|A model for the mechanism of theta phase precession and memory formation in the hippocampla-enthorhinal network (Yamaguchi 2003) According to the neuronal properties of theta phase precession reported by O’Keefe and Recce (1993) and by Skaggs et al (1996) , a theoretical model was proposed by Yoko Yamaguchi (2003). The model hypothesize that theta phase precession is generaged in the entorhinal cortex and transmitted to the hippocampal cells to store a simple time series as asymmetric connections based on the asymmetric time window of synapric plasticity or STDP. The neurla mechanism of theta phase pecession was hypothesized as phase locking of nonlinear coupled oscillations, where individual neural oscsillators gradually changes the intrinsic frequencies.
Encodig: Under the input of a time series, tneurons in the superficial layers of he entorhinal cortex are activated to give theta phase precession. Their activities are transmitted to CA neuons to cause asymmetric connections in the associative memory network.
Retrieva;: Partial input to the entorhinal cortex can generate reactivation of CA3 as pattern completion of the sequence memory. This reactivation is transmitted to CA1 and then to the deeper layer of the entorhinal cortex. Thus, temporal bugger of the time sequence stored in the hippocampus can be reactivated and transfered to outside of the hippocampus, such as neocortical areas.