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Plasticity in the entorhinal cortex suppresses memory for contextual fear
April E Hebert1, Pramod K Dash
1The Vivian L. Smith Center for Neurologic Research, Department of Neurobiology and Anatomy, The University of Texas Medical School, Houston, Texas 77225, USA.
Summary
The entorhinal cortex (EC) plays a role in suppressing context-specific fear memory. Blocking extracellular signal-regulated kinase (ERK) activity in the EC mimics additional training effects on fear responses.
Area of Science:
- Neuroscience
- Molecular Biology
- Behavioral Science
Background:
- The hippocampus is implicated in fear conditioning.
- The role of the entorhinal cortex (EC), a key hippocampal structure, remains unclear.
- Extracellular signal-regulated kinase (ERK) cascade activity is crucial for long-term memory, including fear memory.
Purpose of the Study:
- To investigate the role of ERK activity in the EC during fear conditioning.
- To determine if inhibiting ERK in the EC affects fear memory recall.
- To elucidate the EC's contribution to the temporal aspects of fear memory.
Main Methods:
- Fear conditioning in rodents.
- Measuring ERK activity in the EC post-conditioning.
- Infusing ERK inhibitors (PD098059, UO126) into the EC at different time points.
- Assessing freezing behavior (a measure of fear) 48 hours after training.
Main Results:
- ERK activity in the EC increased 90 minutes after fear conditioning.
- Inhibiting ERK in the EC 40 minutes post-training, but not 10 minutes post-training, increased context-specific freezing.
- Inhibited animals exhibited anticipatory freezing, peaking at the time of the training shock.
Conclusions:
- ERK-mediated plasticity in the EC normally suppresses context-specific fear memory, particularly its temporal patterning.
- Blocking EC ERK plasticity enhances fear memory recall and mimics effects of additional training.
- The EC is critical for regulating the temporal dynamics of fear memory.