title: Establishing task- and modality-dependent dissociations between the semantic and default mode networks.
abstract: The default mode network (DMN) and semantic network (SN) are two of the most extensively studied systems, and both are increasingly used as clinical biomarkers in neurological studies. There are strong theoretical reasons to assume a relationship between the networks, as well as anatomical evidence that they might rely on overlapping cortical regions, such as the anterior temporal lobe (ATL) or angular gyrus (AG). Despite these strong motivations, the relationship between the two systems has received minimal attention. We directly compared the SN and DMN using a large (n = 69) distortion-corrected functional MRI (fMRI) dataset, spanning a range of semantic and nonsemantic tasks that varied input modality. The results showed that both networks fractionate depending on the semantic nature of the task, stimulus type, modality, and task difficulty. Furthermore, despite recent claims that both AG and ATL are semantic hubs, the two areas responded very differently, with results supporting the role of ATL, but not AG, in semantic representation. Specifically, the left ATL was positively activated for all semantic tasks, but deactivated during nonsemantic task performance. In contrast, the left AG was deactivated for all tasks, with the level of deactivation related to task difficulty. Thus, ATL and AG do not share a common interest in semantic tasks, but, rather, a common "disinterest" in nonsemantic tasks. The implications for the variability in the DMN, its cognitive coherence, and interpretation of resting-state fMRI data are discussed.
authors.affiliation: Neuroscience and Aphasia Research Unit, University of Manchester, Manchester M13 9PL, United Kingdom; matt.lambon-ralph@manchester.ac.uk gina.humphreys@manchester.ac.uk.
authors.forename: Gina F
authors.initials: GF
authors.lastname: Humphreys
authors.affiliation: Neuroscience and Aphasia Research Unit, University of Manchester, Manchester M13 9PL, United Kingdom;
authors.forename: Paul
authors.identifier: http://orcid.org/0000-0002-3248-3225
authors.initials: P
authors.lastname: Hoffman
authors.affiliation: Neuroscience and Aphasia Research Unit, University of Manchester, Manchester M13 9PL, United Kingdom; Grupo de Neuropsicología y Neuroimagen Funcional, Departament de Psicologia Bàsica, Clínica i Psicobiologia, Universitat Jaume I, 12071 Castellon, Spain;
authors.forename: Maya
authors.initials: M
authors.lastname: Visser
authors.affiliation: Neuroscience and Aphasia Research Unit, University of Manchester, Manchester M13 9PL, United Kingdom; Eleanor M. Saffran Center for Cognitive Neuroscience, Temple University, Philadelphia, PA 19122.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Binney
authors.affiliation: Neuroscience and Aphasia Research Unit, University of Manchester, Manchester M13 9PL, United Kingdom; matt.lambon-ralph@manchester.ac.uk gina.humphreys@manchester.ac.uk.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Lambon Ralph
mesh_terms: D001931:Brain Mapping; D006801:Humans; D008279:Magnetic Resonance Imaging; D012660:Semantics
keywords: angular gyrus; anterior temporal lobe; default mode network; distortion-corrected fMRI; semantic network