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. Author manuscript; available in PMC: 2015 Jan 15.
Published in final edited form as: Neuroimage. 2013 Jun 14;85(0 2):656–666. doi: 10.1016/j.neuroimage.2013.06.022

FIGURE 2.

FIGURE 2

Model of separate phases of encoding and retrieval (SPEAR) during different phases of hippocampal theta rhythm (Hasselmo et al., 2002a). A. Encoding. At the peak of the LFP in region CA1 stratum pyramidale (s. pyr), synaptic input from entorhinal cortex is strong (thick arrows), driving activity in CA3 and CA1. Synapses from CA3 to CA1 have weak transmission (thin arrows), causing less retrieval, but can undergo long-term potentiation (LTP) to encode new associations. B. Retrieval. At the trough of the LFP, synaptic input from entorhinal cortex is weaker (thin arrows), but synaptic transmission from CA3 is strong, allowing retrieval of previously stored associations to drive spiking in region CA1. LTP is weak (No LTP) to prevent encoding of retrieved activity as new.