Coherence Analysis of Physiological Signals

Coherence is one of the connectivity measure studied widely. It is the function of correlation between the two simultaneously acquired signals. Photoplethysmography is widely used in the healthcare because of its non-invasiveness, reliability and ability to predict the cardiovascular parameters indirectly. Photoplethysmogram (PPG) is the process of applying a light source and photo sensor to an appendage and measuring the light that is reflected by the skin. Electroencephalogram (EEG) is an electrical signal in micro volts captured non-invasively from brain, which provides important and unique information about the brain. Reflectance type of PPG sensor (source-IR LED of 860 nm wavelength and 5 mm diameter with OPT 101 as a detector) is developed to capture PPG from cranial region (CPPG). Estimation of coherence is carried out between concurrent EEG-EEG, EEG-CPPG, PPG-PPG, PPG-PP, PP-PP signal captured from various body sites. Various Cardiovascular Parameters were estimated from these captured signals and further their Statistical Analysis was carried out.