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5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
- About Us
Nerves Beat to Own Uneven Drum
18 October 1996 8:00 pm
You might think there's little that's random about the start of a 100-meter race. But the time it takes an individual sprinter to react to the starting gun can vary randomly by up to a tenth of a second. Now scientists have a better understanding of why it's impossible for sprinters--or anybody else--to control reaction times precisely: Individual nerve cells that govern reactions vary in how long it takes them to prod you into action, says a report in today's issue of Science.
In the study, neuroscientist Jeffrey Schall of Vanderbilt University and grad student Doug Hanes trained monkeys to do a reaction-time task in which the animals fix their eyes on a dot in the middle of a blank computer screen and, when that dot disappears and another appears to the right or the left, shift their gaze to the new dot. The researchers recorded the firing of single neurons in a brain region that controls eye movements.
In hundreds of trials, the monkeys' reaction times varied from roughly 150 to 400 milliseconds, and the response time depended on how fast the neurons increased their firing rate to a level that seemed to trigger the eye movement. It's as if a bucket must be filled to the brim for a response to occur, but the water flow is different every time you turn on the tap, says Schall. ``To see [this variability] at a single-cell level is really incredible,'' says Gordon Logan, a psychologist at the University of Illinois, Urbana-Champaign.
The new view of a neural threshold for reactions might just improve the understanding of certain neurological conditions. For example, Parkinson's patients have slowed reaction times in eye-movement tests, something that could arise, says Schall, if ``the threshold has been raised to a higher level, or the cells accumulate activity abnormally slowly.''