Abstract
Pyramidal tract neurons (PTs) represent the major output cell type of the neocortex. To investigate principles of how the results of cortical processing are broadcasted to different downstream targets thus requires experimental approaches, which provide access to the in vivo electrophysiology of PTs, whose subcortical target regions are identified. On the example of rat barrel cortex (vS1), we illustrate that retrograde tracer injections into multiple subcortical structures allow identifying the long-range axonal targets of individual in vivo recorded PTs. Here we report that soma depth and dendritic path lengths within each cortical layer of vS1, as well as spiking patterns during both periods of ongoing activity and during sensory stimulation, reflect the respective subcortical target regions of PTs. We show that these cellular properties result in a structure–function parameter space that allows predicting a PT’s subcortical target region, without the need to inject multiple retrograde tracers.
Highlights
Pyramidal tract neurons (PTs) represent the major output cell type of the neocortex
These findings indicate that—similar to intratelencephalic PNs (ITs)—stimulus features may be differentially extracted by PTs via long-range target-specific subnetworks[14], which could be reflected by the target-specific embedding of somata and dendrites into the cortical circuitry
We determined the respective numbers of PTs that project longrange axons to four of the major subcortical targets of vS11, 8, 16, 17 (Fig. 1a): the posterior medial division of the thalamus (POm), the superior colliculus of the tectum (SC), the pontine nucleus (Pons), and the subnucleus caudalis of the spinal trigeminal tract in the brain stem (Sp5C)
Summary
Pyramidal tract neurons (PTs) represent the major output cell type of the neocortex. To investigate principles of how the results of cortical processing are broadcasted to different downstream targets requires experimental approaches, which provide access to the in vivo electrophysiology of PTs, whose subcortical target regions are identified. Recent studies suggested that neurons within the class of ITs may have different functional roles when processing the same sensory stimulus, depending on the cortical area into which they project their respective long-range axons. We find that soma depth location and layer-specific dendrite distributions allow predicting the respective subcortical target area of PTs, and that spiking patterns during both periods of ongoing activity and during whisker stimulation are target-related. These findings indicate that—similar to ITs—stimulus features may be differentially extracted by PTs via long-range target-specific subnetworks[14], which could be reflected by the target-specific embedding of somata and dendrites into the cortical circuitry
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