Sleep deprivation can affect your ability to make sense of what you see, according to a new study by neuroscience researchers at the Duke-NUS Graduate Medical School in Singapore.
Using MRI to measure blood flow in the brains of volunteers, the researchers found that even after sleep deprivation, participants had periods of near-normal brain function in which they were able to complete tasks quickly.
However, periods of slow response and severe declines in visual processing were mixed in with these periods of normalcy.
"Interestingly, the team found that a sleep-deprived brain can normally process simple visuals, like flashing checkerboards. But the 'higher visual areas' - those that are responsible for making sense of what we see - didn't function well," said Dr. Michael Chee, lead author and professor at the Neurobehavioral Disorders Program at Duke-NUS.
"Herein lies the peril of sleep deprivation," he added.
The research team, including colleagues at the University of Michigan and University of Pennsylvania, used magnetic resonance imaging to measure blood flow in the brain during speedy normal responses and slow "lapse" responses.
Study subjects were asked to identify letters flashing briefly in front of them. They saw either a large H or S, and each was made up of smaller Hs or Ss. Sometimes the large letter matched the smaller letters; sometimes they didn't. Scientists asked the volunteers to identify either the smaller or the larger letters by pushing one of two buttons.
During slow responses, sleep-deprived volunteers had dramatic decreases in their higher visual cortex activity. At the same time, as expected, their frontal and parietal 'control regions' were less able to make their usual corrections.
Scientists also could see brief failures in the control regions during the rare lapses that volunteers had after a normal night's sleep. However, the failures in visual processing were specific only to lapses that occurred during sleep deprivation.
The scientists theorize that this sputtering along of cognition during sleep deprivation shows the competing effects of trying to stay awake while the brain is shutting things down for sleep.
The brain ordinarily becomes less responsive to sensory stimuli during sleep, Chee said.
This study has implications for a whole range of people who have to struggle through night work, from truckers to on-call doctors.
"The periods of apparently normal functioning could give a false sense of competency and security when in fact, the brain's inconsistency could have dire consequences," Chee said.
"The study task appeared simple, but as we showed in previous work, you can't effectively memorize or process what you see if your brain isn't capturing that information.
"The next step in our work is to see what we might do to improve things, besides just offering coffee, now that we have a better idea where the weak links in the system are," he added.
The study is published in the Journal of Neuroscience on May 21.