Posts tagged perception
Articles and news from the latest research reports.
Brain waves encode rules for behavior
One of the biggest puzzles in neuroscience is how our brains encode thoughts, such as perceptions and memories, at the cellular level. Some evidence suggests that ensembles of neurons represent each unique piece of information, but no one knows just what these ensembles look like, or how they form.
A new study from researchers at MIT and Boston University (BU) sheds light on how neural ensembles form thoughts and support the flexibility to change one’s mind. The research team, led by Earl Miller, the Picower Professor of Neuroscience at MIT, identified groups of neurons that encode specific behavioral rules by oscillating in synchrony with each other.
The results suggest that the nature of conscious thought may be rhythmic, according to the researchers, who published their findings in the Nov. 21 issue of Neuron.
“As we talk, thoughts float in and out of our heads. Those are all ensembles forming and then reconfiguring to something else. It’s been a mystery how the brain does this,” says Miller, who is also a member of MIT’s Picower Institute for Learning and Memory. “That’s the fundamental problem that we’re talking about — the very nature of thought itself.”
Optical Illusions Show How We See
Imagine… as you wake later than usual rolling over towards the window, you notice that it’s a gorgeous day outside. Warm, yellow sunlight shines in through glass illuminating floating “dust angles.” On the other side of the glass, past the oak tree with yellowing leaves, you see a brilliant blue sky. For the first time it occurs to you that a blue sky is a contradiction: the sky at night is devoid of color, so why during the day does the world seem to be shrouded in a blanket of blue? Years previously as a child full of questions you asked your parents, but the answer they offered seemed somehow inadequate at the time… less than magical. And so the question remains… as it does the most of us.
The answer is this: The sky isn’t actually colored at all (not blue or yellow or red or green). Rather, it’s your mind that’s colored. The world around us is physics devoid of meaning, whereas our perception of the world is meaning devoid of physics. In terms of physics, the light in the sky is heavily biased towards smaller wavelengths (around 450 nanometers). This is because the air itself scatters smaller wavelengths of light more than it does larger ones. Which means the air in the sky is like a filter, letting primarily medium to long wavelengths through more easily than short wavelengths. Hence why the sky is composed primarily of shorter wavelengths (and so appears bluish), whereas the light from sun is composed primarily of longer wavelengths (and so appears more reddish). While the differential scattering of sunlight by the air explains the non-uniform distribution of wavelengths across the sky, it doesn’t explain why shorter wavelengths are seen as blue and the longer ones as red.
Fantasy-Reality Confusion a Primary Cause of Childhood Nighttime Fears
From monsters under the bed to bogeymen in the closet, most children experience nighttime fears at some point in their development. And while most grow out of them without any professional intervention, others contend with persistent and extended periods of these fears, with a risk of developing anxiety problems later in life.
As part of a large-scale project on nighttime fears funded by the Israeli Science Foundation, Prof. Avi Sadeh of Tel Aviv University’s School of Psychological Sciences is exploring how these fears fit into the normal developmental process — and when they become a problem. Together with Dr. Jonathan Kushnir, who completed his Ph.D. studies in the field in Prof. Sadeh’s lab, MA student Tamar Zisenwine, and Ph.D. student Michal Kaplan, he discovered that a child’s ability to differentiate fact from fiction has a huge impact on overcoming terror of things that go bump in the night.
In their study, published in Child Psychiatry and Human Development, the researchers found that preschoolers with persistent nighttime fears were far less able to distinguish reality from fantasy compared to their peers. The research will help clinicians and parents alike to develop interventions that can better soothe fretful children, he says, noting that a strong imagination can ultimately be used to the child’s psychological advantage.
Wired for Harmony?
Many creatures, such as human babies, chimpanzees, and chicks, react negatively to dissonance—harsh, unstable, grating sounds. Since the days of the ancient Greeks, scientists have wondered why the ear prefers harmony. Now, scientists suggest that the reason may go deeper than an aversion to the way clashing notes abrade auditory nerves; instead, it may lie in the very structure of the ear and brain, which are designed to respond to the elegantly spaced structure of a harmonious sound.
"Over the past century, researchers have tried to relate the perception of dissonance to the underlying acoustics of the signals," says psychoacoustician Marion Cousineau of the University of Montreal in Canada. In a musical chord, for example, several notes combine to produce a sound wave containing all of the individual frequencies of each tone. Specifically, the wave contains the base, or "fundamental," frequency for each note plus multiples of that frequency known as harmonics. Upon reaching the ear, these frequencies are carried by the auditory nerve to the brain. If the chord is harmonic, or "consonant," the notes are spaced neatly enough so that the individual fibers of the auditory nerve carry specific frequencies to the brain. By perceiving both the parts and the harmonious whole, the brain responds to what scientists call harmonicity.
In a dissonant chord, however, some of the notes and their harmonics are so close together that two notes will stimulate the same set of auditory nerve fibers. This clash gives the sound a rough quality known as beating, in which the almost-equal frequencies interfere to create a warbling sound. Most researchers thought that phenomenon accounted for the unpleasantness of a dissonance.
Women’s body talk: perception stronger than reality?
How women think their friends feel about their bodies influences their own body concerns, according to a new study by Dr. Louise Wasylkiw and Molly Williamson from Mount Alison University in Canada. Their work, which examines the role of friends in young women’s body concerns, is published online in Springer’s journal Sex Roles.
Research shows that friends influence how girls and women view and judge their own body weight, shape and size. What Wasylkiw and Williamson’s work sheds light on, is how much of a young woman’s body concerns are shaped by her perceptions of peers’ concerns with their own body versus her peers’ actual body concerns.
Learning a New Sense
Rats use a sense that humans don’t: whisking. They move their facial whiskers back and forth about eight times a second to locate objects in their environment. Could humans acquire this sense? And if they can, what could understanding the process of adapting to new sensory input tell us about how humans normally sense? At the Weizmann Institute, researchers explored these questions by attaching plastic “whiskers” to the fingers of blindfolded volunteers and asking them to carry out a location task. The findings, which recently appeared in the Journal of Neuroscience, have yielded new insight into the process of sensing, and they may point to new avenues in developing aids for the blind.
The idea of an untethered consciousness is something we can understand, even when we don’t suppose it is found in nature.
Why Children Think They Are Invisible when Covering Their Eyes
Dr. James Russell and a research team at the University of Cambridge recently published work on young children’s conception of personal visibility, which furthers the understanding of cognitive development and of our emerging sense of self.
The research involved children three to four years of age. Researchers placed an eye mask on each of the children and asked them if they could be seen when wearing it. They then asked each child if an adult who was wearing a similar mask could be seen. The majority of the children involved in the study believed they were not visible when wearing the mask. Most also believed that the adult wearing the eye mask was also hidden.
Additional tests revealed a unique layer of complexity, demonstrating that although the children thought they were invisible when there eyes were covered, they still believed that their head and body were able to be seen.
The research team concluded by process of elimination that the factor that makes children believe they are visible is eye contact with another person.
“… it would seem that children apply the principle of joint attention to the self and assume that for somebody to be perceived, experience must be shared and mutually known to be shared, as it is when two pairs of eyes meet,” the researchers reported. “Young children’s natural tendency to acquire knowledge intersubjectively, by joint attention, leads them to undergo a developmental period in which they believe the self is something that must be mutually experienced for it to be perceived.”
Evidently, children only believe they exist when making eye contact with another person. The implications point to a simple but necessary way to make children feel present and involved. Cultures worldwide seem to have some version of “peek-a-boo,” as a quick Google image search reveals. Lack of eye contact in children has been linked as an early sign of autism, while the presence of eye contact is associated with empathy. Dr. Russell’s team seems to have discovered a key facet of cognitive development.
The results of Dr. Russell’s study were published in the Journal of Cognition and Development.
(Source: united-academics.org)
Music in Our Ears: The Biological Bases of Musical Timbre Perception
Timbre is the attribute of sound that allows humans and other animals to distinguish among different sound sources. Studies based on psychophysical judgments of musical timbre, ecological analyses of sound’s physical characteristics as well as machine learning approaches have all suggested that timbre is a multifaceted attribute that invokes both spectral and temporal sound features. Here, we explored the neural underpinnings of musical timbre. We used a neuro-computational framework based on spectro-temporal receptive fields, recorded from over a thousand neurons in the mammalian primary auditory cortex as well as from simulated cortical neurons, augmented with a nonlinear classifier. The model was able to perform robust instrument classification irrespective of pitch and playing style, with an accuracy of 98.7%. Using the same front end, the model was also able to reproduce perceptual distance judgments between timbres as perceived by human listeners. The study demonstrates that joint spectro-temporal features, such as those observed in the mammalian primary auditory cortex, are critical to provide the rich-enough representation necessary to account for perceptual judgments of timbre by human listeners, as well as recognition of musical instruments.
Foggy perception slows us down
Fog is an atmospheric phenomenon that afflicts millions of drivers every day, impairing visibility and increasing the risk of an accident. The ways people respond to conditions of reduced visibility is a central topic in vision research. It has been shown that people tend to underestimate speeds when visibility is reduced equally at all distances, as for example, when driving with a uniformly fogged windshield. But what happens when the visibility decreases as you look further into the distance, as happens when driving in true fog? New research by Paolo Pretto at the Max Planck Institute for Biological Cybernetics in Tübingen published in eLife, reveals that people tend to overestimate their speed when driving in fog-like conditions and therefore naturally tend to drive at a slower pace.