE 7(10): e47539. doi:10.1371/journal.pone.0047539 

Image Credit: wilsx4 on Flickr CC-by license