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- Lying awake all night is known to have a negative impact on our mental health
- Researchers found that limited sleep may, however, be even worse
- Limited sleep activates fear in the brain, which can be problematic for people with fear-related disorders
Sleep deprivation is known for causing harm to our mental state, like disrupted learning and memory, which highlights the importance of getting enough sleep for memory retention.
Fear conditioning is one of the reasons why memory and learning are important. Fear conditioning is a behavioural model which allows humans (and animals) to learn to predict aversive events. Recently, researchers found that getting only a restricted amount of sleep affects the brain’s ability to unlearn fear-related memories.
Fear conditioning experiments
A team of researchers, led by Anne Germain (from the Department of Psychiatry at University of Pittsburgh), conducted a study which aimed to assess the impact of total and partial sleep loss on fear conditioning and extinction learning (a gradual decrease in conditioned response) in the brain.
The experiment was conducted in a sleep laboratory and involved 150 healthy adults who were divided into three groups: one-third who got to sleep normally throughout the night, one-third who slept only half the night and a third who did not sleep at all.
One of the co-authors, Dr Pace-Schott, explains: “Our team used a three-phase experimental model for the acquisition and overcoming of fearful memories while their brains were scanned using functional magnetic resonance imaging.”
In order to condition participants, they were shown three colours of which two were accompanied by mild shocks. After conditioning, participants partook in the fear extinction part of the experiment, where only one of the colours was shown without any shock. This was done to show participants that it was now safe.
In the final part of the experiment, researchers examined the brain activity of the subjects when they were presented with the colours they were shown earlier.
Limited sleep worse than no sleep
In people who got normal sleep, brain imaging showed that areas responsible for emotional regulation were activated. Conversely, in people who got restricted sleep, brain imaging showed the least activity in the area of the brain that controls emotion, and that areas associated with fear were triggered instead.
Interestingly, brain activity in people who were sleep-deprived looked similar to those who were well-rested. This finding indicates that being sleep-deprived may be better than sleeping for a limited time, especially in those who suffer from fear-related disorders such as anxiety and posttraumatic stress disorder.
Researchers also warned that individuals in professions that are often paired with limited sleep – like medical and military staff – should be aware of the psychological effects of restricted sleep.
