I once was privileged to witness a controlled wrecking on a college campus. The goal of the project was not to destroy the whole structure, a three-story laboratory building, but only the two-storied annex. This "surgical cut" was executed using a hulky excavator armed with a oversized pneumatic jackhammer. The hammer was shaped like a giant tooth with which the operator probed the structures' beams. The operator gingerly moved the tooth about the building, gently probing here and there, constantly searching for the critical junctions that, once the jackhammer was unleashed, would only let the annex collapse. The operator approached the job with extreme diligence. The pneumatic hammer was activated with utmost nimbleness, leaving the observer with the impression that the person at the controls was able to sense the softening of the structure through the machine's tooth. Although the procedure was carried out with urgency, progress was excruciatingly slow. No mistakes were allowed. Blows were dealt with a sensitive touch. Despite the formidable challenge, the annex eventually turned into a pile of rubble while the main building remained unharmed. In the end, a lady with a big happy grin stepped from the cab to the ovations of a small crowd of academic onlookers that had gathered.
The operator's performance impressed so profoundly, because she appeared to control the excavator as if it were part of her body. In support of this idea, the machine mediates impact and vibration, providing meaningful tactile and proprioceptive feedback to the operator. Combined with visual and auditory cues, this feedback may produce an accurate perception of the machine's precise dimensions and forces of engagement can be gauged with the necessary accuracy. Reinforced by the continued use of successful strategies, connections between nerve cells strengthen, forming new networks that ultimately represent the machine in the mind as an extended part of the body.
Such plasticity of nerve cell networks is fundamental to the demonstration reported by Sandra Blakeslee in her article entitled "Monkey’s Thoughts Propel Robot, a Step That May Help Humans" in The New York Times on Jan. 15, 2008, that a monkey in the U.S. could steer a robot's walk in Japan with neuronal action potentials, that is electric nerve cell signals, recorded from her brain. The work was carried out in Miguel Nicolelis' laboratory at Duke University. The monkey was trained to walk on a treadmill while watching on a video screen the back of the robot walking on a similar mill, seemingly ahead of her. Microwire electrodes were implanted through an opening in the skull into the monkey's somatic sensory and motor cortex to record nerve cell signals. Signals that control leg movements were transmitted to Japan via the internet and fed to the robot's computer controlling its walk. The monkey was rewarded with treats for keeping the robot walking on the belt. Eventually, she managed to keep the robot on the move, while giving herself a rest.
The computer monitor shown in the Reuters video at 0:18 minutes:seconds displays electrical nerve cell activity in the monkey's cortex acquired with a
Plexon's multichannel acquisition processor. The large window on the right side depicts recordings from 128 electrodes arrayed in a matrix of 16 x 8 channels. Each electrode picks up electrical spikes from a number of cells. However, particularities in spike shape can be used to identify individual cells. The sorting of nerve cells by wave form is displayed in the windows on the left. The upper window depicts the spikes recorded from one electrode. The red, green, yellow and blue traces identify the spikes of four nerve cells. The isolated spike wave forms are shown separately in the window below. The upper window is shown enlarged at 0:23. The electrode channel from which the recordings were taken is framed in red on the left border of the enlarged matrix window at 0:28. Only the nerve cell signals essential to the control of the monkey's legs were used to control the robot's walk.
The success of this demonstration doubtlessly constitutes a formidable achievement of science and engineering. Yet, the greatest accomplishment resides in the monkey's brain. Similar to the big machine operator, the monkey experienced positive reinforcement when the robot walked successfully. During training, nerve cells in the monkey's motor cortex must have modified their connections such that their signals could be correctly interpreted by the robot's computer to keep the machine on the treadmill. As Eugen Herrigel so befittingly described in
Zen in the Art of Archery
the arrow, i.e. the nerve cell signals, and the bull's-eye, i.e. the robot, must fuse into one to get the job done.
The technology of controlling computers with nerve cell signals has been already applied to humans.
Kennedy and Bakay (1998) demonstrated that a paralyzed patient could intentionally move a cursor on a computer monitor with nerve cell signals recorded from an electrode implanted into motor cortex. Eliminating the need for an opening in the skull,
Birbaumer and others (2006) showed that recordings of small electrical currents on the scalp can be used to work a word processor. Nerve cells may even be able to control computers directly one day.
Peter Fromherz and colleagues successfully grew endings of nerve cells onto silicon wafers in tissue culture and provided evidence that the nerve cell signals influenced the flow of electrons in the semiconductor (
Fromherz and others, 1991). The implementation of this idea
in vivo is not entirely utopian. Damaged peripheral nerve cell fibers are known to regenerate and may establish functional connections (
Melzer and Smith, 1995).
Addenda
- Richard Allen Greene reports in his post entitled "Brain-Twitter project offers hope to paralyzed patients" on CNN today on exciting progress that Adam Wilson and Justin Williams at the University of Wisconsin have made in developing a method with which electrical signals of nerve cells in the brain recorded from the scalp can be used to compose a message on Twitter, opening up a new avenue for paralyzed people to communicate (04/23/09).
- On National Public Radio's All Things Considered today, Michele Norris anchored a segment entitled "Your Brain On Twitter: No Hands Necessary" on brain wave-controlled Twitter messages (04/24/09).
- This short, but impressive video clip below superbly corroborates my observation. Bionic legs will assist us on our first steps into a very useful direction (07/18/10).
- Today, Diane Rehm interviewed Miguel Nicolelis on her show with the title "Miguel Nicolelis: 'Beyond Boundaries'". Dr. Nicolelis is a lead investigator in this research and discusses his fascinating insights (03/16/11).
- Nicolelis and others (2011) published the proof of concept for nerve cell activity-controlled movements of a virtual limb combined with feedback through electrical microstimulation of nerve cells in somatic sensory cortex in this week's issue of Nature (10/06/11).
References
- Birbaumer N, Weber C, Neuper C, Buch E, Haapen K, Cohen L (2006) Physiological regulation of thinking: brain-computer interface (BCI) research. Prog Brain Res 159: 369-391.
- Fromherz P, Offenhäusser A, Vetter T, Weis J (1991) A neuron-silicon junction: a Retzius cell of the leech on an insulated-gate field-effect transistor. Science 252: 1290-1293.
- Kennedy PR, Bakay RA (1998) Restoration of neural output from a paralyzed patient by a direct brain connection. Neuroreport 9: 1707-1711.
- Melzer P, Smith CB (1995) Whisker follicle removal affects somatotopy and innervation of other follicles in adult mice. Cereb Cortex 5:301-306.
- O’Doherty JE, Lebedev MA, Ifft PJ, Zhuang KZ, Shokur S, Bleuler H, Nicolelis, MAL (2011)
Active tactile exploration using a brain–machine–brain interface. Nature doi:10.1038/nature10489.
whose thoughts are still remembered after more than 2,400 years worked with very little overhead.
