Posts tagged perception

July 11, 2012

An inflated sense of memory function in people with dementia may influence their likelihood of seeking help, new Flinders University research shows.

As part of her PhD, Flinders research associate Dr. Chris Materne studied the disparity between memory perception and performance in people with dementia.

In the first stage of the project, Dr. Materne analysed data from the Australian Longitudinal Study of Aging which showed that most survey participants believed their memory had remained stable over the 11-year assessment, despite tests showing a decline in memory performance.

She then conducted an intervention with 13 individuals, from a larger group of 23 people with dementia, using spaced retrieval memory training to help them achieve a specific task or activity, such as remembering to lock the front door or keep their glasses in the same spot.

“Spaced retrieval works by helping people remember specific information or tasks by getting them to respond to a prompt question over progressively increasing intervals of time,” Dr. Materne said.

“In one case we helped a man remember to put his glasses in the same place because he was always losing them which made both him and his wife quite distressed,” she said.

“We think the training taps into procedural memory so it becomes habitual rather than explicit memory, such as memory for facts, which tends to decline before procedural memory when you have dementia.”

The technique was conducted once a week for six weeks, with seven out of the 13 participants still able to perform their nominated activity or task after six months.

The 23 participants were also asked to rate their performance based on a specific question, such as how many people they could name in a photo with 10 faces.

While most respondents were initially over-confident in their abilities, with some claiming to be able to name all 10 faces, their perceptions did change over time to more accurately reflect their cognitive function.

About one third of family carers, however, initially considered their loved ones memory to be better than what the person with dementia actually reported.

“In the longitudinal sample people didn’t feel their memory had changed over time because the questions were more general but when we asked specific, detailed questions about memory in the smaller study, the respondents came to recognise their declining performance.”

Dr. Materne said the research highlighted the need for more comprehensive assessments when diagnosing dementia to increase the accuracy of peoples’ perceptions, and therefore their likelihood of seeking help.

Provided by Flinders University

Source: medicalxpress.com

July 9, 2012

(Medical Xpress) — Have you ever found yourself paying attention to the sound of your footsteps when walking down a quiet corridor? Or perhaps you enjoy creating rhythmic patterns by tapping on a surface? Almost every bodily movement we make generates an impact sound and a team of academics have been studying whether the perception of the physical dimensions of our body can be challenged by spatially altering the ‘action’ sounds we make.

Self-action sounds help us understand physical properties of objects and our own body. Picture by Antonio Caballero

The research team from Royal Holloway, University of London conducted various experiments to determine whether our action sounds influence the way we picture ourselves and whether these perceptions change when the sound is manipulated.

Dr Manos Tsakiris from Royal Holloway said: “These sounds provide an important source of information about the physical properties of the objects and the space around us, but they also inform us about the physical properties of one’s own body, although we are mostly not aware of this process.”

The study, Action sounds recalibrate perceived tactile distance, is published in Current Biology and shows that increasing the distance to sound events produced when tapping on a surface with one’s arm influences the subsequent judgments of distance between two objects touching the arm. “Participants did not report feeling their own arm extended as a result of this test possibly because it is difficult for someone to accept that the dimensions of their body can change from one minute to the other. However, the increase in reported distance between two points touching one’s arm do suggest an unconscious change in the way participants mentally represented their arm, as if they would represent this arm as being longer,” Dr Tajadura-Jiménez explains.

The researchers hope this study could have clinical applications and help in the way chronic pain is treated or help motivate older people to move further or for longer than they previously thought was possibly by manipulating the action sounds they make.

Provided by Royal Holloway, University of London

Source: medicalxpress.com

June 29, 2012

Scientists at Arizona State University have discovered that honey bees may teach us about basic connections between taste perception and metabolic disorders in humans.

Honey bees may help scientists understand how food-related behaviors interact with internal metabolism and how to manipulate those behaviors to control metabolic disorders. Photo by: Christofer Bang

By experimenting with honey bee genetics, researchers have identified connections between sugar sensitivity, diabetic physiology and carbohydrate metabolism. Bees and humans may partially share these connections.

In a study published in the open-access journal PLoS Genetics (Public Library of Science), Gro Amdam, an associate professor, and Ying Wang, a research scientist, in the School of Life Sciences in ASU’s College of Liberal Arts and Sciences, explain how for the first time, they’ve successfully inactivated two genes in the bees’ “master regulator” module that controls food-related behaviors. By doing so, researchers discovered a possible molecular link between sweet taste perception and the state of internal energy.

“A bee’s sensitivity to sugar reveals her attitude towards food, how old the bee is when she starts searching for nectar and pollen, and which kind of food she prefers to collect,” said Wang, the lead author of the paper. “By suppressing these two ‘master’ genes, we discovered that bees can become more sensitive to sweet taste. But interestingly, those bees also had very high blood sugar levels, and low levels of insulin, much like people who have Type 1 diabetes.”

In Amdam’s honey bee lab at ASU, scientists suppressed two genes including vitellogenin, which is similar to a human gene called apolipoprotein B, and ultraspiracle, which partners with an insect hormone that has some functions in common with the human thyroid hormone. The team is the first in the world to accomplish this double gene-suppressing technique. Researchers used this method to understand how the master regulator works.

“Now, if one can use the bees to understand how taste perception and metabolic syndromes are connected, it’s a very useful tool,” said Amdam, who also has a honey bee laboratory at the Norwegian University of Life Sciences. “Most of what we know about deficits in human perceptions is from people who are very sick or have had a brain trauma. We know shockingly little about people in this area.”

The researchers are now considering how, exactly, the bees’ sweet taste was enhanced by the experiment. The most metabolically active tissue of the bee, called the fat body, may hold the key. The fat body is similar to the liver and abdominal fat in humans, in that it helps store nutrients and create energy.

Amdam explains that taste perception evolved as a survival mechanism, for bees as well as for people. For example, bitter foods may be poisonous or sweet taste may signal foods rich in calories for energy. For all animals, taste perception must communicate properly with one’s internal energetic state to control food intake and maintain normal life functions. Without this, poorly functioning taste perception can contribute to unhealthy eating behaviors and metabolic diseases, such as diabetes and obesity.

“From this study, we realized we can take advantage of honey bees in understanding how food-related behaviors interact with internal metabolism, as well as how to manipulate these food-related behaviors in order to control metabolic disorders,” added Amdam.

Provided by Arizona State University

Source: PHYS.ORG

ScienceDaily (June 13, 2012) — Ever wonder why Jimi Hendrix’s rendition of “The Star-Spangled Banner” moved so many people in 1969 or why the music in the shower scene of “Psycho” still sends chills down your spine?

Jimi Hendrix (Credit: Public domain image, courtesy of UCLA)

A UCLA-based team of researchers has isolated some of the ways in which distorted and jarring music is so evocative, and they believe that the mechanisms are closely related to distress calls in animals.

They report their findings in the latest issue of the peer-reviewed scientific journal Biology Letters, which publishes online June 12.

"Music that shares aural characteristics with the vocalizations of distressed animals captures human attention and is uniquely arousing," said Daniel Blumstein, one of the study’s authors and chair of the UCLA Department of Ecology and Evolutionary Biology.

Read more …

June 12, 2012

Financial loss can lead to irrational behavior. Now, research by Weizmann Institute scientists reveals that the effects of loss go even deeper: Loss can compromise our early perception and interfere with our grasp of the true situation. The findings, which recently appeared in the Journal of Neuroscience, may also have implications for our understanding of the neurological mechanisms underlying post-traumatic stress disorder.

The experiment was conducted by Dr. Rony Paz and research student Offir Laufer of the Neurobiology Department. Subjects underwent a learning process based on classic conditioning and involving money. They were asked to listen to a series of tones composed of three different notes. After hearing one note, they were told they had earned a certain sum; after a second note, they were informed that they had lost some of their money; and a third note was followed by the message that their bankroll would remain the same. According to the findings, when a note was tied to gain, or at least to no loss, the subjects improved over time in a learned task – distinguishing that note from other, similar notes. But when they heard the “lose money” note, they actually got worse at telling one from the other.

Functional MRI (fMRI) scans of the brain areas involved in the learning process revealed an emotional aspect: The amygdala, which is tied to emotions and reward, was strongly involved. The researchers also noted activity in another area in the front of the brain, which functions to moderate the emotional response. Subjects who exhibited stronger activity in this area showed less of a drop in their abilities to distinguish between tones.

Paz: “The evolutionary origins of that blurring of our ability to discriminate are positive: If the best response to the growl of a lion is to run quickly, it would be counterproductive to distinguish between different pitches of growl. Any similar sound should make us flee without thinking. Unfortunately, that same blurring mechanism can be activated today in stress-inducing situations that are not life-threatening – like losing money – and this can harm us.”

That harm may even be quite serious: For instance, it may be involved in post-traumatic stress disorder. If sufferers are unable to distinguish between a stimulus that should cause a panic response and similar, but non-threatening, stimuli, they may experience strong emotional reactions in inappropriate situations.

This perceptional blurring may even expand over time to encompass a larger range of stimuli. Paz intends to investigate this possibility in future research.

Provided by Weizmann Institute of Science

Source: medicalxpress.com

June 5, 2012

(Medical Xpress) — Using transcranial magnetic stimulation (TMS), an international team led by French researchers from the Centre de Recherche de l’Institut du Cerveau (CNRS) has succeeded in enhancing the visual abilities of a group of healthy subjects. Following stimulation of an area of the brain’s right hemisphere involved in perceptual awareness and in orienting spatial attention, the subjects appeared more likely to perceive a target appearing on a screen. This work, published in the journal PLoS ONE, could lead to the development of novel rehabilitation techniques for certain visual disorders. In addition, it could help improve the performance of individuals whose tasks require very high precision.

TMS is a non-invasive technique that consists in sending a magnetic pulse into a given area of the brain. This results in an activation of the cortical neurons located within the range of the magnetic field, which modifies their activity in a painless and temporary manner. For several years, scientists have been looking at the possibility of using this technique to enhance certain brain functions in healthy subjects.

In this respect, the team led by Antoni Valero-Cabré has carried out research involving the stimulation of a region of the right cerebral hemisphere known as the frontal eye field. Strictly speaking, this is not a primary visual area but it participates in the planning of ocular movements and the orientation of each individual’s attention in the visual space. In a first experiment, a group of healthy subjects tried to distinguish a very low contrast target appearing on a screen for just 30 ms. In some of the tests, the subjects received a magnetic pulse lasting between 80 and 140 ms on this frontal region before the target appeared. The researchers found that the success rate was higher when using TMS. The visual sensitivity of healthy subjects was temporarily increased by around 12%. In a second experiment, the subjects were shown a fleeting visual cue indicating the spot where the target could appear. In this configuration, the enhancement of visual sensitivity, which remained of the same order, was only apparent when the cue indicated the correct location of the target.

Although cerebral functions such as conscious vision are highly optimized in healthy adults, these results show that there is a significant margin for improvement, which can be “enhanced” by TMS. This technique could be tested for the rehabilitation of patients suffering from cortical damage, due for example to a cardiovascular accident, and for that of patients with retinal disorders. The second experiment suggests that rehabilitation based on both TMS and visual cues could be more selective than the use of stimulation alone. The researchers want to further explore this possibility using repetitive TMS, which, in this case, could make it possible to obtain long-lasting modification of cerebral activity.

Furthermore, according to the researchers, TMS could be used in the near future to increase the attentional abilities of individuals performing tasks that require good visual skills.

Provided by CNRS

Source: medicalxpress.com

ScienceDaily (May 22, 2012) — Researchers at Barrow Neurological Institute at St. Joseph’s Hospital and Medical Center have unveiled how and why the public perceives some magic tricks in recent studies that could have real-world implications in military tactics, marketing and sports.

A professional magician believed that if he moved his hand in a straight line while performing a trick the audience would focus on the beginning and end points of the motion, but not in between. In contrast, he believed if he moved his hand in a curved motion the audience would follow his hand’s trajectory from beginning to end. (Credit: © luzitanija / Fotolia)

Susana Martinez-Conde, PhD, of Barrow’s Laboratory of Visual Neuroscience, and Stephen Macknik, PhD, of Barrow’s Laboratory of Behavioral Neurophysiology are well known for their research into magic and illusions. Their most recent original research projects, published in Frontiers in Human Neuroscience, offer additional insight into perception and cognition.

One of the studies was initiated by professional magician Apollo Robbins, who believed that audience members directed their attention differently depending on the type of hand motion used. Robbins believed that if he moved his hand in a straight line while performing a trick the audience would focus on the beginning and end points of the motion, but not in between. In contrast, he believed if he moved his hand in a curved motion the audience would follow his hand’s trajectory from beginning to end.

By studying the eye movements of individuals as they watched Robbins perform, Barrow researchers confirmed Robbins’ theory. Perhaps more importantly, they also found that the different types of hand motion triggered two different types of eye movement. The researchers discovered that curved motion engaged smooth pursuit eye movements (in which the eye follows a moving object smoothly), whereas straight motion led to saccadic eye movements (in which the eye jumps from one point of interest to another).

"Not only is this discovery important for magicians, but the knowledge that curved motion attracts attention differently from straight motion could have wide-reaching implications — for example, in predator-prey evasion techniques in the natural world, military tactics, sports strategies and marketing," says Martinez-Conde. This finding is believed to be the first discovery in the neuroscientific literature initiated by a magician, rather than a scientist.

In another study, the researchers worked with professional magician Mac King to investigate magicians’ use of social cues — like the position of their gaze — to misdirect observers.

They studied a popular coin-vanishing trick, in which King tosses a coin up and down in his right hand before “tossing” it to his left hand, where it subsequently disappears. In reality, the magician only simulates tossing the coin to the left hand, an implied motion that essentially tricks the neurons into responding as they would have if the coin had actually been thrown.

The Barrow researchers discovered that social misdirection does not always help magic. By presenting two different videos of King — one in which the audience could see his face and another in which his face was hidden — they found that social misdirection did not play a role in this particular trick.

"We wondered if the observer’s perception of magic was going to be different if they could see the magician’s head and eye position. To our surprise, it didn’t matter," says Martinez-Conde. "This indicates that social misdirection in magic is more complicated than previously believed, and not necessary for the perception of all magic tricks."

Source: Science Daily

When the rings of dynamic patterns are presented to the same eye (left column), the subject is able to consciously perceive the target pattern-the stripes in the center of the ring. When the two are presented to different eyes (right column), the dynamic pattern suppresses perception of the target pattern. Under both conditions, participants were asked to perform a task that focused attention on the target (top row) or on letters presented outside the target area (bottom row). Credit: 2012 Masataka Watanabe

From a purely intuitive point of view, it is easy to believe that our ability to actively pay attention to a target is inextricably connected with our capacity to consciously perceive it. However, this proposition remains the subject of extensive debate in the research community, and surprising new findings from a team of scientists in Japan and Europe promise to fuel the debate.

Resolving how these aspects of perception are managed requires a detailed understanding of how the visual centers in our brain process information. A region known as V1 has been investigated as it represents the first portion of the visual cortex to receive and process signals transmitted from the retina.

Many researchers favor a model in which functions pertaining consciousness are widely spread among the whole visual system, including V1. The classical model, which assumes that the neural mechanism of consciousness is integrated into a narrow subset of brain structures, referred to as a homunculus, or ‘little human’, is almost defunct. However, a modern version of this model is under debate. It proposes that the neural mechanism of consciousness is a privileged set of cortical areas, a subpopulation of neurons, or certain neural dynamics (e.g. oscillations); while there are also visual systems that have nothing to do with conscious vision, explains Masataka Watanabe a researcher investigating brain function at the University of Tokyo, Japan.

Watanabe cites studies proposing that visual attention as processed within V1 may be only minimally impacted by conscious perception; but, the experimental data have been contradictory. For example, studies using a technique called functional magnetic resonance imaging (fMRI) to map brain activity have indicated that V1 contributes to both attention and awareness in humans. However, invasive electrophysiological studies in non-human primates yielded different results. “You would find only 10 to 15% of neurons in V1 that are barely modulated by awareness, and 85% or so that are not modulated at all,” says Watanabe. To resolve this ambiguity, he, Kang Cheng from the RIKEN Brain Science Institute, Wako, and their colleagues designed an experiment that examined both processes independently. Surprisingly, their results may lend support the modern homunculus model. 

Read more …