Using MRI scans, researchers have discovered how sleep deprivation can impact the parts of the brain where food-related choices are made, potentially explaining how obesity is linked to a lack of slumber.
The study, which was presented at SLEEP 2012
, the 26th annual meeting of the Associated Professional Sleep Societies (APSS), on Sunday, used functional magnetic resonance imaging (fMRI) to study the brain waves of 23 otherwise healthy adults, according to the American Academy of Sleep Medicine
Subjects were divided into two groups: one of which received a normal night's sleep, and one of which were sleep deprived for an evening. Afterwards, participants in each group rated how much they craved specific food items while inside the fMRI scanner. The study showed that the sleep deprived subjects demonstrated impaired brain activity in their frontal lobe, a region described as "critical" for behavior control and making complex choices, suggesting that sleep loss could adversely impact the food choices that people make.
"Our goal was to see if specific regions of the brain associated with food processing were disrupted by sleep deprivation," lead author Stephanie Greer, a graduate student at the Sleep and Neuroimaging Laboratory at the University of California, Berkeley
, said in a statement.
She added that the researchers "did not find significant differences following sleep deprivation in brain areas traditionally associated with basic reward reactivity... Instead, it seems to be about the regions higher up in the brain, specifically within the frontal lobe, failing to integrate all the different signals that help us normally make wise choices about what we should eat."
A similar study, conducted by St. Luke's - Roosevelt Hospital Center
and Columbia University
, likewise conducted fMRI tests on 25 men and women of average weight, some of whom had received just four hours of sleep while others were permitted nine hours of slumber. Afterwards, each were shown images of both healthy and unhealthy food.
"The same brain regions activated when unhealthy foods were presented were not involved when we presented healthy foods," principal investigator Dr. Marie-Pierre St-Onge said in a statement Sunday. "The unhealthy food response was a neuronal pattern specific to restricted sleep. This may suggest greater propensity to succumb to unhealthy foods when one is sleep restricted."
"The results suggest that, under restricted sleep, individuals will find unhealthy foods highly salient and rewarding, which may lead to greater consumption of those foods," St-Onge added. "Indeed, food intake data from this same study showed that participants ate more overall and consumed more fat after a period of sleep restriction compared to regular sleep. The brain imaging data provided the neurocognitive basis for those results."
The Sleep and Neuroimaging Laboratory at the University of California, Berkeley also determined, using fMRI scans, that sleep loss can also heighten a person's level of anxiety. As part of this study, they scanned the brains of 18 subjects, some of whom had slept normally and some of whom were sleep deprived.
"During both sessions, participants were exposed to an emotional task that involved a period of anticipating a potentially negative experience (an unpleasant visual image) or a potentially benign experience (a neutral visual image)," the American Academy of Sleep Medicine announced in a June 10 media release.
"The fMRI scans showed that sleep deprivation significantly amplified the build-up of anticipatory activity in deep emotional brain centers, especially the amygdala, a part of the brain associated with responding to negative and unpleasant experiences," they added. "In some of these emotional centers of the brain, sleep deprivation detrimentally triggered an increase in anticipatory reaction by more than 60 percent."
Furthermore, they discovered that the impact of that sleep deprivation was relative to a person's natural levels of anxiety - i.e., that individuals who tended to be more anxious in general were also most vulnerable to the effects caused by a lack of sleep. These results, the researchers explain, suggest that anxiety could enhance the "emotional dysfunction and risk" normally linked with inadequate rest.
"Anticipation is a fundamental brain process, a common survival mechanism across numerous species," lead author Andrea Goldstein said. "Our results suggest that just one night of sleep loss significantly alters the optimal functioning of this essential brain process, especially among anxious individuals. This is perhaps never more relevant considering the continued erosion of sleep time that continues to occur across society."