Posterior parietal cortex of the rat: Architectural delineation and thalamic differentiation

Abstract

This study refines the characterization of the rat parietal cortical domain in terms of cyto‐ and chemoarchitecture as well as thalamic connectivity. We recognize three subdivisions of the posterior parietal cortex (PPC), which are architectonically distinct from the neighboring somatosensory and visual cortices. Furthermore, we show that the different parietal areas are differently connected with thalamic nuclei. The medial portion of PPC (mPPC) is connected primarily with the medial portion of the lateral posterior nucleus (LP), whereas the lateral portion (lPPC) connects with the posterior complex (Po). The more caudolateral part of PPC (PtP) also projects to Po but can be distinguished from lPPC based on architectonic criteria. The primary somatic and visual cortices, neighboring PPC, are preferentially connected with the primary ventral posterior and dorsolateral geniculate nuclei, respectively, and less with the associational Po and LP. Particularly the border between the secondary visual cortex and the PPC has been a matter of controversy, but here we show that, although PPC subareas are connected with Po and medial LP, the medial and lateral secondary visual cortices are connected with lateral LP and a portion of medial LP different from that connected with PPC. The resulting delineations and specifications of connectivity with thalamic nuclei together with upcoming studies of cortical connectivity will facilitate detailed studies on the role of the subdivisions of PPC in the rat as diverse, higher order associative cortical areas, comparable to those described in the primate.for J. Comp. Neurol. 524:3774–3809, 2016. © 2016 Wiley Periodicals, Inc.

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

“…Importantly, we reconciled widely used but disparate nomenclatures that refer to PPC (Paxinos & Franklin, ) versus the extrastriate areas around it (Montero, ; Olavarria & Montero, ; Olavarria et al., ; Wang & Burkhalter, ). We further confirmed our coordinates for PPC on the basis of projections to associative thalamic nuclei, which corresponded to thalamic projection patterns in rats (Bucci et al., ; Chandler et al., ; Kolb & Walkey, ; Olsen & Witter, ), mice (Harvey et al., ) and several other mammalian species (Donoghue & Ebner, ; Olson & Lawler, ; Padberg & Krubitzer, ; Schmahmann & Pandya, ).…”

“…As with rats, PPC in the mouse is located between visual and somatosensory cortices (Paxinos & Franklin, 2012), and the existing data suggests that it has similar patterns of cortico-cortical and thalamic connectivity (Harvey et al, 2012;Kolb & Walkey, 1987;Oh et al, 2014;Olsen & Witter, 2016;Reep et al, 1994;Wilber, Clark, Demecha et al, 2014). More detailed aspects of mouse PPC anatomy, including the boundaries which distinguish it from neighboring areas, its laminar organization and chemoarchitectural profile remain ill-defined.…”

Parahippocampal and retrosplenial connections of rat posterior parietal cortex

“…The PPC and V2 and their respective subdivisions are cytoarchitectonically distinct areas with different thalamic connections (Olsen and Witter, ). It is therefore noteworthy that all areas appear to be reciprocally connected to all divisions of the PHR and to RSC area 30, albeit with subtle topographical differences (Fig.…”

Do the anterior and lateral thalamic nuclei make distinct contributions to spatial representation and memory?

“…The lateroposterior thalamus, which is often characterized as a rodent homologue to the mammalian pulvinar, generally has a stronger reciprocal relationship with primary and secondary visual cortical regions (Nakamura et al, 2016;Roth et al, 2016). For instance, some recent work has indicated that the lateroposterior thalamus constitutes the strongest thalamic output to postrhinal and posterior parietal regions Nakamura et al, 2015;Olsen & Witter, 2016;Pereira et al, 2016), perhaps suggesting that this region has a greater role in guiding orientation in relation to visual-spatial targets.…”

“…A final consideration that has received limited attention is whether the anterior and lateral thalamus might have a role in spatial and contextual representations in postrhinal and parietal cortical targets (Olsen & Witter, 2016;Pereira et al, 2016;Wilber et al, 2015). For instance, the parietal cortex contains directionally modulated neural populations that fire in a distal spatial framework , but also contains neural populations that fire in relation to egocentric body-turns and egocentric relationship with proximal visual cues (McNaughton et al, 1993).…”