Visual to default network pathways: A double dissociation between semantic and spatial cognition

Tirso Gonzalez-Alam, Katya-Krieger-Redwood, Dominika Varga, Zhiyao Gao, Aidan Horner, Tom Hartley, Magdalena Sliwinska, David Pitcher, Jonathan Smallwood, Elizabeth Jefferies 

Abstract

The Default Mode Network (DMN) often deactivates to visual input yet it can couple to visual cortex, and it is composed of multiple subsystems that might differ in their degree of visual coupling or in the memory representations that they support. We used a combination of univariate, connectivity and multivariate fMRI analyses across three samples (combined N > 250) to investigate the architecture connecting visual cortex to DMN, and the engagement of visual-DMN pathways in memory-guided decisions across two domains (semantic and spatial). Participants learned virtual environments consisting of buildings populated with objects, with half of the buildings containing objects from a single semantic category allowing them to associate space with meaning. In a second session, they made spatial and semantic decisions about these buildings and objects in the scanner. We found semantic and spatial judgements engaged distinct DMN subsystems. Frontotemporal DMN regions were primarily engaged by semantic judgements and showed stronger connectivity to object perception regions in lateral ventral occipital cortex, while medial temporal DMN regions were more strongly recruited during spatial judgements and showed stronger connectivity to medial visual regions involved in processing scenes. Clusters in angular gyrus and ventral lateral occipital cortex, topographically situated between these pathways, were implicated in the integration of semantic and spatial information, suggesting a mechanism for the interaction of these distinct visual-to-DMN pathways. These results show how processing streams that capture different unimodal to heteromodal transformations relevant to conceptual and spatial processing might interact at multiple levels of the cortical hierarchy to produce coherent cognition.