EEG and Brain Connectivity: A Tutorial - Bio-Medical Instruments, Inc.

27- How to compute Auto-channel Cross-Frequency Coherence (ACC)
(same channel different frequencies)
The procedure is:
1- Transform the digital value of the EEG time series x t in channel X
to a new time series x’ t by multiplying each time point by a sine
wave at frequency 1 and a cosine wave at frequency 1. Then, low
pass filter and compute the square root of the sum of squares of the
cospectrum and quadspectrum at each point of time to produce the
new time series x’ t (see section 9).
2- Transform the digital value of the EEG time series x t in channel X
to a new time series x’’ t by multiplying each time point by a sine
wave at frequency 2 and a cosine wave at frequency 2. Then low
pass filter and then compute the square root of the sum of squares
of the cospectrum and quadspectrum at each point of time to
produce the new time series x’’ t (see section 9).
3- Compute the coherence of the two time series x’ t and x’’ t from the
same channel for the two frequencies 1 and 2 for each instant of
time.
28- How to compute Cross-Channel Cross-Frequency Coherence
(CCC) (different channels different frequencies).
The procedure is:
4- Transform the digital value of the EEG time series x t in channel X
to a new time series x’ t by multiplying each time point by a sine
wave at frequency 1 and a cosine wave at frequency 1. Then, low
pass filter and compute the square root of the sum of squares of the
cospectrum and quadspectrum at each point of time to produce the
new time series x’ t .
5- Transform the digital value of the EEG time series y t in channel Y
to a new time series y’ t by multiplying each time point by a sine
wave at frequency 2 and a cosine wave at frequency 2. Then low
pass filter and then compute the square root of the sum of squares
of the cospectrum and quadspectrum at each point of time to
produce the new time series x’ t .