by Dr. Baris Yesilyurt
Brain Products Germany GmbH
“Berlin, Berlin, wir fahren nach Berlin” … (“Berlin, Berlin, we are heading to Berlin …”)
That is the whoop of joy of German football fans, which the fans roar, when their football team manages to get through to the final of DFB (German Football Association) Cup. They scream ‘we are heading to Berlin’, as for more than 3 decades the final of the DFB Cup has always taken place in the historical Olympia Stadium of Berlin. This slogan expresses the joy, this slogan expresses the expectation, and this slogan expresses the fascination associated not only with this event, but also with Berlin itself – the exciting and beautiful capital of Germany. That was also the reason, why we chose this slogan as our mantra in planning our first fNIRS meets EEG in the conference hall of the charming and historical Technology and Innovation Park in Berlin. Our aim was to organize a meeting, which all EEG and fNIRS fans would attend with pleasure and simply enjoy. As is right and proper, we planned 2 halves separated by a let’s get together night out for half-time.
The hot topics that our fans wanted us to focus on were: EEG-fNIRS Fusion, Data Acquisition and Data Analysis and so our roadmap was:
1) interactive presentations on Soft- and Hardware components, on data acquisition and on data analysis
2) invited talks on different applications by leading researchers of their fields
and last but not least
3) hands-on sessions on EEG-fNIRS, on mobile NIRS Imaging and on hyperscanning.
By the way our final tickets were free of charge and available for all EEG and fNIRS fans. And our little stadium (more than 60 EEG and fNIRS fans) was completely booked within just a few weeks of registration opening.
We started the first half with a kick-off presentation by Prof. Dr. Randal Barbour. Dr. Barbour (SUNY Downstate Medical Center and CEO of NIRx Medical Technologies LLC) started the ball running with an overview of the history and company structure of NIRx. We also received a brief walkthrough of his scientific work and some interesting hints on future directions.
Dr. Barbour then passed the ball on to our first Keynote Striker, Prof. Dr. Hellmuth Obrig (Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig). The title of Dr. Obrig’s presentation was: “More than two Decades of Exposure to the Near-Infrared: Some Thoughts on Strengths and Limitations of a ‘Promising Tool’”. In his talk, Dr. Obrig provided an insight into how NIRS measures the changes in neuronal activity, what exactly it measures, what are the advantages of fNIRS compared to other neuroimaging modalities and for which particular applications fNIRS is better suited rather than other neuroimaging modalities. We also learned from Dr. Obrig the reasons for combining NIRS with EEG.
Dr. Christoph Schmitz (Managing Director of NIRx Medizintechnik GmbH) then received the ball to guide us through to “NIRS Instrumentation” presenting the current NIRx NIRS Imaging Systems and very exciting new developments including:
(1) spring loaded fiber holders and twin-tipped optodes for easy and quick subject preparation, in other words the ‘fit the cap and start recording’ concept
(2) Laser Extension Module for NIRScout including as many as up to 8 Wavelengths to explore functional brain activity from different perspectives beyond oxy- and deoxyhemoglobin
(3) Avalanche Photo-Diode Extension Module for achieving higher signal-to-noise ratio
(4) new features in NIRStar (NIRx’ recording software) – 3 color calibration, predefined optode placements chosen from a drop down menu, etc. – for even more intuitive use.
Dr. Schmitz also mentioned ongoing and upcoming projects – e.g. wireless fNIRS.
So far we had gained information on the how and why fNIRS, now we were ready for a live demonstration to witness the theory in real life. Lamija Pasalic (Director of Scientific Support, NIRx Medizintechnik GmbH) introduced us NIRx’s portable device NIRSport by taking the example of a finger tapping task, while the subject was both sitting and moving around. The subject was Dr. Schmitz himself and he proved that he’s not only an excellent director and developer but also quite a good fNIRS subject. During the demo, we also had the opportunity to experience the new spring loaded fibre holders in operation: Lamija – despite of her long hair – fitted a cap with spring loaded holders herself and started recording the NIRS without any further preparation. This concept facilitates the subject preparation a lot and transforms many ‘tough’ subjects into easy to prepare subjects.
Easy to prepare subjects are also infants, this we have learned from our next keynote striker Prof. Dr. Judit Gervain (Université Paris Descartes in Paris). Her exciting presentation was about “Using NIRS to explore newborn speech perception”. With Dr. Gervain’s talk we received in-depth information about use of fNIRS in infants in context of speech perception at young age. One of the important findings of Dr. Gervain and her team was that newborns possess sophisticated speech perception abilities and their language network exhibits similarity with the adult language network.
After the initial domination of NIRS, EEG got into the game with the exciting presentation of Prof. Dr. Stefan Debener (University of Oldenburg in Oldenburg). Dr. Debener presented his recent study on “Association of Concurrent fNIRS and EEG Signatures in Response to Auditory and Visual Stimuli”. Beyond background information relating to methodology and application, Dr. Debener explained us that the different parameters of the EEG signal correlate well with oxy- and deoxyhemoglobin changes measured by fNIRS. For the visual part of the study, to investigate the relationship between neuronal activity assessed by EEG and hemodynamic response recorded by NIRS, Dr. Debener and his team used a checkerboard paradigm. Which was in fact a nice assist for me, as I used a similar set-up and paradigm for the live EEG-fNIRS demonstration: our actiCAP active electrode System together with BrainAmp DC amplifier plus a NIRScout 8×8 NIRS Imaging system.
As both BrainVision Recorder and NIRStar recording software enable online averaging of stimulus locked responses, during the simultaneous recording we could already observe the real-time formation of VEPs and oxy-/deoxy-hemoglobin responses plus the activation pattern on a 3D Cortex Model. By the way, even though we recorded the EEG in an environment which, given the expected electrical interference, would be a nightmare for every EEG researcher, thanks to actiCAP we were able record a quite clean physiological signal even without any notch filtering. There was no noteworthy electrical interference coming from the NIRS equipment either.
An additional note: the cap that we used had a total of 130 positions – the standard cap coming with the NIRx systems. Since size and shape of the optodes and actiCAP electrodes are similar, every position in the cap can be used for either EEG or NIRS. That is, the cap is not only suitable for visual related studies, but also for studies concerning the other cortical areas as well. Despite the versatility of this cap, Ali Zaidi (Max Planck Institute for Biological Cybernetics in Tübingen) did not need a cap for his studies. The topic of Mr. Zaidi’s presentation was namely “Simultaneous epidural fNRIS and intra-cortical electrophysiology as a new tool for studying neurovascular coupling”. By measuring fNIRS epidurally and electrophysiology intra-cortically, Mr. Zaidi and his collaborators were able to detect single-trial responses to visual stimuli on a trial-by-trial basis and observed a positive correlation between stimulus-induced modulation of [HbO] and [HbR] signals and strength of neural modulation. This very exciting talk was the last tackle before the end of the first half. Directly after that, we heard the half-time-whistle and we met up again at one of the Berlin’s hip bars to relax and recharge our batteries for the second half.
On the second day, we set up 4 hands-on training areas for; simultaneous EEG-fNIRS, multi-subject (hyperscanning) recordings, NIRS instrumentation and for NIRS data analysis, where the fans had the opportunity to work with Brain Products Germany and NIRx staff to setup experiments, collect data, and walk through software analysis capabilities.
At the final whistle the winners were obvious: We all were.
One step back to the background:
As functional near infrared spectroscopy technology has been continuously evolving there is a growing interest in integrating fNIRS into neuroscientific research. We might call it a rebirth, even a reincarnation. After its introduction, functional magnetic resonance imaging (fMRI) became namely the widely used research tool and dominated the field for many years. Yet, evolving from a few channel, rather costly system that has the size of a refrigerator into a multichannel, portable/wearable, affordable, easy-to-use system that has the size of a book, e.g. NIRSport of NIRx, fNIRS turned into an attractive tool for many applications again. fNIRS is attractive not only as stand-alone modality but also as multi-modal imaging instrument particularly in combination with EEG. These 2 techniques fix particularly well each other’s weakness and offer an easy to combine platform to take a closer (in time and in space) look at the neuronal processes in the brain.
By the way, why easy to combine? Well, the size and design of the NIRx NIRS optodes match well the size and design of Brain Products’ actiCAP electrodes. That is, you can easily use your existing actiCAP system, in most of the cases even the actiCAP EEG caps to add fNIRS as a complementary modality or vice versa. In addition, the components of the NIRx’s NIRS equipment are designed to be lightweight and compact – just like the actiCAP. It can hence be used in a broad spectrum of studies, for which other modalities are not really appropriate; e.g. infant studies, where lightweight and quick setup are absolutely necessary, or sports studies, where wearable systems are needed to allow subjects’ free mobility.
Our motivation in organizing this workshop was hence to review, discuss, and try out the new concepts, inform our users more about the fNIRS Instrumentation, EEG – fNIRS fusion and exchange ideas.
©Brain Products GmbH 2015