Local activation of CA1 pyramidal cells induces theta phase precession

Hippocampal theta phase precession is involved in spatiotemporal coding and generating multineural spike sequences, but how precession originates remains unresolved. To determine whether precession can be generated directly in CA1 and disambiguate multiple competing mechanisms, we used optogenetic activation to impose artificial place fields in pyramidal cells of mice running on a linear track. More than a third of the CA1 artificial fields exhibited synthetic precession that persisted for a full cycle. In contrast, artificial fields in the parietal cortex did not exhibit synthetic precession. The findings are incompatible with precession models based on inheritance, spreading activation, dual-input, or inhibition-excitation summation. Thus, a precession generator resides locally within CA1.