Optical sensing of neural activity in brain tissues

This study, for the first time to our knowledge, demonstrated the spectral measurement of neural activity in brain tissues. Since the conventional optical sensing methods of brain activity suffered from the time delay of several seconds, this paper is aimed to a fundamental study for the development of a fast sensing technique free from the latency. For this purpose, we first investigated how the optical properties of the brain tissue change during neural activation even without the neurovascular coupling. We monitored the near-infrared (NIR) transmission and reflection spectra of a rat cortical slice while electrically evoking and recording neural activity. As the result, we found an optical change closely correlated with neural activity, which was verified by using the tetrodotoxin (TTX). In addition, we constructed a novel neuron model to verify our hypothesis on the origin of the optical signals.