A novel whole-cell mechanism for long-term memory enhancement

PLoS One. 2013 Jul 11;8(7):e68131. doi: 10.1371/journal.pone.0068131. Print 2013.

Abstract

Olfactory-discrimination learning was shown to induce a profound long-lasting enhancement in the strength of excitatory and inhibitory synapses of pyramidal neurons in the piriform cortex. Notably, such enhancement was mostly pronounced in a sub-group of neurons, entailing about a quarter of the cell population. Here we first show that the prominent enhancement in the subset of cells is due to a process in which all excitatory synapses doubled their strength and that this increase was mediated by a single process in which the AMPA channel conductance was doubled. Moreover, using a neuronal-network model, we show how such a multiplicative whole-cell synaptic strengthening in a sub-group of cells that form a memory pattern, sub-serves a profound selective enhancement of this memory. Network modeling further predicts that synaptic inhibition should be modified by complex learning in a manner that much resembles synaptic excitation. Indeed, in a subset of neurons all GABAA-receptors mediated inhibitory synapses also doubled their strength after learning. Like synaptic excitation, Synaptic inhibition is also enhanced by two-fold increase of the single channel conductance. These findings suggest that crucial learning induces a multiplicative increase in strength of all excitatory and inhibitory synapses in a subset of cells, and that such an increase can serve as a long-term whole-cell mechanism to profoundly enhance an existing Hebbian-type memory. This mechanism does not act as synaptic plasticity mechanism that underlies memory formation but rather enhances the response of already existing memory. This mechanism is cell-specific rather than synapse-specific; it modifies the channel conductance rather than the number of channels and thus has the potential to be readily induced and un-induced by whole-cell transduction mechanisms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Excitatory Postsynaptic Potentials / drug effects
  • Excitatory Postsynaptic Potentials / physiology*
  • Learning / drug effects
  • Learning / physiology
  • Memory, Long-Term / drug effects
  • Memory, Long-Term / physiology*
  • Models, Neurological
  • Nerve Net / drug effects
  • Nerve Net / metabolism
  • Nerve Net / physiology
  • Neuronal Plasticity / drug effects
  • Neuronal Plasticity / physiology
  • Neurons / drug effects
  • Neurons / metabolism
  • Neurons / physiology
  • Olfactory Pathways / drug effects
  • Olfactory Pathways / physiology
  • Rats
  • Receptors, GABA-A / metabolism
  • Synapses / drug effects
  • Synapses / physiology*
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology
  • alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / pharmacology

Substances

  • Receptors, GABA-A
  • alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid

Grant support

This study was funded by “Israel Science Foundation”, grant number 47013. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.