Sleep eases pain and anxiety in the brain
The neuroscience of sleep helps explain how sleep helps us learn and forget. It also sheds light on sleep’s pain-relieving and anti-anxiety effects.
For example, a study published last year found that a brain area associated with pain sensitivity (called the somatosensory cortex) is hyperactive in sleep-deprived participants. The findings suggested that not getting enough sleep interferes with the brain’s pain-processing neural circuits.
Additionally, the same study found that activity in the nucleus accumbent area of the brain had dropped after a sleepless night. The nucleus acumens releases the neurotransmitter dopamine, which heightens feelings of pleasure and decreases sensations of pain.
“Sleep loss not only amplifies the pain-sensing regions in the brain but blocks the natural analgesia centers, too,” explains the senior study author Matthew Walker, a professor of neuroscience and psychology at the University of California in Berkeley.
The team also found that the brain’s insula, which evaluates pain signals and prepares the pain response, was also underactive in sleep-deprived people.
Sleeplessness interferes with this “critical neural system that assesses and categorizes the pain signals and allows the body’s natural painkillers to come to the rescue,” notes Adam Krause, the study’s lead author.
Deep sleep relieves anxiety in key brain region
As to the anxiolytic effects of sleep, functional MRI scans and polysomnograms have shown that the medial prefrontal cortex in the brain is key. This region deactivated after a sleepless night in some studies co-led by the same Prof. Walker.
Previous research suggests that the medial prefrontal cortex helps calm anxiety and reduce stress levels. In Prof. Walker’s research, other regions associated with processing emotions were hyperactive in sleep-deprived patients.
“Without sleep,” Prof. Walker explains, “it’s almost as if the brain is too heavy on the emotional accelerator pedal, without enough brake.” A sleepless night caused anxiety levels to spike by up to 30% in their study, report the scientists.
Furthermore, the study found that anxiety levels dropped after a full night of sleep and that this decrease was even sharper in participants who spent more time in the deep non-REM stage of sleep.
“Deep sleep had restored the brain’s prefrontal mechanism that regulates our emotions, lowering emotional and physiological reactivity, and preventing the escalation of anxiety.”
– Eti Ben Simon, study co-author