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"Why do we sleep? We spend a third of our lives doing so, and all known animals with a nervous system either sleep, or show some kind of related behaviour. But scientists still don't know what the point of it is. There are plenty of theories. Some researchers argue that sleep has no specific function, but rather serves as evolution's way of keeping us inactive, to save energy and keep us safely tucked away at those times of day when there's not much point being awake. On this view, sleep is like hibernation in bears, or even autumn leaf fall in trees. But others argue that sleep has a restorative function-something about animal biology means that we need sleep to survive. This seems like common sense. Going without sleep feels bad, after all, and prolonged sleep deprivation is used as a form of torture. We also know that in severe cases it can lead to mental disturbances, hallucinations and, in some laboratory animals, eventually death. Waking up after a good night's sleep, you feel restored, and many studies have shown the benefits of sleep for learning, memory, and cognition. Yet if sleep is beneficial, what is the mechanism? Recently, some neuroscientists have proposed that the function of sleep is to reorganize connections and "prune" synapses-the connections between brain cells. Last year, one group of researchers, led by Gordon Wang of Stanford University reviewed the evidence for this idea in a paper called Synaptic plasticity in sleep: learning, homeostasis and disease."

"On a hot summer day 15 years ago in Parma, Italy, a monkey sat in a special laboratory chair waiting for researchers to return from lunch. Thin wires had been implanted in the region of its brain involved in planning and carrying out movements. Every time the monkey grasped and moved an object, some cells in that brain region would fire, and a monitor would register a sound: brrrrrip, brrrrrip, brrrrrip. A graduate student entered the lab with an ice cream cone in his hand. The monkey stared at him. Then, something amazing happened: when the student raised the cone to his lips, the monitor sounded - brrrrrip, brrrrrip, brrrrrip - even though the monkey had not moved but had simply observed the student grasping the cone and moving it to his mouth. The researchers, led by Giacomo Rizzolatti, a neuroscientist at the University of Parma, had earlier noticed the same strange phenomenon with peanuts. The same brain cells fired when the monkey watched humans or other monkeys bring peanuts to their mouths as when the monkey itself brought a peanut to its mouth. Later, the scientists found cells that fired when the monkey broke open a peanut or heard someone break a peanut. The same thing happened with bananas, raisins and all kinds of other objects. "It took us several years to believe what we were seeing," Dr. Rizzolatti said in a recent interview. The monkey brain contains a special class of cells, called mirror neurons, that fire when the animal sees or hears an action and when the animal carries out the same action on its own. But if the findings, published in 1996, surprised most scientists, recent research has left them flabbergasted. Humans, it turns out, have mirror neurons that are far smarter, more flexible and more highly evolved than any of those found in monkeys, a fact that scientists say reflects the evolution of humans' sophisticated social abilities. The human brain has multiple mirror neuron systems that specialize in carrying out and understanding

"Researchers led by New York University neuroscientist Joseph LeDoux recently claimed to be the first scientists to erase a single memory. Working with rats, LeDoux's team first taught the animals to fear both a beep and a siren by giving them an electric shock every time either of the tones sounded. Then LeDoux gave half the rats the drug U0126, which is known to interfere with memory storage, and replayed the beep without electric shocks. A day later, when LeDoux played back both tones to the rats, the animals that hadn't been given the drug were still fearful of both sounds. But the rats that had been given the memory-blocking drug weren't afraid of the beep, which they had last heard while under the influence of U0126. advertisement | article continues below Click here! Exactly how U0126 exerts its amnesiac effect is unknown, but it may block the synthesis of proteins that help strengthen connections between neurons and establish memories. The opportunity for erasure occurs during the act of retrieving a memory because that's when the memory is being updated and stabilized again for long-term storage. "Only those memories that are activated are vulnerable," LeDoux says. Drugs like U0126 may someday help sufferers of traumatic memories. A small group of human studies have been done on a drug called propranolol, which blocks the action of stress neurotransmitters that help cement memories in the brain, but LeDoux's work shows the potential for greater precision. "You might be able to reduce the traumatic impact of memories in people with PTSD," says LeDoux. "The good news is you wouldn't be erasing their memory bank." "

"A MOTHER sits in a playroom with her young son. The phone rings. When she picks it up, a researcher watching through a two-way mirror asks her to look into her son's eyes and ''show him, in the way that feels most natural for you, that you love him''. The mother is doing her best to connect, but this little boy won't return her gaze. He looks at her mouth, where the words are coming from, but it's as if he can't understand what she means. Advertisement: Story continues below Robert Thompson and Jon Venables killed UK toddler James Bulger. Robert Thompson and Jon Venables killed UK toddler James Bulger. Mark Dadds says some children literally cannot see the love in their mother's eyes. Professor Dadds, a parenting expert from the University of New South Wales, has just published results of his work in the British Journal of Psychiatry and the Journal of Child Psychiatry and Psychology that suggest the ability to make eye contact is vital in learning how to love other people. For the past five years, he has been working with children referred to his Sydney clinic for sustained rages, continual aggression, calculated violence and, occasionally, cruelty to animals. These are children with some of the worst behavioural problems, who score highly for ''callous, unemotional'' traits. In his studies in both Sydney and London, it was these children who did not meet their mother's gaze, even when told they were loved. People marvel at the resilience of children who overcome appalling family backgrounds to make good lives. We understand when childhood trauma sends a child off the rails. But we also have to accept that even good parents can have mean children - how else to explain families where only one child seems to be callous and unemotional, while the siblings are not? Dadds distinguishes between children who are emotionally ''hot'' - those who lash out at the world - and the much smaller subset of ''cold'' children - the ones who don't react emotionally, don't car

"As neurologists, psychologists and biologists have zeroed in more and more precisely on the physical causes of mental disorders, they have found themselves addressing a much deeper mystery, a set of interrelated conundrums probably as old as humanity: What, precisely, is the mind, the elusive entity where intelligence, decision making, perception, awareness and sense of self reside? Where is it located? How does it work? Does it arise from purely physical processes-pulses of electricity zapping from brain cell to brain cell, helped along their way by myriad complex chemicals? Or is it something beyond the merely physical-something ethereal that might be close to the spiritual concept of the soul? Great thinkers have had no shortage of ideas on the subject. Plato was convinced that the mind must be located inside the head, because the head is shaped more or less like a sphere, his idea of the highest geometrical form. Aristotle insisted that the mind was in the heart. His reasoning: warmth implies vitality; the blood is warm; the heart pumps the blood. By the Middle Ages, though, pretty much everyone agreed that the mind arose from the brain -- but still had no clear idea how it arose. Finally, in the 17th century, the French philosopher Rena Descartes declared that the mind, while it might live in the brain, was a nonmaterial thing, entirely separate from the physical tissues found inside the head. Furthermore, said Descartes in one of history's most memorable sound bites, "Cogito, ergo sum" (I think, therefore I am). His point: consciousness is the only sure evidence that we actually exist. Until just a few years ago, unraveling the relationship of mind and brain was beyond the realm of observation and experimentation. But science has finally begun to catch up with philosophy. Using sensitive electrodes inserted deep into the gray matter of test animals, researchers have watched vision as it percolates inward from the eye's retina to the inner brain. Powerful te

"Humans are storytelling machines. We don't passively perceive the world - we tell stories about it, translating the helter-skelter of events into tidy narratives. This is often a helpful habit, helping us make sense of mistakes, consider counterfactuals and extract a sense of meaning from the randomness of life. But our love of stories comes with a serious side-effect: like all good narrators, we tend to forsake the facts when they interfere with the plot. We're so addicted to the anecdote that we let the truth slip away until, eventually, those stories we tell again and again become exercises in pure fiction. Just the other day I learned that one of my cherished childhood tales - the time my older brother put hot peppers in my Chinese food while I was in the bathroom, thus scorching my young tongue - actually happened to my little sister. I'd stolen her trauma. The reason we're such consummate bullshitters is simple: we bullshit for each other. We tweak our stories so that they become better stories. We bend the facts so that the facts appeal to the group. Because we are social animals, our memory of the past is constantly being revised to fit social pressures. The power of this phenomenon was demonstrated in a new Science paper by Micah Edelson, Tali Sharot, Raymond Dolan and Yadin Dudai. The neuroscientists were interested in how the opinion of other people can alter our personal memories, even over a relatively short period of time. The experiment itself was straightforward. A few dozen people watched an eyewitness style documentary about a police arrest in groups of five. Three days later, the subjects returned to the lab and completed a memory test about the documentary. Four days after that, they were brought back once again and asked a variety of questions about the short movie while inside a brain scanner. This time, though, the subjects were given a "lifeline": they were shown the answers given by other people in their film-viewing g

"These points are extremely well-taken, particularly his last comments about the use of brain scans as indications of the brain's functions. I'm delighted to see a scientist of Gazzaniga's stature provide these cautions. Others have also worried about the over-interpretations of brain scans, a question I raised in my Psychology Today blog posting "MRI's: The new phrenology?" How many times have you heard the expression "the brain lights up"? The brain does not behave in technicolor; it's just that the colors make for a better story when researchers are trying to sell their results to the public and funding agencies. It's important that we not over-interpret the pretty colors that brain scans provide but instead recognize that everyone's brain is a little bit different and that activity in a region doesn't signify exactly what a person is thinking or feeling. I hope that we will keep these cautions in mind even as brain scans become more and more commonplace. "

"Exposure to even dim light at night is enough to cause physical changes in the brains of hamsters that may be associated with depression, a new study shows."