INTPSY-10732; No of Pages 2 International Journal of Psychophysiology xxx (2013) xxx–xxx
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Editorial
Mobile EEG: Towards brain activity monitoring during natural action and cognition
In 1938, the Canadian psychologist, neurologist and physiologist Herbert Jasper, who was a pioneer of the EEG technology, sent Hans Berger in Jena, Germany, a Christmas card (Fig. 1). It is known that Jasper greatly admired Berger for his discovery of the human EEG. The delicate card he drafted shows a self-portrait along with his EEG traces recorded while he was smoking a pipe. Interestingly, the EEG traces are recorded with a small coil galvanometer and the Christmas greetings are embedded into brain oscillations — with a rather good signal-to-noise ratio (SNR). In our opinion, the card is clearly too carefully drawn to be considered simply a joke. While we cannot be certain, we speculate that Herbert Jasper illustrated to Hans Berger his vision about the future of EEG. So, what exactly was Jaspers' vision, and how does it relate to the current state of the art in EEG technology, 75 years later? Firstly, Herbert Jasper illustrated a very tight, near real-time relationship between mental processes and EEG traces. His card should of course be considered only a metaphor, expressing this ridiculously tight link between inner speech and raw EEG data. Yet, the interesting aspect may be the SNR he envisioned. With a good SNR, it should be possible to decode at least a small number of different mental states from the EEG at near real-time speed, that is, without averaging over many trial repetitions. Is this possible nowadays? The brain–computer interface (BCI) technology is probably the most successful single-trial EEG application at present (for another application, see for instance, the Special Issue on Integration of EEG and fMRI, edited by C.S. Herrmann & S. Debener in 2008 in this journal). Advances in EEG signal processing, such as spatial filter development
and adaptive machine learning algorithms, as well as ongoing efforts in the development of powerful BCI paradigms have moved the field forward. Accordingly, BCI research has clearly matured over the last decade and become widely available; this is reflected by an almost exponentially-rising number of publications (Wolpaw and Wolpaw, 2012). We speculate that over the next decade, BCI applications will leave the laboratory and show robust performance in real-life environments, such as at patient bedside, at patient home environments for long-term monitoring (Askamp et al., in this issue), or as a neuro-rehabilitation training tool, for prosthesis and wheelchair control, or for the monitoring of mental states and attention of healthy individuals at various workplaces. Regarding the latter issue, the contribution of Wascher and coworkers to this special issue is of particular importance, as they demonstrate nicely that wireless EEG can be used to analyze event-related EEG activity in a complex simulated working situation involving complex motor actions (Wascher et al., in this issue). Regarding the use of mobile EEG for motor rehabilitation, the study of Wong and coworkers is of interest, as they show systematic changes in EEG spectra during motor skill acquisition — with a dry consumer EEG system (Wong et al., in this issue). Moreover, Sterr and colleagues review and conceptualize the role of mobile EEG for the application of imagery-based motor rehabilitation. They conclude that the advent of mobile EEG will help to bring this promising rehabilitation approach to its full potential (Cranczioch et al., in this issue). In light of exciting findings on the role of motor imagery for motor rehabilitation (Buch
Fig. 1. Christmas card drafted by Herbert Jasper in 1938 and sent to Hans Berger in Jena, Germany. Reprinted with permission from the Deutsches Museum, Munich, Germany. 0167-8760/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ijpsycho.2013.10.008
Please cite this article as: De Vos, M., Debener, S., Mobile EEG: Towards brain activity monitoring during natural action and cognition, Int. J. Psychophysiol. (2013), http://dx.doi.org/10.1016/j.ijpsycho.2013.10.008
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Editorial
et al., 2008), highly portable easy to set-up new EEG systems could lead to a breakthrough in BCI and neurofeedback protocols, simply because frequent, hassle-free use of those protocols has not been possible so far. The contribution of Huster and colleagues, in this issue documents very nicely the current challenges in neurofeedback research, and provides a new neurofeedback software solution (Huster et al., in this issue). A combination of the new generation of mobile EEG devices, requiring very little application and set-up time, with user-friendly oneclick software solutions (Kaufmann et al., 2012) will help patients significantly to modulate their brain activity patterns to an extent that could be clinically relevant. While the time-course of exercise-induced brain plasticity in the presence of brain injury is not well understood (Voss et al., 2013), it is conceivable that continuous, frequent training over longer periods of time facilitates compensatory brain plasticity and neural repair, and this clearly benefits from user-friendly EEG devices. Secondly, on his Christmas card, Herbert Jasper also illustrated a fairly small coil galvanometer. Note that this was in the very early days of EEG, when EEG recording hardware probably required space in the range of several square meters. Yet the device he envisioned was not a bulky science fiction, but rather a delicate, unobtrusive device easily tolerating daily-life actions (such as having a smoke). In our view, the possibility of brain activity monitoring under truly mobile, natural recording conditions is closely linked to the development of small, wireless and head-mounted recording devices (see De Vos et al., in this issue). Several contributions to this special issue deal with hardware development and validation, following this line of reasoning. It is interesting to note that companies with an established reputation in stationary EEG amplifier development have only recently become interested in small and wireless EEG. On the other hand, companies with a focus on the consumer market have developed low-cost, mobile EEG systems and have been successful by targeting, for instance, the computer gamer community. Simply assuming that those cheap consumer devices give poor signal quality would be unfair. However, consumer EEG devices have been ignored by research laboratories until recently, and hence only a very few validation studies exist at present. Our own experience with a modified consumer EEG system showed that the original device was not able to deliver good signal quality. A modification of the hardware, however, led to substantial improvements such that EEG recordings are possible while individuals behave naturally, like walking outdoors (Debener et al., 2012). Our follow-up study with the same device is published in this special issue (De Vos et al., in this issue) and demonstrates a good EEG signal quality during outdoor walking, such that single-trial P300 analysis becomes possible. Complementary to our miniaturized EEG approach is the mobile Brain/Body Imaging (Mobi) approach from Gramann et al. In combination with traditional high-density EEG, other physiological measures can be recorded simultaneously in order to study the link between brain and behavior during complex actions (Gramann et al., in this issue). Whereas currently available mobile EEG devices, such as the one used in our lab, have limitations, they may serve as an inspiration for a new generation of EEG devices. This new generation should be small, very lightweight and avoid cable motion. In addition, such a device should communicate wirelessly and reliably with a portable computer, or even better with a smartphone or tablet device (Stopczynski et al., in this issue). This system design, when used with wet electrodes offers brain activity tracking under natural recording conditions. While dry electrodes have been developed and improved over time, to the best of our knowledge no validation study exists showing that these devices tolerate subject movement. On the other hand wet electrodes can be made very small (Nikulin et al., 2010) and be positioned at unobtrusive sites (Kidmose et al., 2013) and therefore seem a promising compromise between signal quality, portability and usability. The combination of dedicated mobile EEG amplifiers with unobtrusive small wet electrodes
is an exciting possibility for cognitive neurosciences, as it offers better external and ecological validity than lab psychophysiology alone. Notably, for the near future, it is only EEG technology that may be made small enough to allow a high degree of mobility. Portable functional near infrared spectroscopy (NIRS) systems have been developed as well (Piper et al., 2013), but the sensor skin contact may be even more fragile in spectroscopy than in electrophysiology, thus limiting the degree of mobility that could be reached with NIRS. We hope this special issue is of interest to readers of the International Journal of Psychophysiology. This journal has a very good record of publishing well-controlled laboratory psychophysiology research. The new generation of mobile EEG devices available soon will enable us to monitor human brain activity in action, in real-life environments. We firmly believe that this will help to boost the external validity of psychophysiology research, and uncover new areas of application. References
Askamp, 2014. Mobile EEG in epilepsy. Int. J. Psychophysiol. pp xx-xx. Buch, E., Weber, C., Cohen, L.G., Braun, C., Dimyan, M.A., Ard, T., Mellinger, J., Caria, A., Soekadar, S., Fourkas, A., Birbaumer, N., 2008. Think to move: a neuromagnetic brain-computer interface (BCI) system for chronic stroke. Stroke 39 (3), 910–917. Cranczioch, 2014. Mobile EEG and its potential to promote the theory and application of imagery-based motor rehabilitation. Int. J. Psychophysiol. xx-xx. Debener, S., Minow, F., Emkes, R., Gandras, K., De Vos, M., 2012. How about taking a low-cost, small, and wireless EEG for a walk? Psychophysiology 49 (11), 1449–1453. De Vos, 2014. Towards a truly mobile auditory brain-computer interface: Exploring the P300 to take away. Int. J. Psychophysiol. xx-xx. Gramann, 2014. Imaging Natural Cognition in Action. Int. J. Psychophysiol. xx-xx. Huster, 2014. Brain computer interfaces for EEG neurofeedback: peculiarities and solutions. Int. J. Psychophysiol. xx-xx. Kaufmann, T., Völker, S., Gunesch, L., Kübler, A., 2012. Spelling is just a click away–a usercentered brain–computer interface including auto-calibration and predictive text entry. Front. Neurosci. 7, 129. Kidmose, P., Looney, D., Ungstrup, M., Rank, M.L., Mandic, D.P., 2013. A study of evoked potentials from Ear-EEG. IEEE Trans. Biomed. Eng. 60 (10), 2824–2830. Nikulin, V.V., Kegeles, J., Curio, G., 2010. Miniaturized electroencephalographic scalp electrode for optimal wearing comfort. Clin. Neurophysiol. 121 (7), 1007–1014. Piper, S.K., Krueger, A., Koch, S.P., Mehnert, J., Habermehl, C., Steinbrink, J., Obrig, H., Schmitz, C.H., 2013. A wearable multi-channel fNIRS system for brain imaging in freely moving subjects. Neuroimage (pii: S1053-8119(13)00700-3). Stopczynski, 2014. Smartphones as Pocketable Labs: Visions for Mobile Brain Imaging and Neurofeedback. Int. J. Psychophysiol. xx-xx. Voss, M.W., Vivar, C., Kramer, A.F., van Praag, H., 2013. Bridging animal and human models of exercise-induced brain plasticity. Trends Cogn. Sci. 17 (10), 525–544. Wascher, 2014. Towards the measurement of event-related EEG activity in real-life working environments. Int. J. Psychophysiol. xx-xx. Wolpaw, J., Wolpaw, E., 2012. Brain-Computer Interfaces: Principles and Practise. Oxford Press. Wong, 2014. Spectral modulation of frontal EEG during motor skill acquisition: a mobile EEG study. Int. J. Psychophysiol. xx-xx.
Maarten De Vos Methods in Neurocognitive Psychology, Department of Psychology, University of Oldenburg, Germany Research Center Neurosensory Science, University of Oldenburg, Germany Cluster of Excellence Hearing4all, University of Oldenburg, Germany Corresponding author at: Department of Psychology, University of Oldenburg, D-26111 Oldenburg, Germany. Tel.: +49 441 798 2940; fax: +49 441 798 5522. E-mail address:
[email protected]. Stefan Debener Neuropsychology Lab, Department of Psychology, University of Oldenburg, Germany Research Center Neurosensory Science, University of Oldenburg, Germany Cluster of Excellence Hearing4all, University of Oldenburg, Germany
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Please cite this article as: De Vos, M., Debener, S., Mobile EEG: Towards brain activity monitoring during natural action and cognition, Int. J. Psychophysiol. (2013), http://dx.doi.org/10.1016/j.ijpsycho.2013.10.008
