Scientists Reveal The Secret Of Cuddles
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SCIENTISTS REVEAL THE SECRET OF CUDDLES
By Gaia Vince
July 28, 2002
Scientists have discovered why being cuddled feels so good - human skin has
a special network of nerves that stimulate a pleasurable response to
The revelation came after doctors realised that a woman with no sense of
touch still felt a "pleasant" sensation when her skin was caressed.
Normal touch is transmitted to the brain through a network of
fast-conducting nerves, called myelinated fibres, which carry signals at 60
metres per second. But there is a second slow-conducting nerve network of
unmyelinated fibres, called C-tactile (CT), the role of which was unknown.
The CT network carries signals at just one metre per second.
"It must be used for unconscious aspects of touch because it is so slow,"
says Håkan Olausson, who led the study at the Department of Clinical
Neurophysiology at Sahlgrenska University Hospital, Sweden. "It seems the CT
network conveys emotions, or a sense of self."
"This study definitely helps our understanding of how touch systems work,"
says Brian Fiske, assistant editor at Nature Neuroscience. "The researchers
were very fortunate to have found a patient who had lost the main touch
receptors but still had the slow CT fibres."
Below the nose
Scientists have known for some time that myelinated nerve fibres transmit
information about touch, such as its strength and position. But the function
of CT fibres was a mystery. This was because it is impossible to distinguish
the CT fibre signals from those of the continuously activated fast
The patient examined by the Swedish researchers had a disorder that left her
with no myelinated touch fibres in her body below the level of her nose. But
her CT fibres remained intact.
Olausson stroked the patient's arm and hand with a paintbrush. Although she
could not feel touch, tickle or vibration, the patient said she experienced
a "pleasant" pressure when her arm was caressed with a paintbrush.
MRI scans of her brain revealed that the stroking activated insular region
of the cerebral cortex associated with emotional response.
The researchers concluded that the CT system may be of important for
emotional, hormonal and behavioural responses to tactile stimulation.
"They are the opposite to pain fibres and give the message that the touch is
non- harmful," Olausson told New Scientist. "Stimulation of CT fibres is
probably linked to the release of pleasure hormones, like oxytocin. Studies
have shown that if you stroke infants, their levels of oxytocin increase."
Further research by the Swedish team suggests that CT fibres are only
present in hairy skin - the patient showed no response to the palm of her
hand being stroked.
Olausson speculates that because the hand is used for so many critical
tasks, it needs to be very sensitive to touch and therefore has a greater
density of faster- conducting nerves.
Journal reference: Nature Neuroscience (DOI: 10.1038/nn896)
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