Presentation
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Functional dissociations of the default mode network reflect the type of representation and not perceptual engagement
Poster A21 in Poster Session A, Tuesday, October 24, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Beth Jefferies1, Meichao Zhang2, Katya Krieger-Redwood1, Jonathan Smallwood3; 1University of York, UK, 2Chinese Academy of Sciences, 3Queen's University, Canada
The default mode network (DMN) enables us to deploy representations from long-term memory to understand the significance of perceptual inputs like words and pictures (e.g. semantic cognition), but DMN also supports internally directed cognition decoupled from the external environment (e.g. in autobiographical memory and mind-wandering). These processes differ in both the need to interface with perceptible events and in the type of representation to be accessed. A challenge therefore is to understand whether functional subdivisions within DMN reflect the type of representation being accessed or perceptual engagement, since these aspects of tasks are often confounded in the literature. We performed functional magnetic resonance imaging as participants were asked to perform semantic and episodic tasks. For the semantic task, participants were required to either (1) judge whether a currently presented word was semantically related to a previous word (Semantic Coupled) or (2) generate word that was semantically related to a previous word (Semantic Decoupled); for the episodic task, they were required to either (3) recognise a learned word list (i.e., Episodic Coupled) or (4) recall a list of words in the absence of external input (Episodic Decoupled). Distinct DMN regions responded selectively to semantic and episodic task states regardless of whether they were perceptually coupled or not. Dorsomedial DMN was associated with semantic cognition, while core DMN regions in medial parietal regions were recruited in both episodic tasks. Both dorsomedial and core DMN exhibited stronger activation during perceptually coupled states, showing that DMN is not inherently biased towards internal aspects of cognition. In addition, core DMN can change its patterns of functional connectivity with task-relevant regions to support different task states. In conclusion, DMN supports different types of memory-based representations that can be accessed from both sensory inputs and during internal thought.
Topic Areas: Meaning: Lexical Semantics,