FORMATION of a memory is widely believed to leave a 'trace' in the brain - a fleeting pattern of electrical activity which strengthens the connections within a widely distributed network of neurons, and which re-emerges when the memory is recalled. The concept of the memory trace was first proposed nearly a century ago, but the nature of the trace, its precise location in the brain and the underlying neural mechanisms all remain elusive. Researchers from University College London now report that functional magnetic resonance (fMRI) can be used to decode individual memory traces and to predict…
ALZHEIMER'S Disease is the most common form of dementia, affecting an estimated 30 million people worldwide. The cause of the condition is unknown, but the prime suspect is amyloid-beta (Aβ), a 42-amino acid peptide which accumulates within neurons to form insoluble structures called senile plaques that are thought to be toxic. Aβ is synthesized in all neurons; it is associated with the cell membrane, and is thought to be involved in cell-to-cell signalling, but its exact role has eluded researchers. A new study published in the open access journal PLoS One now shows that Aβ is a potent…
THE perception and recognition of faces is crucial for the social situations we encounter every day. From the moment we are born, we prefer looking at faces than at inanimate objects, because the brain is geared to perceive them, and has specialized mechanisms for doing so. Such is the importance of the face to everyday life, that we see faces everywhere, even when they are not there. We know that the ability to recognize faces varies among individuals. Some people are born with prosopagnosia, the inability to recognize faces, and others acquire the condition as a result of brain damage. At…
I 'M pleased to announce that my post about dinosaur brains and behaviour is featured in Open Lab 2009, the annual anthology of the best science writing on blogs. The book has just been published and is now available at Lulu.com, in hard copy or as a Kindle-compatible PDF. This is the third Neurophilosophy post to be published in this series of books: my posts about the discovery of the neuron and the history of trepanation were included in the 2006 and 2007 editions, respectively. This blog has also been selected as a finalist in the first annual Research Blogging Awards. I thought it might…
REMOVAL of specific parts of the brain can induce increases in a personality trait which predisposes people to spirituality, according to a new clinical study by Italian researchers. The new research, published earlier this month in the journal Neuron, provides evidence that some brain structures are associated with spiritual thinking and feelings, and hints at individual differences that might make some people more prone than others to spirituality. Cosimo Urgesi of the University of Udine and his colleagues combined pre- and post-surgical personality assessments with advanced lesion…
Click to enlarge THIS cartoon by Dwayne Godwin, a professor of neurobiology at Wake Forest University School of Medicine, and Jorge Cham, the former researcher and cartoonist who created PhD Comics, has won first place in the informational graphics category of the 2009 International Science and Engineering Visualization Challenge.  The New York Times has a slide show of the winning entries, and today's issue of Science contains a special feature about the competition. To see the full size infographic, click on the image above, or visit Godwin's public engagement page, where it, and others in…
WHEN it comes to making decisions, timing can be everything, but it is often beneficial to conceal the decision that has been made. Take a game of poker, for instance: during each round, the player has to decide whether to bet, raise the stakes, or fold, depending on the hand they have been dealt. A good player will have perfected his "poker face", the blank expression which conceals the emotions he feels and the decisions he makes from the other players sitting at the table. Increasing numbers of researchers are using brain scanning techniques to perform what is commonly referred to as "…
IF a rapid series of taps are applied first to your wrist and then to your elbow, you will experience a perceptual illusion, in which phantom sensations are felt along the skin connecting the two points that were actually touched. This feels as if a tiny rabbit is hopping along your skin from the wrist to the elbow, and is therefore referred to as the "cutaneous rabbit". The illusion indicates that our perceptions of sensory inputs do not enter conscious awareness until after the integration of events occuring within a certain time window, and that the sensory events taking place at a certain…
HOW does the brain encode the spatial representations which enable us to successfully navigate our environment? Four decades of research has identified four cell types in the brains of mice and rats which are known to be involved in these processes: place cells, grid cells, head direction cells and, most recently, border cells. Although the functions of most of these cell types are well characterized in rodents, it remains unclear whether they are also found in humans. A new functional neuroimaging study, by researchers from University College London, published online in the journal Nature,…
"WHEN a man sits with a pretty girl for an hour," said Albert Einstein, "it seems like a minute. But let him sit on a hot stove for a minute, and it's longer than any hour." Einstein was describing one of the most profound implications of his Theory of General Relativity - that the perception of time is subjective. This is something we all know from experience: time flies when we are enjoying ourselves, but seems to drag on when we are doing something tedious. The subjective experience of time can also be manipulated experimentally. Visual stimuli which appear to be approaching are perceived…
OUR ability to use and manipulate numbers is integral to everyday life - we use them to label, rank, count and measure almost everything we encounter. It was long thought that numerical competence is dependent on language and, therefore, that numerosity is restricted to our species. Although the symbolic representation of numbers, using numerals and words, is indeed unique to humans, we now know that animals are also capable of manipulating numerical information. One study published in 1998, for example, showed that rhesus monkeys can form spontaneous representations of small numbers and…
VIEWING a stimulus for a prolonged period of time results in a bias in the perception of a stimulus viewed afterwards. For example, after looking at a moving stimulus for some time, a stationary stimulus that is viewed subsequently appears to drift in the opposite direction. These after-effects reveal to us the properties of our perceptual system. They occur because the neurons which are sensitive to the initial stimulus re-calibrate their responses; they adapt to compensate for the earlier enduring stimulus, and so can continue to encode current stimuli efficiently. It was long thought that…
WE tend to assume that we see our surroundings as they really are, and that our perception of reality is accurate. In fact, what we perceive is merely a neural representation of the world, the brain's best guess of its environment, based on a very limited amount of available information. This is perhaps best demonstrated by visual illusions, in which there is a mismatch between our perception of the stimulus and objective reality. Even when looking at everyday objects, our perceptions can be deceiving. According to the New Look approach, first propounded in the 1940s by the influential…
HOW do you react when you see somebody else in pain? Most of us can empathize with someone who has been injured or is sick - we can quite easily put ourselves "in their shoes" and understand, to some extent, what they are feeling. We can share their emotional experience, because observing their pain activates regions of the brain which are involved in processing the emotional aspects of pain. But can seeing somebody else in pain actually cause pain in the observer? People with mirror-touch synaesthesia are known to experience touch sensations when they see others being touched, and this may…
MEMORY is one of the biggest enduring mysteries of modern neuroscience, and has perhaps been researched more intensively than any other aspect of brain function. The past few decades have yielded a great deal of knowledge about the cellular and molecular mechanisms of memory, and it is now widely believed that memories are formed as a result of biochemical changes which ultimately lead to the strengthening of connections between nerve cells. It is, however, also clear that memories are not encoded at the level of single neurons. Instead, the memory trace is thought of as a flurry of…
IN February of this year, Jacopo Annese (above), a neuroanatomist and radiologist at the University of California, San Diego travelled to Boston to take delivery of a brain. For Annese, collecting brains is not unusual - he is, after all, director of UCSD's Brain Observatory, which will eventually become a comprehensive library of brains donated by people who had neurological conditions such as Alzheimer's Disease, as well as by healthy people of all ages. This time though, the brain he collected was very special: it belonged to the amnesic patient Henry Molaison,  who for more than 50 years…
SYNAESTHESIA is a neurological condition in which there is a merging of the senses, so that activity in one sensory modality elicits sensations in another. Although first described by Francis Galton in the 1880s, little was known about this condition until recently. A rennaissance in synaesthesia research began about a decade ago; since then, three previously unrecognized forms of the condition have been described, and hypotheses for how it arises have been put forward. Two new studies now provide some insight into time-space synaesthesia, the least researched of all the forms of this…
IMAGINE sitting in a noisy restaurant, across the table from a friend, having a conversation as you eat your meal. To communicate effectively in this situation, you have to extract the relevant information from the noise in the background, as well as from other voices. To do so, your brain somehow "tags" the predictable, repeating elements of the target signal, such as the pitch of your friend's voice, and segregates them from other signals in the surroundings, which fluctuate randomly. The ability to focus on your friend's voice while excluding other noises is commonly referred to as the…
A novel temporal illusion, in which the cause of an event is perceived to occur after the event itself, provides some insight into the brain mechanisms underlying conscious perception. The illusion, described in the journal Current Biology by a team of researchers from France, suggests that the unconscious representation of a visual object is processed for around one tenth of a second before it enters conscious awareness. Chien-Te Wu and his colleagues at the Brain and Cognition Research Centre in Toulouse used a visual phenomenon called motion-induced blindness, in which a constantly…
FOLLOWING the surgical removal of a body part, amputees often report sensations which seem to originate from the missing limb. This is thought to occur because the brain's model of the body (referred to as the body image) still contains a representation of the limb, and this leads to the experience that the missing limb is still attached to their body. Occasionally, amputees say that they cannot move their phantom limbs - they are perceived to be frozen in space, apparently because they cannot be seen. Yet, research shows that the body image is malleable and easily manipulated. And according…