Dorsal prefrontal and premotor cortex of the ferret as defined by distinctive patterns of thalamo-cortical projections

Susanne Radtke-Schuller,Shihab A Shamma,Jennifer K Bizley,Gerd Schuller,Jonathan B Fritz,Stephen M Town,Diego Elgueda,Pingbo Yin

doi:10.1007/s00429-020-02086-7

Abstract

Recent studies of the neurobiology of the dorsal frontal cortex (FC) of the ferret have illuminated its key role in the attention network, top-down cognitive control of sensory processing, and goal directed behavior. To elucidate the neuroanatomical regions of the dorsal FC, and delineate the boundary between premotor cortex (PMC) and dorsal prefrontal cortex (dPFC), we placed retrograde tracers in adult ferret dorsal FC anterior to primary motor cortex and analyzed thalamo-cortical connectivity. Cyto- and myeloarchitectural differences across dorsal FC and the distinctive projection patterns from thalamic nuclei, especially from the subnuclei of the medial dorsal (MD) nucleus and the ventral thalamic nuclear group, make it possible to clearly differentiate three separate dorsal FC fields anterior to primary motor cortex: polar dPFC (dPFCpol), dPFC, and PMC. Based on the thalamic connectivity, there is a striking similarity of the ferret’s dorsal FC fields with other species. This possible homology opens up new questions for future comparative neuroanatomical and functional studies.

Highlights

The ferret is a promising animal model for exploring the neurobiology of the frontal cortex (FC)
In order to be compatible with previous nomenclature for the carnivore brain, the proreal gyrus (PRG) was introduced in the ferret atlas separately, instead of merging this dorsal rostral part of the ferret’s FC with the orbital gyrus (OBG) (Nigel et al 1998; Kroenke et al 2014)
The PRG constitutes the anterior frontal lobe and mainly corresponds to the dorsal prefrontal cortex (dPFC) (Radtke-Schuller 2018). It is roughly delimited by the proreal fissure adjacent to the OBG, medially, it borders on the medial FC (MFC)

Summary

Introduction

The ferret is a promising animal model for exploring the neurobiology of the frontal cortex (FC). It has gained increasing interest as a result of recent studies on the role of the dorsal FC in top-down cognitive control of sensory processing (Fritz et al 2010; Francis et al 2018; Bimbard et al 2018; Elgueda et al 2019), in goal-directed behavior (Zhou et al 2016), in the interactions in the frontoparietal attention network (Sellers et al 2016), and as a model system to study the effects of anesthesia (Sellers et al 2013, 2015; Wollstadt et al 2017). The extent of the ferret prefrontal cortex (PFC) as a whole was previously explored in a comprehensive connectivity study (Duque and McCormick 2010), and the ferret’s FC subdivisions have been delineated based on cyto- and myeloarchitectural criteria (RadtkeSchuller 2018). The present study focuses on the thalamic connectivity of the dorsal FC fields of the ferret

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Discussion

Conclusion