Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mathematical keys to a sixth sense -- the lateral-line system

31.08.2009
Basic discoveries suggest robotics applications

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.

Original papers:

"Hydrodynamic Object Recognition: When Multipoles Count," Andreas B. Sichert, Robert Bamler, and J. Leo van Hemmen, Physical Review Letters, 102, 058104 (2009)

-- Link: http://dx.doi.org/10.1103/PhysRevLett.102.058104

"Wake Tracking and the Detection of Vortex Rings by the Canal Lateral Line of Fish," Jan-Moritz P. Franosch, Hendrik J. A. Hagedorn, Julie Goulet, Jacob Engelmann, and J. Leo van Hemmen, Physical Review Letters 103, 078102 (2009)

-- Link: http://dx.doi.org/10.1103/PhysRevLett.103.078102

See also: "Following in the wake," Nature 460, 1061 (27 August 2009)
-- Link: http://dx.doi.org/10.1038/4601061a
Contact:
Prof. Dr. Leo van Hemmen
Technische Universitaet Muenchen
Physics Department T35, Chair for Theoretische Biophysics
James-Franck-Str., D 85747 Garching
Tel.: +49 89 289 12362
Fax: +49 89 289 14656
E-mail: lvh@tum.de
Internet: http://www.T35.ph.tum.de/
Technische Universitaet Muenchen (TUM) is one of Germany's leading universities. It has roughly 420 professors, 6,500 academic and non-academic staff (including those at the university hospital "Rechts der Isar"), and 23,000 students. It focuses on the engineering sciences, natural sciences, life sciences, medicine, and economic sciences. After winning numerous awards, it was selected as an "Elite University" in 2006 by the Science Council (Wissenschaftsrat) and the German Research Foundation (DFG). The university's global network includes an outpost in Singapore. TUM is dedicated to the ideal of a top-level research based entrepreneurial university.

Patrick Regan | EurekAlert!
Further information:
http://www.tum.de

More articles from Physics and Astronomy:

nachricht Basque researchers turn light upside down
23.02.2018 | Elhuyar Fundazioa

nachricht Attoseconds break into atomic interior
23.02.2018 | Max-Planck-Institut für Quantenoptik

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>