Timing and specificity of feed-forward inhibition within the LGN.
Local interneurons provide feed-forward inhibition from retinal ganglion cells (RGCs) to thalamocortical (TC) neurons, but questions remain regarding the timing, magnitude, and functions of this inhibition. Here, we identify two types of inhibition that are suited to play distinctive roles. We recorded excitatory and inhibitory postsynaptic currents (EPSCs/IPSCs) in TC neurons in mouse brain slices and activated individual RGC inputs. In 34% of TC neurons, we identified EPSCs and IPSCs with identical thresholds that were tightly correlated, indicating activation by the same RGC. Such "locked" IPSCs occurred 1 ms after EPSC onset. The remaining neurons had only "nonlocked" inhibition, in which EPSCs and IPSCs had different thresholds, indicating activation by different RGCs. Nonlocked inhibition may refine receptive fields within the LGN by providing surround inhibition. In contrast, dynamic-clamp recordings suggest that locked inhibition improves the precision of synaptically evoked responses in individual TC neurons by eliminating secondary spikes.
Blitz
Dawn M
DM
Neurobiology Department, Harvard Medical School, Boston, Massachusetts 02115, USA.
Regehr
Wade G
WG
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005829:Geniculate Bodies / Q000502:physiology*; D007395:Interneurons / Q000502:physiology*; D051379:Mice; D009433:Neural Inhibition / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D012165:Retinal Ganglion Cells / Q000502:physiology*; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*; D013997:Time Factors; D014785:Vision, Ocular / Q000502:physiology; D014794:Visual Fields / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology*