Category Archives: General

Transcutaneous Vestibular Stimulator

Posted on 26/08/2011 by | 1 comment

Vestibular stimulators stimulate the vestibular organ (located in the ‘labyrinth of the inner ear’) and can therefore have a direct effect on the balance of a person. Triggered by some movies that show the impressive and funny effects that Vestibular Stimulators can offer, our group decided to build a very simple stimulator to experience the effects ourselves. We also have been informed that there might be interest for this type of stimulators for medical experiments, so there’s more behind it than just fun.

Transcutaneous Vestibular Stimulation uses electrodes that are put behind the ear of the subject (being ourselves in our experiments) and a current is injected. We decided to make the stimulator remote controlled to give the subject more freedom.

We could keep writing a lot more about this stimulator, but movies might be much more self explaining and fun to watch. Therefore, simply click the following link to see the effects of Vestibular Stimulators:

Movie 1

Movie 2

Marijn

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Posted in Brain-Machine Interfaces, Electronics, General, Neurostimulation and Neuromodulation

The Voices of DAC—A chip in your brain?

Posted on 23/08/2011 by | Leave a comment

Jan Rabaey, UC Berkeley, about brain-machine interfaces. Click here to watch the video.

This talk covers a little bit of transcutaneous signal and energy transfer, recording of brain signals, polymer electrode arrays, brain waves, EEG, ECoG, epilepsy, neurostimulation, DBS, 65nm, microwatt, pulsed waveform, temperature rise, digital amplifier, subthreshold logic, interference, frequency agile radios, security, neural dust…

Wouter

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Posted in Brain-Machine Interfaces, Electronics, General

Timing in the brain not only a matter of time

Posted on 23/08/2011 by | Leave a comment

In the Proceedings of the Royal Society B (Biology) of August 10, 2011, interested readers can read in an article by James Heron that  "duration perception […] may be mediated via a system of duration-selective ‘channels’, which
are differentially activated depending on the match between afferent
duration information and the channels’ ‘preferred’ duration." This is an interesting postulation which may, however, be incorrect, as, to the best of my knowledge (though I am not a physician), there are no particular channel-like structures associated with our sensors (ears and eyes) that can be held responsible for our understanding of how long a particular event lasts. 

From a mathematical and engineering perspective it is also known that there exists a strong relation between time and frequency, taught to us in high school when we learn about the meaning of T = 1/f, T being the period of a (periodical) signal and f its frequency. Some people are known for having an "absolute pitch", sometimes erroneously called "absolute hearing", in the sense that they recognize exactly the pitch of a tone they hear. Most people do not have this remarkable talent, but are nevertheless still pretty good at estimating the approximate pitch of a tone they hear.

Also, it is known that events seem to last longer when they are dull or not exciting and its opposite is probably best illustrated by the expression "time flies when you’re having fun", Also, and this many of us have experienced during the ELCA music festival of last March, sometimes, when excited, a little bit tensed or under pressure, musicians have a tendency to play their songs faster, with more beats per minute, without being aware of it. Apparently, in a more stressful situation, our notion of time becomes related to a faster clock, or a shorter time duration. Finally, it is known that when people are feverish, also their notion of time changes.

The above relation between time and frequency and thus pitch and the experience of time and frequency stretch depending on our excitement, suggest, at least to me, that our notion of time is not so much related to a static entity in the form of a channel, but rather is linked to our internal oscillatory processes, as, e.g., happen in the brain between its various hierarchical layers, or in our lifesupporting master clock, the heart. It would be interesting to see whether the above states of excitement also affect the frequency of our brain waves (alpha, beta and gamma waves). If so, the issue of reliable tinnitus detection (see Senad’s previous post) may become more patient and situation-specific and thus more difficult to implement.

Stay tuned 😉

Wouter

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Posted in General, Understanding the Brain

A first proof-of-principle of a Tinnitus detector circuit

Posted on 27/07/2011 by | 1 comment

Tinnitus is a condition in which a patient perceives an auditory phantom sound that can take the form of ringing, buzzing, roaring or hissing in the absence of an external sound. Approximately a billion of people suffer from tinnitus worldwide, while in 2% – 3% of the population, tinnitus significantly degrades quality of life of the patients and can lead to insomnia, anxiety and depression.

Currently, there are no proven treatments for tinnitus. However, recent research has shown that tinnitus patients can benefit from electrical brain stimulation. In addition, it has been shown that there is a link between tinnitus perception and a change in the energy levels of several electrocortigography (ECoG) / electroencephalography (EEG) frequency bands. For example, the energies of theta (4-8Hz) and low-gamma (30-50Hz) waves increase, while the energy of alpha (8-12Hz) waves decreases during active tinnitus perception. The same studies suggest that the intensity of the tinnitus perception correlates with the amount of the energy increased in the gamma band.

The real-time tinnitus detection method proposed by the BME group detects tinnitus by comparing ECoG/EEG signal energies from different locations in the brain according to a tinnitus "signature". First, the proposed strategy selects appropriate ECoG/EEG bands per channel by means of band-pass filters. Next, their extracted energies are compared to their counterparts from a different (healthy) location. Tinnitus is detected only if higher theta and gamma energies while lower alpha energy is found when compared to the signals from this healthy region. The applicability of the detector is verified by means of circuit simulations with real neural waveforms and is able to successfully detect tinnitus.

Are you interested in any progress related to the tinnitus detector circuit? Stay tuned.

Senad 

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Posted in Education, Electronics, General, Neurostimulation and Neuromodulation, Understanding the Brain

Small chip to overcome inflammation of joints

Posted on 18/07/2011 by | 1 comment

Today, the Telegraaf and Nu.nl report that a team of the Dutch rheumatologist Paul-Peter Tak of the Amsterdam Academic Medical Center will implant a kind of pacemaker, its size in the order of a bout a square centimeter, that will deliver stimuli to the vagus nerve for about one minute a day. By doing so, it is expected that inflammation of the joints of patients that suffer from rheumatoid arthritis can be reduced or even completely stopped.

Of course, what can be deduced from the article is that this pacemaker, electronics-wise, is nothing more than a simple blinking light with a timer, which can be implemented by means of a miniature microcontroller and a battery. However, it is also obvious that electrical stimulation of the vagus nerve, albeit at its infancy, is already very promising and a possible treatment of a wide range of neural disorders and pain is dawning at the horizon.

Wouter

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Posted in Electronics, General, Neurostimulation and Neuromodulation

Be gentle to the heart, otherwise you’ll lose it

Posted on 15/07/2011 by | Leave a comment

Researchers at the Max Planck Institute and Cornell University have come up with a low-energy pulse sequence to
restart hearts and make implants last longer is what we can read in IEEE Spectrum today. Other advantages of using a train (a burst) of pulses instead of using a single (tonic) pulse are that defibrillation becomes less painful to the patient and is less likely to evoke fibrillation elsewhere in the heart. The new therapy still has to be tested on patients, though. 

From this, it is only a small step towards realizing that other types of tissue should be stimulated with burst-like or even more exotic yet gentle pulses, too. In the Biomedical Electronics Group of Delft University of Technology, we’re working on interfacing with the brain in a more natural manner. Stay tuned…

Wouter

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Posted in General, Neurostimulation and Neuromodulation, Pacemakers

New way of data conversion

Posted on 08/07/2011 by | 1 comment

Analog-to-digital converters (ADCs) are indispensable building blocks of wearable and implantable biomedical data acquisition systems. Ultra-low-power ADCs for biomedical signal sensing have witnessed a dramatically reduced power consumption in recent years, but we have to admit that our biomedical systems need more breakthroughs than just squeezing harder in conventional ways.

As is known to all, many biomedical signals are born with a sparse nature. A large amount of redundant digital samples will be thus generated if we use Nyquist-rate ADCs to convert such signals. Most likely, ADC power savings are not a major concern in a system in which transmission power dominates the overall power consumption. However, if this is not the case, from a signal point of view, new ways of sampling or sensing are necessary to further improve the performance of the whole system.

A new and promising ADC approach for biomedical data acquisition is based on so-called level-crossing (LC) sampling, in which samples are generated only when the input signal crosses the threshold levels, so there is no redundant sample in this case. However, the conventional LC-ADC utilizes power hungry comparators and DACs, which causes the LC-ADC to consume much more power than ultra-low-power Nyquist ADCs (e.g., SAR ADCs). In our new approach (mentioned by Wouter earlier in the weblog), innovations at both system level and circuit level enble us to design a more power-efficient LC-ADC. Power consumption is now in the range of hundreds of nanowatts. We are currently investigating the possiblity to further improve its performance and reliability.

Yongjia

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Posted in Electronics, General, Medical Body Area Networks

In case you’ve just missed it…

Posted on 30/06/2011 by | Leave a comment

Fixing the Brain-Computer Interface

Researchers are addressing the sizable population for whom
BCI doesn’t work

By Erica
Westly  /  June 2011

New website (in Dutch): http://www.braininnovations.nl/

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Posted in General

It takes some cooking to prepare a good meal

Posted on 24/06/2011 by | Leave a comment

Frequent readers of this weblog may have started to wonder whether the activities of the Biomedical Electronics Group have gradually fainted and dissolved in eternity, its members have all become hobos and it all ended in a big dream. Bzinga. The truth is, of course, that everybody is very busy and under the yoke of some deadline or another.

Senad and June been working very hard on a first proof-of-principle of a Tinnitus detector circuit. Such a circuit should allow for detection of the spatial properties of tinnitus and give objective information on its severity. This could, in turn, lead to more refined or adjusted stimulation therapies. Don’t sell your mother for it, yet, but expectations are high. The findings will be worked out in a manuscript, to be submitted to the annual BioCAS Conference today.

On the detection side of things, Yongjia has been working very hard on the new type of level-crossing analog-to-digital converter, described in an earlier weblog. Also this work will be submitted to the BioCAS Conference.

Duan Zhao received the good news that our paper (together with the Holst Centre) on a reconfigurable subsampling receiver has been accepted for presentation and publication at the PIMRC Conference in Toronto. Congratulations. He just returned from a visit to his home country and we’re happy to have him back again.

Of course there is more that can be reported, such as the coming ELCA day trip, the preparations for organizing BioCAS 2013 in Delft, the IMDI NeuroControl, more power-efficient neurostimulation circuits, higher-efficiency RF energy harvesting circuits, June’s paper that got accepted in Transactions on Circuits and Systems-I: Regular Papers (congrats, too), Sandro’s and Senad’s paper that enjoyed the same fate (congrats, too), STW Perspectief and how the Dutch Ministries of Economical Affairs, Agriculture and Innovation and of Health, Wellbeing and Sport have no clue on how to increase valorization in the Netherlands (as witnessed yesterday at the MedTech West Event), but this would make good stuff for another blog. So stay tuned!

Wouter

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Posted in General

Mr. Brain: The Role of Neuroscience in Crime Investigation

Posted on 08/06/2011 by | 1 comment

More than a week ago, Wouter recommended a Dutch documentary ‘Mystery of the brain’. I believe that the documentary must be very interesting but unfortunately I don’t understand Dutch… What a pity.

I also would like to share my experience with you all in a way that is more relaxing. There is a Japanese TV series called “Mr. Brain” that we can watch online at http://www.youtube.com/watch?v=pKjHIIK7qew&feature=related.

After being busy with my research, watching it reminds me of myself and my work. It makes me smile sometimes. In these series, we will see how the detective and the neuroscientist deal with each other in a bitter-sweet-funny way. Understanding the brain helps a lot in interpreting the evidences that are left behind at the crime scene. Whenever the story goes to a complicated theory of neural processing there will be animations popping up to explain in a very cute way.

It is also good for kids, I think.

A few useful things I got from watching it:

  • I enjoy eating bananas more
  • I know where to sit in front of the girl I meet for the first time
  • Color comes first, shape follows but sound is the most powerful
  • We are using only 5% of our brain. There are still more than enough resources in our brain
  • For creativity, just don’t give up

Like Neil Yongjia said before singing: “I hope you’ll enjoy.”

June

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Posted in General