Posts tagged visual memory
Articles and news from the latest research reports.
Important advance in brain mapping and memory
“When a tiger starts to move towards you, you need to know whether it is something you are actually seeing or whether it’s just something that you remember or have imagined,” says Prof. Julio Martinez-Trujillo of McGill’s Department of Physiology. The researcher and his team have discovered that there is a clear frontier in the brain between the area that encodes information about what is immediately before the eyes and the area that encodes the abstract representations that are the product of our short-term memory or imagination. It is an important advance in brain mapping and opens the doors to further research in the area of short-term memory.
These finding, which are described in an article just published in Nature Neuroscience, resolve a question that has occupied neuroscientists for years. Namely that of how and where exactly in the brain the visual information coming from our eyes is first transformed into short-term memories. “We found that while one area in the brain processes information about what we are currently seeing, an area right beside it stores the information in short-term memory,” says McGill PhD student Diego Mendoza-Halliday, first author of the article. “What is so exciting about this finding is that until now, no one knew the place where visual information first gets transformed into short-term memory.”
The researchers arrived at this conclusion by measuring the neuronal activity in these two areas in the brains of macaques as they first looked at, and then after a short time (1.2 - 2 seconds) remembered, a random sequence of dots moving across a computer screen like rainfall. What surprised Martinez-Trujillo and his team was how clearly demarcated the divide was between the activities and functions of the two brain areas, and this despite the fact that they lie side-by-side.
“It is rare to find this kind of sharp boundary in biological systems of any kind,” says Martinez-Trujillo. “Most of the time, when you look at the function of different brain areas, there is more of a transitional zone, more grey and not such a clear border between black and white. I think the evolutionary reason for this clear frontier is that it helped us to survive in dangerous situations.”
The discovery comes after five years spent by Martinez-Trujillo and his team doing research in the area. Despite this fact, he acknowledges that there was a certain amount of serendipity, and a lot of technological help involved in being able to capture a signal that travels for 3 milliseconds and fires synapses in neurons that lie right beside one another.
Martinez-Trujillo and his team continue to work on mapping the receptors and connectivity between these two areas of the brain. But what is most important for him is to try and relate this discovery to schizophrenia and other diseases that involve hallucinations, and in order to do so he is working with a psychiatrist at Montreal’s Douglas Hospital.
(Image: Bigstock)
The study, part-funded by the Medical Research Council (MRC) and published online in PNAS, challenges the idea that suppressed memories remain fully preserved in the brain’s unconscious, allowing them to be inadvertently expressed in someone’s behaviour. The results of the study suggest instead that the act of suppressing intrusive memories helps to disrupt traces of the memories in the parts of the brain responsible for sensory processing.
The team at the MRC Cognition and Brain Sciences Unit and the University of Cambridge’s Behavioural and Clinical Neuroscience Institute (BCNI) have examined how suppression affects a memory’s unconscious influences in an experiment that focused on suppression of visual memories, as intrusive unwanted memories are often visual in nature.
After a trauma, most people report intrusive memories or images, and people will often try to push these intrusions from their mind, as a way to cope. Importantly, the frequency of intrusive memories decreases over time for most people. It is critical to understand how the healthy brain reduces these intrusions and prevents unwanted images from entering consciousness, so that researchers can better understand how these mechanisms may go awry in conditions such as post-traumatic stress disorder.
Participants were asked to learn a set of word-picture pairs so that, when presented with the word as a reminder, an image of the object would spring to mind. After learning these pairs, brain activity was recorded using functional magnetic resonance imaging (fMRI) while participants either thought of the object image when given its reminder word, or instead tried to stop the memory of the picture from entering their mind.
The researchers studied whether suppressing visual memories had altered people’s ability to see the content of those memories when they re-encountered it again in their visual worlds. Without asking participants to consciously remember, they simply asked people to identify very briefly displayed objects that were made difficult to see by visual distortion. In general, under these conditions, people are better at identifying objects they have seen recently, even if they do not remember seeing the object before—an unconscious influence of memory. Strikingly, they found that suppressing visual memories made it harder for people to later see the suppressed object compared to other recently seen objects.
Brain imaging showed that people’s difficulty seeing the suppressed object arose because suppressing the memory from conscious awareness in the earlier memory suppression phase had inhibited activity in visual areas of the brain, disrupting visual memories that usually help people to see better. In essence, suppressing something from the mind’s eye had made it harder to see in the world, because visual memories and seeing rely on the same brain areas: out of mind, out of sight.
Over the last decade, research has shown that suppressing unwanted memories reduces people’s ability to consciously remember the experiences. The researchers’ studies on memory suppression have been inspired, in part, by trying to understand how people adapt memory after psychological trauma. Although this may work as a coping mechanism to help people adapt to the trauma, there is the possibility that if the memory traces were able to exert an influence on unconscious behaviour, they could potentially exacerbate mental health problems. The idea that suppression leaves unconscious memories that undermine mental health has been influential for over a century, beginning with Sigmund Freud.
These findings challenge the assumption that, even when supressed, a memory remains fully intact, which can then be expressed unconsciously. Moreover, this discovery pinpoints the neurobiological mechanisms underlying how this suppression process happens, and could inform further research on uncontrolled ‘intrusive memories’, a classic characteristic of post-traumatic stress disorder.
Dr Michael Anderson, at the MRC Cognition and Brain Sciences Unit said: “While there has been a lot of research looking at how suppression affects conscious memory, few studies have examined the influence this process might have on unconscious expressions of memory in behaviour and thought. Surprisingly, the effects of suppression are not limited to conscious memory. Indeed, it is now clear, that the influence of suppression extends beyond areas of the brain associated with conscious memory, affecting perceptual traces that can influence us unconsciously. This may contribute to making unwanted visual memories less intrusive over time, and perhaps less vivid and detailed.”
Dr Pierre Gagnepain, lead author at INSERM in France said: “Our memories can be slippery and hard to pin down. Out of hand and uncontrolled, their remembrance can haunt us and cause psychological troubles, as we see in PTSD. We were interested whether the brain can genuinely suppress memories in healthy participants, even at the most unconscious level, and how it might achieve this. The answer is that it can, though not all people were equally good at this. The better understanding of the neural mechanisms underlying this process arising from this study may help to better explain differences in how well people adapt to intrusive memories after a trauma”
Remember that sound bite you heard on the radio this morning? The grocery items your spouse asked you to pick up? Chances are, you won’t.
Researchers at the University of Iowa have found that when it comes to memory, we don’t remember things we hear nearly as well as things we see or touch.
“As it turns out, there is merit to the Chinese proverb ‘I hear, and I forget; I see, and I remember,” says lead author of the study and UI graduate student, James Bigelow.
“We tend to think that the parts of our brain wired for memory are integrated. But our findings indicate our brain may use separate pathways to process information. Even more, our study suggests the brain may process auditory information differently than visual and tactile information, and alternative strategies—such as increased mental repetition—may be needed when trying to improve memory,” says Amy Poremba, associate professor in the UI Department of Psychology and corresponding author on the paper, published this week in the journal PLoS One.
Bigelow and Poremba discovered that when more than 100 UI undergraduate students were exposed to a variety of sounds, visuals, and things that could be felt, the students were least apt to remember the sounds they had heard.
In an experiment testing short-term memory, participants were asked to listen to pure tones they heard through headphones, look at various shades of red squares, and feel low-intensity vibrations by gripping an aluminum bar. Each set of tones, squares and vibrations was separated by time delays ranging from one to 32 seconds.
Although students’ memory declined across the board when time delays grew longer, the decline was much greater for sounds, and began as early as four to eight seconds after being exposed to them.
While this seems like a short time span, it’s akin to forgetting a phone number that wasn’t written down, notes Poremba. “If someone gives you a number, and you dial it right away, you are usually fine. But do anything in between, and the odds are you will have forgotten it,” she says.
In a second experiment, Bigelow and Poremba tested participants’ memory using things they might encounter on an everyday basis. Students listened to audio recordings of dogs barking, watched silent videos of a basketball game, and touched and held common objects blocked from view, such as a coffee mug. The researchers found that between an hour and a week later, students were worse at remembering the sounds they had heard, but their memory for visual scenes and tactile objects was about the same.
Both experiments suggest that the way your mind processes and stores sound may be different from the way it process and stores other types of memories. And that could have big implications for educators, design engineers, and advertisers alike.
“As teachers, we want to assume students will remember everything we say. But if you really want something to be memorable you may need to include a visual or hands-on experience, in addition to auditory information,” says Poremba.
Previous research has suggested that humans may have superior visual memory, and that hearing words associated with sounds—rather than hearing the sounds alone—may aid memory. Bigelow and Poremba’s study builds upon those findings by confirming that, indeed, we remember less of what we hear, regardless of whether sounds are linked to words.
The study also is the first to show that our ability to remember what we touch is roughly equal to our ability to remember what we see. The finding is important, because experiments with nonhuman primates such as monkeys and chimpanzees have shown that they similarly excel at visual and tactile memory tasks, but struggle with auditory tasks. Based on these observations, the authors believe humans’ weakness for remembering sounds likely has its roots in the evolution of the primate brain.
Video Gamers Really Do See More
Hours spent at the video gaming console not only train a player’s hands to work the buttons on the controller, they probably also train the brain to make better and faster use of visual input, according to Duke University researchers.
"Gamers see the world differently," said Greg Appelbaum, an assistant professor of psychiatry in the Duke School of Medicine. "They are able to extract more information from a visual scene."
It can be difficult to find non-gamers among college students these days, but from among a pool of subjects participating in a much larger study in Stephen Mitroff’s Visual Cognition Lab at Duke, the researchers found 125 participants who were either non-gamers or very intensive gamers.
Each participant was run though a visual sensory memory task that flashed a circular arrangement of eight letters for just one-tenth of a second. After a delay ranging from 13 milliseconds to 2.5 seconds, an arrow appeared, pointing to one spot on the circle where a letter had been. Participants were asked to identify which letter had been in that spot.
At every time interval, intensive players of action video games outperformed non-gamers in recalling the letter.
Earlier research by others has found that gamers are quicker at responding to visual stimuli and can track more items than non-gamers. When playing a game, especially one of the “first-person shooters,” a gamer makes “probabilistic inferences” about what he’s seeing — good guy or bad guy, moving left or moving right — as rapidly as he can.
Appelbaum said that with time and experience, the gamer apparently gets better at doing this. “They need less information to arrive at a probabilistic conclusion, and they do it faster.”
Both groups experienced a rapid decay in memory of what the letters had been, but the gamers outperformed the non-gamers at every time interval.
The visual system sifts information out from what the eyes are seeing, and data that isn’t used decays quite rapidly, Appelbaum said. Gamers discard the unused stuff just about as fast as everyone else, but they appear to be starting with more information to begin with.
The researchers examined three possible reasons for the gamers’ apparently superior ability to make probabilistic inferences. Either they see better, they retain visual memory longer or they’ve improved their decision-making.
Looking at these results, Applebaum said, it appears that prolonged memory retention isn’t the reason. But the other two factors might both be in play — it is possible that the gamers see more immediately, and they are better able make better correct decisions from the information they have available.
To get at this question, the researchers will need more data from brainwaves and MRI imagery to see where the brains of gamers have been trained to perform differently on visual tasks.
The woman who can’t recognise her face
"I’ve been in a crowded elevator with mirrors all around, and a woman will move and I’ll go to get out the way and then realise: ‘oh that woman is me’."
Heather Sellers has prosopagnosia, more commonly known as face blindness. “I can’t remember any image of the human face. It’s simply not special to me,” she says. “I don’t process them like I do a car or a dog. It’s not a visual problem, it’s a perception problem.”
Heather knew from a young age that something was different about the way she navigated her world, but her condition wasn’t diagnosed until she was in her 30s. “I always knew something was wrong – it was impossible for me to trust my perceptions of the world. I was diagnosed as anxious. My parents thought I was crazy.”
The condition is estimated to affect around 2.5 per cent of the population, and it’s common for those who have it not to realise that anything is wrong. “In many ways it’s a subtle disorder,” says Heather. “It’s easy for your brain to compensate because there are so many other things you can use to identify a person: hair colour, gait or certain clothes. But meet that person out of context and it’s socially devastating.”
As a child, she was once separated from her mum at a grocery store. Store staff reunited the pair, but it was confusing for Heather, since she didn’t initially recognise her mother. “But I didn’t know that I wasn’t recognising her.”
Chaos explained
Heather was 36 when she stumbled across the phrase face blindness in a psychology textbook. “When I saw those two words I knew instantly that was exactly what I had – that explained all the chaos.”
She found her way to Harvard neuroscientist Brad Duchaine who diagnosed her as having one of the three worst cases of the disorder that he had ever seen.
So what’s it like to not recognise anyone you know? Heather says the biggest difficulty with the disorder is recognising people who she is close to – the people that are most important to recognise. In the school where she teaches English she is fine, because she recognises people by their clothes or hair and asks her students to wear name badges.
But it can be harder in social settings. Once she went up to the wrong person at a party and put her arm around him thinking he was her partner. And at college men would phone her angry that she had walked straight past them after they had had a date. “At the time I was thinking ‘I didn’t see you, why is everyone making my life so difficult?’”
It’s not just other people Heather doesn’t recognise – she can’t identify her own face either. “A few times I have been in a crowded elevator with mirrors all around and a woman will move, and I will go to get out the way and then realise ‘oh that woman is me’.” She also finds it unsettling to see photos and not recognise herself in them.
Face processing
To try and understand the condition, Duchaine and his colleagues recorded brain activity while 12 people with prosopagnosia looked at famous and non-famous faces. The team found that part of the brain responsible for stored visual memory was activated in six people when they saw the famous faces.
But another component of brain activity thought to represent a later stage of face processing wasn’t triggered. “Some part of their brain was recognising the face,” says Duchaine, but the brain was failing to pass this information into higher-level consciousness (Brain).
"There may be training where we give people feedback and say ‘look you recognise that face even though you’re not aware of it’," says Duchaine.
Now Zaira Cattaneo at the University of Milano-Bicocca in Italy and colleagues have identified the specific brain areas that allow us to recognise our friends. The team used transcranial magnetic stimulation to block two vital aspects of face processing in people without prosopagnosia. Targeting the left prefrontal cortex blocked the ability to distinguish individual features like the nose and eyes, and blocking the right prefrontal cortex impaired the ability to distinguish the location of those features from one another (NeuroImage).
"We made performance worse," says Cattaneo. "We want to make it better." Now the team are trying to activate these areas of the brain. "The aim is to enhance face recognition abilities by directly modulating excitability in the prefrontal cortices," says Cattaneo.
Would Heather want a cure, should one be found? “I can’t imagine what you see when you see a face, and it’s scary,” she says. “I go back and forth on what I’d do. I’ve done so much work in figuring out how to chart my world, I’d need to do a whole new rewrite. But it would be fascinating.”
Strobe Eyewear Training Improves Visual Memory
ScienceDaily (July 23, 2012) — Stroboscopic training, performing a physical activity while using eyewear that simulates a strobe-like experience, has been found to increase visual short-term memory retention, and the effects lasted 24 hours.
(Credit: Image courtesy of Duke University)
Participants completed a memory test that required them to note the identity of eight letters of the alphabet that were briefly displayed on a computer screen. After a variable delay, participants were asked to recall one of the eight letters. On easy-level trials, the recall prompt came immediately after the letters disappeared, but on more difficult trials, the prompt came as late as 2.5 seconds following the display. Because participants did not know which letter they would be asked to recall, they had to retain all of the items in memory.
"Humans have a memory buffer in their brain that keeps information alive for a certain short-lived period," said Greg Appelbaum, assistant professor of psychiatry at Duke University and first author of the study. "Wearing the strobe eyewear during the physical training seemed to boost the ability to retain information in this buffer."
The strobe eyewear disrupts vision by only allowing the user to see glimpses of the world. The user must adjust their visual processing in order to perform normally, and this adjustment produces a lingering benefit; once participants removed the strobe eyewear, there was an observed boost in their visual memory retention, which was found to last 24 hours.
Earlier work by Appelbaum and the project’s senior researcher, Stephen Mitroff, had shown that stroboscopic training improves visual perception, including the ability to detect subtle motion cues and the processing of briefly presented visual information. Yet the earlier study had not determined how long the benefits might last.
"Our earlier work on stroboscopic training showed that it can improve perceptual abilities, but we don’t know exactly how," says Mitroff, associate professor of psychology & neuroscience and member of the Duke Institute for Brain Sciences. "This project takes a big step by showing that these improved perceptual abilities are driven, at least in part, by improvements in visual memory."
"Improving human cognition is an important goal with so many benefits," said Appelbaum, also a member of the Duke Institute for Brain Sciences. "Interestingly, our findings demonstrate one way in which visual experience has the capacity to improve cognition."
Source: Science Daily