This Sixth Edition of the Protocol Guide reflects our current approach, including infra-low frequency, Alpha-Theta and Synchrony neurofeedback. The infra-low training frequencies discussed in this 2017 edition of the Protocol Guide apply only when using the 1 or 2 channel infra-low frequency HD application in Cygnet. We have continually refined our neurofeedback training and assessment methods based on optimization of clinical effects. This has led us to a better understanding of electrode placement options and to increased training frequency range and specificity. Beginning in 1989 with standard beta and SMR frequency ranges, we gradually extended to lower training frequencies over a number of years, as we sought more calming effects with highly aroused nervous systems. In 2006 this took us into the infra-low frequency range of the EEG, below 0.1 Hz. Since 2006 we have continued to extend the range down to lower training frequencies. And we have continued to optimize the hardware and software to function in this infra-low frequency range. With our new lower frequency range, we are now achieving consistently stronger training effects, especially for severe and chronic conditions.