The links below are to two videos created using BrainAvatar’s Live sLORETA Projector (LLP), demonstrating the brain origin of Infra-Slow Fluctuations, also known as Infra-Low Frequency (ILF) and also as Infra-Slow Oscillations (ISO). The recordings were taken by Mark Smith. The LLP projections were created by taking the 19-channel recordings with an electrocap fitted with Silver/Silver Chloride sensors and playing the EEG back through the LLP projector. The user band was set with a low cutof of 0.002 Hz and a high cutoff of 0.01 Hz to show the signals in this band. The images clearly show the brain origin of the signals, which are not artifact according to these findings. There has been controversy over training of this signals, with some claims that they are artifactual, due to variations in skin potential, amplifier drift, or other non-brain sources. These videos show that the distribution of ISF signals is definitely of cortical brain origin, and that it has a distribution different from other frequency bands. It appears that the ISF signals may underly higher frequency rhythms, and reflect general activation of brain regions. If these fluctuations were due to superficial sources such as skin potential or amplifier drift, they would not produce the type of meaningful distributions shown here, and would not appear so well related to the higher frequency brain rhythms. This is therefore an existence proof that ISF signals can be shown to have their origin in the brain and reflect brain processes. This particular example shows left frontal activation, as well as a small amount of activity in the midline associated with the cingulate and parietal areas. This finding and the associated methods should help to open a new door to the study of these extremely low frequency fluctuations in the EEG, for assessment and training.
The first video shows a single moment of EEG filtered using passband of 0.002 to 0.01 Hz, and showing the brain distribution of the instantaneous signal:
The second video shows a playback of approximately 4 seconds of EEG, showing the time variation in the ISF signal, as it moves in the brain.