EEG consumer BCIs spanked by the Schwartzinator

Forbes has a fun little story on the state of consumer BCIs that hits on the major consumer players, but also throws real BCIs researchers John Wolpaw and Andy Schwartz into the fray. Each echos the officially sanctioned position of their respective scalp electrode versus implanted microwire/fancier probe electrode camp.

I prefer to call this the Head-Computer Interface versus Brain-Computer Interface debate. I try to be even keeled on the subject. EEG is obviously a worthwhile endeavor because there's none of that messy surgery involved, and thus appeals to a very large audience (at least in the near term). Hey, if you get a signal that can be controlled by the user reliably and with an acceptable level of precision, you have something useful. BUT, EEG is a degraded, garbled, sloppy signal prone to nearly limitless interference sources. Anything that can bork an implanted BCI can bork an EEG-based system, but EEG throws the doors open to the world because you are essentially wearing an antenna (or several).

One major problem with EEG is the fallacy that somehow destroyed information can be recovered by some form of fancy filtering. This is simply not so. Think of the electrode as a point of convergence for all electromagnetic signals of a measurable intensity. Even after narrowing frequency bands and implementing funky probabilistic decoders, any squiggle can be the convergence of several squiggles of indeterminable sources. In other words, at a specific time, a signal of amplitude +5 can be two signals of +4 and +1, -2 and +7, or 5 signals of +1-4-2+3+7. And don't even start with harmonics.

The second problem is population size. I know we like to think that motor cortex responds to only movement. It makes life easier. What life? Life in La-La-Land. MI responds to visual stimuli, movement preparation, auditory stimuli, imagined movements, movement related words (heard, internally rehearsed or spoken), reward, attention, cutaneous and proprioceptive feedback, and a bunch of other factors I'm not even mentioning. Until the impact of these influences is understood and quantified, there will not be any BCI that translates the neural activity for "move my arm to point x,y,z". EEG will never have the fidelity to isolate the differences feedback has at the single neuron level, so the nature of the recorded signal will never allow the 'direct' mapping of neural activity to output. That is, the activity that once gave rise to movement can never be harnessed with an acceptable degree of control to recreate the movement. Yes, I am using the word never. Never. There, I said it again.

Like I said, this isn't an attack on EEG, just reality. Different uses for different technologies. I can drive a car on a road. That doesn't mean I can drive a road, or that a road has no use.

Carbon nanotubes on and in the brain

Now that the embargo is lifted, I can talk about an interesting little ditty in Nature Nanotechnology on the use of carbon nanotubes as electrodes (kinda).

The miracle material that has been lauded as the solution to all the world's problems, from space elevators to unsightly scars, appears to integrate with neuronal membrane and conduct electricity with the greatest of ease. One interesting use being discussed is bridging between distal and proximal locations on a single neuron, which would effectively increase the response to inputs that would generally be more muffled by the distance from the soma.

Other possible uses include use as deep stimulating electrodes or electrode tips. Current DBS electrodes are huge compared to the areas they target, and damage is a very real possibility. On the topic of damage, carbon nanotubes are perhaps best known for their tensile strength and flexibility, making them perfect for navigating the densely packed, 3 pound lump of existence creating muck in the skull.

The paper is geared toward the interaction with the neuron's membrane. One thing that might shed some light on this interaction (my words, and I'm not a materials scientist, so i could be completely wrong on this) is a couple previous studies on nanotubes causing cancerous tumors. The effect was likened to asbestos, and injection caused significant inflammation. This could be due to these being shorter fragments or location of the injection, but the interaction with cellular membranes could also be key. To be fair, carbon nanotubes are also being touted as a means to precisely deliver anti-cancer treatments and drugs, so don't think I'm poo-pooing the research by bringing up the cancer link. I'm just pointing out the phenomenon because it might help explain or support the present paper.

It would be worth looking into the scale of the tubes, since a nanotube bridge would also be a cytoplasmic bridge (they are 'tubes'). How big that empty core is would be an important question, since other macromolecules and ions could be shuttled through the new proximal dendrite bypass. As a final thought, if the material itself is conductive, any passing active fiber could unintentionally influence the neuron. If carbon nanotubes are good conductors, then every segment becomes an en passant synapse without any neurotransmitter specificity. Maybe that matters, maybe not. I'm sure we'll see.

I did a quick once over of the paper, and might post a little more later, but I thought it was worth mentioning ASAP and in its own post. At this time of year, interesting papers can sneak by without much notice.

Presto-whammo, excite-thalamo!

I would be remiss to skip a big story that has hit nearly every major media outlet. A 38-year old man in a minimally conscious state was aroused from his 'slumber' via stimulation of the "central thalamus". I'll leave you to read any one of the below reports, but I want to highlight the issues brought up by Wired. In short, they question the rise of what might be called the cognitive life support system, and when it would be ethical to "pull the plug".

Nature news
Nature news and views

N. D. Schiff, J. T. Giacino, K. Kalmar, J. D. Victor, K. Baker, M. Gerber, B. Fritz, B. Eisenberg, J. O’Connor, E. J. Kobylarz, S. Farris, A. Machado, C. McCagg, F. Plum1, J. J. Fins & A. R. Rezai.
Behavioural improvements with thalamic stimulation after severe traumatic brain injury.
Nature 448, 600-603 (2 August 2007)

Reports:
Retrospectacle
Neurodudes
Yahoo!