Notes on Neocortical Interneurons

Parvalbumin-expressing (PV) cells

  • Fast-spiking, GABAergic
  • Two types of PV cells classified by axonal contacts to target pyramidal cells.
  • (1) Axo-somatic or axo-dendritic (proximal dendrites)
  • (2) Axo-axonic: strongly “edits” firing in an inhibitory manner
  • In layer II/III of the primary somatosensory cortex, PV cells have high connectivity both to and from excitatory pyramidal neurons. This facilitates a strong inhibitory loop, damping the region most of the time

Somatostatin-expressing (Sst) cells

  • GABAergic
  • Sst cells target distal excitatory pyramidal cell dendrites, often in layer I
  • Sst cells receive excitatory inputs from nearby pyramidal cells. The unique molecular properties of these synapses cause the Sst cells to hyperpolarize more slowly between inputs, enabling integration of bursts of firing from the pyramidal cells. This is not the case for other types of cortical cells

Sst Cell Spikes Diagram

Vasoactive intestinal peptide-expressing (VIP) cells

  • GABAergic
  • Inhibits other inhibitory neurons. They more frequently inhibit Sst cells than PV cells

Neurogliaform cells

  • GABAergic
  • Neurogliaform cells do not have post-synaptic partners. Instead, they release GABA into the extracellular space, thus increasing IPSPs in their general area

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