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zoom RSS なでられると気持ちが良くなることを伝える神経線維

<<   作成日時 : 2009/04/14 00:28   >>

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 ユニリーバの科学者らのチームが、皮膚から気持ちの良さを伝える神経線維を特定した。4-5cm/秒という一定のスピードでなでられる必要があるという。触覚がどのように人間関係を維持するかに理解するのに役立つだろうという。
 何年もの間科学者は、多くの人が苦しんでいるから、苦痛を解明しようとしてきた。末梢神経が傷害されるニューロパチーでは、しばしば原因不明の激痛に悩まされる。
 この研究では研究者は、逆の感覚である「快感pleasure」に取り組んだ。
 前腕を違う速度でなでたときにどう反応したかを検査した。快感を得たときは、無髄の"C-tactile"神経線維が刺激されたとわかった。最適な速度でないと神経線維は活性化しなかった。毛深い皮膚にあるが、手のひらには見つからないということもわかった。
 赤ん坊をあやす母親が使ったり、愛情を示すためにカップルが使ったりする速度と同じであるという。
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Page last updated at 23:02 GMT, Sunday, 12 April 2009 00:02 UK
Scientists find 'pleasure nerves'
http://news.bbc.co.uk/2/hi/health/7992299.stm
画像Mother and baby
Mothers use touch to sooth their babies

Scientists say they understand more about how the body responds to pleasurable touch.

A team, including scientists from the Unilever company, have identified a class of nerve fibres in the skin which specifically send pleasure messages.
And people had to be stroked at a certain speed - 4-5cm per second - to activate the pleasure sensation.
They say the study, published in Nature Neuroscience, could help understand how touch sustains human relationships.

There are some mechanisms in place that are associated with behaviour and reward which are there to ensure relationships continue
Professor Francis McGlone

For many years, scientists have been trying to understand the mechanisms behind how the body experiences pain, and the nerves involved in conveying those messages to the brain.
This is because people can suffer a great deal.
Neuropathy, where the peripheral nervous system is damaged, can be very painful and sometimes the messaging system goes wrong a people feel pain even when there is no cause.

Hairy skin
But the researchers involved in this work were looking to understand the opposite sensation - pleasure.
This research, which also involved experts at the University of Gothenburg in Sweden and at the University of North Carolina, recorded nerve responses in 20 people.
They then tested how people responded to having their forearm skin stroked at a range of different speeds.
They identified "C-tactile" nerve fibres as those stimulated when people said a touch had been pleasant.
If the stroke was faster or slower than the optimum speed, the touch was not pleasurable and the nerve fibres were not activated.
The scientists also discovered that the C-tactile nerve fibres are only present on hairy skin, and are not found on the hand.
Professor Francis McGlone, now based at Unilever after an academic career where he carried out research into nerve response, says this is likely to be a deliberate "design".
"We believe this could be Mother Nature's way of ensuring that mixed messages are not sent to the brain when it is in use as a functional tool."
He said the speed at which people found arm-stroking pleasurable was the same as that which a mother uses to comfort a baby, or couples use to show affection.
Professor McGlone said it was part of the evolutionary mechanism that sustained relationships between adults, or with children.
"Our primary impulse as humans is procreation, but there are some mechanisms in place that are associated with behaviour and reward which are there to ensure relationships continue."
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Nature Neuroscience
Published online: 12 April 2009 | doi:10.1038/nn.2312

Coding of pleasant touch by unmyelinated afferents in humans

Line S Löken1,2, Johan Wessberg1, India Morrison1,2, Francis McGlone3,4 & Håkan Olausson1,2

Pleasant touch sensations may begin with neural coding in the periphery by specific afferents. We found that during soft brush stroking, low-threshold unmyelinated mechanoreceptors (C-tactile), but not myelinated afferents, responded most vigorously at intermediate brushing velocities (1-10 cm s-1), which were perceived by subjects as being the most pleasant. Our results indicate that C-tactile afferents constitute a privileged peripheral pathway for pleasant tactile stimulation that is likely to signal affiliative social body contact.
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1. Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden.
2. Department of Clinical Neurophysiology, Sahlgrenska University Hospital, Gothenburg, Sweden.
3. Department of Neurological Sciences, University of Liverpool, Liverpool, UK.
4. Sensation, Perception and Behaviour Group, Unilever R&D, Wirral, Cheshire, UK.

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