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 cyto‐ and 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. This revealed that extrastriate area A was largely contained within lateral PPC, that medial PPC overlapped with the anterior portion of area AM, and that anterior RL overlapped partially with area PtP. 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.

Area-specific mapping of binocular disparity across mouse visual cortex

“…In primates, vision and arm/hand movements are used in a coordinated fashion for object interaction, reflected by activity of neurons in the "parietal reach region" within the posterior parietal cortex (Rizzolatti et al 1990;Andersen and Buneo 2002). Of note, area RL in the mouse has been proposed to be part of the rodent posterior parietal cortex (Hovde et al 2018).…”

Action representation in the mouse parieto-frontal network

“…Although it was long thought that rodent brains lacked the prerequisite complexity to subserve higher cognitive functions, a growing body of work shows that both rats and mice exhibit accomplished performance in sensory-motor tasks such as virtual navigation (49) and evidence-based decision making (20,50), and they show stimulus history effects (51)(52)(53). In terms of anatomy, although PPC and M2 are considerably less elaborate in mice than primates, there are several features common to both species which could support action recognition, including strong input from higher visual areas (54,55) and dense reciprocal connectivity between PPC and M2 (56)(57)(58)(59). Given the anatomical and functional similarities, we reasoned that neurons in the rodent PPC-M2 circuit might exhibit mirror-like responses to the observation and execution of the same actions, and were surprised by the effective absence of observational tuning in both areas.…”

Mesoscale cortical dynamics reflect the interaction of sensory evidence and temporal expectation during perceptual decision-making

“…Tracking the ongoing stimulus, visual cortical areas VISp and VISpm responded transiently and bidirectionally to pro-licking (high speed) and anti-licking (low speed) stimulus information with short latencies. In anterior visual areas VISa, VISal, and VISrl, which form the core of the mouse posterior parietal cortex (Hovde et al, 2018), bidirectional responses to fluctuations in the visual stimulus speed were sustained over hundreds of milliseconds. This observation is consistent with electrophysiological recordings in rats, which suggest that posterior parietal cortex faithfully represents accumulated sensory evidence (Hanks et al, 2015).…”