Young dentate granule cells mediate pattern separation, whereas old granule cells facilitate pattern completion.

Area of Science:

• Neuroscience
• Cellular Biology
• Cognitive Science

Background:

• Adult neurogenesis in the dentate gyrus generates new granule cells (GCs).
• Young adult-born GCs are highly active, while older ones are less so.
• The distinct functional roles of young versus aged adult-born GCs in memory are not fully understood.

Purpose of the Study:

• To investigate the differential roles of young and aged adult-born GCs in memory functions.
• To determine if specific memory processes, like pattern separation and completion, are mediated by GCs of different ages.

Main Methods:

• Generation of a transgenic mouse model to selectively inhibit the output of older adult-born GCs.
• Assessment of pattern separation abilities in mutant mice using contextual tasks.
• Evaluation of pattern completion recall speed in the same mutant mice.

Main Results:

• Mice with inhibited older GCs showed normal or enhanced pattern separation.
• Ablation of young GCs impaired pattern separation.
• Mutant mice exhibited deficits in rapid pattern completion.
• Young adult-born GCs are essential for pattern separation, while older GCs support rapid pattern completion.

Conclusions:

• Pattern separation relies on young, newly integrated adult-born GCs.
• Older adult-born GCs contribute to rapid memory recall via pattern completion.
• The function of adult-born GCs evolves from pattern separation to pattern completion as they age.