Microglial activity during postnatal development is required for infantile amnesia in mice

Area of Science:

• Neuroscience
• Developmental Biology
• Immunology

Background:

• Infantile amnesia, the inability to recall early childhood memories, is poorly understood.
• Microglia, the brain's immune cells, are involved in synaptic development and memory.
• Their specific role in infantile amnesia is unclear.

Purpose of the Study:

• To investigate the mechanistic basis of infantile amnesia.
• To determine the role of microglia in regulating infant memory persistence and accessibility.

Main Methods:

• Used mouse models to study infantile amnesia and microglial function.
• Profiled microglial morphology changes during early development.
• Pharmacologically inhibited microglial activity during a critical postnatal window.
• Used activity-dependent tagging to track infant memory engrams.
• Examined microglia-engram cell interactions in the amygdala.

Main Results:

• Microglial activity changes paralleled the onset of infantile forgetting.
• Inhibiting microglia prevented infantile amnesia for contextual fear memory.
• Microglial inhibition altered engram size, amygdala reactivation, and microglia-engram interactions.
• Microglial dysfunction was linked to a lack of infantile amnesia in maternal immune activation models.

Conclusions:

• Microglia are key regulators of infant memory retrieval in mice.
• Microglial activity directly influences the persistence of early life memories.
• Microglial dysfunction may contribute to memory impairments in neurodevelopmental disorders.