PART human, part machine, the cyborg is a familiar figure in science fiction. The Borg, the Six Million Dollar Man and Robocop are all attempts to depict the cyborg's mix of flesh and steel, neurons and chips, blood and pneumatics.
|Not so much science fiction: with the cyborg snail, are we nearer human cyborgs?|
Such cybernetic organisms lead us to ponder how much of a human being could be replaced with technology while preserving its humanity. They also prompt questions about what we mean by life, and how it will evolve.
However, Hollywood's oft-quoted doomsday scenario in which humans are replaced by machines could prove wide of the mark: in the future, humans could first augment their abilities with prostheses, and then, eventually, flesh might merge with silicon. Resistance is futile, as the Borgs chant in Star Trek.
While cyborgs remain largely in the domain of science fiction, relevant technology - wearable PCs, artificial limbs and hearts, cochlear implants or experiments to implant microchips to restore vision - is beginning to appear.
Some, however, claim that we are already cyborgs given our dependence on computers. Our communication with them, using buttons, keyboards and mice, is primitive however and falls far short of a fusion of the two dominant forms of information processing on the planet - nerve and transistor.
Now, however, progress is being made. Enter the "robosnail". A rudimentary "cyborg" with a snail brain has been created: nerve cells from a pond snail, Lymnaea stagnalis, have been grown on a computer chip and, for the first time, a "conversation" has been set up between real and silicon brains.
The nerve-microchip, reported in the latest Proceedings of the National Academy of Sciences, was created at the Max Planck Institute in Martinsried, near Munich, by Prof Peter Fromherz and a doctoral student Gunther Zeck.
Making a chip "talk" to a nerve is tricky: a bolt of electricity from an electrode can cause corrosion that poisons, heats and damages the nerve. Prof Fromherz instead used an electrical field in the chip to induce charges within a neighbouring nerve cell that, above a certain level, triggered it to fire an electrochemical signal, as happens in real life.
Snail brain cells - bigger and easier to manipulate than our own - were attached to electronic devices on a silicon chip by the microscopic "picket fences" of a polymer. Each cell was positioned over a transistor, a device that can amplify tiny voltages to record signals from the nerve, and a stimulator to prod the cell into activity with electrical fields. Once incubated in a nutrient medium, the nerve cells sprouted tendrils and formed junctions, or synapses, with each other.
Prof Fromherz then sent a signal from the chip to a snail brain cell, which passed it to an adjacent cell, which passed it back to the chip. "This is the first hybrid signal loop," he said, "from semiconductor to neuronal net back to the semiconductor chip."
Although this cyborg brain is primitive, he hopes that the research will one day help doctors to understand how to rewire damaged nerves or connect them to the microelectronics that control an artificial limb. It could even equip computers with biological senses, so they could hear and touch as we do.
He believes that the most immediate application of his work will be to help to understand the brain. Plans are under way to grow a garden of neurons on 15,000 transistors. When the number or nerves in a network grows large enough (we have one million million), the team may even see the first glimmers of what happens in a living brain.
If it all seems rather too fantastic, even Prof Fromherz acknowledges in his latest paper that this fundamental step in neuroelectrical engineering contains "a touch of science fiction".