Architecture and organization of mouse posterior parietal cortex relative to extrastriate areas

Abstract

The posterior parietal cortex (PPC) is a multifaceted region of cortex, contributing to several cognitive processes including sensorimotor integration and spatial navigation.Although recent years have seen a considerable rise in the use of rodents, particularly mice, to investigate PPC and related networks, a coherent anatomical definition of PPC in the mouse is still lacking. To address this, we delineated the mouse PPC using cytoand chemoarchitectural markers from Nissl-, parvalbumin-and muscarinic acetylcholine receptor M2-staining. Additionally, we performed bilateral triple anterograde tracer injections in primary visual cortex (V1) and prepared flattened tangential sections from one hemisphere and coronal sections from the other, allowing us to co-register the cytoarchitectural features of PPC with V1 projections. In charting the location of extrastriate areas and the architectural features of PPC in the context of each other, we reconcile different, widely used conventions for demarcating PPC in the mouse.Furthermore, triple anterograde tracer injections in PPC showed strong projections to associative thalamic nuclei as well as higher visual areas, orbitofrontal, cingulate and secondary motor cortices. Retrograde circuit mapping with rabies virus further showed that all cortical connections were reciprocal. These combined approaches provide a coherent definition of mouse PPC that incorporates laminar architecture, extrastriate projections, thalamic, and cortico-cortical connections.

Decision and navigation in mouse parietal cortex

“…Moreover, for the majority of PPC cells, activity in the playback condition was not predictable from the preferences for position and heading estimated during the task. This is perhaps remarkable, given that parietal areas of the mouse cortex are considered to overlap with visual areas RL, A, and AM (Hovde et al, 2018; Kirkcaldie, 2012), which contain retinotopic visual representations (Garrett et al, 2014; Wang and Burkhalter, 2007). By comparison, responses measured in primary visual cortex (V1) during the task and during playback were in better agreement (Figure 4—figure supplement 2b).…”

Functional Architecture and Encoding of Tactile Sensorimotor Behavior in Rat Posterior Parietal Cortex

“…Our PPC recordings were therefore targeted more lateral compared with a subset of studies (Nitz, 2006(Nitz, , 2012Wilber et al, 2014Wilber et al, , 2017Hanks et al, 2015), but closely resemble PPC coordinates in others (Kolb and Walkey, 1987;Reep et al, 1994;Whitlock, 2014;Licata et al, 2017;Mimica et al, 2018;Nikbakht et al, 2018). Based on anatomical coordinates, our recordings thus include PPC subdomains 'RL', 'A,' and potentially (part of) 'AM' (Wang et al, 2012;Hovde et al, 2019) and a very small portion of V1. It is, however, almost certain that anatomical borders do not translate one-to-one to discrete functional zones (Olsen and Witter, 2016).…”

“…We defined PPC as the cortical area posterior to S1, delineated on the mediolateral axis by the borders of the (posteromedial) barrel subfield, and on the anteroposterior axis within 1200 m posterior of the barrel subfield edge. This location corresponds to rostrolateral (RL) and anterior (A) PPC subregions (Wang et al, 2012;Hovde et al, 2019). Our PPC recordings were therefore targeted more lateral compared with a subset of studies (Nitz, 2006(Nitz, , 2012Wilber et al, 2014Wilber et al, , 2017Hanks et al, 2015), but closely resemble PPC coordinates in others (Kolb and Walkey, 1987;Reep et al, 1994;Whitlock, 2014;Licata et al, 2017;Mimica et al, 2018;Nikbakht et al, 2018).…”

Extrastriate connectivity of the mouse dorsal lateral geniculate thalamic nucleus

“…Although it is difficult to directly compare functional imaging in the horizontal plane with coronal anatomical sections, many of these visual areas appear to be overlapped with other well‐defined brain regions, including the posterior parietal cortex (PTLp) and postrhinal cortex, which are known to process a variety of multimodal sensory and motor stimuli (Eacott & Gaffan, ; Freedman & Ibos, 2018; Whitlock, ). Using cyto‐ and chemo‐architectonic evidence confirmed by thalamic connectivity, Hovde and colleagues defined the borders of the parietal cortex and repeated the Wang and Burkhalter experiments to show that visual area RL was largely contained within the PTLp (Hovde, Gianatti, Witter, & Whitlock, ). In addition, parts of visual areas A and AM were also found to be included in the parietal cortex.…”