Network Neuroscience of Human Multitasking: Local Features Matter

The neural basis of multitasking costs is subject to continuing debate. Cognitive theories assume that overlap of task representations may lead to between-task crosstalk in concurrent task processing and thus requires cognitive control. Recent research suggests that modality-based crosstalk contributes to multitasking costs, involving central overlap of modality-specific representations. Consistently increased costs for specific modality pairings (visual-vocal and auditory-manual vs. visual-manual and auditory-vocal) were demonstrated (modality-compatibility effect), which were recently linked to representational overlap in the auditory cortex. However, it remains unclear whether modality-based crosstalk emerges from overlapping patterns of global brain connectivity and whether resolving it requires additional involvement of cognitive control as reflected in the fronto-parietal control network. This preregistered functional imaging study investigates these questions in 64 healthy, young human adults. Specifically, we focus on the modality-compatibility effect in multitasking by employing functional connectivity (FC) analysis. First, we tested the FC similarity between the single-task networks. Second, we compared the strength of the control network in whole-brain FC between dual tasks. We found no evidence for different FC similarities of single-task networks between modality pairings and no additional involvement of the control network during dual tasks. However, post-hoc connectivity analysis revealed a brain-behavior correlation for the modality-compatibility effect in dual tasks. This effect was locally restricted to FC between lateral frontal and sensory auditory regions, providing evidence for the modality-based crosstalk theory. More generally, the findings suggest that robust behavioral differences in multitasking are not necessarily related to global functional connectivity differences but to local connectivity changes. SignificanceOur lives are dominated by multitasking. Understanding the neurocognitive mechanisms of multitasking and its associated limitations is relevant for safety-relevant consequences. Here, we investigate functional brain-connectivity patterns associated with modality-based crosstalk in multitasking, describing unintentional exchange of information between two tasks, leading to robust dual-task costs. Our network analyses revealed no significant difference between single or dual tasks with varying degrees of modality overlap on the whole-brain level. However, specific connections between cognitive control-related frontal and sensory-related regions were associated with individual multitasking performance, emphasizing that behavioral differences can arise from specific neural interactions rather than from widespread network reconfigurations. These findings advance our understanding of the underlying mechanisms responsible for modality-based crosstalk, providing practical implications for human-machine interactions.