Delta (2-4 Hz)
Delta Rule
Focus calls for less Delta across the whole brain. Increases in Delta during Focus meditations are associated with drowsiness (Dunn et al. 1999, Cahn et al. 2010). Focus meditations are an activating practice. Therefore, rewarding less Delta across all sites supports increased brain activation and prevents sleepiness, a common impediment in meditation when first starting out. In addition, lower frontal Delta signals a brain that is less distracted in meditation than during normal waking states (Cahn et al. 2013).
Delta Weights
Levels 1 and 2 meditators are assigned a rule weight of -1 because these levels will benefit the most from lower Delta to ward off sleepiness during their meditations. Generally speaking, Levels 1 and 2 meditators have not developed enough sustained attention in their practice to ward off slow-frequency drowsiness. Experienced meditators (Levels 3 and 4) have less need to stay away from Delta.