Fishy Sixth Sense: Mathematical Keys To Fascinating Sense Organ

Fish and some amphibians possess a unique sensory capability in the so-called lateral-line system. It allows them, in effect, to "touch" objects in their surroundings without direct physical contact or to "see" in the dark. Professor Leo van Hermmen and his team in the physics department of the Technische Universitaet Muenchen are exploring the fundamental basis for this sensory system. What they discover might one day, through biomimetic engineering, better equip robots to orient themselves in their environments.

With our senses we take in only a small fraction of the information that surrounds us. Infrared light, electromagnetic waves, and ultrasound are just a few examples of the external influences that we humans can grasp only with the help of technological measuring devices – whereas some other animals use special sense organs, their own biological equipment, for the purpose. One such system found in fish and some amphibians is under investigation by the research team of Professor Leo van Hemmen, chair of theoretical biophysics at TUM, the Technische Universitaet Muenchen.

Even in murky waters hardly penetrated by light, pike and pickerel can feel out their prey before making contact. The blind Mexican cave fish can perceive structures in its surroundings and can effortlessly avoid obstacles. Catfish on the hunt follow invisible tracks that lead directly to their prey. The organ that makes this possible is the lateral-line system, which registers changes in currents and even smaller disturbances, providing backup support for the sense of sight particularly in dark or muddy waters.
This remote sensing system, at first glance mysterious, rests on measurement of the pressure distribution and velocity field in the surrounding water. The lateral-line organs responsible for this are aligned along the left and right sides of the fish's body and also surround the eyes and mouth. They consist of gelatinous, flexible, flag-like units about a tenth of a millimeter long. These so-called neuromasts – which sit either directly on the animal's skin or just underneath, in channels that water can permeate through pores – are sensitive to the slightest motion of the water. Coupled to them are hair cells similar to the acoustic pressure sensors in the human inner ear. Nerves deliver signals from the hair cells for processing in the brain, which localizes and identifies possible sources of the changes detected in the water's motion.
These changes can arise from various sources: A fish swimming by produces vibrations or waves that are directly conveyed to the lateral-line organ. Schooling fishes can recognize a nearby attacker and synchronize their swimming motion so that they resemble a single large animal. The Mexican cave fish pushes a bow wave ahead of itself, which is reflected from obstacles. The catfish takes advantage of the fact that a swimming fish that beats its tail fin leaves a trail of eddies behind. This so-called "vortex street" persists for more than a minute and can betray the prey.
For the past five years, Leo van Hemmen and his team have been investigating the capabilities of the lateral-line system and assessing the potential to translate it into technology. How broad is the operating range of such a sense organ, and what details can it reveal about moving objects? Which stimuli does the lateral-line system receive from the eddy trail of another fish, and how are these stimuli processed? To get to the bottom of these questions, the scientists develop mathematical models and compare these with experimentally observed electrical nerve signals called action potentials. The biophysicists acquire the experimental data – measurements of lateral-line organ activity in clawed frogs and cave fish – through collaboration with biologists. "Biological systems follow their own laws," van Hemmen says, "but laws that are universally valid within biology and can be described mathematically – once you find the right biophysical or biological concepts, and the right formula."
The models yield surprisingly intuitive-sounding conclusions: Fish can reliably fix the positions of other fish in terms of a distance corresponding to their own body length. Each fish broadcasts definite and distinguishing information about itself into the field of currents. So if, for example, a prey fish discloses its size and form to a possible predator within the radius of its body length, the latter can decide if a pursuit is worth the effort. This is a key finding of van Hemmen's research team.
The TUM researchers have discovered another interesting formula. With this one, the angle between a fish's axis and a vortex street can be computed from the signals that a lateral-line system acquires. The peak capability of this computation matches the best that a fish's nervous system can do. The computed values for nerve signals from an animal's sensory organ agree astonishingly well with the actual measured electrical impulses from the discharge of nerve cells. "The lateral-line sense fascinated me from the start because it's fundamentally different from other senses such as vision or hearing, not just at first glance but also the second," van Hemmen says. "It's not just that it describes a different quality of reality, but also that in place of just two eyes or ears this sense is fed by many discrete lateral-line organs – from 180 in the clawed frog to several thousand in a fish, each of which in turn is composed of several neuromasts. The integration behind it is a tour de force."
The neuronal processing and integration of diverse sense impressions into a unified mapping of reality is a major focus for van Hemmen's group. They are pursuing this same fundamental investation through the study of desert snakes' infrared perception, vibration sensors in scorpions' feet, and barn owls' hearing.
"Technology has overtaken nature in some domains," van Hemmen says, "but lags far behind in the cognitive processing of received sense impressions. My dream is to endow robots with multiple sensory modalities. Instead of always building in more cameras, we should also along the way give them additional sensors for sound and touch." With a sense modeled on the lateral-line system, but which would function as well in air as under water, robots might for example move safely among crowds of people. But such a system also offers many promising applications in the water. Underwater robots could use it to orient themselves during the exploration of inaccessible cave systems and deep-sea volcanoes. Autonomous submarines could also locate obstacles in turbid water. Such an underwater vehicle is currently being developed within the framework of the EU project CILIA, in collaboration with the TUM chair for guidance and control technology.
Further research includes collaborations with the excellence cluster CoTeSys (Cognition for Technical Systems) and the newly created Leonardo da Vinci Center for Bionics at TUM, as well as with the chair for humanoid robots and the Bernstein Center for Computational Neuroscience.
ScienceDaily (Aug. 30, 2009)

Brain develops motor memory for prosthetics, study finds

July 21st, 2009

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Signals from the brain's motor cortex were translated by a "decoder" into deliberate movements of a computer cursor creating a kind of brain cybernetics. The task involved moving the cursor from a central starting point to a nearby target. UC Berkeley researchers have learned that the brain is capable of developing a motor memory of the task, much like it masters other physical skills such as riding a bike or playing tennis, but with the added distinction that the control is of a device separate from one's own body. Credit: Illustration by John Blanchard

"Practice makes perfect" is the maxim drummed into students struggling to learn a new motor skill - be it riding a bike or developing a killer backhand in tennis. Stunning new research now reveals that the brain can also achieve this motor memory with a prosthetic device(brain cybernetics), providing hope that physically disabled people can one day master control of artificial limbs with greater ease.

In this study, to be published July 21 in the open-access journal PLoS Biology, macaque monkeys using brain signals learned how to move a computer cursor to various targets. What the researchers learned was that the brain could develop a mental map of a solution to achieve the task with high proficiency, and that it adhered to that neural pattern without deviation, much like a driver sticks to a given route commuting to work.

The study, conducted by scientists at the University of California, Berkeley, addresses a fundamental question about whether the brain can establish a stable, neural map of a motor task to make control of an artificial limb more intuitive.

"When your own body performs motor tasks repeatedly, the movements become almost automatic," said study principal investigator Jose Carmena, a UC Berkeley assistant professor with joint appointments in the Department of Electrical Engineering and Computer Sciences, the Helen Wills Neuroscience Institute, and the Program in Cognitive Science. "The profound part of our study is that this is all happening with something that is not part of one's own body. We have demonstrated that the brain is able to form a motor memory to control a disembodied device in a way that mirrors how it controls its own body. That has never been shown before."

Researchers in the field of brain-machine interfaces, including Carmena, have made significant strides in recent years in the effort to improve the lives of people with physical disabilities. An April 2009 survey by the Christopher and Dana Reeve Foundation found that nearly 1.3 million people in the United States suffer from some form of paralysis caused by spinal cord injury. When other causes of restricted movement are considered, such as stroke, multiple sclerosis and cerebral palsy, the number of Americans affected jumps to 5.6 million, the survey found.

Already, researchers have demonstrated that rodents, non-human primates and humans are able to control robotic devices or computer cursors in real time using only brain signals. But what had not been clear before was whether such a skill had been consolidated as a motor memory. The new study suggests that the brain is capable of creating a stable, mental representation of a disembodied device so that it can be controlled with little effort.

To demonstrate this, Carmena and Karunesh Ganguly, a post-doctoral fellow in Carmena's laboratory, used a mathematical model, or "decoder," that remained static during the length of the study, and they paired it with a stable group of neurons in the brain. The decoder, analogous to a simplified spinal cord, translated the signals from the brain's motor cortex into movement of the cursor.

It took about four to five days of practice for the monkeys to master precise control of the cursor. Once they did, they completed the task easily and quickly for the next two weeks.

As the tasks were being completed, the researches were able to monitor the changes in activity of individual neurons involved in controlling the cursor. They could tell which cells were firing when the cursor moved in specific directions. The researchers noticed that when the animals became proficient at the task, the neural patterns involved in the "solution" stabilized.

"The solution adopted is what the brain returned to repeatedly," said Carmena.

That stability is one of three major features scientists associate with motor memory, and it is all too familiar to music teachers and athletic coaches who try to help their students "unlearn" improper form or techniques, as once a motor memory has been consolidated, it can be difficult to change.

Other characteristics of motor memory include the ability for it to be rapidly recalled upon demand and its resistance to interference when new skills are learned. All three elements were demonstrated in the UC Berkeley study.

In the weeks after they achieved proficiency, the primates exhibited rapid recall by immediately completing their learned task on the first try. "They did it from the get-go; there was no need to retrain them," said Carmena.

Real-life examples of resistance to interference, the third feature of motor memory, include people who return to an automatic transmission car after learning how to drive stick-shift. In the study, the researchers presented a new decoder - marked by a different colored cursor - two weeks after the monkeys showed mastery of the first decoder.

As the monkeys were mastering the new decoder, the researchers would suddenly switch back to the original decoder and saw that the monkeys could immediately perform the task without missing a beat. The monkeys could easily switch back and forth between the two decoders, showing a level of neural plasticity never before associated with the control of a prosthetic device, the researchers said.

"This is a study that says that maybe one day, we can really think of the ultimate neuroprosthetic device that humans can use to perform many different tasks in a more natural way," said Carmena.

Yet, the researchers acknowledged that prosthetic devices will not match what millions of years of evolution have accomplished to enable animal brains to control body movement. The complexity of wiring one's brain to properly control the body is made clear whenever one watches an infant's haphazard attempts to find its own hands and feet.

"Nevertheless, beyond its clinical applications, which are very clear, this line of research sheds light on how the brain assembles and organizes neurons, and how it forms a motor memory to control the prosthetic device," Carmena said. "These are important, fundamental questions about how the brain learns in general."

Source: University of California - Berkeley (news : web)
found at physorg.com

Singularity University graduates solutions for the future

The inaugural graduates of Singularity University, a Silicon Valley school backed by NASA, Google Inc., and tech industry luminaries like Ray Kurzweil, unveiled their grand visions on Thursday for leveraging emerging technologies to solve humanity's great challenges.

Before a filled conference room at NASA Ames Research Center in Moffett Field, the students faced the dual pressures of presenting what were both final class projects for the faculty on hand, as well as business pitches to the venture capitalists and business leaders in attendance. Most, if not all, of the four teams hope to secure the funding necessary to transform their ideas into viable ventures.

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The stated mission of the unaccredited university, founded in 2008, is to foster leaders who will build on rapid advances in and convergence across areas like biotechnology, supercomputing, nanotechnology and robotics to address intractable problems.

"It is only the scale of these exponentially growing technologies that has the ability to address the major challenges of humanity, whether it's energy and the environment, or poverty and disease," said Kurzweil, a renowned futurist and author of "The Singularity Is Near."

During the nine-week interdisciplinary graduate studies program, the 40 students were asked to develop projects that could help 1 billion people within 10 years. The individuals divided themselves into four teams focused on different challenges.

Four teams

Team Xidar Global Disaster Response developed new systems to facilitate communications in the aftermath of a disaster, including smart phone applications that provide GPS-based evacuation guidance or relay vital signs from "eTriage" bracelets.

"We're calling for an entirely new communication architecture," said Christian Tom, 22, who recently graduated from Stanford.

Lest it all seem pie in the sky, he noted the team members are in the process of incorporating a company and applying for patents.

Team Domus 3D Printing presented a plan to scale up advances in 3-D printing technologies, already employed to create miniature prototypes of buildings and consumer products, to create the actual components of affordable housing from materials like cement or polymers.

Team One Global Voice devised a text message-based information sharing system that enables marketplaces, job boards and other means of accelerating economic development in developing countries.

Finally, Team Gettaround proposed an "intelligent transportation grid" that would make vehicle use safer and more efficient by using censors and cell phones to provide real-time travel updates, enabling owners to rent their autos when they're not using them and, eventually, taking advantage of "autonomous" or self-driving vehicles.

40 top students

The 40 students - some recent college graduates, some the chief executives of existing companies - were accepted into the course from a field of more than a thousand applicants. Their bios are rife with advanced degrees from Harvard, MIT, Stanford and the like.

The university's board of trustees include: Kurzweil; Peter Diamandis, CEO of the X PRIZE Foundation, which awards multimillion-dollar prizes to organizations that achieve breakthroughs in genomics, energy, medicine and other fields; and Robert Richards, the founder of Odyssey Moon Ltd., which is attempting to commercialize trips to the moon.

Subsequent graduate programs at Singularity University will include around 120 students. Tuition is $25,000. The school is also gearing up to offer three- and nine-day executive programs, limited to 25 and 50 individuals, respectively.

Margo Lipstin, 23, a Team Domus member who studied the ethics of science at Stanford, said she was drawn to Singularity University because of its emphasis on real life applications. Technology is developing so rapidly and changing the world so dramatically that it's no longer possible to separate ideas from practice, she said.

"The theories are very powerful and we need to understand what values they espouse, and what is the vision for the world we're trying to reach with them," she said.

E-mail James Temple at jtemple@sfchronicle.com.

This article appeared on page C - 1 of the San Francisco Chronicle

Read more: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2009/08/27/BUUQ19EJIL.DTL&type=tech#ixzz0PUsqdhQk