ABSTRACT
Optical imaging is becoming increasingly attractive for in vivo brain imaging due to its inherent sensitivity to blood oxygenation and hemodynamics. In the previous chapters, various optical neuroimaging methods have been described. In the context of microscopic techniques, the main limitation remains the intense photon scattering, which confines the effective imaging depth of even the most advanced wide-field microscopy methods to superficial brain vasculature (Kalchenko et al., 2014), also necessitating removal of the scalp and/or skull. Other advanced techniques, such as two-photon microscopy, can access deeper subcortical structures, such as the hippocampus, by displacing large chunks of overlying structures (Mizrahi et al., 2004). Alternatively, other invasive approaches, e.g. optogenetic fiber probes, are used to visualize and manipulate neurons, in which case the readings of real-time activity are still bounded to small volumes. More generally, volumetric real time observations of fast neural activity with state-of-the-art optical microscopy are limited to depths below ~1 mm and FOV below 1 mm3 in scattering intact brains.
