Tag: Neuron

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News on Health & Science

Mind Power Moves Paralysed Limbs

Scientists have shown it is possible to harness brain signals and redirect them to make paralysed limbs move.

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The technology bypasses injuries that stop nerve signals travelling from the brain to the muscles, offering hope for people with spinal damage.

So far the US team from the University of Washington have only tested their “brain-machine interfaces” in monkeys.

The hope is to develop implantable circuits for humans without the need for robotic limbs, Nature reports.

Wired up
Spinal cord injuries impair the nerve pathways between the brain and the limbs but spare both the limb muscles and the part of the brain that controls movement – the motor cortex.

“Similar techniques could be applied to stimulate the lower limb muscles during walking” Says Lead researcher Dr Chet Moritz

Recent studies have shown that quadriplegic patients – people who have paralysis in all four limbs – can consciously control the activity of nerve cells or neurons in the motor cortex that command hand movements, even after several years of paralysis.

Using a gadget called a brain-machine interface, Dr Chet Moritz and colleagues re-routed motor cortex control signals from the brains of temporarily paralysed monkeys directly to their arm muscles.

The gadget, which is the size of a mobile phone, interprets the brain signals and converts them into electrical impulses that can then stimulate muscle to contract.

By wiring up artificial pathways for the signals to pass down, muscles that lacked natural stimulation after paralysis with a local anaesthetic regained a flow of electrical signals from the brain.

Life-changing
The monkeys were then able to tense the muscles in the paralysed arm, a first step towards producing more complicated goal-directed movements, such as grasping a cup or pushing buttons, say the researchers.

Lead researcher Dr Chet Moritz said: “This could be scaled to include more muscles or stimulate sites in the spinal cord that could activate muscles in a coordinated action.”

“Similar techniques could be applied to stimulate the lower limb muscles during walking.”

The scientists found the monkeys could learn to use virtually any motor cortex nerve cell to control muscle stimulation – it did not have to be one that would normally controlled arm movement. And their control over the muscles improved with practice.

The researchers say they need to do trials in humans, meaning a treatment could be decades away.

Dr Mark Bacon, head of research at the UK charity Spinal Research, said: “This is clearly a step in the right direction and proves the principle that artificially transducing the will to move generated in the brain with relevant motor activity can be achieved.

“However, these results have been produced in experimental models where there is no injury per se.”

He said injury-induced changes to the nerve circuits might hinder the technology’s application in real life.

Also, brain-machine interfaces communicate in only one direction – in this case from the brain to the muscle.

“Sensory feedback, so important for fine control of movements and dexterity, is still some way away,” he said.

Sources: BBC NEWS:15 October 2008

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Positive thinking

Fearlessness Can be Taught

The brain can produce antidepressants with the right signal, a finding that suggests that meditating, or going to your “happy place,” tru ly works, scientists reported .

Mice, who were forced to swim endlessly until they surrendered and just floated, waiting to drown, could be conditioned to regain their will to live when a tone they associated with safety was played.

The experiment suggests that there are good ways to teach people this skill, and points to new routes for developing better antidepressants, said Dr Eric Kandel of the Howard Hughes Medical Institute and Columbia University in New York, who led the research.

“The happy place works. This is like going to the country,” Kandel said in a telephone interview.

Writing in the journal Neuron, Kandel’s team said they used classical conditioning to train mice. They had already conditioned some mice to fear a neutral tone by playing the sound when they shocked the animals’ paws. After a while, the tone itself creates fear. “It scares the hell out of the animal,” Kandel said.

They decided to reverse the study — they played the tone when they were not shocking the mice. “It learned that the only time it was really safe is when the tone comes on,” Kandel said.

To make a mouse depressed, they used a method favored by drug companies called learned helplessness. “You put an animal into a pool of water and it can’t get out. It gives up and it stops swimming and it just floats,” Kandel said. “When you give the animal an antidepressant, it starts swimming again. When we played the tone, it started to swim again just as it did with the antidepressant.”

Further experiments showed the tone and an antidepressant drug worked synergistically, he said. When they looked at the brains of their mice, they saw using the conditioned “safety” tone activated a different pathway than the drugs did.

It affected dopamine, while antidepressants work on serotonin. Both are message-carrying molecules called neurotransmitters. The conditioning also affected a compound called brain-derived neurotrophic factor or BDNF —which helps nourish and encourages the growth of brain cells. The learned safety did not affect serotonin.
Mice conditioned by the “safety” tone also had more newborn brain cells in the dentate gyrus, a part of the brain linked with learning and depression.

When Kandel’s team used radiation to slow the birth of new cells in the dentate gyrus, the effects of learned safety and of antidepressants were blunted.

Kandel noted that antidepressant drugs appear to work, in part, by encouraging the growth of new brain cells — as does psychotherapy.

“Learning involves alterations in the brain and gene expression,” Kandel said. “Psychotherapy is only a form of learning.”

This shows how effective psychotherapy, meditation and other stress-reduction tools may be, and it could help in the design of new drugs, Kandel said. “This opens up new pathways that may profitable,” he said.

Sources: The Times Of India

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News on Health & Science

Plastic Bottles are Deadly for Your Brain

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Plastic containers may be deadly for your brain. Canadian researchers have found that Bisphenol A (BPA), the chemical used in making plastic containers, might be responsible for impairing many brain functions such as learning and remembering.

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They also fear that it could be a factor behind Alzheimer’s, schizophrenia and depression.

BPA is globally used in making plastic water bottles, baby food bottles, food containers and dental prostheses.

In their study, the researchers at the University of Guelph near here found that BPA might be leaking into the solid or liquid foods kept in the plastic containers.

When these foods and liquids are consumed, they said, the chemical might be getting into the human system, disrupting communication between brain neurons which is vital in understanding and remembering.

According to researcher Neil MacLusky, the slow doses of this chemical badly impair the formation of synapses in the areas of the human brain linked to learning.

As part of their study, the researchers fed African green monkeys at St. Kitts Island with foods containing low levels of BPA for a month.

After that period, they found that the chemical had slowed down the synapses in the monkey brain.

MacLusky said this process was linked to the hormone oestrogen.

“Oestrogen enhances the rate at which some types of synapses are formed and is vital in maintaining normal neuronal structure in regions of the brain that control learning, memory and mood state,” he said in a TV interview.

When monkeys had BPA in their system, he said, it seriously impaired this process, affecting their ability to remember.

Sources: The Times Of India

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Featured

Why Migraines Strike

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A migraine is more than just a headache; it is intensely painful and has distinct phases. The disorder used to be considered vascular, but recent research has revealed it to be neurological in origin, related to a wave of nerve cell activity that sweeps across the brain.

The root of migraine may reside in brain stem malfunctioning. Debate still swirls about the precise cause of migraines, but new discoveries are already permitting the development of new treatments.

At the moment, only a few drugs can prevent migraines, all of them developed for other diseases such as hypertension, depression and epilepsy. But they work in only 50 percent of patients, and even then, only 50 percent of the time, and can also induce a range of potentially serious side effects.

New techniques are now being tested, such as drugs that work by preventing gap junctions, a form of ion channel, from opening, thereby halting the flow of calcium between brain cells.

Sources:
Scientific American July 2008

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Featured

Love Hormone

Breastfeeding an infantImage via Wikipedia

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Scientists have cracked the mystery of a mother’s selfless love for her child.

Science has finally cracked the mystery of a mother’s selfless love. The tenderness, intimacy and selflessness with which a mother interacts with her infant has been revered and celebrated through the ages as one of the most beautiful and inspiring manifestations of human behaviour.

Now a new study says the credit for triggering this altruistic love may go to the suckling baby.

Reported by a team of researchers from France, Italy and the UK, the work unravels the mechanism by which a nursing baby triggers a chain of chemical events that lead to a rush of the “love” hormone, oxytocin, in the brain of the mother. The findings appear in the journal PLoS Computational Biology.

Scientists have known for a while that oxytocin — also called the hormone of trust and lust — when released in the blood causes milk to be let down from the mammary glands. But they didn’t have any clue about the exact cascade of events that leads to the release of oxytocin in the brain.

What was known before the study is how a few thousand neurons, specialised to release oxytocin, are marshalled together to produce a sufficiently intense outburst during events such as childbirth, breastfeeding or even an orgasm.

“For 30 years we have known that these spurts arise because, during suckling, the oxytocin neurons fire together in dramatic synchronised bursts, but exactly how these bursts come about had puzzled us,”says Jianfeng Feng, a neuroscientist at the University of Warwick who led the study.

The scientists found that in response to suckling, the neurons start releasing oxytocin from their dendrites (protrusions on the branches for receiving electric signals from other brain cells) as well as nerve endings. The finding came as a surprise as dendrites were earlier thought to be that part of a neuron which receive rather than transmit information.

Dendrites usually create a weak network of connection between neurons. According to the researchers, the release of oxytocin from them allows for a massive spurt in communication between the neurons. This coordinates a “swarm” of oxytocin producing factories, leading to massive bursts of release at intervals of five minutes or so.

The scientists liken the event to a flock of birds or insects undertaking a closely coordinated action without a leader to guide.

“The dendrites do much more than just receive information,” Feng, who is also the director of the Centre for Computational Systems Biology at Fudan University in China, told KnowHow.

Oxytocin, the brain chemical that works as a trigger for love and affection in females, is stored in the pituitary gland from where it is discharged into the blood. Interestingly, it is released not only during a surge of maternal love but also romantic love. According to Semir Zeki, regarded as the doyen of neurobiology, oxytocin — quite like vasopressin in males — is released in the blood during a sexual orgasm. Copious amounts of oxytocin are detected in a woman’s blood during childbirth as well.

Because of the role it plays in releasing milk, the chemical is being used indiscriminately by the dairy industry to make milching animals produce even more milk. It is also used arbitrarily by some clinics and midwifes to make labour pain free, often risking the lives of babies.

Another interesting brain study recently found that this trust-building hormone reduces neuronal activity and weakens the connections in the amygdala, which serves as the brain’s fear hub.

Feng thinks similar triggers may be at work during other natural processes where abundant quantities of oxytocin are released into the blood.

Sources: The Telegraph (Kolkata, India)

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