June 26, 2015
Dear Suzuki-san,
We want to thank you for the generous opportunity you provided for us to evaluate the Astem
hb13 portable NIRS device over an extended period. We are impressed with the device and would liketo provide some feedback and details of the testing that we performed over the last several months.
Our interest in the device is multiple-fold including using it for evaluation of language, motor
performance, cognitive function tasks and clinical evaluation. Over the course of our evaluation wewere able to complete two pilot data collections that we would like to share here as well as some of thedetails of our experience. A brief outline and some example data is provided below:
Study 1. Stroop Task: Classic cognitive task.
We are interested in the neural responses associated with conflict. The classic Stroop task is acognitive tool designed to introduce conflict in a decision making task and has been well studied using
other methods including EEG and fMRI. We wanted to test the hb13 device for determining differences
between congruent and incongruent stimuli in an experimental paradigm with known results. To dothis, we employed a Stroop task using the hb13 and observed expected hemodynamic responses forcongruent and incongruent trials. The data is shown below in Figure 1.

Figure 1. Setup of NIRS optodes and results for a single subject.
Hirsch, J. et al, 2014, Yale University.
We placed the optodes as lateral as possible bilaterally on subjects. Optode placement was calibratedusing a Polhemus 3D digitizer and MNI coordinates are provided for each data trace. The data in thetraces represent a block where subjects responded to incongruent or congruent stimuli for 15 seconds
and rested for 15 seconds. The dashed vertical line shows the transition between task and rest. The

results show that the hb13 is capable of recording responses consistent with known hemodynamic
responses and discriminates differences in amplitude in responses to congruent and incongruent stimuli.
Study 2. Language Task: Dialog between two individuals.
We are also interested in studying real-world language tasks using NIRS. Our goal was to study
the responses in Broca’s area concurrently in a pair of subjects while interacting in a dialogue. Subjects
were provided stimuli in 30 second blocks which displayed a picture that was the focus of the discussion.
Every 30 seconds the picture changed and the alternate subject would respond to the previous
comments from their partner and continue a new statement regarding the new picture. The duration ofthe task was 6 minutes total. The setup and placement of the optodes is shown in Figure 2. The insert
shows the data from two subjects participating in this task. MNI coordinates (as determined using thePolhemus 3D digitizer) are provided for reference. Event triggered results indicate an alternating
pattern of activity in Broca’s area between subject 1 and 2.

Figure 2. Interactive language task.
Hirsch, J. et al, 2014, Yale University.
Benefits
The hb13 is a small and wireless NIRS device which provides a truly portable functional brain
imaging tool that can be used in many real world tasks. The integration of motion data and surface
blood flow information is in line with the current thinking regarding signal processing of NIRS data.
Simple placement of optodes on subjects allows for data collection to be performed without lengthy
training of students and researchers. Further, while the price is still high, it is an order of magnitude
cheaper than other NIRS devices on the market.
Drawbacks

In our testing we found a few items that could be changed or improved. First, while theBluetooth communication is a benefit in making the unit portable, we found some issues with respect tothe Bluetooth stack on various computers. There is a lot of inconsistency in the drivers provided and it
made it difficult to relay the data. It might be nice to have a wired option as well to accommodate forthis. Additionally, we were not 100% sure in the software what the purpose of dragging the optodes tothe model’s face is? It seems that this can be eliminated, but became a bit problematic on very highresolution displays. We found that when running the software at 1200p or above, this dragging did notwork and required us to change the resolution of the monitor to run the software. Finally, while thepass-through COM communication was working well, we would have also liked to see the ability of thesoftware to accept a trigger input from an external device natively. Occasionally, we found data was
dropped over Bluetooth pass-through and we had to resynchronize the files manually.
Questions and possible suggestions
We occasionally found some responses in subjects that showed reversal of activity from what
we expected. For example, in a 30 second block design where the first 15 seconds were stimulus andthe last 15 seconds were rest, the data seemed to drift. At the beginning of the 6 minute trial theresponses were following a hemodynamic response in the first 15 second block, but by the end of thetrial, the responses were coming in the last 15 seconds. This was random, but always was coming when
we lost our triggering system, so we had no way to accommodate for this variability. A trigger input tothe device would accommodate for this. We are also wondering if the surface optodes would provide
more optimized data if they were slightly further apart. We did not have a chance to evaluate surface
data in detail and perform controlled studies, but we are wondering what the targeted depth ofpenetration of these recordings is? We performed 3D digitizing of the optodes using NIRS-SPM withgood results, but would have liked to have some indication on the back of the rubber holders for the LEDand detectors where the locations were to be even more accurate for this. It may not be necessary
given the 3cm channel area, but it does make the procedure a bit simpler.
Overall and closing thoughts
We are pleased with the responses from the hb13 NIRS device in the two paradigms we presentto you here. The ability of the hb13 to record hemodynamic activity appears to be robust and we areinterested in further use of the hb13 in paradigms that involve subjects that cannot come in to the laband for clinical evaluation for both psychiatric and motor dysfunction. We are interested in the ability of
the hb13 to discriminate cortical from surface responses but did not have an opportunity to explore thiscapability in detail. The simplicity of placement of optodes is a real benefit of the device and allows for avery fast setup. The wireless nature of communication is both a convenience and a drawback (seebelow). The battery life was good as well as the build quality. The operation was simple and thesoftware provided worked as expected. We did not use the analysis tools provided as we built our own.
We also found the accelerometer data useful for single subject data, but obviously was not applicable inthe dialog task.
We are interested in further use of the hb13 in our research especially to compare and validate
the results to our new 140 channel Shimadzu LABNIRS. We would like to be able to initially test
paradigms using the large machine to determine activity and specificity of regions of interest. After
that, studies can be carried out in the field or at remote locations that the LABNIRS would beimpractical.

In the future, we are interested in purchasing one or more of the hb13 units, however this iscontingent on acquiring funding. Because of this, we would like to ask if it would be possible tonegotiate a discount (perhaps at cost) on an hb13 unit for further comparison to data collected on theLABNIRS in the future. It would be our goal to publish this data and would be of great benefit to us in
our current and future studies. We are happy to discuss the use of the hb13 further with you and are
happy to provide other insights or comments on the use of the system. Please feel free to contact us
directly or via Yumie-san. Again, we greatly appreciate your generous offer of letting us evaluate theunit and we are very impressed with its capabilities.

Best regards and thank you again,Joy, Hirsch, PhD
Professor of Psychiatry and Neurobiology
Departments of Psychiatry and Neurobiology
Director, Brain Function Laboratory
Member, Integrated Neuroscience Program
Yale School of Medicine
Visiting Professor of University College London
Institute of Cognitive Neuroscience
Sr Investigator, Haskins Laboratories
300 George St, Suite 902
New Haven, CT 06511
Phone mobile: 917 494-7768
e-mail: joy.hirsch@yale.edu
e-mail: joyhirsch@yahoo.com
website: www.fmri.org
www.medicine.yale.edu/lab/hirsch

Adam Noah, PhD
Associate Research Faculty
Brain Function Lab
Department of Psychiatry
Yale School of Medicine
adam@adamnoah.com
adam.noah@yale.edu

Xian, Zhang, PhD
Associate Research Faculty
Brain Function Lab
Department of Psychiatry
Yale School of Medicine
Xzhang63@gmail.com