Brain responses to a 6-Hz binaural beat: effects on general theta rhythm and frontal midline theta activity (Jirakittayakorn & Wongsawat, 2017)
An EEG study asking the direct question: does listening to a 6 Hz binaural beat actually change theta activity? The authors reported increased theta power emerging within 10 minutes of listening, including frontal midline theta — the rhythm associated with meditative attention. It's a single lab's result with a modest sample, so treat it as encouraging rather than settled, but it's one of the few papers that measures the brain instead of just asking people how they feel.
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