|A Ticklish Question|
|By Ellen Kuwana |
Neuroscience for Kids Staff Writer
December 5, 2000
"I'm Going to Tickle You!"When someone threatens to tickle you and then comes toward you with fingers extended, chances are you will burst out laughing, even if you haven't been tickled yet. Martin Ingvar and his team of researchers at the Karolinska Institute in Stockholm, Sweden, wanted to find out what your brain is doing when this happens. Using a brain scan called functional magnetic resonance imaging (fMRI), they compared brain images of what happens during an actual tickle with those of an anticipated tickle.
They found that an anticipated tickle activated the same areas of the brain as a real tickle. The main areas that "lit up" were the primary somatosensory cortex and secondary somatosensory cortex indicating that the brain appears to be able to predict what the sensation is going to be. Why might this be a good thing? Visualizing possible outcomes might speed up response time to potentially dangerous stimuli such as rapidly approaching objects and may be important for avoiding or catching objects.
Another Ticklish QuestionHave you wondered why you can't tickle yourself? This is the question that Sarah-Jayne Blakemore, Daniel Wolpert and Chris Frith researched at the Institute of Neurology, University College London in England. They used fMRI to peer into the brains of subjects while the people were tickling themselves or having their palms tickled by someone else.
Their results suggest that you can't tickle yourself because your brain predicts the tickle from information it already has about, say, your fingers moving. Certain areas of the brain including the secondary somatosensory cortex and the anterior cingulate cortex are less active when you tickle yourself. The people in the study also reported that they were much more "ticklish" when another person tickled them than when they tickled themselves. Another part of the brain, the cerebellum, also responded differently depending on where the touch originated (from self or from another person). The cerebellum controls balance and coordination, so it might be involved in predicting what effect movement of one part of the body has on other body parts.
Why Is This Research Important?Anytime scientists learn something about how the brain works normally, it sheds light on what might be happening when something goes wrong with the brain. In this case, information about how the brain distinguishes self-generated touch from touch generated externally could help unravel one of the mysteries of schizophrenia. Schizophrenics often have trouble distinguishing external events from self-generated ones. As Dr. Firth, a co-worker of Dr. Blakemore, explains it, there is a problem with self-monitoring. He gives an example of a person with schizophrenia:
"My fingers pick up the pen, but I don't control them. What they do has nothing to do with me."
People with schizophrenia often believe that they are being touched, even when no one is actually touching them. Some people with schizophrenia "hear voices" (auditory hallucinations) when in fact there is no one around.
To support this theory of a defect in self-monitoring in schizophrenics, Frith and colleagues compared patients who had symptoms of schizophrenia with patients who did not. The patients with no symptoms reported that they were much more "ticklish" when another person tickled them as compared with when they tickled themselves (this is consistent with reports from the study above). Those who had experienced auditory hallucinations and other symptoms of schizophrenia reported no difference in how ticklish they were -- they experienced the same degree of tickishness whether another person tickled them or when they tickled themselves!
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