[accessibleimage] Working in combination, human senses ...


http://www.signonsandiego.com/news/science/20070315-9999-lz1c15senses.html

Working in combination, human senses seem almost superheroic

There is, it seems, no such thing as a common sense. 

Researchers are increasingly teasing out evidence that our five basic
senses add up to a whole lot more than most of us realize or appreciate.
Indeed, by combining and exploiting our basic senses in novel and
unexpected ways, humans perceive far more than they can simply see, taste,
touch, smell or hear, scientists say. 

For example: 

A UC Riverside psychology professor and others have documented the ability
of blindfolded volunteers to employ bat-like echolocation to move
successfully within unfamiliar spaces and identify shapes simply by the
sounds moving around them. 

A Florida-based institute is working on a helmet equipped with cameras,
sonar and other equipment that would transmit images and other data to the
brain ? via the tongue. 

A Canadian researcher says he has empirically tested the presence of a
?sixth sense? ? the ability to detect change or danger without conscious
awareness. At the same time, researchers in St. Louis report possibly
finding the part of the brain where the sixth sense resides. 

?Our brains are perfectly capable of taking many different sensory inputs
and combining them in unusual ways,? said Vilyanur S. Ramachandran,
director of the Center for Brain and Cognition at UCSD. ?Intersensory
interaction is what paved the way for higher intelligence capacity in
humans.? 


Bat people
In his 1974 essay ?What Is It Like to Be a Bat?? philosopher Thomas Nagel
observed that bat sonar, or echolocation, was so unlike any human sense,
so beyond our experience or imagination, that we could never really answer
his question. 

Nagel was wrong. There is growing evidence that humans possess at least a
rudimentary ability to echolocate ? that is, to interpret sounds bouncing
off surrounding objects to discern one's place. 

The phenomenon, of course, is well-established among blind people, but it
also has been documented among sighted people, especially after a little
training. 

?There's nothing categorically different with the brain or sensory
perceptions of blind people,? said Lawrence D. Rosenblum, a professor of
psychology at UC Riverside. ?They don't have or develop new mental
processes. They simply (echolocate) better by virtue of having more
experience.? 


 
Rosenblum and others have conducted experiments in which blind and sighted
but blindfolded subjects are asked to walk toward a movable wall placed at
varying distances from their starting point. The subjects are told to
signal when they begin to sense the presence of the wall and to walk as
close as possible to the wall without touching it. 

Blind participants typically perform well, often detecting the wall
several feet before contact and moving within a few inches without
touching. Sighted but blindfolded subjects tend to start out shakily but
improve with training. 

In one experiment, sighted subjects were able to detect walls 36 to 144
inches in front of them simply by listening to sounds bouncing off of the
surfaces. 

?We are much more sensitive to everyday aspects of acoustics than we
assume,? said Rosenblum. ?Test subjects usually begin by saying there's no
way they will be able to do what we ask, but usually they do quite well.
We use sound in ways we're not consciously aware of.? 

In a different set of experiments, Rosenblum asked blindfolded subjects to
identify various rooms on campus ? a bathroom, the gym, a walk-in closet ?
by the ambient sound. Or identify the shapes of objects placed in front of
an array of speakers emitting white noise. The participants were
remarkably accurate. 

?It's all about hearing the silent world,? said Rosenblum. ?Lots of
things, like an empty room, don't make a sound, but they do structure it.
They give it shape, which people can see without seeing. I have had
students listen to sounds broadcast between two boards and be able to tell
me whether there was enough space between the boards for them to fit
through.? 

Tongue-tied

Paul Bach-y-Rita has a favorite saying: ?We don't see with our eyes.? 

What the University of Wisconsin neuroscientist means is that vision is
fundamentally the product of the brain: Light enters the eyes, gets
converted into electrical signals and sent, via the optic nerve, to the
brain's primary visual cortex for interpretation. The eyes are just tools
to do the job. 

But they are not the only tools. For much of the past 40 years,
Bach-y-Rita and others have explored and exploited the brain's amazing
plasticity when it comes to sensory input. 



Advertisement Early in his career, Bach-y-Rita designed a glove for
leprosy patients who had lost the sense of touch in their hands. The glove
was equipped with transducers in the fingertips that transmitted pressure
signals to electrodes attached to the forehead. Patients reported being
able to distinguish between smooth and rough surfaces with their hands,
quickly forgetting where the information was actually coming from. 
In the 1980s, Bach-y-Rita attached a microphone to a belt, which vibrated
in different ways to reflect various detected sound frequencies. Deaf
users said the belt helped them better read lips. 

Most of Bach-y-Rita's recent work has focused on using the tongue as a
surrogate for eyes. The neuroscientist has tested devices that convert
camera images into patterns of electric impulses that can be felt when a
flexible cable is pressed against the tongue, which has more tactile nerve
endings than any part of the body other than the lips. 

The results are far from perfect vision. The electric signals produce only
a crude tingling sense of what's being seen. But blindfolded volunteers
reportedly have been able to grab objects placed in front of them, catch
rolling balls and even recognize large letters on a poster. 

?The tongue is an excellent pathway to the brain,? said Bach-y-Rita. ?It's
rich in nerve endings and highly integrated into the brain. And it's the
brain, really, that is important. It's the brain that's making sense of
the information.? 

Bach-y-Rita's pioneering work is being carried forward by researchers at
the Institute for Human and Machine Cognition in Pensacola, Fla. With
funding from the Department of Defense and elsewhere, institute engineers
are trying to create wearable devices that would amplify the senses of
soldiers and other users. 

Marines, for example, might someday wear helmets with cameras providing
360-degree night vision. Ocean divers could wear small sonar systems
offering a better ?view? into dark or murky waters. In both cases, the
visual information would be delivered to the brain through a mouth cable
tipped with 144 microelectrodes. 

Current technology is still a long way from making those efforts a
reality, but Anil Raj, an institute research scientist, said early
prototypes have been intriguing. In tests, Raj said blindfolded volunteers
(including him) wearing tongue-attached ?Brain Ports? have ?seen? basic
objects. 

?I have recognized my hand reaching out to a cup on a table,? said Raj.
?It's all in gray scales, pretty rough shapes and movement. The brain does
a lot of filling in the gaps, making the picture complete, especially when
you add other sensory input like touch. 

?But we expect to get better with higher resolution imagery.? 

Sixth sense

People talk about the five basic senses, but clearly there are more. The
question, of course, is how many? 

Conservative estimates put the number at 10 or so, and include such
abilities as sensing temperature and blood pressure. More radical notions
add things like joint position, body movement, blood-sugar levels and
feelings associated with a full bladder, empty stomach or thirst. Some
researchers argue that humans may possess 30 or more senses. 

No sense is more mysterious than the so-called sixth: the inexplicable
awareness that something is about to happen or something is not quite
right. 

At one time or another, most people say they have experienced this
sensation. It has been suggested that a sixth sense is the sum of the
other five senses combined. 

Ronald Rensink, a professor of psychology at the University of British
Columbia, suggests, however, that it's more likely the sixth sense is a
mode of unexplained, unconscious visual perception. 

Rensink calls it ?mindsight,? a still largely unexplained ability to sense
a change but not actually see it ? at least initially. 

In experiments designed to detect mindsight, Rensink has shown volunteers
a series of photographic images on a computer screen, each lasting for a
quarter of a second, alternating with a brief blank gray screen. 

Sometimes the images were unchanged throughout the sequence. Sometimes
Rensink inserted a slightly different image. Volunteers were asked to
press a button when they had a ?feeling? something was different and again
when they actually saw or recognized the difference. 

Most of the participants pressed the button only when they actually
noticed a change, but about one-third reported sensing a difference in the
image before they could specifically identify it. 

To test whether they were simply guessing, Rensink ran control experiments
in which the images remained the same. The same volunteers confidently
noted no image change in the control experiments. 

Rensink says mindsight is not a simple precursor to normal visual
perception because it isn't related to when a person detects a change and
when he or she identifies its cause. Sometimes the identification happens
simultaneously; sometimes it takes a few moments. 

Rensink speculates that what's happening is that some visual clues aren't
being processed as vision per se, but rather are triggering other
perceptual systems in the brain. 

?I would define it as a mode of visual perception, a type of vision that
results in a 'gut feeling' or 'sense' of something happening,? he said. 

?It's not really a sixth sense because you still need light entering the
eyes (as stimulus). But what you're getting isn't an image, but a feeling.
You can't see it, but you know something has changed.? 

The phenomenon, said Rensink, suggests that the conscious mind isn't the
only thing dictating our perceptions and reactions. Some decisions, it
seems, are coming from parts of the brain not directly associated with
conscious thought. 

?Humans appear to have a highly effective 'pattern-matching' system that
is unconscious but highly intelligent,? Rensink said. ?These unconscious
systems often communicate with the conscious mind by such gut feelings. 

?The feelings are sometimes incorrect ? and so need to be treated
cautiously ? but they often contain useful information and should be
respected. We shouldn't disregard them as 'just a feeling.' ? 

Researchers at Washington University in St. Louis think they may have
identified the likely source of that feeling in the brain. 

Located near the top of the front lobes and along the walls that divide
the left and right hemispheres, the anterior cingulate cortex (ACC) is
believed to help mediate between fact-based reasoning and emotional
responses, such as love and fear. 

In a paper published in 2005, Joshua Brown, a research associate in
psychology, and colleagues proposed that the ACC also warns of dangers not
yet consciously recognized. 

The conclusion is based in part on a series of experiments in which
volunteers were given mental tasks while attached to brain-imaging
equipment. The tasks, such as quickly pushing correct buttons at specific
cues, created mental conflicts. 

The scientists noted that, as the level of difficulty and conflict
increased, the ACC became more active, appearing to direct responses even
when the participants were consciously unaware of the cues. 

?Our brains are better at picking up subtle warning signs than we
previously thought,? Brown said. 

?In the past, we found activity in the ACC when people had to make a
difficult decision among mutually exclusive options, or after they made a
mistake. But now we find that this brain region can actually learn to
recognize when you might make a mistake, even before a difficult decision
has to be made.? 




Lisa Yayla
Huseby Kompetansesenter 
Oslo Norway
lisa.yayla@xxxxxxxxxx

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