The document discusses neuroimaging techniques such as functional near-infrared spectroscopy (fNIRS). fNIRS uses near-infrared light to monitor changes in oxygenated and deoxygenated hemoglobin in the brain in response to neural activity. It provides a portable, low-cost way to monitor brain activity and oxygenation levels during cognitive tasks. The document discusses how fNIRS works, its applications in detecting brain activity and lie detection by measuring hemodynamic responses in the prefrontal cortex. It also compares fNIRS to other neuroimaging techniques such as fMRI and discusses its potential for use in brain-computer interfaces.

1. M. Raihan
Lecturer, North Western Universiy, Bangladesh
Email: raihanbme@gmail.com

2. What is Neuroimaging
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Neuroimaging is a branch of medical imaging that
focuses on the brain. In addition to diagnosing disease
and assessing brain health, neuroimaging also studies:
How the brain works
How various activities impact the brain

3. Types of Neuroimaging Techniques
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Computed axial tomography
Diffuse optical imaging
Magnetic resonance imaging (MRI)
Functional magnetic resonance imaging (fMRI)
Positron emission tomography (PET)
Single-photon emission computed tomography (SPECT)
Cranial ultrasound
Electroencephalography (EEG)
Optical Brain Imaging: near infrared spectroscopy (NIRS)

4. What is fNIR
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NIRS (near-infrared spectroscopy) for the purpose of functional
neuroimaging.
Using fNIR, brain activity is measured through hemodynamic
responses associated with neuron behavior.
Provides real-time monitoring of tissue oxygenation in the brain
as subjects take tests, perform cognitive tasks, and/or receive
stimulation.
By measuring changes in near-infrared light, it allows
researchers to monitor blood flow in the front part of the brain.

5. How fNIR Works
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It allows functional imaging of brain activity (or activation) through monitoring of
blood oxygenation and blood volume in the pre-frontal cortex.
It does this by measuring changes in the concentration of oxy- and deoxy-haemoglobin
(Hb) as well as the changes in the redox state of cytochrome-c-oxidase (Cyt-Ox) by their
different specific spectra in the near-infrared range between 700-1000 nm.
The functional near-infrared spectroscopy (fNIRS) sensor is attached to the subject’s
forehead and can be monitored either connected directly to a computer, or a portable
computing device that records the subject’s data as he or she engages in specific tasks.
The data is recorded and then analyzed for changes in the blood flow or its
oxygenation levels of the brain before, during, and after the task.
Hypotheses can then be tested about how brain activity is being affected by certain
tasks or behaviors.

6. fNIR Overview of the System
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7. fNIR Overview of the System
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8. Comparison of fNIR with other
Neuroimaging modalities
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Neuroimaging techniques such as functional magnetic resonance imaging
(fMRI) and positron emission tomography (PET) have been widely used to
image brain functions in humans1.
fMRI is noninvasive and has excellent spatial resolution, but is also expensive,
highly sensitive to motion artifact, confines the participants to restricted
positions inside the magnet
Difficult to integrate with other imaging modalities [such as
electroencephalogram (EEG)], and exposes participants to
loud noises1.
PET also requires a restricted range of motion and confinement, and requires
the injection of radioactive materials1.
1. N. Daimiwal, M. Sundhararajan and R. Shriram, "Non Invasive FNIR and FMRI system for Brain Mapping", International Journal of Scientific and Research Publications, vol. 3, no. 2, pp. 1-4, 2013.

9. Continue
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The Functional Magnetic Resonance Imaging (fMRI) is used to examine the
anatomy of the brain. It can detect precisely which part of the brain is handling
critical functions such as thought, speech, movement and sensation, which is
called brain mapping1.
 It is used to assess the effects of stroke, trauma or degenerative disease (such
as Alzheimer's) on brain function1.
 fMRI uses the same machine as in MRI and same approach with the difference
that rather than designing it to look at the static structure of the brain it is
designed to look at the flow of blood in the brain1.
The fNIR is implemented using continuous wave near-infrared spectroscopy
(NIRS) which allows portable, low-cost and low-power instrumentation. Three
distinct types of NIRS implementation have been developed; time domain,
frequency domain and continuous wave spectroscopy measurements2.
1. N. Daimiwal, M. Sundhararajan and R. Shriram, "Non Invasive FNIR and FMRI system for Brain Mapping", International Journal of Scientific and Research Publications, vol. 3, no. 2, pp. 1-4, 2013.
2. K. Izzetoglu, S. Bunce, M. Izzetoglu, B. Onaral and K. Pourrezaei, "Functional near-infrared neuroimaging", The 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society,
pp. 5333-5336, 2004.

10. Continue
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11. Continue
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Method Measures/Stimulates Portability/Mobility Cost Spatial
Resolution
Temporal
Resolution
fNIRS Oxyhemoglobin &
Deoxyhemoglobin
High Low Moderate Low
MRI Gray matter volume None High High NA
fMRI Relative blood
oxygen
None High High Low
EEG Summated post-
synaptic electrical
activity
Moderate Low Low High
ERP Stimulus or response
related electrical
activity
Moderate Low Low High
TMS Brain activation or
inhibition
Low Moderate High High

12. EEG & NIRS
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Near Infrared Spectroscopy (NIRS) is a functional imaging technique, that employs low-energy
optical radiation (mostly in 2-3 different wavelengths) to assess absorption changes in the
underlying brain tissue.
In fact, these absorption changes reflect the changes in local concentration of oxy- and deoxy-
hemoglobin, which in turn are related to and triggered by the alternation in neuronal activity.
NIRS is a non-invasive imaging tool and utilizes endogenous chromospheres to assess brain’s
functional activity.
EEG and NIRS are sensitive to different cascade of events that are yet linked to the very same
neuronal activities.
Both modalities possess complementary temporal and spatial features.
The combination of EEG and fNIRS offers therefore the possibility to examine brain’s
functional activity more comprehensively.

13. Continue
13-Mar-18 10:26 PM 13EEG fNIR

14. Continue
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fMRI is superior to fNIRS in terms of spatial
resolution, spatial coverage and being able to
address deeper brain areas related questions
It has one big disadvantage: immobility.
That is, the feature of NIRS, that it is much more
compact even mobile, makes it a good companion
for the EEG.

15. Sensor Placement(EEG vs. NIRS)
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EEG holders –such as our actiCAP or EasyCap standard holders – offer a good platform to
accommodate NIRS optodes and EEG electrodes in the same cap.
Hence usually these EEG caps are used for the combined measurements.
In addition, these caps come with non-built-in electrodes; that is this setup can be used
to realize several electrode-optode-configurations it is recommended to use caps made
of black fabric in order to decrease the unwanted optical reflection.
The NIRS and EEG sensor scan either be placed jointly – same position holds both type of
sensor – or alternately.
The former one is certainly more challenging, and used more frequently in case the area
of interest is limited, for instance during baby measurements.
The joint placement is possible only if ring EEG electrodes and transparent gel is used
and the NIRS optode is small enough to fit into the slit of the electrode.

16. Data Stream Synchronization
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During the combined measurement, the EEG and NIRS
systems are working independently, therefore the same
time point has to be marked in both data streams.
This is typically done by the triggers: the same marker
signal has to be sent to the EEG and to the NIRS system.
The hardware based TTL triggers offer the highest
possible precision.
These shared markers make it possible to identify and
analyze the recordings acquired exactly in the same time.

17. Brain Activity With fNIR
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fNIR is the only stand-alone and field-
deployable technology able to determine
localized brain activity.
fNIR can be readily integrated with other
physiological and neurobehavioral
measures that assess human brain activity,
including eye tracking, pupil reflex,
respiration and electrodermal activity. fNIR
can also complement other techniques.
It has also been shown that fNIR can
effectively monitor attention and working
memory in real-life situations.
fNIR can be used in lie detection

18. Lie Detection Using fNIR
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Involves complex neuronal activities in addition to
several physiological changes in the body1.
A polygraph, which can measure some of the
physiological responses from the body, has been
widely employed in lie-detection1.
Lie detection can become more precise if the
neuronal changes that occur in the process of
deception can be isolated and measured1.
1. M. Bhutta, M. Hong, Y. Kim and K. Hong, "Single-trial lie detection using a combined fNIRS-polygraph system", Frontiers in Psychology, vol. 6, pp. 1-9, 2015.

19. Lie Detection (Case-1)
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16 healthy male subjects (13 were right handed and 3 were left handed)1.
Instructed to steal either a 5000 KRW note or a 10,000 KRW note from the drawer of
a table and keep it in his pocket1.
Taken to another room for questioning1.
Interrogator was totally unaware of the stolen note1.
10 question sessions, each session comprising five random questions, were
presented on a computer screen1.
Combined fNIRS-polygraph system for single trial lie detection was compared with
each fNIRS and polygraph system1.
The fNIRS system decodes deception based on the hemodynamic changes of oxy-
hemoglobin measured at the prefrontal cortex, and the polygraph operates on the
basis of physiological responses from the body such as respiration and electrodermal
activities1.
1. M. Bhutta, M. Hong, Y. Kim and K. Hong, "Single-trial lie detection using a combined fNIRS-polygraph system", Frontiers in Psychology, vol. 6, pp. 1-9, 2015.

20. Lie Detection (Case-1)
13-Mar-18 10:26 PM 201. M. Bhutta, M. Hong, Y. Kim and K. Hong, "Single-trial lie detection using a combined fNIRS-polygraph system", Frontiers in Psychology, vol. 6, pp. 1-9, 2015.
Figure: Comparison of classification accuracies of individual modalities and the combined system1
Figure: fNIR Data classification1

21. Lie Detection (Case-2)
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Investigated the hemodynamic response of human brain activity
during answering lie with respect to true2.
Mock lying protocol (A written lying protocol) and during that
time their hemodynamic responses are collected from prefrontal
cortex by fNIR device2.
Specific positions of prefrontal cortex with activation intensity
(activation range) are identified while participants lie2.
Five healthy subjects among them 3 male (mean age 24) and 2
female (age 30 years) participated in this proposed research
work2.
2. M. Rahman and M. Ahmad, "Lie detection from fNIR signal and NeuroImage", 2016 International Conference on Medical Engineering, Health Informatics and Technology (MediTec), 2016.

22. Lie Detection (Case-2)
13-Mar-18 10:26 PM 222. M. Rahman and M. Ahmad, "Lie detection from fNIR signal and NeuroImage", 2016 International Conference on Medical Engineering, Health Informatics and Technology (MediTec), 2016.
Figure: Neuroimage of The Subjects During True And Lie Answers2
Figure: Questions for Telling Truth And Lie2

23. What we can and cannot (yet)
do with fNIRS
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Functional near infrared spectroscopy (NIRS) is a relatively new technique
complimentary to EEG for the development of brain-computer interfaces
(BCIs).
NIRS-based systems for detecting various cognitive and affective states such
as mental and emotional stress have already been demonstrated in a range of
adaptive human–computer interaction (HCI) applications.
Within the human–computer interaction community, NIRS has been primarily
used in two ways:
1) For evaluating human–machine interactions and more recently
2) As additional input to adapt user interfaces and computer systems
based on the user’s cognitive state which is generally referred to as a
passive brain–computer interface.
2. M. Rahman and M. Ahmad, "Lie detection from fNIR signal and NeuroImage", 2016 International Conference on Medical Engineering, Health Informatics and Technology (MediTec), 2016.

24. What we can and cannot (yet)
do with fNIRS
13-Mar-18 10:26 PM 24
Functional near infrared spectroscopy (NIRS) is a relatively new technique
complimentary to EEG for the development of brain-computer interfaces
(BCIs)1.
NIRS-based systems for detecting various cognitive and affective states such
as mental and emotional stress have already been demonstrated in a range of
adaptive human–computer interaction (HCI) applications1.
Within the human–computer interaction community, NIRS has been primarily
used in two ways1:
1) For evaluating human–machine interactions and more recently
2) As additional input to adapt user interfaces and computer systems
based on the user’s cognitive state which is generally referred to as a
passive brain–computer interface.
1. M. Strait and M. Scheutz, "What we can and cannot (yet) do with functional near infrared spectroscopy", Frontiers in Neuroscience, vol. 8, 2014..

25. Applications of recent NIRS
based systems1
13-Mar-18 10:26 PM 251. M. Strait and M. Scheutz, "What we can and cannot (yet) do with functional near infrared spectroscopy", Frontiers in Neuroscience, vol. 8, 2014..

26. Continue1
13-Mar-18 10:26 PM 261. M. Strait and M. Scheutz, "What we can and cannot (yet) do with functional near infrared spectroscopy", Frontiers in Neuroscience, vol. 8, 2014..

27. Continue1
13-Mar-18 10:26 PM 271. M. Strait and M. Scheutz, "What we can and cannot (yet) do with functional near infrared spectroscopy", Frontiers in Neuroscience, vol. 8, 2014..

28. Continue1
13-Mar-18 10:26 PM 281. M. Strait and M. Scheutz, "What we can and cannot (yet) do with functional near infrared spectroscopy", Frontiers in Neuroscience, vol. 8, 2014..

29. Thank You
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