This study suggests some measurable effects, though not as simple and direct as the appearance of an EEG band at the target frequency: http://www.researchgate.net/publication/239803901_EEG_Cohere...
This study suggests some measurable effects, though not as simple and direct as the appearance of an EEG band at the target frequency: http://www.researchgate.net/publication/239803901_EEG_Cohere...