Remote photonic sensing of cerebral hemodynamic changes via temporal spatial analysis of acoustic vibrations

Abstract

A novel photonic method for remote monitoring of task‐related hemodynamic changes in human brain activation is presented. Physiological processes associated with neural activity, such as nano‐vibrations due to blood flow and tissue oxygenation in the brain, are detected by remote sensing of nano‐acoustic vibrations using temporal spatial analysis of defocused self‐interference random patterns. Temporal nanometric changes of the speckle pattern due to visual task‐induced hemodynamic responses were tracked by this method. Reversing visual checkerboard stimulation alternated with rest epochs, and responsive signals were identified in occipital lobe using near‐infrared spectroscopy. Temporal vibrations associated with these hemodynamic response functions were observed using three different approaches: (a) single spot illumination at active and control areas simultaneously, (b) subspots cross‐correlation‐based analysis, and (c) multiwavelength measurement using a magnitude‐squared wavelet coherence function. Findings show remote sensing of task‐specific neural activity in the human brain.

Remote photonic detection of human senses using secondary speckle patterns

“…Brain activity analysis using electroencephalography (EEG) has received considerable attention 2 – 6 , particularly in relation to the five basic human senses: sight 2 , touch 7 , hearing 8 , 9 , smell 10 – 13 and taste 14 . In addition to EEG, a number of optical techniques have also been employed for monitoring the human brain activity using image contrast analysis 15 , 16 and cross-correlation based analysis of a laser speckle imaging 17 . While these methods mainly deal with a laser speckle image and its relation to temporal fluctuations, extracting semantic information from sensory activity is still lacking.…”

“…Therefore, when a rough surface is illuminated by a laser beam, the back scattered light forms secondary speckle patterns, which are possible to image clearly by a digital camera with defocused optics. Analysis of temporal changes in the spatial distribution of the speckle patterns can be related to nano-vibrations of the illuminated surface due to the hemodynamic process associated with the transient flow of the blood occurring during human brain activation 17 .…”

Remote Photonic Detection of Human Senses Using Secondary Speckle Patterns

“…Brain activity analysis using electroencephalography (EEG) has received considerable attention [2][3][4][5][6] , particularly in relation to the ve basic human senses: sight 2 , touch 7 , hearing 8,9 , smell [10][11][12][13] and taste 14 . In addition to EEG, a number of optical techniques have also been employed for monitoring human brain activity using image contrast analysis 15,16 and cross-correlation based analysis of a laser speckle imaging 17 . While these methods mainly deal with a laser speckle image and its relation to temporal uctuations, extracting semantic information from sensory activity is still lacking.…”

“…Therefore, when illuminated by a laser beam, the back scattered light forms secondary speckle patterns, which are possible to image by a digital camera with defocused optics. Analysis of temporal changes in the spatial distribution of the speckle patterns can be related to nano-vibrations in the illuminated surface due to the hemodynamic process associated with the transient ow of blood occurring during human brain activation 17 .…”

“…Speckle-based remote sensing has been used for the development of different biomedical applications, such as monitoring heart rate 18 , breathing 19 , blood pressure 20 , blood oximetry 21 , blood coagulation 22,23 , bone fractures 24 , melanoma 25 , and neural activity 17 . Prior methods for classifying speckle patterns used a single frame 26 or full video frame-by-frame 21 obtained by averaging the model predictions on all frames of the video and providing a threshold for selecting the desired output.…”