Weekly science column

Here’s this week’s science column, just a trifle later than usual…


Edward Willett

Why we make mistakes

The holidays are supposed to be a time of rest and relaxation, but if you’re like me, after several nights of parties, you feel pretty much as sleep-deprived as you did before the holidays, if not more so.

Also if you’re like me, when you get tired you begin to make more miksates–er, mistakes, ranging from typographical errors (which is what I notice most) to potentially disastrous errors in judgment while operating a nuclear reactor (not a problem for me personally, I hasten to assure my neighbors).

A new study by researchers at Cambridge University has shed some light on these kinds of mistakes.

In the study, volunteers took part in a 10-minute test in which they were shown random numbers on a computer screen approximately once per second. Every time they saw a number, they clicked the mouse button–unless they saw the number three, in which case they were not to click. While this was going on, the volunteers’ brainwaves were being monitored.

The researchers discovered that the volunteers were more likely to make a mistake following a drop in levels of a brainwave labeled P300. In other words, the kind of simple slip-ups we all make from time to time, but especially when we’re sleep-deprived or our body clocks are screwed up from jet lag or shift work, are a result of the failure of our brains to produce a high enough level of the P300 brainwave to generate a response.

The brain generates the P300 brainwave about a third of a second after a sensory stimulus of some kind. For example, if you’re driving your car and someone steps off the curb in front of you, the eye transmits the image to your brain, which sends out the P300 brainwave a third of a second later. If that P300 brainwave isn’t as strong as it should be, it may not generate the necessary physical response (“Slam on the brakes!”) and the unwary pedestrian may pay the penalty.

The Cambridge scientists are now pursuing their research with patients suffering from sleep disorders and children who suffer from attention disorders and poor performance at school. On a practical level, they say it might be possible to measure P300 levels with simple electrode pads on the skull, which would give an indication as to how likely someone is to make mistakes–and whether that someone should be allowed to operate a vehicle–or a nuclear reactor. (They could call it the “brainalyzer” instead of the “breathalyzer”.)

The importance of sleep to the proper operation of the brain was brought home by another study earlier this year, in which researchers from the University of Pennsylvania found that for mice, at least, the best way to make sense of new information is to–just as the old adage has it–“sleep on it.”

The scientists used mild electric shocks to generate fear in mice. Some were placed in a distinctive setting just before receiving the shock, so they would learn to fear that setting; others heard a tone shortly before a shock was administered, so they would learn to fear that tone.

The mice were put back in the same situations 24 hours later, then watched to see which of them froze–an indication that they recognized the situation and were afraid of getting shocked again. The researchers found that mice exposed to the audible tone, then deprived of sleep, remained fearful the next day, whereas mice placed in a distinctive setting, then deprived of sleep, were less likely to be fearful the next day. This suggests that sleep is important to the consolidation of what’s called contextual memory (memory of spatial orientation and recognition of physical surroundings) whereas sleep deprivation doesn’t affect cued memory (recollection of specific facts or events–such as hearing a particular tone) in the same way.

By varying when the sleep deprivation took place, the researchers were also able to pinpoint the window during which the mice needed to sleep for optimal learning. They found that the five hours following learning were the crucial period. Mice deprived of sleep during those five hours suffered learning impairment, while sleep deprivation from five to 10 hours after the learning experience did not impair learning. No similar studies have yet been carried out on humans.

A lucky few people emerge from the holidays not only sleep-deprived, but in love. No studies I’m aware of blame falling in love on lack of sleep, but there is new research providing insight into the neurobiological basis of feelings of intense romantic love.

Unfortunately, you’ll have to wait for my Valentine’s Day column to find out about it. In the meantime, get some sleep.

Permanent link to this article: https://edwardwillett.com/2004/01/weekly-science-column/

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