Home > Conscious > Chapter 4 > 4.4. Slow Oscillations


In earlier literature, the term "slow oscillation" often referred to the frequency below 1 Hz. However, this range actually contains two bands with entirely different roles: 0.1-1 Hz may abolish consciousness whereas < 0.1 Hz is crucial for the creation and operation of the conscious system. Most researchers now use "slow oscillation" for 0.1-1 Hz and call < 0.1 Hz "infra-slow oscillation" (ISO).


Figure 4-10. Slow oscillation in a single neuron. [Source: Crunelli et al, 2011]

Figure 4-10 shows an example for the slow oscillation in a single neuron. Each cycle consists of two states: UP and DOWN. During the UP state, the neuron fires at high frequency, but becomes silent in the DOWN state. An ISO can also contain faster oscillations, such as α, β and θ rhythms. The organization of faster oscillation within slower oscillation is known as "nested oscillation", "cross-frequency coupling" or "phase-amplitude coupling". They play key roles in the conscious system (Section 5.5).