Bio‐Optical Signals

Abstract

Neuroimaging techniques aim to provide information regarding the physiological changes that take place during activation of the brain in cognitive tasks. One such system, recently established, is the functional near‐infrared spectroscopy that uses light sources in the range of 650–950 nm to probe the underlying brain regions. The main absorbers of light within this range is the oxygenated hemoglobin (HbO 2 ) and deoxygenated hemoglobin (Hb). The signal obtained from the prefrontal cortex of humans during cognitive tasks show that the increase of ([HbO 2 ]) concentration surpasses that of ([Hb]), which means that regional cerebral blood flow to the activated region has increased to compensate for the demand in oxygen and glucose utilization. This article aims to present the underlying physical and physiological principles giving rise to biooptical signals of the brain.

Literature Review of Deep Learning for Physiological signal Analysis

“…Bio-optical signals are the result of the optical functions of the biological systems, occurring naturally or induced by the measurement [86]. Bio-optical signals are acquired by using a light source aimed at a body part with a detector or camera collecting the reflected or transmitted light through the tissues under investigation [87]. This article only takes into account bio-optical signals produced by PPG, however, other signals or procedures can be used to obtain optical function information as Functional Near-Infrared Spectroscopy (fNRIS) [88] or Pentacam [89], nonetheless, they cannot be classified as bio-optical signals.…”