Biology / Thought

Tickle me schizophrenic


Watch out for the schizophrenics” by daniestrydom

By Julian Pearce

You may be sitting around alone, punching yourself in the crotch, or maybe you’re tickling your own armpit and you wonder why it just doesn’t feel the same as when someone else is doing it to you. Well, according to some fascinating new research, this may be a neurological process we come hard-wired with.

This intriguing hypothesis comes from a study by the Institute of Cognitive Neuroscience at University College London, which postulates this process may be located in an area of the brain named the cerebellum. This brain structure, which is involved in monitoring movements of the body, may in fact predict sensations when your own body causes them, but not when others do.

Sarah-Jane Blakemore, a research fellow at the Institute of Cognitive Neuroscience explains, “When you try to tickle yourself, the cerebellum predicts the sensation and this prediction is used to cancel the response of other brain areas to the tickle.”

It has been shown that brain areas involved in sensation — such as the somatosensory cortex, which processes touch, and the anterior cingulate cortex, which processes ‘pleasant’ information — are less active when self-tickling.

Other research has suggested that our brains may reduce the sensation of our own actions in order to increase the sensation of alien force, such as someone touching your ear lobe. Neuroscientist Daniel Wolpert and colleagues developed what is known as the “tit-for-tat” test, which used two robotic levers capable of applying force and recording the amount of force applied to them.

This study recruited pairs of subjects and had them face each other, with the levers placed between them. Participants placed their right index finger on one of the levers and their left index finger in a mold beneath the other. A lever separated each subject’s right index finger from their partner’s left. When one subject pushed down on a lever with their right finger, the lever applied a force to their partner’s left. The second subject could then reciprocate. The levers recorded the forces each subject applied as the game progressed. Subjects were told to push back with the same amount of force and no more—tit-for-tat.

Results showed that all subjects retaliated with an increased force over time. In other words, they detected more force than there actually was. However, when participants carried out the experiment alone, that is, they applied force to themselves, it was found that in order to feel greater force, subjects would push on the button harder, regardless of how little or how much force the robot inflicted. This led Wolpert and his colleagues to suggest we may indeed possess a neurological process, whose main purpose is to dull the sensation of our own movements.

“…[Our] brains may reduce the sensation of our own actions in order to increase the sensation of alien force”


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But what happens if this process doesn’t function properly? To test this question, they ran the tit-for-tat experiment again, but this time with schizophrenics. They hypothesised that schizophrenic subjects would more accurately and more often apply the correct amount of force in retaliation to the force applied by the robot. But why? Well, those suffering from schizophrenia have trouble sensing their own actions, and even attribute these sensations to alien force, unlike a healthy subject whose brain dulls and subdues their own movements, knowing it to be their own. Results showed that schizophrenics were considerably better at pushing back on themselves with the same amount of force applied by the robot. In other words, their brains could not discount the sensation of their own movements the same way a healthy person could. In other words again, they could potentially tickle themselves and it feel as if someone else is doing it.

So next time you find yourself trying to tickle your own foot and failing, don’t despair, all is not lost. Just look on the bright side, your cerebellum, and your somatosensory cortex, and your anterior cingulate cortex are working fine. Feel better now?

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