Hacking the brain: Brain-to-computer-interface hardware moves from the realm of research
Advances in both hardware and software are making an accurate and economical brain-to-computer interface feasible.
Margery Conner, Technical Editor -- EDN, November 18, 2010
At A Glance
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An accurate, low-cost BCI (brain-to-computer
interface) can help realize the science-fiction
ideal in which there’s no need to speak,
gesture, or type into a keyboard to communicate
with machinery: You just think—and
the machine responds. BCI technology is not
just the domain of sci-fi junkies: An obvious
use for BCI control is in medical therapeutic
equipment for paralyzed patients or for
research into brain conditions, such as Parkinson’s disease or epilepsy.
Other possible applications include game-control interfaces
and military equipment. For example, the Defense Advanced Research
Projects Agency’s bionic-arm project to improve the state
of the art for prosthetics partially funded research into BCIs at the
University of Utah. Plus, the growing use by the military of remotely
piloted aircraft highlights the potential the military sees for BCI.The brain is a 3-lb bag of fluids and neurons that communicate by firing off tiny electrical pulses. There are several ways to track these electrical signals: One requires going beneath the skull and implanting electrodes onto or into the brain itself. This approach is risky business and so far has found use only for therapeutic purposes—for example, for the study and treatment of epilepsy. Another method, ECOG (electrocorticography), dates back to the 1950s. It places electrodes directly on the exposed surface of the brain but still beneath the skull to record electrical activity from the cerebral cortex.
More recent work by researchers
at the University of Utah uses silicon
electrodes the size of baby aspirin that
float above the brain but still under
the skull. In microECOG, the device
comprises an array of electrodes rather
than just one (Figure 1 and Reference
1). The researchers placed arrays
of tiny electrodes between the skull
and the brain. They found that these
electrodes can accurately detect the
brain’s signals that control arm movements.
Surgeons placed two kinds of
microECOGs on the brains of severely
epileptic patients. Parts of the patients’
skulls had been temporarily removed
for placement of the larger ECOG electrodes,
which locate and treat the brain
area responsible for epileptic seizures.
These larger, metallic, button-like
electrodes are numbered in the figure.
Figure 1 (left) also shows two micro-ECOG arrays, each with 16 microelectrodes
that connect to microwires that pass through the orange and green
tubes. Photo-editing software outlined
the electrodes in the figure. Figure 1
(right) shows one microECOG array
with 32 microelectrodes that connects
with microwires entering through a
clear tube at the bottom of the figure.
The green wires connect to the large,
conventional ECOG electrodes.
ECOG and microECOG are intermediate
steps between electrodes that
penetrate the brain and EEG (electroencephalography),
which places electrodes
outside the skull on the scalp.
Compared with the risky, surgical nature
of ECOG, EEG is a relatively simple
procedure that relies on electrodes
anchored through an adhesive to the
scalp. However, to reach electrodes on
the scalp, the brain’s electrical signals
must travel through the skull. Bone
conductivity is low, and signals attenuate
rapidly. By the time the brain’s signals
make it through the surrounding
membrane, skull, skin, and hair, these
already-faint signals are vanishingly
small. EEGs for medical purposes use
electrodes that require a conductive
jelly that can be messy to apply and remove.
These medical-grade EEG-sensor
systems can cost tens of thousands
of dollars, keeping research into BCIs
within the realm of academia and medical
research (Figure 2).However, the lucrative gaming market, in which thought control of games is a novel gimmick, and military applications are driving the interest in BCI devices, which are starting to appear at prices far below the tens of thousands of dollars you can expect to pay for medical-research-quality EEG. Recently, products such as Emotiv’s Epoc and NeuroSky’s Mindset have become available for approximately $150 to $300.
How likely is it that EEG-based headsets can contribute to robust BCI-hardware approaches? Following a BCI workshop early this year at the Massachusetts Institute of Technology, Rod Furlan, Singularity University founder, summarized his thoughts on invasive versus noninvasive BCIs (Reference 2). “As noninvasive interfaces are generally limited to reading brain states, it is unlikely they will be able to evolve into robust input and output solutions,” he said. “Consensus among the experts in the room was that EEG is probably a dead end because, while it provides great temporal resolution, its maximum achievable spatial resolution will probably fall short of the requirements of future applications.”
Tan Le, co-founder and president of EEG-headset maker Emotiv, explains the human brain, the limitations of EEG, and Emotiv’s approach (Reference 3). “Our brain is made up of billions of neurons, around 170,000 km of combined axon length,” she says. “When these neurons interact, the chemical reaction emits an electrical impulse, which can be measured. The majority of our functional brain is distributed over the outer surface layer of the brain. To increase the area that’s available for mental capacity, the brain surface is highly folded. This folding presents a significant challenge for interpreting surface electrical impulses because everyone’s cortex is folded differently. Even though a signal comes from the same functional part of the brain, by the time the structure has been folded, its physical location is very different between individuals, even identical twins.
“[Emotiv created] an algorithm that ‘unfolds’ the cortex [to] map the signal closer to its source and make it able to work across a mass population. EEG measurements typically involve a hair net with an array of sensors. The Emotiv headset is a 14-channel, high-fidelity EEG-acquisition system and requires no scalp prep [and] no conductive gel. It only takes a few minutes to put on and for the signals to settle. It’s wireless and costs only a few hundred dollars.”
Pull it out of the box, connect it to
your PC, place it on your head, spend
a few moments on the canned exercises
that let the headset algorithms learn
your brain-wave pattern, and you can
begin manipulating virtual images on
your PC with your brain (Figure 3).
Pretty neat, huh?
Emotiv officials didn’t like the fact that Brocious had cracked the encryption and posted his library. They claimed that doing so could force the company out of business (Reference 5). Emotiv sells a $700 developer’s version of the headset that allows access to the data, but it is not an open environment; the company controls access. Apparently, Emotiv is working to close the encryption hole and thus end Cody’s project.
Other approaches
Alternatives to EEG exist for measuring small signals on the surface of the head. One such technology, EOG (electrooculography), employs eye polarization. The back of the eye is more negative than the front of the eye because of the large populations of neurons on the retina. As the eye moves, the electric field surrounding the eye also moves. Electrodes on the left and right side of the face and above and below the eyes can measure these fields. An electrode behind the ear serves as a reference voltage.
Waterloo Labs comprises a group of engineers at National
Instruments that builds and documents electronics projects
using the company’s components. Its implementation of
an EOG-measurement device that controls the Mario video
game provides a good example of the design challenges of
acquiring small differential signals in a noisy environment,
such as the head (Reference 6). A National Instruments
RIO (rapid input/output) single-board computer performs
the signal processing for the EOG. A custom daughterboard
performs signal acquisition, amplification, filtering, and digitization
(Figure 4).The inputs to the EOG are the bipotential signals measured at the electrodes; these signals are smaller than those of background environmental noise, such as RF-communication signals or 60-Hz ac-mains noise. Fortunately, each electrode picks up the same noise, making the interference the common signal. Amplifying the difference between the electrodes and rejecting everything common to them yield the EOG’s signal. The Waterloo Labs engineers used an Analog Devices 8221 instrumentation amplifier because of its low noise and high common-mode rejection.
Whenever metal, such as that composing an electrode, touches an electrolytic solution, such as human skin, a potential difference—the half-cell potential— results. The 8221 amplifies the half-cell potential along with the EOG signal. If the amplifier’s gain is too high, the half-cell potential swamps the EOG’s signal. The half-cell potential cannot overpower a gain of 10, which is enough to distinguish it from the noise. The circuit next uses a highpass RC filter set to 0.1 Hz to reject the half-cell voltage. Without the half-cell constant, the circuit can further amplify the signal, carefully adding no noise back in after all that work rejecting it. It uses two low-noise, high-offset amplifiers to keep the signal clean. The final stage uses a lowpass filter set to 50 Hz to remove any high-frequency noise, including 60-Hz ac-mains voltage, and then an ADC.
As for electrical isolation, the EOG receives its power from a 9V battery, so it has no dangerous voltages. However, the video-game controller, the TV display, and the RIO all use 120V wall power, so if there’s a short in the transformer, the EOG user will get a 120V jolt of electricity across the face. To avoid this painful scenario, the circuit uses an isolated AD7401 ADC that magnetically couples the signal across a dielectric gap so that there is no electrical connection between the EOG and the RIO. The AD7401 can withstand 120V wall power for an indefinite amount of time and more than 3000V for as long as a minute.
You can reach Technical Editor Margery Conner at 1-805-461-8242 and margery.conner@ cancom.com.
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References |
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For More Information |
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Analog Devices |
Emotiv |
MIT |
National Instruments |
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NeuroSky |
Singularity University |
University of Utah |
Waterloo Labs |
Talkback
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Hi, the same system of EOG developed by Waterloo Labs was developed 1 year earlier by a mexican institute and presented in NIWeek 2009 in order to control a wheelchair...just for reference.
Rafael Mendoza - 2011-3-3 10:54:29 PST -
This is very encouraging for hacking the brain but it needs more R&D work, experiments and real testing of different individuals and records the original thoughts of the brain coming from the individual and compare with the results based on recorded electrical pulses which are translated into "words." The accuracy as well as reliability and repeatability of the BCI recorded data should be thoroughly be analyzed in orderly fashion in order to improve accuracy of the recorded data.
Questions to be addressed.
1. Would it be affected by interferences coming from the outside world such as RFI, EMI and other disturbances to create false signal(s)from the brain activity?
2. Would it be possible that the brain activity comprises and electrical pulse signals and that signals be modulated into the brain frequency (BF) the carrier and be radiated into the space just like the RF signals but it would be BF signals?
3. If this BCI would have an accuracy within 95%; would it be possible that this device is good for interviewing job applicants, looking evidences for suspected criminals, terrorists interrogations, hacking another brain, etc.?
4. Would it be possible if item 3 can be done to recall of the previous brain acitivities as well as future brain activities?
Believer - 2010-14-12 08:18:40 PST -
its good, but it should be assured that electromagnetic interference of the electrodes used will not affect the real human brain nerves and its signals.
Anish.H - 2010-22-11 20:37:25 PST -
while one can foresee significant benefits that might result from this type of technology, the simple fact that any encryption algorithm can be broken given enough time and money suggests a truly frightening Orwellian prospect could arise...
Imagine if one were to try using a wireless networking schema to transport data from the device... tapping into those free-space signals is not impossible or improbable once the signals from the Human Brain have been sufficiently amplified and categorized.
while a leap of immagination is still required, reading a mind may not be that far off... for good or for ill; who protects us all from misuse... Big Brother? Obama? I THINK NOT!!!
hg - 2010-22-11 13:49:22 PST -
Cody Brocious emailed me with some clarifications about his project and said:
"1) Emokit is fully able to pull the unfiltered EEG data out of the stream; all that's unknown at this point are the contact quality and battery meter data.
2) There's no way Emotiv can "close the hole" as there is none. As long as their product does its processing in software rather than hardware, Emokit can and will still work. I fully intend to reverse-engineer any future modifications they make."
For Cody's Hardware Manifesto, read this:
edn.com/article/511501-Hacking_the_brain_Brain_to_computer_interface_hardware_moves_from_the_realm_of_research.php
Margery Conner - 2010-22-11 12:05:15 PST
