Amnesia for context fear is caused by widespread disruption of hippocampal activity

Amnesia for context fear is caused by widespread disruption of hippocampal activity

The hippocampus plays an essential role in the formation and retrieval of episodic memories in humans and contextual memories in animals. However, amnesia is not always observed when this structure is compromised. To determine why this is the case, we compared the effects of several different circui...

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Bibliographic Details
Published in:Neurobiology of learning and memory Vol. 175; p. 107295
Main Authors: Krueger, Jamie N., Wilmot, Jacob H., Teratani-Ota, Yusuke, Puhger, Kyle R., Nemes, Sonya E., Crestani, Ana P., Lafreniere, Marrisa M., Wiltgen, Brian J.
Format: Journal Article
Language:English
Published: United States Elsevier Inc 01-11-2020
Subjects:
Amnesia - physiopathology
Animals
Chemogenetics
Conditioning, Psychological - physiology
Context fear
Designer Drugs
Fear
GABAergic Neurons - metabolism
GABAergic Neurons - physiology
Hippocampus
Hippocampus - cytology
Hippocampus - physiopathology
Memory
Memory, Episodic
Mental Recall - physiology
Mice
Optogenetics
Pyramidal Cells - metabolism
Pyramidal Cells - physiology
Receptors, Drug
Retrieval
Retrieval
Context fear
Optogenetics
Memory
Chemogenetics
Hippocampus
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Summary:The hippocampus plays an essential role in the formation and retrieval of episodic memories in humans and contextual memories in animals. However, amnesia is not always observed when this structure is compromised. To determine why this is the case, we compared the effects of several different circuit manipulations on memory retrieval and hippocampal activity. Mice were first trained on context fear conditioning and then optogenetic and chemogenetic tools were used to alter activity during memory retrieval. We found that retrieval was only impaired when manipulations caused widespread changes (increases or decreases) in hippocampal activity. Widespread increases occurred when pyramidal cells were excited and widespread decreases were found when GABAergic neurons were stimulated. Direct hyperpolarization of excitatory neurons only moderately reduced activity and did not produce amnesia. Surprisingly, widespread decreases in hippocampal activity did not prevent retrieval if they occurred gradually prior to testing. This suggests that intact brain regions can express contextual memories if they are given adequate time to compensate for the loss of the hippocampus.
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ISSN:1074-7427
1095-9564
DOI:10.1016/j.nlm.2020.107295