Monthly Archives: February 2011

Engineers performing Brain Surgery!

The fact that we think that science is fun might not come as a surprise anymore if you have been following this blog lately. But besides fun, science can also be very tasty. Last saturday the Biomedical Group gathered around a very tasty Chinese dinner (very well prepared by a few of our students).

The dessert was very much in the spirit of our group: a brain-shaped pudding. Being familiar with brains, everybody proceeded with great enthousiasm to study it. For all of us it must have been the first brain surgery we ever did. And something tells us that it might not have been the last time!

Marijn

 

Fry in your brain, or fryin’ your brain

Yesterday, I watched a very impressive two-part television documentary made by Stephen Fry, entitled "The Secret Life of the Manic Depressive" and filmed in 2006. The documentary is about his struggle with manic depression, which he prefers to call "bipolar disorder" as this is its official name and definitively does not involve a state of continuous depression. Bipolar disorder is often treated with mood stabilizing medications and, sometimes, other psychiatric drugs. However, these are not always effective and often cause a lot of side-effects.

The second part of the documentary is about Stephen wondering whether he should consider taking drugs or other kinds of psychiatric treatment, as it looks like his symptoms are getting worse over time. So in this part he visits a few people he knows and that have also been diagnosed with bipolar and are using some form of therapy. Among them is Andy Behrman, also known as "Electroboy". According to his website www.electroboy.com, "after two unsuccessful years of experimenting with all different combinations of medication to stabilize his wild mood swings, he opted for intensive bouts of electroshock therapy," [Ed.] also known as "electroconvulsive therapy", or ECT in short, "as a last resort. He was temporarily cured."

Electroshock therapyThis, of course, brings back memories of one of the famous scenes of the movie "One flew over the cuckoo’s nest", in which Jack Nicolson rallies the patients of a mental institution together to take on the oppressive Nurse Ratched, a woman more a dictator than a nurse. He finally receives ECT to calme him down. As you can see from the picture at left, the applied ECT therapy used to be quite agressive, leading to brain convulsions and seizures or even memory loss, and has therefore been classified as "high risk" by the American Food and Drug Administration, or FDA for short.

Coincidentally, the American Psychiatric Association recently stated that the FDA should move the procedure to a medium risk state as they believe the current devices are not as brute force as their older siblings. Opponents, however, state that ECT may lead to memory loss and all sorts of other complications. If you want to decide for yourself, please check out the following YouTube movie: http://www.youtube.com/watch?v=zYl13Relzbs.

My personal opinion is that, though the doctors try to do a professional job, the applied therapy is not very patient specific and the majority of parameters are determined purely on a trial-and-error basis. Adding this to the fact that ECT is not the primary therapy, but merely serves to evoke a seizure (like you have during an epileptic insult), which is the actual therapy, makes me wonder whether there aren’t any prospects of developing a better therapy, which is better tailored to the disorder at hand and, of course, better to the patient.

Anyway, this was my sermon for the late Monday morning. If you are interested in watching "The Secret Life of the Manic Depressive", just let me know and I’ll see what I can do.

Wouter 

Rats go wireless in an analog fashion

Rat carrying wireless systemThis little image on the left shows a rat carrying a wireless system, partly mounted on his head, partly realized as a kind of a backpack. It has been developed by researchers at Harvard University in close collaboration with colleagues at California Institute of Technology and is being used for neurological research on rats in the wild. According to Nature (Febr. 25, online) the entire systems comprises "a tetrode microdrive, for chronic positioning of electrodes in the brain; an integrated circuit for high channel-count neural recordings; and a radio-frequency wireless transmitter. The device takes up to 64 analog voltage signals from neurons in the brain and muliplexes them into one signal that appears in a temporally interleaved fashion, one after the other. Then that signal is transmitted by analog FM radio to a receiver."

The article further reports that good old FM (frequency modulation) transmission has been used as it outperforms digital wireless communication on weight, power drain, throughput and distance.

So why does analog FM outperform its digital counterparts, such as FSK, QPSK, QAM and OFDM? Before answering this question it is important to realize that from a channel-capacity perspective (as defined by Shannon) there is no preference for analog modulation over digital modulation. The answer thus has to follow from practical considerations. Digital modulation implies that the information is transmitted over the wireless radio channel in a digital fashion. As all information in nature, also neural signals are analog in nature and thus, in order to prepare the neural signals for their wireless journey, they have to be converted to the digital domain by analog-to-digital conversion (ADC). This thus requires at least one ADC. Often, depending on the digital modulation type used, channel coding is performed prior to the digital modulation. As a consequence, with these additional blocks, the entire transmitter becomes more complex, which, in turn, entails a larger power consumption and, when battery-operated, a larger battery and thus a larger weight on the head or back of the rat.

Another reason why analog FM may outperform its digital counterparts lies in the frequency spectrum of the transmitted radio signal. FM produces an almost flat frequency spectrum. As a consequence, it is relatively immune to frequency-selective fading, which is good for radio communication over relative long distances. Also, FM transmission does not require a highly linear power amplifier. This is good for its power efficiency and thus for the overall energy efficiency of the transmitter.

One final remark. From the picture it looks like the rat is loaded with a transmitter that has been implemented using discrete components, rather than with a single chip (or integrated circuit, IC). Many of the blocks needed for digital transmission could be implemented with a much smaller form factor and consuming less power when realized on-chip, rendering the antenna the largest component and the largest power consumer. In such a case the choice for either analog or digital could have just as well turned upside down.

Wouter

Cochlear Implants: A message from patients to researchers

From the information below I feel that as researchers we need to develop cochlear implants (CIs) further. This I consider my duty!!

cochlear Ltd.From "Events and Research in Speech, Language, and Hearing Disorders":

CI user’s mom said "I have a baby with CI and I wish researchers can find a very reliable way to do totally implanted CI, because I think people need hearing always and in each condition."

"I feel that we are placing to much hope into the development of a completely internal implant being released in our lifetime. I have a son who has bilateral implants and it would be amazing if he could swim, bathe, sleep and have sound during these activities. But the fact that he can have sound all of the other time is a modern-day miracle and we are so thankfull to all people putting in endless hours of research!"

"I’ve been fitted with a cochlear implant for about a year and still can’t really enjoy music. Will a new fully implantable one improve the sound quality and enable people to hear music?"

Cochlear Implant Swimming Youtube Video, Click here:

CI user’s mom said "Thanks for this video. Since I watched this video, I have taken my daughter swimming a lot more and she enjoys it way more than before. Before we would spend about 5-10 minutes in the pool. Now she wants to spend all day."

Wannaya/.

Brain vs. Computer

The brain is an amazing thing. That mysterious little jelly pudding up there in your head has an unsurpassed computing power that we all use everyday to at least some extent. Humans have always been amazed by the brain and there has been a strong trend throughout history to build machines which can take over some of that computing power.

From the first electronic computer Colossus (using 1500 vacuum tubes and used to crack the Enigma code during World War II) until recently the IBM Watson: a computer which is able to understand natural questions, which can perform reasoning based on a huge amount of information stored in its memory and can come up with the correct answer. And all that within 3 seconds.

Watson consists of 90 IBM Power 750 servers, 15 Terabytes of RAM, 2880 processor cores and can operate at 80 teraflops. Very impressive specifications. A couple of days ago Watson competed in a Jeopardy! game against two humans and he managed to win quite impressively (although he made one quite shameful mistake).

Watson competing against humans

So does that mean that a bunch (ok, quite a big bunch) of processors can immitate the human brain? Well, to some degree it has proven it can. But the brain can do a lot more than understanding and answering questions. And besides functionality there is another factor, just like Dr. Bernard S. Meyerson, IBM’s vice president for innovation, mentioned: "The fact is that a human being is impossible to beat right now, in the sense of power efficiency, because you’ve got this little 20-watt thing, the brain, going up against many kilowatts."

So does this fact mean all the efforts made by the researchers are in vain? Definitely not, of course. It just means that we will have to keep using our little 20 watt miracle in order to come up with even smarter machines!

 Marijn van Dongen

Cell phones affect the glucose concentration in the brain close to the antenna

The Journal of the American Medical Association will soon publish an article on the effects of the use of a cell phone on the glucose concentration in the region of the brain close to the antenna. According to the Preliminary Communication published today, the brain cells exposed to 50 minutes of radiation from the cell phone had a significant increase in their glucose metabolism of about 7 percent. Its clinical significance, however, is yet unknown.

Though I understand the clinical study conducted and the scientific method applied, there are some comments that I would like to vent.

The first one is about the state of the mobile phones used. The article mentions that they were on for 50 minutes. But what does "on" mean exactly? Were they just on standby, waiting for a call? Was a call being made? If so, for how long? Was there any data passed between the cell phone and its base station? But the total "talk time", or better, transmission time, is not revealed in the article.

Moreover, its is known that the amount of power transmitted by the cell phone depends on the distance to the base station. Fortunately, the cell phone decreases its output power when channel conditions are good enough, thereby extending its talk time and reducing co-channel interference. This thus implies that the amount of radiated power is another unknown in this study.

Finally, and this becomes evident from a literature study and experiments conducted by our own Mark Stoopman, the amount of energy being absorbed by brain tissue strongly depends on the frequency being used. This, in turn, depends on the type of service (GSM, UMTS, etc.) and the provider being used. GSM 1800, for instance, in use by, e.g., T-Mobile, leads to more tissue absorption than GSM 900.

All-in-all, a lot of unknows, if you ask me.

Wouter

Would you allow your brain to drive your car?

German scientists have managed to develop a car that can be controlled by signals recorded from the brain. These signals are captured by a brain interface based on electro-encephalography (EEG) sensors, which was originally designed for gaming.

  

Click here for a video that highlights the thought-powered driving system on a trip to the airport. More information on the BrainDriver can be found here.

Currently, the system still experiences serious latency, as the brain waves first have to be analyzed, clustered and classified — I’d recommend a multi-wavelet transform for doing so — before appropriate action can be taken. It still will take a while before we really can take our hands off the wheel, sit back and imagine we’re at our destination already.

Micropower scavenged UWB radios

The windmill is a beautiful artifact and very recognizable in the Dutch landscape. It converts wind energy into rotational motion, and is one of the earliest energy harvesters in history. Today, research on energy harvesting is not only focussing on generating megawatts of electrical power, but also deals with micropower harvesters that can for example be used to power small wireless sensors or RFID tags.

Micopower energy harvesters can convert energy from the environment (vibrations, thermal difference, solar, RF) into electrical energy that can be stored in a capacitor or battery.

This allows wireless sensors to transmit their payload once the harvester has collected enough energy. Thus, in principle, the wireless sensor can have an infinite lifetime. Of course, the amount of energy that can be harvested depends on the application. One of the reasons why micropower scavenged wireless sensors are not yet widely used today is that current radio solutions such as ZigBee or Bluetooth consume (much) more power than the harvester can deliver.

A promising solution for this problem is to use Ultra-WideBand communication. UWB radio makes use of carrierless, short duration pulses to transfer the information. Since the radio can be switched off during the time laps between two pulses, the average power consumption can be low enough so that it can be combined with an energy harvester. That’s why in this group we are working on energy scavenged UWB radios since they seem to be the perfect match. Another distinct advantage is that UWB communication can offer accurate localization within a few cm’s. This means that finding your missing car, laptop or wife will be a piece of cake without ever having to change the radio battery!

Mark Stoopman

Current between the ears…

 "Current between the ears" 

In the weekend edition of a major Dutch newspaper (called the Volkskrant), the science section immediately got my attention. "Current between the ears". Since most people seem to have a brain between their ears, this article might be telling us about neural stimulation.

And so it did! It describes a technique called ‘Transcranial Direct Current Stimulation’ (tDCS). Two external electrodes are placed on the head of the subject. By sending a DC current in the order of 1mA through these electrodes the brain functionality can be influenced.

At the positive electrode, the tissue potential is slightly elevated. This means that the threshold for neurons to become activated is decreased and therefore the part of the brain close to the positive electrode becomes more active. The opposite holds for the negative electrode: this part becomes less active.

In this way it is possible to either stimulate or suppress particular neural functions. It can for example be used to temporarily increase the memory ability of the brain. Or to suppress mechanisms that lead to addiction. Or to help depression patients by suppressing the part that is associated with bad feelings.

The big advantage of this technology is obviously that is is non-invasive. That must however also be a disadvantage. To support 1mA currents, the electrode must be quite big in order not to exceed their charge injection limitations. This means that the spatial resolution of this method must be quite poor: a relatively large area is affected using this method. 

Nevertheless the article shows some interesting results, both obtained by the department of Developmental Psychology of the UvA and by research groups throughout the world. Once again it shows the fascinating world that opens up as soon as we apply (electrical) technology to the most complex organ we have: our brain.

Marijn van Dongen 

Are we all cyborgs now?

Check it out for yourself at TED.com, in this inspiring talk by Amber Case. Keep an eye on your self, though.

TED logo

Another one, highly recommended, is by Oliver Sacks, the famous neurologist and author (e.g., of the book Musicophilia). In this presentation, he points out an interesting link between visual hallucinations and tinnitus. Click here.