sight is really as much a function of our brains as our eyes,RELATED People born blind can see during a near-death experience

Brain can 'see' in the dark: Study

PTI | Nov 3, 2013, 06.06 AM IST

comments

Share More

READ MORE University of Rochester|darkness|brain

At least 50 per cent of people can see the movement of their own hand even when it is pitch dark, a new study said.

People born blind can see during a near-death experience

www.near-death.com/experiences/evidence03.html‎

Yet, she appears to have been able to see during her NDE. ... roof of the building itself, during which time she had a brief panoramic view of her surroundings.

WASHINGTON: At least 50 per cent of people can see the movement of their own hand even when it is pitch dark, a new study, that used computerised eye-trackers, has found.

Even in the absence of all light, the brain keeps track of the body, researchers said.

Neuroscientists and psychologists discovered that the mind continues to perceive motion in complete darkness. Their findings suggest that 50 per cent of the population sees in the dark without realising it.

"Seeing in total darkness? According to the current understanding of natural vision, that just doesn't happen," says Duje Tadin, a professor of brain and cognitive sciences at the University of Rochester who led the investigation.

"But this research shows that our own movements transmit sensory signals that also can create real visual perceptions in the brain, even in the complete absence of optical input," said Tadin.

Through five separate experiments involving 129 individuals, the authors found that this eerie ability to see our hand in the dark suggests that our brain combines information from different senses to create our perceptions.

The ability also "underscores that what we normally perceive of as sight is really as much a function of our brains as our eyes," said first author Kevin Dieter, a post-doctoral fellow in psychology at Vanderbilt University.

For most people, this ability to see self-motion in darkness probably is learned, the authors conclude.

"We get such reliable exposure to the sight of our own hand moving that our brains learn to predict the expected moving image even without actual visual input," said Dieter.

The study was published in journal Psychological Science.

Left or right wagging tail means different things among dogs

Subodh Varma, TNN | Nov 1, 2013, 04.01 PM IST

comments

Share More

READ MORE tail wagging|dog wagging tail

There is more to the dog wagging its tail than meets the eye, scientists have found. The rightward wag and the leftward wag mean different things to dogs. This happens because dogs, like humans, have asymmetrically organized brains, with the left and right sides playing different roles, thescientific study published in the journal Current Biology on Thursday, suggests.

The Italian research team led by Giorgio Vallortigara of the Center for Mind/Brain Sciences of the University of Trento had earlier found that dogs wag to the right when they feel positive emotions (upon seeing their owners, for instance) and to the left when they feel negative emotions (upon seeing an unfriendly dog, for example). That biased tail-wagging behavior reflects what is happening in the dogs' brains. Left-brain activation produces a wag to the right, and right-brain activation produces a wag to the left.

But does that tail-wagging difference mean something to other dogs? Yes it does, the new study shows.

While monitoring their reactions, the researchers showed dogs videos of other dogs with either left- or right-asymmetric tail wagging. When dogs saw another dog wagging to the left, their heart rates picked up and they began to look anxious. When dogs saw another dog wagging to the right, they stayed perfectly relaxed.

"The direction of tail wagging does in fact matter, and it matters in a way that matches hemispheric activation," says Vallortigara.

A right wag means the left hemisphere of the brain is activated in the dog. That means it is experiencing some positive response. So, another dog observing it would feel a relaxed response. In contrast, a dog showing a left wag activated by the right hemisphere is feeling a negative or withdrawal response. To the observing dog, this would induce an anxious and targeting response as well as increased cardiac frequency.

Vallortigara doesn't think that the dogs are necessarily intending to communicate those emotions to other dogs. Rather, he says, the bias in tail wagging is likely the automatic byproduct of differential activation of the left versus the right side of the brain. But that's not to say that the bias in wagging and its response might not find practical uses; veterinarians and dog owners might do well to take note.

'Mini-neural computer' in the brain discovered

PTI | Oct 28, 2013, 03.46 PM IST

comments

Share More

READ MORE mini-neural computers|UNC School of Medicine|Spencer Smith

WASHINGTON: Scientists have found that dendrites, the branch-like projections of neurons, act as mini-neural computers - actively processing information to multiply the brain's computing power.

Dendrites were thought to be passive wiring in the brain but researchers at the University of North Carolina at Chapel Hill with their colleagues have shown that these dendrites do more than relay information from one neuron to the next.

"Suddenly, it's as if the processing power of the brain is much greater than we had originally thought," said Spencer Smith, an assistant professor in the UNC School of Medicine.

The findings could change the way scientists think about long-standing scientific models of how neural circuitry functions in the brain, while also helping researchers better understand neurological disorders.

Axons are where neurons conventionally generate electrical spikes, but many of the same molecules that support axonal spikes are also present in the dendrites.

Previous research using dissected brain tissue had demonstrated that dendrites can use those molecules to generate electrical spikes themselves, but it was unclear whether normal brain activity involved those dendritic spikes. For example, could dendritic spikes be involved in how we see?

Smith's team found that dendrites effectively act as mini-neural computers, actively processing neuronal input signals themselves.

Researchers used patch-clamp electrophysiology to attach a microscopic glass pipette electrode, filled with a physiological solution, to a neuronal dendrite in the brain of a mouse. The idea was to directly "listen" in on the electrical signalling process.

Once the pipette was attached to a dendrite, Smith's team took electrical recordings from individual dendrites within the brains of anaesthetised and awake mice.

As the mice viewed visual stimuli on a computer screen, the researchers saw an unusual pattern of electrical signals ? bursts of spikes ? in the dendrite.

Smith's team then found that the dendritic spikes occurred selectively, depending on the visual stimulus, indicating that the dendrites processed information about what the animal was seeing.

To provide visual evidence of their finding, Smith's team filled neurons with calcium dye, which provided an optical readout of spiking.

This revealed that dendrites fired spikes while other parts of the neuron did not, meaning that the spikes were the result of local processing within the dendrites.

"All the data pointed to the same conclusion. The dendrites are not passive integrators of sensory-driven input; they seem to be a computational unit as well," Smith said.

The findings were published in the journal Nature.