Revealing the secrets of gentle touch

Stroke the soft body of a newborn fruit fly larva ever-so-gently with a freshly plucked eyelash, and it will respond to the tickle by altering its movement - an observation that has helped scientists at the University of California, San Francisco (UCSF) uncover the molecular basis of gentle touch, one of the most fundamental but least well understood of our senses.

Our ability to sense gentle touch is known to develop early and to remain ever-present in our lives, from the first loving caresses our mothers lavish on us as newborns to the fading tingle we feel as our lives slip away. But until now, scientists have not known exactly how humans and other organisms perceive such sensations.

In an article published online in the journal Nature, the UCSF team has identified the exact subset of nerve cells responsible for communicating gentle touch to the brains of Drosophila larvae - called class III neurons.

They also uncovered a particular protein called NOMPC, which is found abundantly at the spiky ends of the nerves and appears to be critical for sensing gentle touch in flies.

Without this key molecule, the team discovered, flies are insensitive to any amount of eyelash stroking, and if NOMPC is inserted into neurons that cannot sense gentle touch, those neurons gain the ability to do so.

“NOMPC is sufficient to confer sensitivity to gentle touch,” said Yuh Nung Jan, a professor of physiology, biochemistry and biophysics and a Howard Hughes Medical Institute investigator at UCSF. Jan led the study with his wife Lily Jan.

The work sheds light on a poorly understood yet fundamental sense through which humans experience the world and derive pleasure and comfort.

Jan added that while the new work reveals much, many unanswered questions remain, including the exact mechanism through which NOMPC detects mechanical force and the identity of the analogous human molecules that confer gentle touch sensitivity in people.

The discovery is a good example of basic brain research paving the way toward answering such questions. UCSF is a world leader in the neurosciences, carrying out research that spans the spectrum from fundamental questions of how the brain works to the clinical development of new drugs and precision tools to address brain diseases; educating the next generation of neuroscientists, neurologists and neurosurgeons; and offering excellent patient care for neurological diseases.

Why is touch still such a mystery?

Though it is fundamental to our experience of the world, our sense of gentle touch has been the least well understood of our senses scientifically, because, unlike with vision or taste, scientists have not known the identity of the molecules that mediate it.

Scientists generally feel that, like those other senses, the sense of touch is governed by peripheral nerve fibres stretching from the spine to nerve endings all over the body. Special molecules in these nerve endings detect the mechanical movement of the skin surrounding them when it is touched, and they respond by opening and allowing ions to rush in. The nerve cell registers this response, and if the signal is strong enough, it will fire, signaling the gentle touch to the brain.What has been missing from the picture, however, are the details of this process. The new finding is a milestone in that it defines the exact nerves and uncovers the identity of the NOMPC channel, one of the major molecular players involved - at least in flies.

Jan and his colleagues made this discovery through an unusual route. They were looking at the basic physiology of the developing fruit fly, examining how class III neurons develop in larvae.

They noticed that when these cells developed in the insects, their nerve endings would always become branches into spiky “dendrites.”

Wanting to know what these neurons are responsible for, they examined them closely and found the protein NOMPC was abundant at the spiky ends. They then examined a fly genetically engineered to have a non-functioning form of NOMPC and showed that it was insensitive to gentle touch. They also showed that they could induce touch sensitivity in neurons that do not

normally respond to gentle touch by inserting copies of the NOMPC protein into them.

MNT

Want to boost your brain? Take a tip from Mother Nature

Time spent away from electronic gadgets can stimulate creative abilities, a study finds.

Wandering lonely as a cloud high o’er vales and hills may be the best way to recharge your batteries - so long as you leave your conventional battery-powered devices at home.

What writers have known for centuries, scientists are now endeavouring to prove - that contact with nature can boost creativity and problem solving skills. Backpackers who spent four days in the wilderness without access to electronic devices scored 50 percent better on a creativity test at the end of the trip, according to researchers.

The backpackers - 56 in all - joined one of four separate expeditions run by the Outward Bound organisation and took a ten item “creativity test” at the start and end of the hike.

On average they got four out of ten questions right at the start and six right at the end. The researchers used the Remote Associates Test, a standard measure of creative thinking, in which participants are given three words and asked to supply a fourth that is linked with the other three.

For example, the answer to Same/ Tennis/ Head might be Match - because a match is the same, tennis match and match head.

Earlier studies have shown that going for a long walk can improve the accuracy of proof-reading, the ability to perceive an optical illusion and the capacity to repeat a list of numbers backwards.

Yet, the time people spend outdoors and in contact with nature is diminishing. Children spend only 15-25 minutes daily in outdoor play and sport and the average teenager spends more than 7.5 hours a day using mobile phones or computers and watching TV, according to the researchers. Psychologists who led the study said: “Our modern society is filled with sudden events (sirens, horns, ringing phones, alarms, television) that hijack attention. By contrast natural environments are associated with gentle soft fascination, allowing the executive attentional system to replenish.”

“Executive attention” is the ability to switch rapidly among tasks which is important in a modern society but is overtaxed by the constant demands from a technological environment.

However, the authors of the study, published in the online journal Public Library of Science (PLoS) One, say they cannot be sure if the effects they observed were due to exposure to nature or withdrawal of electronic devices - or a combination of both.

“We show that four days of immersion in nature, and the corresponding disconnection from multimedia and technology, increases performance on a creativity, problem-solving task by a full 50 percent,” the researchers conclude.The participants had an average age of 28 and took part in treks in Alaska, Colorado, Washington State and Maine.

The results were controlled for age differences between the groups that took the test, because “as you get older, you have greater verbal abilities,” the researchers said.

The Independent

Feeling lonely linked to increased risk of dementia in later life

Feeling lonely, as distinct from being/living alone, is linked to an increased risk of developing dementia in later life, indicates research published online in the Journal of Neurology Neurosurgery and Psychiatry.

Various factors are known to be linked to the development of Alzheimer's disease including older age, underlying medical conditions, genes, impaired cognition, and depression, say the authors.

But the potential impacts of loneliness and social isolation - defined as living alone, not having a partner/spouse, and having few friends and social interactions - have not been studied to any great extent, they say.

This is potentially important, given the ageing population and the increasing number of single households, they suggest.

They therefore tracked the long term health and wellbeing of more than 2000 people with no signs of dementia and living independently for three years. All the participants were taking part in the Amsterdam Study of the Elderly (AMSTEL), which is looking at the risk factors for depression, dementia, and higher than expected death rates among the elderly.

At the end of this period, the mental health wellbeing of all participants was assessed using a series of validated tests.

They were also quizzed about their physical health, their ability to carry out routine daily tasks, and specifically asked if they felt lonely.

Finally, they were formally tested for signs of dementia.

At the start of the monitoring period, around half (46 percent 1002) the participants were living alone and half were single or no longer married.

Around three out of four said they had no social support. Around one in five (just under 20 percent 433) said they felt lonely. Among those who lived alone, around one in 10 (9.3 percent had developed dementia after three years compared with one in 20 (5.6 percent) of those who lived with others.

Among those who had never married or were no longer married, similar proportions developed dementia and remained free of the condition.

But among those without social support, one in 20 had developed dementia compared with around one in 10 (11.4 percent of those who did have this to fall back on.

NYT

Molecules in the ear converting sound into brain signals identified

For scientists who study the genetics of hearing and deafness finding the exact genetic machinery in the inner ear that responds to sound waves and converts them into electrical impulses, the language of the brain, has been something of a holy grail.

Now this quest has come to fruition. Scientists have identified a critical component of this ear-to-brain conversion - a protein called TMHS. This protein is a component of the so-called mechanotransduction channels in the ear, which convert the signals from mechanical sound waves into electrical impulses transmitted to the nervous system.

“Scientists have been trying for decades to identify the proteins that form mechanotransduction channels,” said Ulrich Mueller, a professor in the Department of Cell Biology who led the new study.

Not only have the scientists finally found a key protein in this process, but the work also suggests a promising new approach toward gene therapy. In the laboratory, the scientists were able to place functional TMHS into the sensory cells for sound perception of newborn deaf mice, restoring their function. “In some forms of human deafness, there may be a way to stick these genes back in and fix the cells after birth,” said Mueller.

TMHS appears to be the direct link between the spring-like mechanism in the inner ear that responds to sound and the machinery that shoots electrical signals to the brain. When the protein is missing in mice, these signals are not sent to their brains and they cannot perceive sound.

Specific genetic forms of this protein have previously been found in people with common inherited forms of deafness, and this discovery would seem to be the first explanation for how these genetic variations account for hearing loss.

Many different structures

The physical basis for hearing and mechanotransduction involves receptor cells deep in the ear that collect vibrations and convert them into electrical signals that run along nerve fibers to areas in the brain where they are interpreted as sound.This basic mechanism evolved far back in time, and structures nearly identical to the modern human inner ear have been found in the fossilised remains of dinosaurs that died 120 million years ago. Essentially all mammals today share the same form of inner ear.

What happens in hearing is that mechanical vibration waves traveling from a sound source hit the outer ear, propagate down the ear canal into the middle ear and strike the eardrum. The vibrating eardrum moves a set of delicate bones that communicate the vibrations to a fluid-filled spiral in the inner ear known as the cochlea. When the bones move, they compress a membrane on one side of the cochlea and cause the fluid inside to move.

Inside the cochlea are specialised “hair” cells that have symmetric arrays of extensions known as stereocilia protruding out from their surface. The movement of the fluid inside the cochlea causes the stereocilia to move, and this movement causes proteins known as ion channels to open. The opening of these channels is a signal monitored by sensory neurons surrounding the hair cells, and when those neurons sense some threshold level of stimulation, they fire, communicating electrical signals to the auditory cortex of the brain.Because hearing involves so many different structures, there are hundreds and hundreds of underlying genes involved - and many ways in which it can be disrupted. Hair cells form in the inner ear canal long before birth, and people must live with a limited number of them.

They never propagate throughout life, and many if not most forms of deafness are associated with defects in hair cells that ultimately lead to their loss. Many genetic forms of deafness emerge when hair cells lack the ability to transduce sound waves into electric signals.

Over the years, Mueller and other scientists have identified dozens of genes linked to hearing loss - some from genetic studies involving deaf people and others from studies in mice, which have inner ears that are remarkably similar to humans.

A clearer picture

What has been lacking, however, is a complete mechanistic picture. Scientists have known many of the genes implicated in deafness, but not how they account for the various forms of hearing loss. With the discovery of the relevance of TMHS, however, the picture is becoming clearer. TMHS turns out to play a role in a molecular complex called the tip link, which several years ago was discovered to cap the stereocilia protruding out of hair cells.

These tip links connect the tops of neighbouring stereocilia, bundling them together, and when they are missing the hair cells become splayed apart.

But the tip links do more than just maintain the structure of these bundles. They also house some of the machinery crucial for hearing - the proteins that physically receive the force of a sound wave and transduce it into electrical impulses by regulating the activity of ion channels.

MNT

Saliva analysis reveals decision-making skills

A study conducted by researchers has demonstrated that cortisol levels in saliva are associated with a person's ability to make good decisions in stressful situations. To perform this study, the researchers exposed the participants (all women) to a stressful situation by using sophisticated virtual reality technology.

The study revealed that people who are not skilled in decision-making have lower baseline cortisol levels in saliva as compared to skilled people.

Cortisol - known as the stress hormone - is a steroid hormone segregated at the adrenal cortex and stimulated by the adrenocorticotropic (ACTH) hormone, which is produced at the pituitary gland.

Cortisol is involved in a number of body systems and plays a relevant role in the muscle-skeletal system, blood circulation, the immune system, the metabolism of fats, carbohydrates and proteins and the nervous system.

Recent studies have demonstrated that stress can influence decision making in people. This cognitive component might be considered one of the human resources for coping with stress.

To verify that decision-making skills might modulate human response to psychosocial stress, the University of Granada researchers evaluated the decision-making process in 40 healthy women. Participants were asked to perform the so-called Iowa Gambling Task.

Next, participants were presented a stressful situation in a virtual environment consisting on delivering a speech in front of a virtual audience. Researchers evaluated the participants’ response to stress by examining the activation of the hypothalamic pituitary adrenal axis, and measuring cortisol levels in saliva at different points of the stressful situation.

Professors Isabel Peralta and Ana Santos state that this study provides preliminary evidence on an existing relationship between decision-making ability - which may play a major role in coping with stress - and low cortisol levels in psychosocially stressful situations.

This means that the effects of psychological stress on the health people with lower cortisol levels might be milder.

MNT