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 hippocampal area CA1 and disambiguate multiple competing
mechanisms, we used closed-loop optogenetics 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 theta cycle. In contrast, artificial fields in the
parietal cortex did not exhibit synthetic precession. The findings are
incompatible with precession models based on inheritance, dual-input,
spreading activation, inhibition-excitation summation, or somato-dendritic
competition. Thus, a precession generator resides locally within CA1.