Increased Entorhinal–Prefrontal Theta Synchronization Parallels Decreased Entorhinal–Hippocampal Theta Synchronization during Learning and Consolidation of Associative Memory
Open Access
- 1 January 2012
- journal article
- Published by Frontiers Media SA in Frontiers in Behavioral Neuroscience
- Vol. 5, 90
- https://doi.org/10.3389/fnbeh.2011.00090
Abstract
Memories are thought to be encoded as a distributed representation in the neocortex. The medial prefrontal cortex (mPFC) has been shown to support the expression of memories that initially depend on the hippocampus (HPC), yet the mechanisms by which the HPC and mPFC access the distributed representations in the neocortex are unknown. By measuring phase synchronization of local field potential (LFP) oscillations, we found that learning initiated changes in neuronal communication of the HPC and mPFC with the lateral entorhinal cortex (LEC), an area that is connected with many other neocortical regions. LFPs were recorded simultaneously from the three brain regions while rats formed an association between an auditory stimulus (CS) and eyelid stimulation (US) in a trace eyeblink conditioning paradigm, as well as during retention 1 month following learning. Over the course of learning, theta oscillations in the LEC and mPFC became strongly synchronized following presentation of the CS on trials in which rats exhibited a conditioned response (CR), and this strengthened synchronization was also observed during remote retention. In contrast, CS-evoked theta synchronization between the LEC and HPC decreased with learning. Our results suggest that communication between the LEC and mPFC are strengthened with learning whereas the communication between the LEC and HPC are concomitantly weakened, suggesting that enhanced LEC–mPFC communication may be a neuronal correlate for theoretically proposed neocortical reorganization accompanying encoding and consolidation of a memory.Keywords
This publication has 69 references indexed in Scilit:
- Eyeblink conditioning contingent on hippocampal theta enhances hippocampal and medial prefrontal responsesJournal of Neurophysiology, 2011
- Theta Modulation in the Medial and the Lateral Entorhinal CorticesJournal of Neurophysiology, 2010
- Coherent Theta Oscillations and Reorganization of Spike Timing in the Hippocampal- Prefrontal Network upon LearningNeuron, 2010
- Theta Oscillations Mediate Interaction between Prefrontal Cortex and Medial Temporal Lobe in Human MemoryCerebral Cortex, 2009
- Cortical efferents of the perirhinal, postrhinal, and entorhinal cortices of the ratHippocampus, 2009
- What Does the Anatomical Organization of the Entorhinal Cortex Tell Us?Neural Plasticity, 2008
- Water deprivation optimizes hippocampal activity and facilitates nictitating membrane conditioning.Behavioral Neuroscience, 1989
- Neuronal sources of theta rhythm in the entorhinal cortex of the ratExperimental Brain Research, 1987
- Neuronal sources of theta rhythm in the entorhinal cortex of the ratExperimental Brain Research, 1987
- Prediction of Learning Rate from the Hippocampal ElectroencephalogramScience, 1978