All techniques, whether mantra, focus on the breath, contemplation of a koan, or any other, are simply the vehicles we use to take us into (hopefully) a meditative state. Put another way, the purpose of repeating a mantra is not to get proficient at repeating a mantra. The purpose is to take us to a meditative state where the mantra slips away and is no longer necessary.
Neural oscillations are rhythmic or repetitive electrochemical activity in the brain and central nervous system. Such oscillations can be characterized by their frequency, amplitude and phase. Neural tissue can generate oscillatory activity driven by mechanisms within individual neurons, as well as by interactions between them. They may also adjust frequency to synchronize with the periodic vibration of external acoustic or visual stimuli.