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.

In conventional neurofeedback we reward the increasing or the inhibiting of a targeted metric or bandwidth. This can be done because of the nature of the signal and equipment we use to measure it. The regular cycling of the sinusoidal signal can be measured by an alternating current amplifier. Tin and gold sensors can hold that signal steady.

ISF, however, is very slow and it ‘meanders.’ It does not present with the steady rhythmic beat that we see in the faster ranges. As we drop lower in frequency, the amplifiers that measure information using alternating current (AC) are unable properly pick up the signal. For the signal to be effectively read, it must be measured with a combination of a direct current (DC) and alternating current.

There are two types of ISF training:Bipolar and sLORETA:
1. ISF Bipolar: In ISF bipolar training, the ‘frequency’ is reinforced differently from traditional neurofeedback. Because the ISF is slow, it doesn’t oscillate the same way that Delta to Gamma do. Training the ISF band by providing feedback as a ‘mirror’ of the ISF wave form – without augmenting or inhibiting amplitude – is the effective method. It is analogous to a room full of tuning forks simultaneously starting to vibrate when one tuning fork is struck. Similarly, the nervous system attempts to synchronize with the movement of the ISF range reflected in the audible tone the client hears from the speakers. By training that ‘organizing rhythm’ we support the client in regulating their autonomic responses which produce the physiological changes associated with ISF training.

2. ISF sLORETA: This form of infraslow neurofeedback training functions similarly to traditional neurofeedback. The protocols reward an increase or decrease in the amplitude of the ISF band, based on the therapy goal of activating or deactivating the given region of the brain. The focus of training are the nodes of autonomic control in the deeper cortex.