I have posted in the Files section some examples of the Bi-Spectrum of the EEG during
sleep and wakefulness that help explain the EEG. As explained by Steriade and Buzsaki
the EEG is a mixture of many different frequencies and separating the rhythms into
different bands is not useful because it is artificial. Sleep and wakefulness actually
contain the same waves but just in different proportions (0.3 to 300 Hz). All EEG waves
share in common the same neural mechanisms and differ primarily by the length of the
inhibitory postsynaptic potentials (IPSPs), e.g., a 4 Hz wave is produced by 250 msec
IPSPs and a 40 Hz wave is produced by 25 msec IPSPs. Also, all EEG waves are
excitability cycles and behave like a "gate" that opens only during the depolarzing phase
for all frequencies of the EEG. EEG waves are nested and organized by the slower
frequencies. The lowest frequencies are those generated by the default networks and
oscillate at about one every 30 seconds to one ever 10 seconds as seen in fMRI studies
(see studies by Raichle). The cortico-thalamic networks operate from about 1 Hz to 300
Hz and are 1/f distributed, i.e., they are the same processes that are nested and
logrithmically scaled along a straight line (see Buzsaki).
The Bi-Spectrum in Neuroguide is a measure of the frequency spectrum of "bursts" of
neural activity and the posted files show how this spectrum differs during sleep and
wakefulness and for different measures.
Phase reset is involved in animating the different "gates" so that different anatomical
'Modules' are cross-frequency phase locked for brief periods of time. During sleep the
'animation' is turned off by increased inhibition and reduced excitation of the thalamus
(see Steriade and Forte, etc.). When we awake from sleep the animation is turned on by
the pontine and mesencephalic reticular formation that excites the thalamus and inhibits
the inhibition.
These are some of the general rules governing the EEG spectrum and they are relevant
for all states of the brain. I will explain these processes in more detail in my book, that I
know people are waiting for but it takes time to figure all of this
Bob
The human EEG is a mixture of waves that are organized into two classes – Default
Mode Network (DMN) and Cortico-Thalamic EEG Networks (CEN). The DMN
synchronizes the CEN, the latter is 1/f distributed from 1 Hz to 300 Hz