Theta rhythmic stimulation of stratum lacunosum-moleculare in rat hippocampus contributes to associative LTP at a phase offset in stratum radiatum.
Computational modeling demonstrates that encoding and context-dependent retrieval of memories in region CA1 of the hippocampus will be most effective when the phase of strongest entorhinal input (to stratum lacunosum-moleculare) is offset from the phase of maximal induction of long-term potentiation at Schaffer collateral synapses (in s. radiatum). This would allow entorhinal input to play a role in both retrieval and encoding without engaging long-term potentiation (LTP) during retrieval. Experiments in brain slice preparations of the hippocampal formation tested the relationship between rhythmic input to s. lacunosum-moleculare and the time of maximal LTP induction at Schaffer collateral synapses in s. radiatum. Analysis of the data demonstrates a statistically significant difference in the induction of LTP for different time intervals between the end of each four-pulse train in s. lacunosum-moleculare and the single pulse s. radiatum stimulation. The time of maximal LTP induction was found to be approximately 30 ms after the end of lacunosum-moleculare stimulation, consistent with the requirements of the model.
Judge
Sarah J
SJ
Department of Psychology, Center for Memory and Brain, Program in Neuroscience, Boston University, 2 Cummington Street, Boston, MA 02215, USA. hasselmo@bu.edu
Hasselmo
Michael E
ME
D000818:Animals; D018728:Entorhinal Cortex / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology*; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D066298:In Vitro Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D013826:Theta Rhythm / Q000379:methods*