女生小视频s have discovered why being cuddled feels so good 鈥� human skin has a special network of nerves that stimulate a pleasurable response to stroking.
The revelation came after doctors realised that a woman with no sense of touch still felt a 鈥減leasant鈥� 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.
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鈥淚t must be used for unconscious aspects of touch because it is so slow,鈥� says H氓kan Olausson, who led the study at the Department of Clinical Neurophysiology at Sahlgrenska University Hospital, Sweden. 鈥淚t seems the CT network conveys emotions, or a sense of self.鈥�
鈥淭his study definitely helps our understanding of how touch systems work,鈥� says Brian Fiske, assistant editor at Nature Neuroscience. 鈥淭he researchers were very fortunate to have found a patient who had lost the main touch receptors but still had the slow CT fibres.鈥�
Below the nose
女生小视频s 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 myelinated fibre.
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鈥檚 arm and hand with a paintbrush. Although she could not feel touch, tickle or vibration, the patient said she experienced a 鈥減leasant鈥� 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.
Hairy skin
The researchers concluded that the CT system may be of important for emotional, hormonal and behavioural responses to tactile stimulation.
鈥淭hey are the opposite to pain fibres and give the message that the touch is non- harmful,鈥� Olausson told New 女生小视频. 鈥淪timulation 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.鈥�
Further research by the Swedish team suggests that CT fibres are only present in hairy skin 鈥� 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.
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