Novel types of frequency filtering in the lateral perforant path projections to dentate gyrus
Abstract
Despite its evident importance to learning theory and models, the manner in which the lateral perforant path (LPP) transforms signals from entorhinal cortex to hippocampus is not well understood. The present studies measured synaptic responses in the dentate gyrus (DG) of adult mouse hippocampal slices during different patterns of LPP stimulation. Theta (5 Hz) stimulation produced a modest within‐train facilitation that was markedly enhanced at the level of DG output. Gamma (50 Hz) activation resulted in a singular pattern with initial synaptic facilitation being followed by a progressively greater depression. DG output was absent after only two pulses. Reducing release probability with low extracellular calcium instated frequency facilitation to gamma stimulation while long‐term potentiation, which increases release by LPP terminals, enhanced within‐train depression. Relatedly, per terminal concentrations of VGLUT2, a vesicular glutamate transporter associated with high release probability, were much greater in the LPP than in CA3–CA1 connections. Attempts to circumvent the potent gamma filter using a series of short (three‐pulse) 50 Hz trains spaced by 200 ms were only partially successful: composite responses were substantially reduced after the first burst, an effect opposite to that recorded in field CA1. The interaction between bursts was surprisingly persistent (>1.0 s). Low calcium improved throughput during theta/gamma activation but buffering of postsynaptic calcium did not. In all, presynaptic specializations relating to release probability produce an unusual but potent type of frequency filtering in the LPP. Patterned burst input engages a different type of filter with substrates that are also likely to be located presynaptically. image
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Aug 01, 2022
- Source ID
- 10.1113/jp283012
Entities
People
- Aliza A. Le
- Benedict S. Pruess
- Benjamin G. Gunn
- Christine M Gall
- Conor D Cox
- Gary Lynch
- Julian Quintanilla
- Julie C Lauterborn
- Yousheng Jia
Organizations
- Eunice Kennedy Shriver National Institute of Child Health and Human Development
- National Institute of Mental Health
- National Institute on Drug Abuse
- National Institutes of Health
- National Science Foundation
- Office of Naval Research
- University of California