Distinct Synchronous Network Activity During the Second Postnatal Week of Medial Entorhinal Cortex Development

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Computational Neuroscience

Background:

• The medial entorhinal cortex (MEC) is crucial for spatial navigation and memory.
• Spatiotemporal tuning of MEC cells emerges around the third postnatal week in rodents.
• Spontaneous synchronized network activity (SSNA) is vital for neuronal circuit development before week 3.

Purpose of the Study:

• To investigate the characteristics and mechanisms of SSNA in the mouse MEC during the second postnatal week.
• To compare SSNA during the second postnatal week with that of the first postnatal week.
• To understand the developmental trajectory of MEC network activity preceding eye opening and spatial exploration.

Main Methods:

• In vitro electrophysiology and calcium imaging techniques were employed.
• Single-cell resolution and multi-layer integration were utilized.
• Pharmacological manipulations assessed the roles of glutamatergic and GABAergic signaling.

Main Results:

• SSNA in the mouse MEC peaks during the second postnatal week and depends on ionotropic glutamatergic signaling.
• Unlike the first postnatal week, MEC network activity during the second week drives neocortical (NeoC) rather than hippocampal networks.
• GABAergic influence on SSNA is age- and receptor-dependent, rather than driving network activity.

Conclusions:

• SSNA in the MEC exhibits partial mechanistic overlap but also unique features between the first and second postnatal weeks.
• Emerging distinct mechanisms suggest evolving roles for the MEC in hippocampal-entorhinal circuitry maturation.
• These findings provide insights into the developmental basis of spatial representation in the brain.