The plots below were created using an sLORETA projection of EEG from the left Parietal Lobe, and correlating Infra-Slow Fluctuations with the magnitude of other brain rhythms. The study was done with one set of data taken using Ag/AgCl sensors, and compared with results using random signals as the EEG. The EEG was gathered and processed at 256 samples/second, and the ISF and magnitude data were analyzed at 8 samples/second. These results clearly show that the ISF signal is correlated with other brain rhythms in a very interesting way, and that random noise is not. There is a correlation between ISF and Delta that is related to the closeness in frequency. However, when real EEG is used, there is an interesting correlation between ISF and the other rhythms which is maximal for delta and theta, and also, significantly, for gamma. The illustration at the end shows in a 60 second epoch what we are now seeing as a typical display, with the ISF signal fluctuating and producing meaningful sLORETA images.
This supports the following conclusions:
ISF is clearly related to the other brain rhythms, and ISF does not behave as if it is uncorrelated noise.
We particularly thank Mark Smith for providing the EEG data for this analysis. We also continue to acknowledge the contributions of the Othmers and EEG Institute in their clinical and research work with this modality.