Impact of light on inner workings of neuronal functions.

The aim of this chapter is to review the molecular mechanisms that underlie the effect of red and near-infrared light --collectively referred to as photobiomodulation (PBM)-- on brain tissue. We discuss the therapeutic potential of PBM in the brain, considering both systemic actions and cell-type-specific responses. The prevailing hypothesis is that PBM enhances mitochondrial activity, leading to increased cellular energy production. While this mechanism may benefit many cell types, the central nervous system (CNS) appears particularly responsive to PBM due to either cell- specific signalling pathways that are highly energy-dependent or the existence of several mechanisms of action for PBM, some of them could be specific to CNS cells. In this chapter, we highlighted studies demonstrating PBM's functional impact on different CNS cell populations in order to identify the molecular and cellular mediators of its effects.