And the brain scans revealed something that the experimenters found very interesting. Participants who had missed a night of sleep were dramatically affected by the images.
"The regions of the brain showed extensive reactivity to the emotionally positive pictures, and it was appearing in the classical reward centers of the brain largely regulated by the chemical dopamine, which is obviously associated with pleasure," Walker said. "It's as though the sleep-deprived brain swings equally in both emotional directions, the negative, and now the positive."
There was significantly less response in the brains of the sleepers.
While conceding that "it's good to enjoy life," Walker said he fears that the euphoria from too little sleep may contribute to various forms of addictive behavior, including drug abuse. Sleep disruption, he noted, is a common problem among drug abusers.
"If insufficient sleep sensitizes the reward networks, then that may, perhaps, predispose people to developing a strong addiction. It becomes a Catch-22," he added. "If they acquire an addiction disorder, that could disrupt their sleep, which could encourage them to take more drugs, and lose more sleep."
Walker has been preaching for years that most of us don't get enough sleep, and yet research in his and many other labs shows that anything less than eight hours can contribute to ineptitude. That's a serious problem in some professions, and he specifically cited military, aviation, and medicine -- three fields where irregular sleep patterns are routine.
"When functioning correctly, the brain finds the sweet spot on the mood spectrum," Walker said. "But the sleep-deprived brain will swing to both extremes, neither of which is optimal for making wise decisions."
Too little of it can make us cranky, difficult, and, it now seems, giddy.