by Prof. Michio Kaku
Is it possible to interface directly with the brain, to harness its fantastic capability?
Scientists are proceeding to explore this possibility with remarkable speed. The first step in attempting to exploit the human brain is to show that individual neurons can grow and thrive on silicon chips. Then the next step would be to connect silicon chips directly to a living neuron inside an animal, such as a worm.
One then has to show that human neurons can be connected to a silicon chip. Last (and this is by far the most difficult part), in order to interface directly with the brain, scientists would have to decode the millions of neurons which make up our spinal cord.
In 1995, a big step was taken by a team of biophysicists led by Peter Fromherz at the Max Planck Institute of Biochemistry just outside Munich. They announced that they had successfully created a juncture between a living leech neuron and a silicon chip. In a dramatic break-through, scientists have been able to weld “hardware” with “wetware.” Their remarkable research has demonstrated that a neuron can fire and send a signal to a silicon chip, and that a silicon chip can make the neuron fire. Their methods should work for human neurons as well.
Of course, neurons are frustratingly thin and delicate, much thinner than a human hair. And the voltages used in experiments would often damage or kill the neurons. To solve the first problem, Fromherz used the neurons from leech ganglia (nerve bundles), which are quite large, about 50 microns across (half the diameter of a human hair). To solve the voltage problem, he brought the leech neurons, using microscopes and computer-controlled micromanipulators, to within 30 microns of a transistor on a chip.
By doing so, he was able to induce signals across this 30 micron gap without exchanging any charges whatsoever. (For example, if you vigorously rub a balloon and place it next to running water, the stream of water will bend away from the balloon without ever touching it. Likewise, the neuron never touches the silicon.)
This has paved the way to developing silicon chips that can control the firing of neurons at will, which in turn could control muscle movements. So far, Fromherz has been able to make as many as sixteen contact points between a chip and a single neuron. His next step is to use the neurons from the hippocampus of rat brains. Although they are much thinner than leech neurons, they live for months, while leech neurons last only for a matter of weeks.
Another step in trying to grow neurons on silicon was achieved in 1996. Richard Potember at Johns Hopkins University succeeded in coaxing the neurons of baby rats to grow on a silicon surface which was painted with certain peptides. These neurons sprouted dendrites and axons, just like ordinary neurons.
The ultimate aim of his group is to grow neurons so their axons and dendrites follow predetermined paths that can create “living circuits” on the silicon surface. If successful, it might allow neurons to conform to the architecture of a logic circuit in a chip. The doctors at the Harvard Medical School’s Massachusetts Eye and Ear Infirmary have already begun taking the next step: getting a team together to build the “bionic eye.” The group expects to conduct human studies with computer chips implanted into the human eye within five years. If successful, they may be able to restore vision for the blind in the twenty-first century.
“We have developed the electronics, we have learned how to put a device into the eye without hurting the eye, and we have demonstrated that the materials are biocompatible,” says Joseph Rizzo. They are designing an implant consisting of two chips, one of which contains a solar panel. Light striking the solar panel will start up a laser beam, which then hits the second panel and sends a message down the wire to the brain. A bionic eye would be of enormous help for the blind who have a damaged retina but whose connection to the brain is still intact. Ten million Americans, for example, suffer from macular degeneration, the most common form of blindness among the elderly. Retinitis pigmentosa, an inherited form of blindness, affects another 1.2 million.
Already, studies have shown that damaged cones and rods in animal retinas can be electrically stimulated, creating signals in the visual cortex of the animal’s brain. This means that, in principle, it may one day be possible to connect directly to the brain artificial eyes which have greater visual acuity and versatility than our own eye. Our eye is essentially the eye of an ape; it can see only certain colors that apes can see, and cannot see colors which are visible to other animals (for example, bees see ultraviolet radiation from the sun, which is used in their search for flowers). But an artificial eye could be constructed with superhuman capabilities, such as telescopic and microscopic vision, or the ability to see infrared and ultraviolet radiation. Thus at some point it may be possible to develop artificial eyesight that exceeds the capability of normal eyesight.
In the world beyond 2020, we may be able to connect silicon microprocessors with artificial arms, legs, and eyes directly to the human nervous system, which would be of enormous help in aiding people with disabilities. But although it may be possible to connect the human body to a powerful mechanical arm, the stunts we saw on the TV show The Six Million Dollar Man would place intolerable stresses on our
skeletal system, rendering most superhuman feats impossible. To have superhuman strength would require superhuman skeletal systems that can absorb the shock and stress of such feats.