November 01, 2009
Sleep Deprivation Cut Mental Function

The brain downshifts to simpler ways of processing information when lacking sleep.

Westchester, Ill. A study in the Nov.1 issue of the journal Sleep shows that sleep deprivation causes some people to shift from a more automatic, implicit process of information categorization (information-integration) to a more controlled, explicit process (rule-based). This use of rule-based strategies in a task in which information-integration strategies are optimal can lead to potentially devastating errors when quick and accurate categorization is fundamental to survival.

The experimental subjects were West Point cadets. So they were at similar ages, pretty healthy, and smarter than the average population. The decay here is an average. I would be curious to know what the outliers looked like. Likely a subset suffered more severe cognitive decay when sleep-deprived.

Results show that sleep deprivation led to an overall performance deficit on an information-integration category learning task that was held over the course of two days. Performance improved in the control group by 4.3 percent from the end of day one to the beginning of day two (accuracy increased from 74 percent to 78.3 percent); performance in the sleep-deprived group declined by 2.4 percent (accuracy decreased from 73.1 percent to 70.7 percent) from the end of day one to the beginning of day two.

According to co-principal investigators W. Todd Maddox, PhD, professor of psychology, and David M. Schnyer, PhD, associate professor of psychology at the Institute for Neuroscience at the University of Texas in Austin, fast and accurate categorization is critical in situations that could become a matter of life or death. However, categorization may become compromised in people who often experience sleep deprivation in fast-paced, high pressure roles such as doctors, firefighters, soldiers and even parents. Many tasks performed on a daily basis require information-integration processing rather than rule-based categorization. Examples include driving, making a medical diagnosis and performing air-traffic control.

It would be useful to know for each person how rapidly their brain function deteriorates with lack of sleep. Even more useful: an easily administered sleep impairment test that would let one know whether one is currently sleep impaired and if so by how much. Think of it as akin to an alcohol breath test to determine whether you are safe to drive. Some who is both sleep impaired and alcohol impaired especially ought not drive.

Here's the part I find especially interesting: Not all of the sleep-deprived subjects shifted to rules-based strategies for processing information. Would a more severe degree of sleep deprivation eventually cause everyone to shift to less effective approaches for cognitive processing?

Maddox and Schnyer were surprised to find that the source of the information-integration deficit was a subgroup of sleep-deprived individuals who shifted from information-integration strategies when rested to rule-based strategies when sleep deprived. Sleep-deprived participants who used information-integration strategies in both sessions showed no drop in performance in the second session, mirroring the behavior of control participants.

A brain scan that measures white matter distribution might provide predictive results over how each person's brain will respond to sleep deprivation.

The study cites previous research suggesting that differences in cortical white matter predict cognitive vulnerability to the effects of sleep deprivation.

What I want: a watch that would let me know with a sliding bar or color coding just how sleep-deprived I am at the moment. While I'm wishing: the watch also ought to tell me about nutrient deficiencies detected by nanosensors embedded in my body. When will we get such a capability? 2020? 2025?

Share |      Randall Parker, 2009 November 01 03:25 PM  Brain Sleep

RBL said at November 1, 2009 7:10 PM:

Good thing you're trying to stay healthy. If you get sick, you'll check in to the hospital, where you'll be attended by sleep-deprived residents working the industry-standard 80 hour work week.

RobQ said at November 4, 2009 7:00 PM:

I think you hit on an important point - it's hard to tell when you're sleep deprived. There are definitely times when I can say to myself "I'm not as smart as I was yesterday", and yet I can't tell in what ways. Things just aren't clicking. But I can tell. It's when I'm in the middle ground that I'm not so sure. When I'm well rested I make great progress at work. It's so wonderful that for a while I don't have trouble going to bed early. And yet, somehow I slip, back to pushing the line on too little sleep. In the trade off between lots of so-so time vs a little super-smart time, I chose the lots of time answer.

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