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

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.