Near infrared (NIR) brain imaging study: neurological responses in the pre-frontal area during

reading vs relaxing

ByAntony ThomasBejoy V MathaiNaveen Balaji

ACKNOWLEDGEMENTS

• We would like the thank Dr. Hanli Lui for providing us with this opportunity to do this hands on project and guiding us through, from beginning till the end.

• We are also thankful to Venkatagiri for his advise and guidance.

• We are very much thankful to Dr. Fenghua Tian, Manish and Sabin for teaching us the basics of the NIRx Instrument and helping us with the data collection.

Introduction• Functional Near Infrared Spectroscopy (fNIRS), is a non-

invasive imaging modality that allows to detect brain activity (or activation) through monitoring of blood oxygenation and blood volume in different region of brain.

• NIRS measures the attenuation of the biological tissue in near infrared spectrum. i.e., using longer wavelengths than those of visible light region that falls between 700 nm – 1000 nm.

• Other brain imaging techniques like MRI and PET are highly expensive, sensitive to motion artifacts, confines the subject to restricted position and expose the subject to harmful material (PET) and loud noise (MRI).

Absorption spectra for oxy and deoxy- haemoglobin

•700 to 900 nanometres is called a “window of transparency” because itallows light to propagate relatively deeply into the tissue before getting absorbed.

Ref:-INVESTIGATION OF BRAIN ACTIVITIES USING TWO STATE-OF-THE-ART DIFFUSE OPTICAL IMAGERS by SURESH PRAJAPATI

Ref:- www.nirx.net

•We are interested in prefrontal area

•This study is useful because it provides unique insights in the field of developmental neuroscience with a non-invasive approach.

Ref:-http://www.beliefnet.com

General block diagram

•Sensor- source and detector ( 760nm and 830nm).•Data acquisition unit.•Processor.

Ref:- International Journal of human-computer interaction, Brain imaging during cognitive task by Izzetoglu et.al

Probe Placement

Probe #1Probe # 20

Probe Arrangement

Protocol:

5 13791113151719

20 18 16 14 12 10 8 6 4 2

19 cms

3 cms

Relaxing20 sec

Reading 20 sec

Relaxing20 sec

•The reading material was based on general knowledge material based on general topics like geography, history, economics etc.

•The room was dark to reduce the interference of external light

Instrumentation

DYNOT System

Ref:- www.nirx.net

Figure: Shows the Front and Back view of the DYNOT System, with labels for various Components

PMD

Fiber optics cableLaser diode controller

Monitoring PC with Keyboard unit

Laser diode

Power supplyOptical Switch

Ref:- www.nirx.net

LD – Laser diode

LDD-Laser diode driver

TECD-Thermo-electric cooler driver

DPS- Digital Phase shifterf1&f2-Laser modulation frequencies

Optical time division multiplexer

Figure: Shows Block Diagram of DYNOT Instrument performing it’s function

Ref:- www.nirx.net

Figure: Shows how multiple optical tomographic data sets are acquired in a continuous fashion at high repetition rates (about several images per second)

Sample rate = 2.42 frames/second

LEGENDTarget

Target

Source

Detector

Direction of activation of source and detector around the target

Process of obtaining One tomographic data set

Ref:- www.nirx.net

Processing

• The raw optical data is processed in MATLAB to obtain the NIRS file.

• HOMER is used to process the NIRS file for Image Reconstruction.

• Images is reconstructed from the oxy and deoxy-hemoglobin using delta Concentration display .

• The spectrally weighted average of the wavelength specific forward models are used.

Raw Optical Data NIRS Data HMR DataImage Reconstruction (HBO , HBR & HBT obtained using delta Concentration)

Result:

Hemodynamic activity of HbOSubject 1 Subject 2 Subject 3

WhileRELAXING

WhileREADING

LeftRight Right Left

Left Left Left

LeftRight

RightRightRight

Hemodynamic activity of HbR

Subject 1 Subject 2 Subject 3

WhileRELAXING

WhileREADING

Right Left

RightRightRight

RightRight

LeftLeftLeft

LeftLeft

Block Averaged Hemodynamic responseSubject 1

dCon

cent

ratio

n (M

olar

)

Time (sec)

HbO

Hb

While RELAXING

While READING

Block Averaged Hemodynamic responseSubject 2

Time (sec)

dCon

cent

ratio

n (M

olar

)

HbO

Hb

While RELAXING

While READING

Block Averaged Hemodynamic responseSubject 3

dCon

cent

ratio

n (M

olar

)

Time (sec)

HbO

Hb

While RELAXING

While READING

Conclusion

• The rise in HbO activity shows the activation of neural activity in the pre frontal region while performing a cognitive task.

• Thus, fNIRS offers the possibility of directly investigating functional connectivity during rest and activation.

• For most language tasks the advantage of the left hemisphere (LH) is one of the best-established facts about the brain.

• Accumulated evidence shows the activity of bilateral components. When it comes to comprehending complex, natural language, the right hemisphere (RH) might play an important role.

Reference

• Prajapati, Suresh “INVESTIGATION OF BRAIN ACTIVITIES USING TWO STATE-OF-THE-ART DIFFUSE OPTICAL IMAGERS”.

• www.nirx.net • en.wikipedia.org• HomER Program User’s Guide Stand-alone executable

version (Version 4.0.0) Release July 28th, 2005

Written by: Theodore Huppert, M.Sc.

David A. Boas, Ph.D.

Thank you&

Questions