ReviewTheta rhythm and the encoding and retrieval of space and time

- Theta rhythm in hippocampus and entorhinal cortex contributes to memory behavior.
- Physiological data suggests separate phases of encoding and retrieval during theta.
- Theta rhythm in entorhinal cells and networks contributes to grid cell periodicity.
- Models of grid cells utilize theta frequency resonance and attractor dynamics.
- Theta rhythm contributes to coding space and time in models of episodic memory.

Physiological data demonstrates theta frequency oscillations associated with memory function and spatial behavior. Modeling and data from animals provide a perspective on the functional role of theta rhythm, including correlations with behavioral performance and coding by timing of spikes relative to phase of oscillations. Data supports a theorized role of theta rhythm in setting the dynamics for encoding and retrieval within cortical circuits. Recent data also supports models showing how network and cellular theta rhythmicity allows neurons in the entorhinal cortex and hippocampus to code time and space as a possible substrate for encoding events in episodic memory. Here we discuss these models and relate them to current physiological and behavioral data.