Encoding of Odor Fear Memories in the Mouse Olfactory Cortex

Area of Science:

• Neuroscience
• Olfactory system
• Memory research

Background:

• Odor memories are crucial for survival and are thought to be encoded in the olfactory cortex.
• The specific neurons and mechanisms underlying olfactory learning and memory have remained elusive.
• Understanding olfactory memory traces is vital for comprehending sensory memory formation.

Purpose of the Study:

• To identify the cellular substrates responsible for encoding olfactory fear memories in the piriform cortex.
• To investigate the role of specific neuronal ensembles in the retrieval and recall of odor-related fear memories.
• To explore the potential of targeting these neuronal ensembles for memory manipulation.

Main Methods:

• Utilized intersectional, cFos-based genetic manipulation ('Fos tagging') to label activated neurons during olfactory fear conditioning.
• Employed chemogenetics to selectively silence or reactivate these Fos-tagged neuronal ensembles in the mouse piriform cortex.
• Assessed the impact of neuronal manipulation on odor fear memory retrieval, odor detection, discrimination, and exploratory behavior.

Main Results:

• Olfactory fear conditioning activated sparse, distributed neuronal ensembles within the piriform cortex.
• Chemogenetic silencing of these ensembles impaired odor fear memory retrieval without affecting basic odor perception.
• Chemogenetic reactivation of fear-conditioned ensembles induced behavioral responses indicative of odor-evoked fear recall.

Conclusions:

• Specific ensembles of piriform cortex neurons constitute a critical olfactory fear memory trace.
• These identified neuronal ensembles are essential for both the storage and retrieval of olfactory fear memories.
• The findings provide a cellular basis for understanding and potentially intervening in olfactory memory processes.