A Layer-specific Corticofugal Input to the Mouse Superior Colliculus

Cereb Cortex. 2018 Aug 1;28(8):2817-2833. doi: 10.1093/cercor/bhx161.

Abstract

In the auditory cortex (AC), corticofugal projections arise from each level of the auditory system and are considered to provide feedback "loops" important to modulate the flow of ascending information. It is well established that the cortex can influence the response of neurons in the superior colliculus (SC) via descending corticofugal projections. However, little is known about the relative contribution of different pyramidal neurons to these projections in the SC. We addressed this question by taking advantage of anterograde and retrograde neuronal tracing to directly examine the laminar distribution, long-range projections, and electrophysiological properties of pyramidal neurons projecting from the AC to the SC of the mouse brain. Here we show that layer 5 cortico-superior-collicular pyramidal neurons act as bandpass filters, resonating with a broad peak at ∼3 Hz, whereas layer 6 neurons act as low-pass filters. The dissimilar subthreshold properties of layer 5 and layer 6 cortico-superior-collicular pyramidal neurons can be described by differences in the hyperpolarization-activated cyclic nucleotide-gated cation h-current (Ih). Ih also reduced the summation of short trains of artificial excitatory postsynaptic potentials injected at the soma of layer 5, but not layer 6, cortico-superior-collicular pyramidal neurons, indicating a differential dampening effect of Ih on these neurons.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Animals, Newborn
  • Auditory Cortex / physiology*
  • Auditory Pathways / physiology*
  • Axons
  • Basic Helix-Loop-Helix Transcription Factors / genetics
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2 / genetics
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2 / metabolism
  • Dendrites
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • In Vitro Techniques
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Mutation / genetics
  • Nerve Net / physiology
  • Patch-Clamp Techniques
  • Pyramidal Cells / cytology
  • Pyramidal Cells / physiology*
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism
  • Superior Colliculi / cytology*
  • Superior Colliculi / physiology*
  • Transduction, Genetic

Substances

  • Basic Helix-Loop-Helix Transcription Factors
  • Repressor Proteins
  • Sim1 protein, mouse
  • Green Fluorescent Proteins
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2