Constrained largely by the slow axon conduction velocity of the neurons, when the available time is short, as is the case of higher frequency oscillations, the participating neurons are confined to a small volume of nervous tissue. In contrast, during slow oscillations many neurons in a large volume of tissue can be recruited to the rhythm. Mainly due to this structural constraint, when multiple rhythms #check details keyword# are present simultaneously, the phase of the slow rhythm(s) modulates the power of the faster one(s). This “cross-frequency phase coupling,” first demonstrated

between theta (0,4 to 9 Hz) and gamma (γ, 30 to 90 Hz) oscillations,12,13 is a general mechanism for all known rhythms ( Figure 2.)14-16 and it undergirds a hierarchical organization of brain rhythms.17 Figure 1. A system Inhibitors,research,lifescience,medical of interacting brain oscillations. Oscillatory

classes in the cortex. Note the linear progression of the frequency classes (written next to commonly used name for each rhythm), on the natural log scale. This geometrical order is despite the fact … Figure 2. Oscillations can route information by multiple mechanisms, (a) View of the brain showing location of computation as revealed by transient γ oscillations Inhibitors,research,lifescience,medical (i-iv) and θ oscillation in the hippocampus (HI) entorhinal cortex (EC). Brain rhythms … Preservation of brain rhythms in the mammalian order The spectral features of the EEG or local field potentials (LFP) recorded from animals with small or large brains are similar, and all known oscillations in humans are present in all other mammals investigated to date, γ oscillations have the same frequency range (30 to 90 Hz) and, Inhibitors,research,lifescience,medical importantly, have the same intermittent nature and likely the same mechanisms in animals with small and large brains.13 Slow oscillations (0.5 to 2 Hz)18 have been observed in the neocortex of all mammals tested. Similarly, sleep spindles have not only the same frequency (12 to 18 Hz) but the duration of the spindles is also similar.19-21 The ultra-slow (0.1 Hz) rhythm (Figure 3) involved large areas of the neocortex and is easily detectable Inhibitors,research,lifescience,medical with functional magnetic resonance imaging (fMRI) as correlated and anticorrelated brain regions in this frequency

range gives rise to the “default” patterns of cortical activity (ie, those brain activity patterns observed in the absence Phosphoprotein phosphatase of specific inputs or tasks) now frequently seen in human subjects.22 The ultra-slow fluctuation of cortical network excitability is robust and has been observed also in monkeys,23 cats,24 and rats21 (Figure 3). Thalamocortical alpha (α) oscillations (8 to 12 Hz) are the characteristic dynamic of sensory and motor systems in their “idling” or non-directed state. In humans, the specific members of the α family rhythms are known as a oscillations of the visual system, mu (μ) rhythms of the sensorimotor system, and tau (τ) rhythms of the auditor)’ system.17,25 Similar α mechanisms have been detected in the gustatory cortex, even in the absence of taste inputs.