Adaptive Content
Matrix

1. Conventions / Review Spectral EEG brainwave indexes

   Five broad bands are conventional, while exact thresholds and mental-state indexes remain non-standardised.

2. Delta / Physiological Review Control of sleep and wakefulness

   Strong delta activity is a defining feature of deep slow-wave sleep; this is an endogenous association, not proof of audio-induced sleep.

3. Alpha / Systematic Review + Meta-analysis EEG biomarkers of relaxation

   Across 54 studies and 2,569 participants, alpha power showed the clearest positive relationship with measured relaxation.

4. Beta / Neuroscience Review Beta oscillations in working memory and executive control

   Beta activity participates in working memory, executive control and sensorimotor processes; it is not a single universal focus switch.

5. Theta / Systematic Review Mindfulness and EEG oscillations

   Alpha and theta increases were the most common mindfulness findings across 56 studies, although results were not uniform.

6. Theta / Experimental EEG Creative problem-solving over time

   Frontal theta increased immediately before responses in one creative problem-solving paradigm; broader creativity is a network phenomenon.

7. Gamma / EEG + fMRI Neural activity before verbal insight

   A brief right-temporal gamma burst preceded reported insight in a verbal task; this does not establish externally induced insight.

Boundary: Band ranges vary across studies, mental states involve interacting networks, and frequency stimulation does not guarantee a corresponding state. The delivery layer remains novel research.