February 7, 2002. Copyright 2001. Graphic News. All rights reserved.

Bionic humans possible in near future

LONDON, February 7, Graphic News: Thinking about moving a lost or paralyzed limb may someday allow individuals to control either the limb itself or a prosthetic, according to researchers reporting in the February 8 issue of the journal ÒScience.Ó

Emerging technologies can now detect neural signals which, once interpreted, will enable assisted motion of a limb or prosthetic, says William Craelius of the Department of Biomedical Engineering at Rutgers University in Piscataway, New Jersey. The majority of these technologies, called Òbrain-computer interfacesÓ or Òbrain machine interfaces,Ó start with ÒreadingÓ motor commands from the brain, and ÒtranslatingÓ them into directions for moving a cursor on a computer screen, for example, or a robotic hand. 

For people with spinal cord injuries, a Òhybrid brain machine interfaceÓ may bypass the spinal cord, picking up information from the brain and using it to stimulate the appropriate muscles. 

ÒMany people can either sense or imagine manipulating a missing or nonfunctional limb,Ó says Craelius. ÒIf individuals can express cognitive control over relevant motor functions somewhere in a residual limb, and a device can pick up and decipher those signals, then mobility can be restored.Ó

One of the first commercially available bionic hands is ÒFreeHand,Ó a device that uses a system known as a Òperipheral-machine interfaceÓ. FreeHand -- which has been approved by the U.S. Federal Drug Administration -- restores grasping to patients with upper-limb paralysis by giving them control over hand muscles through movements of their opposite shoulder. FreeHand then generates radio waves which activate electrodes in the forearm.

A team including Craelius and Sam Phillips at Rutgers University have developed an alternative system known as Òresidual kinetic imaging.Ó

Their ÒDextraÓ hand prothesis picks up minute 3-D forces from muscle activity in the residual limb using pneumatic sensors in a silicone Òsmart sleeve.Ó Pressure transducers feed these signals to a pocket computer, allowing the user to flex and extend all five digits in response to their natural motor pathways. Craelius believes these bionic interfaces could benefit paraplegics, amputees, and those with weak muscles as a result of stroke, spinal cord injury, or neuromuscular disease.

Another bionic breakthrough reported in ÒScienceÓ descibes state-of-the-art retinal implants to restore sight. Normally, light passing through the pupil of the eye is focussed by the lens onto some 130 million photoreceptors -- the rods and cones which register colour and light and dark -- in the outermost layer of the retina. These rods and cones generate electrical and chemical signals which activate neural cells to send signals along 1.2 million optic nerve cells to the rest of the brain.

With a subretinal implant, damaged rods and cones are replaced by a silicon plate carrying thousands of light-sensitive micro-photodiodes, each equipped with a stimulation electrode. Light from the image directly drives the photodiodes, and the electrodes release tiny electric currents which stimulate remaining neural cells.

A team led by Eberhart Zrenner at the University Eye Hospital at Tuebingen in Germany have developed implants less than 100-thousandths of a millimetre thick and just 2-3 mm in diameter. Each implant contains hundreds of thousands of light-sensitive diodes linked to gold or titanium nitride electrode.

These nanotechnologies and bionic interfaces -- which meld man and machine together -- are no longer just the stuff of science fiction. The age of bionic man, and woman, may be just around the corner. 
/ENDS
Source: Science