Cortical layers (L) 5 and 6 are populated by intermingled cell-types with distinct inputs and downstream targets. Here, we made optogenetically guided recordings from L5 corticofugal (CF) and L6 corticothalamic (CT) neurons in the auditory cortex of awake mice to discern differences in sensory processing and underlying patterns of functional connectivity. Whereas L5 CF neurons showed broad stimulus selectivity with sluggish response latencies and extended temporal non-linearities, L6 CTs exhibited sparse selectivity and rapid temporal processing. L5 CF spikes lagged behind neighboring units and imposed weak feedforward excitation within the local column. By contrast, L6 CT spikes drove robust and sustained activity, particularly in local fast-spiking interneurons. Our findings underscore a duality among sub-cortical projection neurons, where L5 CF units are canonical broadcast neurons that integrate sensory inputs for transmission to distributed downstream targets, while L6 CT neurons are positioned to regulate thalamocortical response gain and selectivity.
All data generated or analyzed during this study are included in the manuscript and supporting files. Source data has been provided for Figures 2-7.
- Daniel B Polley
- Ross S Williamson
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Animal experimentation: Animal experimentation: All procedures were approved by the Animal Care and Use Committee at the Massachusetts Eye and Ear Infirmary (protocol number 10-03-006) and followed guidelines established by the National Institutes of Health for the care and use of laboratory animals. All surgeries were performed under isoflurane, or ketamine and xylazine, and every effort was made to minimize suffering.
- Andrew J King, University of Oxford, United Kingdom
© 2019, Williamson & Polley
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