Differences in Intrinsic Properties and Local Network Connectivity of Identified Layer 5 and Layer 6 Adult Mouse Auditory Corticothalamic Neurons Support a Dual Corticothalamic Projection Hypothesis

Cereb Cortex. 2009 Dec;19(12):2810-26. doi: 10.1093/cercor/bhp050. Epub 2009 Apr 7.

Abstract

Intrinsic properties, morphology, and local network circuitry of identified layer 5 and layer 6 auditory corticothalamic neurons were compared. We injected fluorescent microspheres into the mouse auditory thalamus to prelabel corticothalamic neurons, then recorded and filled labeled layer 5 or layer 6 auditory cortical neurons in vitro. We observed low-threshold bursting in adult, but not juvenile, layer 5 corticothalamic neurons that was voltage and time dependent with nonlinear input-output properties, whereas adult layer 6 corticothalamic neurons demonstrated a regular spiking. Layer 5 corticothalamic neurons had larger somata, thicker apical dendrites and were more likely to have a layer 1 apical dendrite than layer 6 neurons. Using laser photostimulation, identified layer 5 corticothalamic neurons received excitatory input from a wide area of layers 2/3, 4, and 5 with widespread gamma-aminobutyric acidergic input from layer 2/3 and lower layer 5, whereas layer 6 corticothalamic neurons from the same cortical column received circumscribed excitatory input and discrete patches of inhibition derived from layer 6 of adjacent columns. These data demonstrate that layer 5 and layer 6 corticothalamic neurons receive unique sets of inputs and process them in different manners, supporting the hypothesis that layer-specific corticothalamic projections play distinct roles in information processing.

Publication types

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

MeSH terms

  • Animals
  • Auditory Cortex / cytology
  • Auditory Cortex / physiology*
  • Female
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Models, Anatomic
  • Models, Neurological
  • Nerve Net / cytology*
  • Nerve Net / physiology*
  • Neural Pathways / cytology
  • Neural Pathways / physiology
  • Sensory Receptor Cells / cytology*
  • Sensory Receptor Cells / physiology*
  • Thalamus / cytology*
  • Thalamus / physiology*