May 22, 2008
Sleep Deprivation and Visual Perception
Neuroscience researchers in Singapore have shown for the first time what happens to the visual perceptions of healthy but sleep-deprived volunteers who fight to stay awake, like people who try to drive through the night.
A study published in the Journal of Neuroscience found that even after sleep deprivation, people had periods of near-normal brain function in which they could finish tasks quickly. However, this normalcy mixed with periods of slow response and severe drops in visual processing and attention.
The scientists 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, "Herein lies the peril of sleep deprivation."
The research team from Duke-NUS Graduate Medical School in Singapore and 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 research team 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.
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," lead author Chee said.
Journal of Neuroscience Abstract