Neuron
Volume 66, Issue 6, 24 June 2010, Pages 921-936
Journal home page for Neuron

Article
Coherent Theta Oscillations and Reorganization of Spike Timing in the Hippocampal- Prefrontal Network upon Learning

https://doi.org/10.1016/j.neuron.2010.05.013Get rights and content
Under an Elsevier user license
open archive

Summary

To study the interplay between hippocampus and medial prefrontal cortex (Pfc) and its importance for learning and memory consolidation, we measured the coherence in theta oscillations between these two structures in rats learning new rules on a Y maze. Coherence peaked at the choice point, most strongly after task rule acquisition. Simultaneously, Pfc pyramidal neurons reorganized their phase, concentrating at hippocampal theta trough, and synchronous cell assemblies emerged. This synchronous state may result from increased inhibition exerted by interneurons on pyramidal cells, as measured by cross-correlation, and could be modulated by dopamine: we found similar hippocampal-Pfc theta coherence increases and neuronal phase shifts following local administration of dopamine in Pfc of anesthetized rats. Pfc cell assemblies emerging during high coherence were preferentially replayed during subsequent sleep, concurrent with hippocampal sharp waves. Thus, hippocampal/prefrontal coherence could lead to synchronization of reward predicting activity in prefrontal networks, tagging it for subsequent memory consolidation.

Highlights

► Hippocampal-prefrontal theta LFP coherence increases at the Y maze fork upon learning ► Pfc interneuron inhibition of pyramidal neurons increases during high coherence ► Pfc neurons shift phase relative to hippocampal theta leading to assembly activation ► Acute dopamine injection in Pfc replicates coherence increases and phase shifts

SYSNEURO

Cited by (0)

6

These authors contributed equally to this work

7

Present address: ENMVI team, CNRS UMR 7102, Université Pierre et Marie Curie, Quai Saint-Bernard 75005 Paris, France