Neurorobotics Reveals Brain Mechanisms of Self-Consciousness

Neurorobotics Reveals Brain Mechanisms of Self-Consciousness

  12:57:00 AM    Science Lover

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A new study uses creative engineering to unravel brain mechanisms associated with one of the most fundamental subjective human feelings: self-consciousness. The research, published in the April 28 issue of the journal Neuron, identifies a brain region called the temporo-parietal junction (TPJ) as being critical for the feeling of being an entity localized at a particular position in space and for perceiving the world from this position and perspective.

A new study uses creative engineering to unravel brain 
mechanisms associated with one of the most fundamental 
subjective human feelings: self-consciousness. The research 
identifies a brain region called the temporo-parietal junction 
(TPJ) as being critical for the feeling of being an entity 
localized at a particular position in space and for perceiving 
the world from this position and perspective. 
(Credit: © paul prescott / Fotolia)

Recent theories of self-consciousness highlight the importance of integrating many different sensory and motor signals, but it is not clear how this type of integration induces subjective states such as self-location ("Where am I in space?") and the first-person perspective ("From where do I perceive the world?"). Studies of neurological patients reporting out-of-body experiences have provided some evidence that brain damage interfering with the integration of multisensory body information may lead to pathological changes of the first-person perspective and self-location. However, it is still not known how to examine brain mechanisms associated with self-consciousness.

"Recent behavioral and physiological work, using video-projection and various visuo-tactile conflicts showed that self-location can be manipulated in healthy participants," explains senior study author, Dr. Olaf Blanke, from the Ecole Polytechnique Fédérale de Lausanne in Switzerland. "However, so far these experimental findings and techniques do not allow for the induction of changes in the first-person perspective and have not been integrated with neuroimaging, probably because the experimental set-ups require participants to sit, stand, or move. This makes it very difficult to apply and film the visuo-tactile conflicts on the participant's body during standard brain imaging techniques."

Making use of inventive neuroimaging-compatible robotic technology that was developed by Dr. Gassert's group at the Swiss Federal Institute of Technology in Zurich, Dr. Blanke and colleagues studied healthy subjects and employed specific bodily conflicts that induced changes in self-location and first-person perspective while simultaneously monitoring brain activity with functional magnetic resonance imaging. They observed that TPJ activity reflected experimental changes in self-location and first-person perspective. The researchers also completed a large study of neurological patients with out-of-body experiences and found that brain damage was localized to the TPJ.

"Our results illustrate the power of merging technologies from engineering with those of neuroimaging and cognitive science for the understanding of the nature of one of the greatest mysteries of the human mind: self-consciousness and its neural mechanisms," concludes Dr. Blanke. "Our findings on experimentally and pathologically induced altered states of self-consciousness present a powerful new research technology and reveal that TPJ activity reflects one of the most fundamental subjective feelings of humans: the feeling that 'I' am an entity that is localized at a position in space and that 'I' perceive the world from here."

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World’s Smallest Microlaser Could Revolutionize Chip Technology

World’s Smallest Microlaser Could Revolutionize Chip Technology

  6:00:00 AM    Science Lover

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The centerpiece of the new microlaser is the electric resonator, 
consisting of two semi-circular capacitors that are connected 
via an inductor (here, a scanning electron microscope image). 
The color intensity represents the strength of the electrical field; 
the color itself, the respective polarity.
(Credit: Photo: ETH Zurich)

ETH-Zurich physicists have developed a new kind of laser that shatters the boundaries of possibility: it is by far the smallest electrically pumped laser in the world and one day could revolutionize chip technology.

It took a good one and a half years from the idea to its inception; a time when Christoph Walther, a PhD student in the Quantum Optoelectronics Group at ETH Zurich, spent days and nights in the FIRST lab. This was because ETH Zurich's state-of-the-art clean-room facility provided him with the ideal conditions to set a new record in laser technology: the physicist teamed up with four colleagues and developed the smallest electrically pumped laser in the world to date.

Much smaller than the wavelength

It's 30 micrometers long -- that's 30 millionths of a meter -- eight micrometers high and has a wavelength of 200 micrometers. This makes the laser considerably smaller than the wavelength of the light it emits -- a scientific first. After all, lasers normally can't be smaller than their wavelength, the reason being that in conventional lasers light waves cause an optic resonator to oscillate -- much like acoustic waves do to the soundbox of a guitar. In doing so, the light waves basically "travel" back and forth between two mirrors. The principle only works if the mirrors are larger than the wavelength of the laser. Consequently, normal lasers are limited in terms of their size.

Other researchers have endeavored to push the boundaries; "But by developing a completely new laser concept we were able to go quite a way below the limit," says Christoph Walther.

Inspired by electronics

In developing their laser concept, Christoph Walther and some of his team mates under his supervisor Jérôme Faist, professor and head of ETH Zurich's Institute of Quantum Electronics, were inspired by electronics. "Instead of the usual optic resonators, we use an electrical resonant circuit made up of an inductor and two capacitors," explains Walther. The light is effectively "captured" in it and induced into self-sustaining electromagnetic oscillations on the spot using an optical amplifier.

"This means the size of the resonator is no longer limited by the wavelength of the light and can in principle -- and that's what makes it so special -- be scaled down to whatever size you want." This prospect especially makes the microlaser interesting for chip manufacturers -- as an optic alternative to the transistors. "If we manage to approximate the transistors in terms of size using the microlasers, one day they could be used to build electro-optic chips with an extremely high concentration of electronic and optic components," says Christoph Walther. These could one day considerably speed up the exchange of data on microprocessors.

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Medical Micro-robots Made As Small As Bacteria

Medical Micro-robots Made As Small As Bacteria

  8:57:00 PM    Science Lover

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Artificial bacterial flagella are about half as long as the thickness of a human hair.
They can swim at a speed of up to one body length per second.
This means that they already resemble their natural role models very closely.
(Credit: Institute of Robotics and Intelligent Systems/ETH Zurich)

For the first time, ETH Zurich researchers have built micro-robots as small as bacteria. Their purpose is to help cure human beings.

They look like spirals with tiny heads, and screw through the liquid like miniature corkscrews. When moving, they resemble rather ungainly bacteria with long whip-like tails. They can only be observed under a microscope because, at a total length of 25 to 60 µm, they are almost as small as natural flagellated bacteria. Most are between 5 and 15 µm long, a few are more than 20 µm.

Mimicking nature

The tiny spiral-shaped, nature-mimicking lookalikes of E. coli and similar bacteria. are called “Artificial Bacterial Flagella” (ABFs), the “flagella” referring to their whip-like tails. They were invented, manufactured and enabled to swim in a controllable way by researchers in the group led by Bradley Nelson, Professor at the Institute of Robotics and Intelligent Systems at ETH Zurich. In contrast to their natural role model, some of which cause diseases, the ABFs are intended to help cure diseases in the future.

The practical realization of these artificial bacteria, the smallest yet created, with a rigid flagellum and external actuation, was made possible mainly by the self-scrolling technique from which the spiral-shaped ABFs are constructed. ABFs are fabricated by vapor-depositing several ultra-thin layers of the elements indium, gallium, arsenic and chromium onto a substrate in a particular sequence. They are then patterned from it by means of lithography and etching. This forms super-thin, very long narrow ribbons that curl themselves into a spiral shape as soon as they are detached from the substrate, because of the unequal molecular lattice structures of the various layers. Depending on the deposited layer thickness and composition, a spiral is formed with different sizes which can be precisely defined by the researchers. Nelson says, “We can specify not only how small the spiral is, but even the scrolling direction of the ribbon that forms the spiral.”

External propulsion via magnetic field

Even before releasing the ribbon that will afterwards form the artificial flagellum, a kind of head for the mini-robot is attached to one of its ends. It consists of a chromium-nickel-gold tri-layer film, also vapor-deposited. Nickel is soft-magnetic, in contrast to the other materials used, which are non-magnetic. Nelson explains that, “This tiny magnetic head enables the ABF to move in a specific way in a magnetic field.” The spiral-shaped ABF swim through the liquid and its movements can be observed and recorded under a microscope.

With the software developed by the group, the ABF can be steered to a specific target by tuning the strength and direction of the rotating magnetic field which is generated by several coils. The ABFs can move forwards and backwards, upwards and downwards, and can also rotate in all directions. Brad Nelson says “There’s a lot of physics and mathematics behind the software.” The ABFs do not need energy of their own to swim, nor do they have any moving parts. The only decisive thing is the magnetic field, towards which the tiny head constantly tries to orientate itself and in whose direction it moves. The ABFs currently swim at a speed of up to 20 µm, i.e. up to one body length, per second. Nelson expects that it will be possible to increase the speed to more than 100 µm per second. For comparison: E. coli swims at 30 µm per second.

Possible applications in medicine

The ABFs have been designed for biomedical applications. For example, they could carry medicines to predetermined targets in the body, remove plaque deposits in the arteries or help biologists to modify cellular structures that are too small for direct manipulation by researchers. In initial experiments, the ETH Zurich researchers have already made the ABFs carry around polystyrene micro-spheres.

At the moment, however, the group is still carrying out basic research. Further investigations will be needed before there can be any practical applications. Nelson explains that, “For applications in the human body, it would first of all be necessary to steer the ABFs precisely, track their route without optical monitoring and guarantee their localization at all times.” If ABFs are to deliver drugs, they would first of all have to be functionalized in a feasible way and then need to be able to release the drugs precisely in situ. The plan is for the ABFs themselves to become even faster and smaller. Nelson is enthusiastic about how ingeniously nature has designed natural bacteria. He is happy that his group’s ABFs already resemble the originals so closely.

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