Recent studies shed light on how sleep deprivation affects brain structure and function.
Even if we don’t suffer from a sleep disorder, sleep is often the first thing that gets cut back to make room on our schedules. However, the consequences of lack of sleep on the brain are serious and far-ranging. This is especially true for those that suffer from chronic insomnia.
It is now widely known that the brain is not a static organ, but more like a dynamic ecosystem, changing both structure and function in response to experience (known as neuroplasticity). Recent studies indicate that sleep deprivation creates network-wide changes in brain structure and function that may account for the negative cognitive and emotional effects.
Sleep deprivation associated with heightened activity in the motor cortex
One study from 2014 demonstrated that people with chronic insomnia showed more plasticity and activity than good sleepers in the part of the brain that controls movement, the motor cortex. They also found more neural excitability in this brain region relative to controls, suggesting that the brain of chronic insomniacs is in a state of heightened informational processing in some regions. However, the actual experience of sleep deprivation can feel like information processing is delayed, with selective attention markedly reduced.
Emotional dysregulation found in sleep-deprived individuals
This is further supported by a study where researchers put sleep-deprived volunteers in an fMRI (functional magnetic resonance imaging) scanner and showed them distressing videos. Those with a previous night of no sleep had significantly more activity in the amygdala and dorsal anterior cingulate cortex, both regions of the brain involved in emotion generation. Chronic hyperactivity in these brain regions associated with long-term insomnia greatly increases the risk of developing an anxiety disorder.
The participants also had reduced activity in the medial prefrontal cortex, a region of the brain known to help control negative emotions. This could explain why chronic sleep deprivation is associated with personality characteristics like reduced patience and flexibility, irritability, and poorer communication.
Sleep deprivation associated with disruption of working memory
Sleep deprivation is also closely linked to poor concentration, and a recent study investigated the neural correlates behind this. In this study, researchers used fMRI to study the working memory of 25 people with primary insomnia and 25 good sleepers. The insomniacs were found to be unable to turn on brain regions critical to a working memory task and did not turn off the ‘mind-wandering’ brain regions irrelevant to the task (known as the default mode network). In fact, the longer the period of sleep deprivation, the worst the accumulating attention deficit. Behavioural consequences of these neural changes of the DMN are reflected in deficiencies in attending to one specific stimulus while ignoring distractors.
This could explain why meditation can be helpful for insomniacs, as meditation has been shown to decrease activity in the default mode network, the region of the brain associated with mind wandering, as well as detecting stimuli in one’s environment and ruminative thinking.
Sleep deprivation associated with reduced cortical grey matter
Structural changes in the brain are also associated with poor sleep quality. A 2014 study found a correlation between poor sleep and reduced grey matter volume in the brain’s frontal lobe, an area crucial to working memory and executive function. However, as is the case in all correlational studies, it is difficult to know whether grey matter deficits are linked causally to insomnia, or are a pre-existing abnormality in the volunteers.