A non-invasive system and method. Sample light is delivered into an anatomical structure, such that a portion of the sample light passes through a target voxel comprising brain matter in the head and is scattered by the head as signal light. The signal light is detected, changes in the level of water concentration or relative water concentration of the target voxel are detected based on the detected signal light, and a level of neural activity is determined within the target voxel based on the determined changes level of the water concentration or relative water concentration of the target voxel.
Optical detection system for determining neural activity in brain based on water concentration