Posts tagged selective attention
Articles and news from the latest research reports.
Tracking the Source of “Selective Attention” Problems in Brain-Injured Vets
An estimated 15-20 percent of U.S. troops returning from Iraq and Afghanistan suffer from some form of traumatic brain injury (TBI) sustained during their deployment, with most injuries caused by blast waves from exploded military ordnance. The obvious cognitive symptoms of minor TBI — including learning and memory problems — can dissipate within just a few days. But blast-exposed veterans may continue to have problems performing simple auditory tasks that require them to focus attention on one sound source and ignore others, an ability known as “selective auditory attention.”
According to a new study by a team of Boston University (BU) neuroscientists, such apparent “hearing” problems actually may be caused by diffuse injury to the brain’s prefrontal lobe — work that will be described at the 167th meeting of the Acoustical Society of America, to be held May 5-9, 2014 in Providence, Rhode Island.
"This kind of injury can make it impossible to converse in everyday social settings, and thus is a truly devastating problem that can contribute to social isolation and depression," explains computational neuroscientist Scott Bressler, a graduate student in BU’s Auditory Neuroscience Laboratory, led by biomedical engineering professor Barbara Shinn-Cunningham.
For the study, Bressler, Shinn-Cunningham and their colleagues — in collaboration with traumatic brain injury and post-traumatic stress disorder expert Yelena Bogdanova of VA Healthcare Boston — presented a selective auditory attention task to 10 vets with mild TBI and to 17 control subjects without brain injuries. Notably, on average, veterans had hearing within a normal range.
In the task, three different melody streams, each comprised of two notes, were simultaneously presented to the subjects from three different perceived directions (this variation in directionality was achieved by differing the timing of the signals that reached the left and right ears). The subjects were then asked to identify the “shape” of the melodies (i.e., “going up,” “going down,” or “zig-zagging”) while their brain activity was measured by electrodes on the scalp.
"Whenever a new sound begins, the auditory cortex responds, encoding the sound onset," Bressler explains. "Attentional focus, however, changes the strength of this response: when a listener is attending to a particular sound source, the neural activity in response to that sound is greater." This change of the neural response occurs because the brain’s "executive control" regions, located in the brain’s prefrontal cortex, send signals to the auditory sensory regions of the brain, modulating their response.
The researchers found that blast-exposed veterans with TBI performed worse on the task — that is, they had difficulty controlling auditory attention — “and in all of the TBI veterans who performed well enough for us to measure their neural activity, 6 out of our 10 initial subjects, the brain response showed weak or no attention-related modulation of auditory responses,” Bressler says.
"Our hope is that some of our findings can be used to develop methods to assess and quantify TBI, identifying specific factors that contribute to difficulties communicating in everyday settings," he says. "By identifying these factors on an individual basis, we may be able to define rehabilitation approaches and coping strategies tailored to the individual."
Some TBI patients also go on to develop chronic traumatic encephalopathy (CTE) — a debilitating progressive degenerative disease with symptoms that include dementia, memory loss and depression — which can now only be definitively diagnosed after death. “With any luck,” Bressler adds, “neurobehavioral research like ours may help identify patients at risk of developing CTE long before their symptoms manifest.”
(Source: newswise.com)
Paying closer attention to attention
Ellen’s (not her real name) adoptive parents weren’t surprised when the school counselor suggested that she might have attention deficit hyperactivity disorder (ADHD).
Several professionals had made this suggestion over the years. Given that homework led to one explosion after another, and that at school Ellen, who is eleven, spent her days jiggling up and down in her seat, unable to concentrate for more than ten minutes, it seemed a reasonable assumption. Yet her parents always felt that ADHD didn’t quite capture the extent of Ellen’s issues over the years. Fortunately the school counsellor was familiar with fetal alcohol spectrum disorder (FASD). When she learned that Ellen’s birth mother had consumed alcohol during pregnancy, she raised the possibility that Ellen’s problems could be attributable to FASD and referred her for further assessment.
It’s a familiar story, and most of us reading about Ellen would assume that she did indeed suffer from ADHD.
But now researchers from McGill have suggested that there may be an overreporting of attention problems in children with FASD, simply because parents and teachers are using a misplaced basis for comparison. They are testing and comparing children with FASD with children of the same physical or chronological age, rather than with children of the same mental age, which is often quite a lot younger.
“Because the link between fetal alcohol syndrome and ADHD is so commonly described in the literature, both parents and teachers are more likely to expect these children to have attention problems,” says Prof. Jacob Burack, a professor in McGill’s Dept. of Educational and Counselling Psychology and the senior author on a recent study on the subject. “But what teachers often don’t recognize is that although the child they are dealing with is eleven years old in chronological terms, they are actually functioning at the developmental age of an eight-year old. That’s a pretty big difference. And when you use mental age as the basis of comparison, many of the attention problems that have been described in children with FASD no longer seem of primary importance.”
The researchers recruited children with FASD whose average chronological age was just under twelve years old. But their average mental age, determined by standard tests, was actually closer to nine-and-a-half years old. (The children were recruited through the Asante Centre for Fetal Alcohol Syndrome in British Columbia, and though the number of children studied may appear small, this is a fairly typical size for studies on FASD, given the difficulties of the diagnostic process.)
These children were then compared with children who were developing typically and whose average chronological age was about eight-and-a-half years old and whose average mental age was similar to that of the group of children diagnosed with FASD.
After using tests to measure specific aspects of attention, the researchers then compared the performance of children with FASD on these tests with the results of children of the same mental age. What they found was that while children like Ellen had difficulties with certain kinds of attention skills, notably in terms of shifting attention from one object to another, there were other areas, such as focus, where they had no significant difficulties at all. So, if we were to compare these aspects of attention to a hockey game, typically these children would have no difficulty focusing on the puck in the arena, but would have problems following the puck being passed from one player to another.
This suggests to Dr. Kimberly Lane, the PhD student who conducted the research, that there is a need to develop a more nuanced understanding of attention skills. “We use words like attention loosely, but it’s really an umbrella term that covers various aspects of attending to different people or events or environments,” says Dr. Lane. “By using more complex assessment techniques of various aspects of attention it will be possible to get a better picture of the attention difficulties faced by children with FASD,” she adds.
“But no matter what the tests say, it’s important for teachers and parents to understand that.the difficulties these children have with attention may be less important than their more general problems, and we need to work with them as they are.”
(Source: mcgill.ca)
Study finds pigeons and other animals, like humans, can place everyday things in categories
Pinecone or pine nut? Friend or foe? Distinguishing between the two requires that we pay special attention to the telltale characteristics of each. And as it turns out, us humans aren’t the only ones up to the task.
According to researchers at the University of Iowa, pigeons share our ability to place everyday things in categories. And, like people, they can hone in on visual information that is new or important and dismiss what is not.
“The basic concept at play is selective attention. That is, in a complex world, with its booming, buzzing confusion, we don’t attend to all properties of our environment. We attend to those that are novel or relevant,” says Ed Wasserman, UI psychology professor and secondary author on the paper, published in the Journal of Experimental Psychology: Animal Learning and Cognition.
Selective attention has traditionally been viewed as unique to humans. But as UI research scientist and lead author of the study Leyre Castro explains, scientists now know that discerning one category from another is vital to survival.
“All animals in the wild need to distinguish what might be food from what might be poison, and, of course be able to single out predators from harmless creatures,” she says.
More than that, other creatures seem to follow the same thought process humans do when it comes to making these distinctions. Castro and Wasserman’s study reveals that learning about an object’s relevant characteristics and using those characteristics to categorize it go hand-in-hand.
When observing pigeons, “We thought they would learn what was relevant (step one) and then learn the appropriate response (step two),” Wasserman explains. But instead, the researchers found that learning and categorization seemed to occur simultaneously in the brain.
To test how, and indeed whether, animals like pigeons use selective attention, Wasserman and Castro presented the birds with a touchscreen containing two sets of four computer-generated images—such as stars, spirals, and bubbles.
The pigeons had to determine what distinguished one set from the other. For example, did one set contain a star while the other contained bubbles?
By monitoring what images the pigeons pecked on the touchscreen, Wasserman and Castro were able to determine what the birds were looking at. Were they pecking at the relevant, distinguishing characteristics of each set—in this case the stars and the bubbles?
The answer was yes, suggesting that pigeons—like humans—use selective attention to place objects in appropriate categories. And according to the researchers, the finding can be extended to other animals like lizards and goldfish.
“Because a pigeon’s beak is midway between its eyes, we have a pretty good idea that where it is looking is where it is pecking,” Wasserman says. “This could be true of any bird or fish or reptile.
“However, we can’t assume our findings would hold true in an animal with appendages—such as arms—because their eyes can look somewhere other than where their hand or paw is touching,” he explains.
Reward linked to image is enough to activate brain’s visual cortex
Once rhesus monkeys learn to associate a picture with a reward, the reward by itself becomes enough to alter the activity in the monkeys’ visual cortex. This finding was made by neurophysiologists Wim Vanduffel and John Arsenault (KU Leuven and Harvard Medical School) and American colleagues using functional brain scans and was published recently in the leading journal Neuron.
Our visual perception is not determined solely by retinal activity. Other factors also influence the processing of visual signals in the brain. “Selective attention is one such factor,” says Professor Wim Vanduffel. “The more attention you pay to a stimulus, the better your visual perception is and the more effective your visual cortex is at processing that stimulus. Another factor is the reward value of a stimulus: when a visual signal becomes associated with a reward, it affects our processing of that visual signal. In this study, we wanted to investigate how a reward influences activity in the visual cortex.”
Pavlov inverted
To do this, the researchers used a variant of Pavlov’s well-known conditioning experiment: “Think of Pavlov giving a dog a treat after ringing a bell. The bell is the stimulus and the food is the reward. Eventually the dogs learned to associate the bell with the food and salivated at the sound of the bell alone. Essentially, Pavlov removed the reward but kept the stimulus. In this study, we removed the stimulus but kept the reward.”
In the study, the rhesus monkeys first encountered images projected on a screen followed by a juice reward (classical conditioning). Later, the monkeys received juice rewards while viewing a blank screen. fMRI brain scans taken during this experiment showed that the visual cortex of the monkeys was activated by being rewarded in the absence of any image.
Importantly, these activations were not spread throughout the whole visual system but were instead confined to the specific brain regions responsible for processing the exact stimulus used earlier during conditioning. This result shows that information about rewards is being sent to the visual cortex to indicate which stimuli have been associated with rewards.
Equally surprising, these reward-only trials were found to strengthen the cue-reward associations. This is more or less the equivalent to giving Pavlov’s dog an extra treat after a conditioning session and noticing the next day that he salivates twice as much as before. More generally, this result suggests that rewards can be associated with stimuli over longer time scales than previously thought.
Dopamine
Why does the visual cortex react selectively in the absence of a visual stimulus on the retina? One potential explanation is dopamine. “Dopamine is a signalling chemical (neurotransmitter) in nerve cells and plays an important role in processing rewards, motivation, and motor functions. Dopamine’s role in reward signalling is the reason some Parkinson’s patients fall into gambling addiction after taking dopamine-increasing drugs. Aware of dopamine’s role in reward, we re-ran our experiments after giving the monkeys a small dose of a drug that blocks dopamine signalling. We found that the activations in the visual cortex were reduced by the dopamine blocker. What’s likely happening here is that a reward signal is being sent to the visual cortex via dopamine,” says Professor Vanduffel.
The study used fMRI (functional Magnetic Resonance Imaging) scans to visualise brain activity. fMRI scans map functional activity in the brain by detecting changes in blood flow. The oxygen content and the amount of blood in a given brain area vary according to the brain activity associated with a given task. In this way, task-specific activity can be tracked.
Dragonflies have human-like ‘selective attention’
In a discovery that may prove important for cognitive science, our understanding of nature and applications for robot vision, researchers at the University of Adelaide have found evidence that the dragonfly is capable of higher-level thought processes when hunting its prey.
The discovery, published online in the journal Current Biology, is the first evidence that an invertebrate animal has brain cells for selective attention, which has so far only been demonstrated in primates.
Dr Steven Wiederman and Associate Professor David O’Carroll from the University of Adelaide’s Centre for Neuroscience Research have been studying insect vision for many years.
Using a tiny glass probe with a tip that is only 60 nanometres wide - 1500 times smaller than the width of a human hair - the researchers have discovered neuron activity in the dragonfly’s brain that enables this selective attention.
They found that when presented with more than one visual target, the dragonfly brain cell ‘locks on’ to one target and behaves as if the other targets don’t exist.
"Selective attention is fundamental to humans’ ability to select and respond to one sensory stimulus in the presence of distractions," Dr Wiederman says.
Associate Professor O’Carroll says this brain activity makes the dragonfly a more efficient and effective predator.
"Recent studies reveal similar mechanisms at work in the primate brain, but you might expect it there. We weren’t expecting to find something so sophisticated in lowly insects from a group that’s been around for 325 million years, Associate Professor O’Carroll says.
"We believe our work will appeal to neuroscientists and engineers alike. For example, it could be used as a model system for robotic vision. Because the insect brain is simple and accessible, future work may allow us to fully understand the underlying network of neurons and copy it into intelligent robots," he says.
Memory load leaves us ‘blind’ to new information
Trying to keep an image we’ve just seen in memory can leave us blind to things we are ‘looking’ at, according to the results of a study by researchers at the Institute of Cognitive Neuroscience.
It’s been known for some time that when our brains are focused on a task, we can fail to see other things that are in plain sight. This phenomenon, known as ‘inattentional blindness’, is exemplified by the famous ‘invisible gorilla’ experiment where people concentrate on a video of players throwing around a basketball and try to count the number of times the ball is thrown, but fail to observe a man in a gorilla suit walk across the centre of the screen.
The new results reveal that our visual field does not need to be cluttered with other objects to cause this ‘blindness’ and that focusing on remembering something we have just seen is enough to make us unaware of things that happen around us.
“An example of where this is relevant in the real world is when people are following directions on a Sat Nav whilst driving,” explains Professor Nilli Lavie from UCL Institute of Cognitive Neuroscience, who led the study. “Our research would suggest that focusing on remembering the directions we’ve just seen on the screen means that we’re more likely to fail to observe other hazards around us on the road, for example an approaching motorbike or a pedestrian on a crossing, even though we may be ‘looking’ at where we’re going.”
Study offers new clue on how brain processes visual information, provides insight into neural mechanisms of attention
July 23, 2012
Ever wonder how the human brain, which is constantly bombarded with millions of pieces of visual information, can filter out what’s unimportant and focus on what’s most useful?
The process is known as selective attention and scientists have long debated how it works. But now, researchers at Wake Forest Baptist Medical Center have discovered an important clue. Evidence from an animal study, published in the July 22 online edition of the journal Nature Neuroscience, shows that the prefrontal cortex is involved in a previously unknown way.
Two types of attention are utilized in the selective attention process – bottom up and top down. Bottom-up attention is automatically guided to images that stand out from a background by virtue of color, shape or motion, such as a billboard on a highway. Top-down attention occurs when one’s focus is consciously shifted to look for a known target in a visual scene, as when searching for a relative in a crowd.
Traditionally, scientists have believed that separate areas of the brain controlled these two processes, with bottom-up attention occurring in the posterior parietal cortex and top-down attention occurring in the prefrontal cortex.
"Our findings provide insights on the neural mechanisms behind the guidance of attention," said Christos Constantinidis, Ph.D., associate professor of neurobiology and anatomy at Wake Forest Baptist and senior author of the study. "This has implications for conditions such as attention deficit hyperactivity disorder (ADHD), which affects millions of people worldwide. People with ADHD have difficulty filtering information and focusing attention. Our findings suggest that both the ability to focus attention intentionally and shifting attention to eye-catching but sometimes unimportant stimuli depend on the prefrontal cortex."
In the Wake Forest Baptist study, two monkeys were trained to detect images on a computer screen while activity in both areas of the brain was recorded. The visual display was designed to let one image “pop out” due to its color difference from the background, such as a red circle surrounded by green. To trigger bottom-up attention, neither the identity nor the location of the pop-out image could be predicted before it appeared. The monkeys indicated that they detected the pop-out image by pushing a lever.
The neural activity associated with identifying the pop-out images occurred in the prefrontal cortex at the same time as in the posterior parietal cortex. This unexpected finding indicates early involvement of the prefrontal cortex in bottom-up attention, in addition to its known role in top-down attention, and provides new insights into the neural mechanisms of attention.
"We hope that our findings will guide future work targeting attention deficits," Constantinidis said.
Provided by Wake Forest University Baptist Medical Center
Source: medicalxpress.com