Posts tagged neuroscience
Articles and news from the latest research reports.
Do brain cells need to be connected to have meaning?
The classic theory of the brain is one of connections, in which the brain consists of a network of neurons that interact with each other to allow us to think, see, interpret, and understand the world around us. In this model, called distributed representation, an individual neuron by itself has no inherent meaning, but only contributes to a pattern of neuronal activity that has meaning. For example, a certain pattern of many neurons fires when you think “dog” and another pattern for “cat.”
"The belief in distributed representation theory is that a concept or object is not represented by a single neuron in the brain but by a pattern of activations over a number of neurons," explains Asim Roy, a professor of information systems at Arizona State University, to Medical Xpress . "Thus there is no single neuron in the brain representing a cat or a dog. Proponents of this theory claim that a cat or a dog is represented by its microfeatures such as legs, ears, body, tail, and so on. However, they think that neurons have absolutely no meaning on a stand-alone basis. Therefore, they go further and claim that these microfeatures are at the subsymbolic level, which means that meaning arises only when you consider the pattern of activations as a whole. Therefore, there are no neurons representing legs, ears, body, tail, etc. The representation is at a much lower level."
Roy is among a number of scientists working in the fields of neuroscience and artificial intelligence (AI) who suspect that the brain may not be as connected as distributed representation suggests. The basis of their alternative model, called localist representation, is that a single neuron can represent a dog, a cat, or any other object or concept. These neurons can be considered symbols since they have meaning on a stand-alone basis. However, as Roy explains, this doesn’t necessarily mean only one neuron represents a dog; such “concept cells” are high-level neurons, which fire in response to the firing of an assortment of low-level neurons that represent the legs, ears, body, tail, etc.
"In localist representation, there could be separate neurons for a dog and a cat, and also neurons for legs, ears, body, tail, etc.," he said. "It’s very similar to the model in my paper for word recognition, which is an old model from James McClelland [Chair of the Psychology Department at Stanford University] and [the late pioneering neuroscientist] David Rumelhart. You have low-level neurons that detect letters of the alphabet and then high-level neurons for individual words. So letter neurons and word neurons, they both exist."
The origins of this dispute between localist and distributed representation goes back to the early ’80s, to a dispute between the symbol processing hypothesis of artificial intelligence (AI) and the subsymbolic paradigm of connectionists. In the past 30 years, the debate has only intensified.
First measurements made of key brain links
Until now, brain scientists have been almost completely in the dark about how most of the nonspecific thalamus interacts with the prefrontal cortex, a relationship believed to be key in such fundamental functions as maintaining consciousness and mental arousal. Brown University researchers performed a set of experiments, described in the Journal of Neuroscience, to explore and measure those circuits for the first time.
Learning to control brain activity improves visual sensitivity
Researchers at the Wellcome Trust Centre for Neuroimaging at UCL used non-invasive, real-time brain imaging that enabled participants to watch their own brain activity on a screen, a technique known as neurofeedback. During the training phase, they were asked to try to increase activity in the area of the brain that processes visual information, the visual cortex, by imagining images and observing how their brains responded.
After the training phase, the participants’ visual perception was tested using a new task that required them to detect very subtle changes in the contrast of an image. When they were asked to repeat this task while clamping brain activity in the visual cortex at high levels, those who had successfully learned to control their brain activity could improve their ability to detect even very small changes in contrast.
This improved performance was only observed when participants were exercising control over their brain activity.
Lead author Dr Frank Scharnowski, who is now based at the University of Geneva, explains: “We’ve shown that we can train people to manipulate their own brain activity and improve their visual sensitivity, without surgery and without drugs.”
In the past, researchers have used recordings of electrical activity in the brain to train people on various tasks, including cutting their reaction times, altering their emotional responses and even improving their musical performance. In this study, the researchers used functional magnetic resonance imaging (fMRI) to provide the volunteers with real-time feedback on brain activity. The advantage of this technique is that you can see exactly where in the brain the training is having an effect, so you can target the training to particular brain areas that are responsible for specific tasks.
"The next step is to test this approach in the clinic to see whether we can offer any benefit to patients, for example to stroke patients who may have problems with perception, even though there is no damage to their vision," adds Dr Scharnowski.
Alzheimer’s researcher reveals a protein’s dual destructiveness – and therapeutic potential
A scientist at the University of British Columbia and Vancouver Coastal Health has identified the molecule that controls a scissor-like protein responsible for the production of plaques – the telltale sign of Alzheimer’s disease (AD).
The molecule, known as GSK3-beta, activates a gene that creates a protein, called BACE1. When BACE1 cuts another protein, called APP, the resulting fragment – known as amyloid beta – forms tiny fibers that clump together into plaques in the brain, eventually killing neural cells.
Using an animal model, Dr. Weihong Song, Canada Research Chair in Alzheimer’s Disease and professor of psychiatry, found that disabling GSK3-beta’s effect in mice resulted in less BACE1 and far fewer deposits of amyloid in their brains. Song’s research, published online in the Journal of Clinical Investigation, also found that such mice performed better than untreated mice on memory tests.
Previous research had shown that GSK3-beta spurred the growth of twisted fibers inside neurons, known as tangles – another hallmark of AD. Song says his discovery of the protein’s dual destructiveness makes it a promising target for drug research.
GSK3-beta, however, is a versatile enzyme that controls many vital physiological functions. The drug used to inhibit GSK3-beta in the mice is too indiscriminate, and could cause several serious side effects, including cancer.
“If we can find a way to stop GSK3-beta’s specific reaction with BACE1, and still leave it intact to perform other crucial tasks, we have a much better chance of treating AD and preventing its progression,” says Song, a member of the Brain Research Centre at UBC and the Vancouver Coastal Health Research Institute (VCHRI), and Director of the Townsend Family Laboratories at UBC.
(Source: publicaffairs.ubc.ca)
University of Minnesota researchers find new target for Alzheimer’s drug development
Researchers at the University of Minnesota’s Center for Drug Design have developed a synthetic compound that, in a mouse model, successfully prevents the neurodegeneration associated with Alzheimer’s disease.
In the pre-clinical study, researchers Robert Vince, Ph.D.; Swati More, Ph.D.; and Ashish Vartak, Ph.D., of the University’s Center for Drug Design, found evidence that a lab-made compound known as psi-GSH enables the brain to use its own protective enzyme system, called glyoxalase, against the Alzheimer’s disease process.
The discovery is published online in the American Chemical Society journal ACS Chemical Neuroscience and presents a new target for the design of anti-Alzheimer’s and related drugs.
“While most other drugs under development and on the market attempt to slow down or reverse the Alzheimer’s processes, our approach strikes at a root cause by enabling the brain itself to fight the disease at a very early stage,” said Vince, the study’s lead researcher and director of the Center for Drug Design. “As is the case with all drug development, these studies need to be replicated in human patients before coming to any firm conclusions.”
Research reveals why some teenagers more prone to binge drinking
New research helps explain why some teenagers are more prone to drinking alcohol than others.
The study, led by King’s College London’s Institute of Psychiatry (IoP) and published in Proceedings of National Academy of Sciences (PNAS)* provides the most detailed understanding yet of the brain processes involved in teenage alcohol abuse.
Alcohol and other addictive drugs activate the dopamine system in the brain which is responsible for feelings of pleasure and reward. Recent studies from King’s IoP found that the RASGRF2 gene is a risk gene for alcohol abuse, however, the exact mechanism involved in this process has, until now, remained unknown.
Professor Gunter Schumann, from the Department of Social, Genetic and Developmental Psychiatry (SGDP) at King’s Institute of Psychiatry and lead author of the study says: “People seek out situations which fulfill their sense of reward and make them happy, so if your brain is wired to find alcohol rewarding, you will seek it out. We now understand the chain of action: how our genes shape this function in our brains and how that, in turn, leads to human behaviour. We found that the RASGRF-2 gene plays a crucial role in controlling how alcohol stimulates the brain to release dopamine, and hence trigger the feeling of reward. So, if people have a genetic variation of the RASGRF-2 gene, alcohol gives them a stronger sense of reward, making them more likely to be heavy drinkers.”
*Paper reference: Stacey, D. et al. ‘RASGRF-2 regulates alcohol-induced reinforcement by influencing mesolimbic dopamine neurone activity and dopamine release’ Proceedings of the National Academy of Sciences (PNAS) 2012
Despite long experience with the ways of the world, older people are especially vulnerable to fraud. According to the Federal Trade Commission (FTC), up to 80% of scam victims are over 65. One explanation may lie in a brain region that serves as a built-in crook detector. Called the anterior insula, this structure—which fires up in response to the face of an unsavory character—is less active in older people, possibly making them less cagey than younger folks, a new study finds.
Both FTC and the Federal Bureau of Investigation have found that older people are easy marks due in part to their tendency to accentuate the positive. According to social neuroscientist Shelley Taylor of the University of California, Los Angeles, research backs up the idea that older people can put a positive spin on things—emotionally charged pictures, for example, and playing virtual games in which they risk the loss of money. “Older people are good at regulating their emotions, seeing things in a positive light, and not overreacting to everyday problems,” she says. But this trait may make them less wary.
To see if older people really are less able to spot a shyster, Taylor and colleagues showed photos of faces considered trustworthy, neutral, or untrustworthy to a group of 119 older adults (ages 55 to 84) and 24 younger adults (ages 20 to 42). Signs of untrustworthiness include averted eyes; an insincere smile that doesn’t reach the eyes; a smug, smirky mouth; and a backward tilt to the head. The participants were asked to rate each face on a scale from -3 (very untrustworthy) to 3 (very trustworthy).
In the study, appearing online in the Proceedings of the National Academy of Sciences, the “untrustworthy” faces were perceived as significantly more trustworthy by the older subjects than by the younger ones. The researchers then performed the same test on a different set of volunteers, this time imaging their brains during the process, to look for differences in brain activity between the age groups. In the younger subjects, when asked to judge whether the faces were trustworthy, the anterior insula became active; the activity increased at the sight of an untrustworthy face. The older people, however, showed little or no activation.
Scientists Discover Children’s Cells Living in Mothers’ Brains
The link between a mother and child is profound, and new research suggests a physical connection even deeper than anyone thought. The profound psychological and physical bonds shared by the mother and her child begin during gestation when the mother is everything for the developing fetus, supplying warmth and sustenance, while her heartbeat provides a soothing constant rhythm.
The physical connection between mother and fetus is provided by the placenta, an organ, built of cells from both the mother and fetus, which serves as a conduit for the exchange of nutrients, gasses, and wastes. Cells may migrate through the placenta between the mother and the fetus, taking up residence in many organs of the body including the lung, thyroid muscle, liver, heart, kidney and skin. These may have a broad range of impacts, from tissue repair and cancer prevention to sparking immune disorders.
It is remarkable that it is so common for cells from one individual to integrate into the tissues of another distinct person. We are accustomed to thinking of ourselves as singular autonomous individuals, and these foreign cells seem to belie that notion, and suggest that most people carry remnants of other individuals. As remarkable as this may be, stunning results from a new study show that cells from other individuals are also found in the brain. In this study, male cells were found in the brains of women and had been living there, in some cases, for several decades. What impact they may have had is now only a guess, but this study revealed that these cells were less common in the brains of women who had Alzheimer’s disease, suggesting they may be related to the health of the brain.
Gustav Metzger Thinks About Nothing
In an attempt to create a visual representation of empty thoughts, artist Gustav Metzger hooked himself up to a robot carving machine, that turned his brainwaves into a sculpture.
This data was then fed to a manufacturing robot, which carved the Null Object sculpture out of a piece of Portland Stone.
The result is a brain-like object, dotted with crystalline, ovoid shapes. Metzger’s empty brain.
The project is being exhibited at London’s Work Gallery, and an accompanying book features further explorations of emptiness, including novelist Hari Kunzru on nothingness as a productive category, and Bronac Ferran on ‘the radical consequences of emptiness’.
Null Object: Gustav Metzger Thinks About Nothing, is at Work Gallery, 10a Acton Street, London WC1X, until 9 February 2013.
Dopamine Not About Pleasure (Anymore)
To John Salamone, professor of psychology and longtime researcher of the brain chemical dopamine, scientific research can be very slow-moving.
“It takes a long time for things to change in science,” he says. “It’s like pulling on the steering wheel of an ocean liner, then waiting for the huge ship to slowly turn.”
Salamone has spent most of his career battling a particular long-held scientific idea: the popular notion that high levels of brain dopamine are related to experiences of pleasure. As increasing numbers of studies show, he says, the famous neurotransmitter is not responsible for pleasure, but has to do with motivation.
He summarizes and comments on the evidence for this shift in thinking in a Nov. 8 review in the Cell Press journal Neuron.