Spontaneous electrical activity in the human fetal cortex in vitro

Area of Science:

• Neuroscience
• Developmental Biology
• Human Physiology

Background:

• Current understanding of human cerebral cortex development relies on fixed postmortem tissues.
• Pioneer cortical neurons, known as subplate neurons, play a crucial role in early brain development.

Purpose of the Study:

• To characterize the synaptic physiology and spontaneous network activity of human subplate neurons using electrophysiological recordings.
• To investigate the presence and function of ionotropic receptors and synaptic contacts in early developing human cortical neurons.

Main Methods:

• Electrophysiological recordings from unfixed human postmortem cortical tissue.
• Characterization of synaptic physiology and spontaneous network activity in subplate neurons.

Main Results:

• Functional glutamate and GABA ionotropic receptors are present on human subplate neurons by 20 gestational weeks.
• Functional synaptic contacts are rare in midgestation human subplate neurons.
• Spontaneous electrical activity, including plateau depolarizations and action potential bursts resembling adult cortical UP and DOWN states, was regularly observed in human subplate neurons.

Conclusions:

• Human subplate neurons exhibit spontaneous network activity similar to adult cortical UP and DOWN states, despite immature morphology and scarce synaptic inputs.
• This early oscillatory pattern is a fundamental aspect of human cortical physiology, present even in the absence of sensory input during development in utero.
• The findings challenge the notion that mature morphology and physiology are prerequisites for generating complex cortical rhythms.