For Making More Accurate Measurements
in fNIRS(functional Near-Infrared Spectroscopy)

For Acquiring Better Data in fNIRS(functional Near-Infrared Spectroscopy)

Japan Optical Functional Brain Imaging Society1

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4-5. Measurements
94-6. Finish of measurements
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5. Measured data and data evaluation
95-1. Examples of measured data
95-2. Noises in measured data105-3. Artifacts
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6. Data analysis
12References
13Appendix 1. Principles of fNIRS
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1. Introduction
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2. Light propagation in absorbing and scattering media 14
3. Principle of measuring the changes in oxy- anddeoxy-hemoglobin concentrations
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4. Path of light propagation
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5. Display of fNIRS data
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6. Limitations of fNIRS measurements and notes forinterpretation of fNIRS data
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Appendix 2. Definitions of technical terms
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Contents
1. Introduction
2
2. Planning of measurements
22-1. Purpose of measurements
22-2. Task designing
32-3. Presenting a stimulus during measurements
52-4. Participants
52-5. Measurement area
52-6. Agreements by participants
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3. Measuring environments
73-1. Rooms for measurements
73-2. Avoiding external disturbances
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4. Process of actual measurements
74-1. Informed consent
74-2. Psychological stability and keeping stablepostures of participants
74-3. Installing probes
84-4. Adjustment of probes and explanation to participants
before measurements8＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

1. Introduction
fNIRS is an abbreviation for functional near-infrared spectroscopy and indicates a novel technology measuring
biological functions, primarily the higher order brain functions, using near-infrared spectroscopy. The Japan Optical
Functional Brain Imaging Society has made this booklet for improvements in the measuring techniques and thereliability of the fNIRS data. This booklet describes the main points about fNIRS measurements to guide beginners inthis field or researchers out of this field toward adequate operations of the instruments and acquiring effective data
without the help of skilled instructors. Appendix 1 describes the principles of fNIRS for measuring the higher orderbrain functions, and the readers are recommended to acquire better data in fNIRS under correct understanding of theprinciples. Also please refer to Appendix 2 for definitions of technical terms. There are two types of fNIRS instruments,
stationary and wearable, which are commercially available, and the contents of this booklet apply to both types ofinstruments.
In most cases of measurements using human subjects, it is necessary to gain approvals from the ethical committeesof the corresponding organizations. This booklet is made with the assumption that the ethical committee approves arenecessary for the measurements. Please refer to the guidelines or regulations established by the government in eachcountry.
2. Planning of measurements
2-1. Purpose of measurements
Note

Decide what brain function you want to measure.

It is necessary to be clear about what brain function you want to measure. In fNIRS experiments, you may want tomeasure how the activity of a brain region of a participant changes in response to the action of some task. However,2

electroencephalography (EEG) as shown in Fig. 2-3. It may be possible to obtain higher reproducibility by checking
the probe positions using equipment like a 3D position sensor.
Two examples in which stable measurement data can be obtained even by beginners are shown below. Once you
observe the specific brain activities in these examples, you may proceed to measurements for observing activities inother brain regions or measurements with the tasks of event related designs in which effective data are somewhat
difficult to be acquired.
2-5-1. Example 1 of the head region for measurements: Finger tapping task
For the finger tapping task mentioned as the example 1 of the task design, Fig. 2-4 shows an example of the headregions with the probe arrangement using two pairs of three by three probes. The red circles, blue circles and whitesquares indicate the source, detector and data points, respectively. In the case of measurements at the motor areas forboth hands, two pairs of the probes are normally arranged symmetrically to the center (Cz) of the line connecting thenasion (Nz) and inion (Iz).

C3C3CZ

C4C4Fig. 2-4 An example showing the head regions with the probe arrangement for the finger tappingtask. The green regions are the estimated motor areas. (Referring “BodyParts3D,Copyright© 2008” under the license CC-BY SA 2.1JP from the Database Center forLife Science, Japan)

2-5-2. Example 2 of the head region for measurements: Verbal fluency task
For the verbal fluency task listed as example 2 of the task design, Fig. 2-5 shows an example of the head regionswith the probe arrangement of five by three probes. The red circles, blue circles and white squares indicate the same asin Fig. 2-4. Because the region around Broca's area is to be measured for the verbal fluency task, the position
corresponding to T3 in the international 10-20 system is marked, and the probes are arranged so that the center probe in
the lowest row is located on the mark.
For more details on the head regions for measurements, please see references No. 1, 2 and 3.

Fig. 2-5 An example showing the head regions with the probe
arrangement for the verbal fluency task. The green region isthe estimated Broca’s area associated with various
language tasks. (Referring “BodyParts3D, Copyright©
2008” under the license CC-BY SA 2.1JP from theT3

Database Center for Life Science, Japan)

7

with the body surface. When the source light far from the body is sent to the body surface by optical fibers, or when
the reemitted light from the body surface is sent to the detector far from the body by optical fibers, the regions of theoptical fibers in contact with the body are defined as the probes. When the source and detector devices are in directcontact with the body, the devices are defined as the probes.
• Rest: A status of a participant under a resting state.
• Smoothing: A method of processing the time-series data to smooth out the short-term fluctuations and highlight
longer-term trends in the time-series data.
• S/N ratio (signal-to-noise ratio): The ratio of the signal intensity in interest to the noise intensity. The reliability of thedata is higher with higher S/N ratios.
• Target task: A task which a participant is given to induce a specific brain activity. “A target task” is frequently called
as “a task” simply.
• Task: A subject which a participant is given to conduct.
• Task design: A design or plan for how to combine the target and control tasks.
• Total-hemoglobin: Naming of the addition of the oxy- and deoxy-hemoglobins, and abbreviated as total-Hb.
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Editing committee:
Chair: Yukio Yamada (The University of Electro-Communications)
Members: Noriyoshi Ichikawa (National Institute of Advanced Industrial Science and Technology)
Mitsuo Ohashi (Spectratech Inc.)
Toru Kaji (Shimadzu Corporation)
Kaoru Sakatani (Nihon University)
Akihio Suzuki (Hitachi Ltd.)
Gentaro Taga (The University of Tokyo)
Nozomi Naoi (International Christian University)
Masato Fukuda (Gunma University)
Yoko Hoshi (Hamamatsu University School of Medicine)Yui Yamaguchi (Shimadzu Corporation)
Eiju Watanabe (Jichi Medical University)
Illustration: Haruko Sohda (Studio Gen)
Proof reading of the Japanese version: Yukari Tanikawa (National Institute of Advanced Industrial Science and Technology)
English corrections and proof reading of the English version: Kenta Watanabe (International Christian University, CUNY HunterCollege), Sakura Kimura (International Christian University)
Copyright: Japan Optical Functional Brain Imaging Society possesses the right of copying, translation, screen presentation,transferring, and communication to public of this publication.
First English edition: Published in ????, 2018
Publisher: Japan Optical Functional Brain Imaging Society
Secretary-general: Kaoru Sakatani, NEWCAT Research Institute, College of Engineering, Nihon University (1 Nakagawara,Tokusada, Tamuramachi, Koriyama, Fukushima Prefecture, Japan 963-8642), Phone/FAX: +81-24-956-8657＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝24