A novel network of multipolar bursting interneurons generates theta frequency oscillations in neocortex

Area of Science:

• Neuroscience
• Cell Biology
• Computational Neuroscience

Background:

• GABAergic interneurons are crucial for regulating neuronal excitability and synchrony.
• Oscillatory activity in neural networks is fundamental for cognitive functions.
• Existing knowledge on interneuron subtypes in the neocortex is continually expanding.

Purpose of the Study:

• To identify and characterize a novel subtype of GABAergic interneuron in the mouse neocortex.
• To investigate the functional properties and network interactions of this new interneuron subtype.
• To elucidate the role of this interneuron subtype in generating network oscillations.

Main Methods:

• Electrophysiological recordings in acute brain slices.
• Morphological and neurochemical characterization of identified interneurons.
• Pharmacological manipulations to probe synaptic mechanisms and network dynamics.

Main Results:

• A new subtype, multipolar bursting (MB) cells, was identified in the mouse neocortex.
• MB cells are parvalbumin-positive and distinct from fast-spiking (FS) cells.
• MB cells form reciprocal connections with pyramidal cells and are coupled via chemical and electrical synapses.
• MB cells innervate FS cells, while FS cells do not innervate MB cells.
• MB cells exhibit paired-pulse facilitation at MB-MB and MB-pyramidal cell synapses.
• Carbachol selectively induced synchronized theta frequency oscillations in MB cells.
• Synchronized oscillations required gap junction coupling and GABAergic transmission, but not glutamatergic input.

Conclusions:

• MB cells constitute a distinct inhibitory network within the neocortex.
• Cholinergic stimulation of MB cells generates rhythmic and synchronous theta frequency activity.
• This MB cell network plays a role in the temporal coordination of principal cell output.