How Does ISF Impact the Brain and Body?

Researchers have proposed that the ISF is generated from two possible sources:

• Neuronal activity (electrical or mechanical stimulation, neurotransmitters, neuronal activity). Neuronal activity results in decreased oxygen. This stimulates calcium waves.
• Spontaneous activity (astrocyte clock gene expression results in calcium waves).

The production of calcium waves induces oscillation in a type of glial cell called ‘astrocytes.’ This astrocytic oscillation triggers burst firing of the neurons, which causes frequencies to actively connect or synchronize and establish cross-frequency coupling.

Calcium waves create vasodilation and oxygen consumption, which results in the BOLD signal we measure in fMRI studies. This is believed to be why the ISF correlates with the BOLD signal.

The various networks – default mode, salience, central executive, and central autonomic – each have primary ‘hubs’ that are densely connected. The main hubs of these networks are collectively referred to as the ‘Rich Club.’ The ‘Rich Club’ has been shown to be bound by the infraslow fluctuation.

ISF is further believed to be both a foundational rhythm and a carrier frequency. Faster frequencies above the alpha band, especially beta and gamma, are informational frequencies. These are ‘nested’ in the infraslow fluctuations. Thus, when the infraslow rhythm fluctuates, faster frequencies change their behaviour in ways that directly correlate with what the ISF is doing. In this way, the ISF is an activating/deactivating signal. It is the control mechanism in the cortex that allows for the binding of faster frequencies and networks.

Following this reasoning, ISF is considered an organizing rhythm that promotes more fluid and timely brain function. In concept, when we train the ISF signal, we are supporting clients in their ability to regulate their systems more globally. Because ISF has such a broad impact on function, it may also support emotional well-being by helping the brain and body maintain better overall balance. This is why we expect to see changes in QEEG metrics from pre- to post-ISF training, even though we are not directly measuring the ISF in a QEEG.

New research reinforces that the organizational effects of the ISF are, in fact, acting on the autonomic nervous system. As a result of this association, training the ISF band helps to regulate the balance between sympathetic (fight, flight or freeze) and parasympathetic (rest, digest) activation.