ISF (infra-slow fluctuations) neurofeedback is an approach that uses extremely slow EEG fluctuations as the feedback mechanism. The client hears and sees feedback that indicates the presence of shifts in slow potentials, which reflect brain excitability in general. Insofar as ISF is based upon the slow changes in postsynaptic potentials in pyramidal neurons, as well as shifts in transmembrane potentials of the glia, it reveals to the client when the brain is undergoing changes in excitability, either to become more excitable, or less excitable, in general.
Consider the analogy of the U.S. senate. 100 senators combine their votes to make decisions on public policy and lawmaking, based on a combination of ideology and specifics. Suppose there are 52 senators rigidly fixed on a conservative agenda, and 48 fixed on an activist agenda. If this situation never changes, then the results of any vote would be “automatic poker,” with no flexibility. There is no possibility that any particular issue will receive an unbiased or considered vote, since all votes are along fixed lines. This is a rigid and inflexible situation. What would it take to introduce some flexibility and choice in this system?
If some (not too few, and not too many) senators decide to reconsider their positions, then there can suddenly be a new flexibility, new options. However, if too many senators start to rethink their positions, chaos might result. There would be an optimal amount of this shifting about, in which enough senators are willing to rethink and possibly change their votes, but not too many. What is needed is a handful of conservatives willing to think a bit more liberal, and few liberals willing to think a bit more conservative. With that addition, the senate becomes a powerful decision-making body, not just a reactive pool of rigid reactive responders.
If it becomes possible to cause 10 of the senators to reconsider their positions and vote more based on consideration of specifics, then the senate has the power to make actual decisions. Indeed, a few senators do appear to have this flexibility, and are able to vote on their own, not based on party lines. In the same way that a few more of this type would have tremendous impact on flexibility and appropriateness of legislative decisions, a brain that has a few more neurons on the edge of decision-making rather than reacting can result in a more decisive and empowered brain. It is on the edge of these shifts that decisions (votes) can be made that instrument change and adaptation, rather than rigidity.
So with ISF training, the brain is being informed when there are shifts in the general excitability of the brain, similar to learning how many senators may be reconsidering their positions. The population dynamics of the EEG make this all possible. In the EEG, we know that as few as 5% of the neurons are sufficient to alter 100% of the EEG activity, because of the amount of cancellation that occurs over the vast number of neurons. The few can make decisions that affect and in fact empower the masses.