Brain cognitive study using diffuse optical probes.

• Main Author: Ng, See Khee.
• Other Authors: Lee Kijoon
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Science::Medicine::Optical instruments
• Online Access: http://hdl.handle.net/10356/50175
• Institution: Nanyang Technological University

Near-infrared spectroscopy (NIRS), a non-invasive technique, uses near-infrared light to measure hemodynamic changes and oxygenation in tissues (e.g. brain) [1]. Measurements obtained are capable of estimating changes in cerebral metabolic rate of oxygen (CMRO2) [2] during normal brain function [3]. Another optical technique, Diffuse Correlation Spectroscopy (DCS) measures speckle variations of NIR light in tissue, through sensitive detection of red blood cell motions [4]. NIRS and DCS are promising brain probes which can replace the expensive PET and fMRI. Furthermore, spectroscopic information detected by NIRS allows less ambiguous analysis of hemodynamic changes than blood oxygen level-dependent in fMRI [5]. By incorporating EEG with these optical probes, both fast electrical signal and slow hemodynamic signal can be observed simultaneously, for a more comprehensive brain study. In this report, the design of self-made tri-modality headband, implementation and analysis of experimental results are presented. Concurrent measurements of EEG and DOS were first conducted to establish understanding of NIRS signal during brain activity. During verbal fluency test, increase oxy-hemoglobin and decrease deoxy-hemoglobin concentrations were observed in the pre-frontal cortex of subjects. Three analytical methods were employed for analysis: Linear fitting, Student’s t-test (Paired Samples) and NIRS-SPM Time Series Analysis. Experimental results were consistent with literatures. Subsequently, DCS experiments were performed. DCS results did not show statistically significant change between rest and brain activation, likely due to indistinct cranial blood flow changes. Nevertheless, NIRS showed significant CMRO2 changes. Hence, future work could include DCS and DOS study on other regions of brain with other activation.