Oscillatory activity in developing prefrontal networks results from theta-gamma-modulated synaptic inputs

Area of Science:

• Neuroscience
• Developmental Neurobiology
• Systems Neuroscience

Background:

• Hippocampal theta-gamma oscillations entrain neonatal prefrontal circuits, aiding cognitive maturation.
• The precise synaptic mechanisms driving these early network oscillations remain largely unknown.

Purpose of the Study:

• To elucidate the synaptic framework underlying early network oscillations in the developing prefrontal cortex.
• To differentiate the synaptic drivers of theta and beta-low gamma oscillations in neonatal rats.

Main Methods:

• In vivo patch-clamp recordings from layer V pyramidal neurons and interneurons in the prelimbic cortex (PL).
• Extracellular recordings from the PL of awake and lightly anesthetized neonatal rats.
• Morphological and neurochemical characterization of recorded neurons.

Main Results:

• All recorded neurons exhibited spontaneous burst firing and received glutamatergic and GABAergic inputs.
• Theta oscillations arise from long-range pyramidal neuron coupling and local interneuron interactions.
• Beta-low gamma activity depends on external glutamatergic drive to prelimbic interneurons.
• High-frequency oscillations in layer V were independent of chemical synaptic interactions.

Conclusions:

• Specific theta-gamma-modulated synaptic interactions form the basis of network oscillations in the developing PL.
• Distinct synaptic mechanisms underlie different frequency bands of early network oscillations, impacting cognitive development.