Distinct CA3 inputs differentially shape the learning-dependent evolution of right CA1 spatial maps.

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Systems Neuroscience

Background:

• Hippocampal CA1 place fields are crucial for spatial memory and navigation.
• The precise role of upstream CA3 inputs in shaping CA1 spatial maps during learning is not fully understood.

Purpose of the Study:

• To investigate the distinct contributions of left and right CA3 hemispheric inputs to CA1 spatial representations during environmental learning in mice.
• To elucidate how these inputs dynamically influence the refinement and stabilization of spatial maps.

Main Methods:

• Two-photon calcium imaging in mice navigating virtual environments.
• Optogenetic inhibition of CA3 projections to CA1.
• Monitoring and perturbing CA3 inputs during learning.
• Axonal recordings to assess spatial activity shifts.

Main Results:

• CA1 spatial maps transitioned from inaccurate to stable representations within approximately 10 laps.
• Right-origin CA3 inputs were more influential during early learning for refining spatial coding.
• Left-origin CA3 inputs became more critical for maintaining stable representations in later learning phases.
• A corresponding temporal shift in spatial activity was observed between left and right CA3 inputs.

Conclusions:

• Distinct CA3 hemispheric inputs play dynamic and temporally segregated roles in the formation of hippocampal CA1 spatial maps.
• These inputs coordinate the refinement and stabilization of spatial representations during the process of environmental familiarization.
• Understanding these input-specific dynamics offers insights into hippocampal learning and memory mechanisms.