Robust but delayed thalamocortical activation of dendritic-targeting inhibitory interneurons.

Journal Article (Journal Article)

GABA-releasing cortical interneurons are crucial for the neural transformations underlying sensory perception, providing "feedforward" inhibition that constrains the temporal window for synaptic integration. To mediate feedforward inhibition, inhibitory interneurons need to fire in response to ascending thalamocortical inputs, and most previous studies concluded that ascending inputs activate mainly or solely proximally targeting, parvalbumin-containing "fast-spiking" interneurons. However, when thalamocortical axons fire at frequencies that are likely to occur during natural exploratory behavior, activation of fast-spiking interneurons is rapidly and strongly depressed, implying the paradoxical conclusion that feedforward inhibition is absent when it is most needed. To address this issue, we took advantage of lines of transgenic mice in which either parvalbumin- or somatostatin-containing interneurons express GFP and recorded the responses of interneurons from both subtypes to thalamocortical stimulation in vitro. We report that during thalamocortical activation at behaviorally expected frequencies, fast-spiking interneurons were indeed activated only transiently because of rapid depression of their thalamocortical inputs, but a subset of layer 5 somatostatin-containing interneurons were robustly and persistently activated after a delay, due to the facilitation and temporal summation of their thalamocortical excitatory postsynaptic potentials. Somatostatin-containing interneurons are considered distally targeting. Thus, they are likely to provide delayed dendritic inhibition during exploratory behavior, contributing to the maintenance of a balance between cortical excitation and inhibition while leaving a wide temporal window open for synaptic integration and plasticity in distal dendrites.

Full Text

Duke Authors

Cited Authors

  • Tan, Z; Hu, H; Huang, ZJ; Agmon, A

Published Date

  • February 12, 2008

Published In

Volume / Issue

  • 105 / 6

Start / End Page

  • 2187 - 2192

PubMed ID

  • 18245383

Pubmed Central ID

  • PMC2538896

Electronic International Standard Serial Number (EISSN)

  • 1091-6490

Digital Object Identifier (DOI)

  • 10.1073/pnas.0710628105


  • eng

Conference Location

  • United States