Old mice fail to integrate a memory update into an existing hippocampal engram

Area of Science:

• Neuroscience
• Aging Research
• Memory Mechanisms

Background:

• Memory updating, the process of modifying existing memories with new information, is crucial for cognitive flexibility.
• Age-related impairments disproportionately affect memory updating compared to memory formation.
• The underlying neuronal mechanisms of age-related memory updating deficits remain largely unknown.

Purpose of the Study:

• To investigate how memory engrams in the dorsal hippocampus encode memory updates in young and aged brains.
• To identify neuronal mechanisms contributing to age-related impairments in memory updating.

Main Methods:

• Utilized chemogenetics to manipulate neuronal activation within the dorsal hippocampus memory engram.
• Compared memory updating processes in young and aged mice.
• Assessed the proportion of original memory engrams re-engaged during memory updating sessions.

Main Results:

• Aged mice re-engaged a smaller proportion of the original memory engram during memory updating.
• Chemogenetically increasing the activation of the original engram alleviated age-related deficits in memory updating.
• Therapeutic strategies promoting engram re-engagement improved memory updating in aged mice.

Conclusions:

• Age-related memory updating impairments are linked to reduced re-engagement of original memory engrams in the dorsal hippocampus.
• Targeting memory engram re-activation presents a potential therapeutic avenue for age-related memory decline.
• This study elucidates a novel mechanism for age-related memory updating deficits and brain information organization.