GABAergic Restriction of Network Dynamics Regulates Interneuron Survival in the Developing Cortex

Area of Science:

• Neuroscience
• Developmental Neurobiology
• Cortical Circuit Assembly

Background:

• Neonatal sensory cortices exhibit spontaneous activity patterns influenced by experience and intrinsic factors.
• The role of these activity patterns in neuronal circuit assembly remains incompletely understood.

Purpose of the Study:

• To investigate how spontaneous activity patterns contribute to the formation of functional neuronal assemblies in the developing somatosensory cortex.
• To elucidate the role of GABAergic signaling in shaping these activity patterns and their impact on interneuron survival during neonatal development.

Main Methods:

• Longitudinal in vivo calcium imaging was performed in unanesthetized mouse pups.
• Functional assemblies of interneurons and pyramidal cells were analyzed in the somatosensory cortex.
• The effects of reduced GABA release and synaptic inputs on network activity and interneuron apoptosis were examined.

Main Results:

• Spatially segregated functional assemblies were observed in the somatosensory cortex by postnatal day 7.
• Reduced GABA release and synaptic inputs disrupted functional topography, increasing network synchrony.
• Aberrant network activity blocked interneuron apoptosis, leading to increased survival of parvalbumin and somatostatin interneurons.
• GABA's effect on apoptosis was mediated by medial ganglionic eminence (MGE)-derived interneurons, but not caudal ganglionic eminence (CGE)-derived interneurons.

Conclusions:

• Immature MGE-derived interneurons are critical for establishing GABA-driven activity patterns during neonatal development.
• These activity patterns are essential for balancing the number of interneurons integrating into maturing cortical networks.
• GABAergic signaling plays a key role in regulating interneuron survival and cortical circuit development.