Isolated from input: Transmodal cortex in the default mode network supports perceptually-decoupled and conceptually-guided cognition

Abstract

The default mode network supports a variety of mental operations such as semantic processing, episodic memory retrieval, mental time travel and mind-wandering, yet the commonalities between these functions remains unclear. One possibility is that this system supports cognition that is independent of the immediate environment; alternatively or additionally, it might support higher-order conceptual representations that draw together multiple features. We tested these accounts using a novel paradigm that separately manipulated the availability of perceptual information to guide decision-making and the representational complexity of this information. Using task based imaging we established regions that respond when cognition combines both stimulus independence with multi-modal information. These included left and right angular gyri and the left middle temporal gyrus. Although these sites were within the default mode network, they showed a stronger response to demanding memory judgements than to an easier perceptual task, contrary to the view that they support automatic aspects of cognition. In a subsequent analysis, we showed that these regions were located at the extreme end of a macroscale gradient, which describes gradual transitions from sensorimotor to transmodal cortex. This shift in the focus of neural activity towards transmodal, default mode, regions might reflect a process of isolation from specific sensory inputs that enables conceptually rich cognitive states to be generated in the absence of input.\n\nHighlights O_LIBrain regions supporting meaning overlap with stimulus independence.\nC_LIO_LIBilateral angular gyri and left MTG respond strongly to both features of cognition.\nC_LIO_LIThese patterns reflect a shift in activity towards regions of transmodal cortex.\nC_LIO_LIComplex memory representations may emerge in cortical areas distant from input.\nC_LI