Exploring the contribution of visual imagery to scene construction – Evidence from Posterior Cortical Atrophy

Abstract

Posterior Cortical Atrophy (PCA) is a rare neurodegenerative syndrome characterised by profound visuoperceptual processing disturbances, attributable to focal parieto-occipital cortical atrophy. Despite relative sparing of the medial temporal lobes, converging evidence reveals significant autobiographical memory impairments in this syndrome, underscoring the crucial role of visual imagery for episodic memory processes. The contribution of visual imagery to complex constructive endeavours, however, remains unclear. Here, we investigated the capacity for atemporal scene construction in 5 well-characterised cases of PCA and contrasted their performance with 10 typical amnestic Alzheimer's Disease (AD) and 10 healthy older Control participants. Behavioural data were analysed using case-Control statistics comparing each PCA patient's scene construction scores to the mean scores of AD and Control groups. In keeping with their clinical phenotype, PCA patients demonstrated significant visuoperceptual and episodic memory impairments on standard neuropsychological tasks. Scene construction performance was grossly impaired in PCA, at a level comparable to that observed in the AD group, manifesting in impoverished and spatially fragmented scenes. Structural neuroimaging confirmed prominent grey matter intensity decrease predominantly in posterior cortical regions in PCA, in the absence of frank hippocampal atrophy. Using an a priori motivated region-of-interest approach across all participants, scene construction performance was found to correlate with grey matter intensity in the left angular gyrus, right precuneus, and right hippocampus. This study is the first to reveal compromised scene construction capacity in PCA, extending our understanding of the cognitive profile of this rare syndrome and pointing towards the fundamental contribution of visual imagery to atemporal forms of imagination.

Pattern similarity and connectivity of hippocampal-neocortical regions support empathy for pain

“…These findings collectively suggest a role of the hippocampus in empathy and mental simulation. Moreover, the MPFC (Benoit et al, 2010(Benoit et al, , 2014Kurczek et al, 2015;Schurz et al, 2015;Bertossi et al, 2016bBertossi et al, , 2016aBarry et al, 2019) and PCC (including precuneus and retrosplenial cortex; Vann et al, 2009;Summerfield et al, 2010;Irish et al, 2015;Schurz et al, 2015;Ramanan et al, 2018) are considered pivotal for mental construction and self-projection as well, and are also engaged during theory of mind Frith, 1999, 2006;Uddin et al, 2007;Mar, 2011). The latter additionally involves the TPJ, possibly signaling perspective taking to simulate the mental stance of another person (Saxe and Kanwisher, 2003;Saxe and Wexler, 2005;Saxe and Powell, 2006).…”

A Domain-General Role for the Angular Gyrus in Retrieving Internal Representations of the External World

“…Beyond autobiographical memory, the AG is particularly sensitive to processing social context (Carter and Huettel, 2013), semantic concepts (Price et al, 2015), narrative content (Hasson et al, 2015), and scenarios involving vivid future thinking and atemporal imagination (Thakral et al, 2017;Ramanan et al, 2018b). Importantly, all of the aforementioned cognitive functions rely on internally generated thought, largely independent of the immediate external environment.…”

Identifying the cognitive processes underpinning hippocampal-dependent tasks

“…Schacter et al, 2012;Stawarczyk & D'Argembeau, 2015). For example, lesions to the parietal cortex impair the subjective experience associated with autobiographical memory (Ciaramelli et al, 2017;Simons, Peers, Mazuz, Berryhill, & Olson, 2010) and posterior parietal damage has been linked to a reduction in scene construction ability (Ramanan et al, 2018). A variety of extra-hippocampal brain regions have been implicated in supporting navigation, and a reliance upon non-hippocampal regions for navigation has been suggested to increase with age (Moffat, Elkins, & Resnick, 2006;Zhong & Moffat, 2018).…”