Studies of patients with tiny electrodes implanted in their brains for purposes of seizure study and control, have shown a unique relationship between Theta brainwaves (4-8Hz) and Gamma brainwaves (36-100Hz approx).
This relationship is called Theta Gamma coupling or phase linking.
In particular the role of this coupling has been proven to be an accurate measure of successful memory encoding in relation to whether or not the memories can be recalled later or not. IE: If this Theta Gamma coupling relationship is measured during a learning process then there is a good chance that the learning will go into long term memory and therefore be easier to recall later.
There is enough evidence to suggest that Theta modulated (controlled) higher frequency Gamma might be involved in memory coding, while Theta modulated lower frequency Gamma might be involved in memory retrieval.
For example a drug known to suppress memory encoding shows a distinct lessening of this higher Gamma activity than without the drug suggesting that this assumption may be correct.
The link between Theta and Gamma is relatively well established but this exact distinction needs further study.
Is it actually Theta that modulates Gamma or the other way around? There is some evidence to suggest Gamma may be like a catalyst of sorts for Theta but so far measurements usually show a shift in Theta before Gamma phase links to it.
One hypothesis that is gaining evidence is that Theta is like the organiser of information and coding of that information for communication between brain regions and that Gamma helps transport and store it.
It seems to do this by way of Theta coherence between brain regions being the trigger for information flow, and Gamma control of neuronal firing delays and cell specific excitation, resulting in the correct information getting to the correct part of the brain.
Theta processes the information while Gamma picks out which bits of it are relevant for certain parts of the brain.
Interfering with this process has proven to also interfere with memory formation and retrieval.(second research link)
This Theta Gamma coupling has also been established during deep meditative states and states of flow in performance tasks suggesting that this relationship is both common and important.
Many of roXiva’s audio visual brainwave entrainment sessions use this coupling effect to enhance learning and deep trance and meditation states.