Biology subjects

Zhou, A. X.

Publications and source records attributed to Zhou, A. X..

3 recordsLinked to original sources

bioRxiv2025

Specialized response of default mode subnetworks and multiple-demand regions to transitions of person, place and time

This study used functional MRI data from the StudyForrest dataset to investigate the role of subnetworks of the default mode network (DMN) during naturalistic stimulus transitions of different types and magnitudes. We found distinct activation profiles within the DMN: the dmPFC subnetwork was specifically associated with character and location transitions, the MTL subnetwork preferred location and temporal transitions, while the Core DMN subnetwork responded to all three transition types. The multiple-demand network instead responded selectively to temporal transitions. These distinct response profiles appeared largely invariant to the semantic distance implied by the transitions. All subnetworks also responded significantly, and in a graded manner, to subjective event boundaries. Results suggest specific roles of the DMN subnetworks in perceiving and segmenting naturalistic events, supporting the view that DMN subnetworks cooperate in interpreting continuous external events and maintaining an updated contextual model of the world.

neuroscience↗

bioRxiv2024

Default Mode Network activation at task switches reflects mental task-set structure

Recent findings challenge traditional views of the Default Mode Network (DMN) as purely task-negative or self-oriented, showing increased DMN activity during demanding switches between externally-focused tasks (Crittenden et al., 2015; Smith et al., 2018; Zhou et al., 2024). However, it is unclear what modulates the DMN at switches, with transitions within a stimulus domain activating DMN regions in some studies but not others. Differences in the number of tasks suggest that complexity or structure of the set of tasks may be important. In this fMRI study, we examined whether the DMNs response to task switches depends on the complexity of the active set of tasks, manipulated by the number of tasks in a run, or abstract task groupings based on instructional order. Core DMN activation at task switches was unaffected by the number of currently relevant tasks. Instead, it depended on the order in which groups of tasks had been learnt. Multivariate decoding revealed that Core DMN hierarchically represents individual tasks, task domains, and higher-order task groupings based on instruction order. We suggest that, as the complexity of instructions increases, rules are increasingly organized into higher-level chunks, and Core DMN activity is highest at switches between chunks.

neuroscience↗

bioRxiv2024

External task switches activate default mode regions without enhanced processing of the surrounding scene

Default mode network (DMN) activity, measured with fMRI, typically increases during internally directed thought, and decreases during tasks that demand externally focused attention. However, Crittenden et al. (2015) and Smith et al. (2018) reported increased DMN activity during demanding external task switches between different cognitive domains, compared to within-domain switches and task repeats. This finding is hard to reconcile with many dominant views of DMN function. Here, we aimed to replicate this DMN task-switch effect in a similar paradigm and test whether it reflects increased representation of broader context, specifically of a scene presented behind the focal task. In Core DMN, we found significant activity for all task switches, compared to task repeats, and stronger activity for switches between rest and task. Although the content of the background scene was attended, recalled, and neurally decodable, there was no evidence that this differed by switch type. Therefore, external task switches activated DMN without enhanced processing of the surrounding scene. Surprisingly, DMN activity at within-domain switches was no less than at between-domain switches. We suggest that modulation of DMN activity by task switches reflects a shift in the current cognitive model and depends on the overall complexity of that model.

neuroscience↗