Home > Conscious > Chapter 4 > 4.5. θ-γ Nested Oscillations



Figure 4-11. θ-γ nested oscillation. "A, B, C, D" represent different items located at distinct phases in a θ cycle. Each item corresponds to a different γ cycle. The items within a θ cycle can be perceived simultaneously. [Source: Zhang et al, 2016.]

The θ-γ nested oscillation (Figure 4-11) encodes the information about memory and sensory inputs (Lisman and Jensen , 2013). For instance, while playing tennis, you may see "a white ball moves rapidly along a direction." This event consists of four items: the ball's shape, color, moving direction and moving speed. Different items are processed by different populations of neurons. The information about an item is represented by the neuronal firing within a γ cycle.

For simplicity, suppose the color is represented by only ten neurons. "0" and "1" denote the states of "resting" and "firing" respectively. In the same γ cycle, some neurons may be at rest while the others are firing. The states of this group of neurons can then represent the color information, such as:


The function of the θ-γ nested oscillation is to arrange different items in order. Each item represented by a γ cycle is placed at a different phase in the θ cycle. In this manner, the brain can process a number of different items simultaneously without being confused. The "working memory" refers to the information that is being processed by the brain, including the items encoded by θ-γ nested oscillation. Since the period of a θ cycle is about seven times the period of a γ cycle, the working memory can store only about seven items, in agreement with the finding of George A. Miller (Miller, 1956).

Not only can we perceive an individual item, but also an entire event at once. As mentioned above, different items are processed by different populations of neurons. Then, how can the brain combine the information of different items? This "binding problem" is at the core of consciousness. Any working theory on consciousness must be able to solve the binding problem. The Geon Hypothesis proposed in Chapter 8 can reasonably explain the binding problem. In short, the ISO-nested α oscillation (ISO-α) may create a system with basic consciousness, which is a geon composed of gravitational (GR) waves only. The information encoded by the θ-γ nested oscillation is carried by GR waves, similar to the information of TV contents carried by electromagnetic waves. Perception of all items in a θ cycle occurs when the θ-γ modulated GR waves are bound with the gravitational geon. The TV set captures the information carried by electromagnetic waves by the "resonance" between its electronic circuits and electromagnetic waves. ISO-α may bind the θ-γ modulated GR waves by "synchronization". Their binding is most likely to happen when the α frequency is twice the θ frequency.