In many physical, biological and technological oscillatory systems, useful functions emerge from collective synchronization of an ensemble of constituent oscillators. Examples include working of neurons in the brain during perceptual and cognitive processes, phase-locking of Josephson junction arrays, the dynamics of power grids. Transitions to synchronization depend on several factors, including interaction time-delays, which are often unavoidable in spatially distributed systems of oscillators like the interactions among brain neurons due to active axonal signal transmission processes. In this talk, I will discuss our recent findings on (i) the effects of time-delayed coupling in synchronization of nonlinear oscillators (theory), and (ii) on oscillatory network activity in the brain during perceptual decision-making processes (experiment).