The debate on the neural basis of multitasking costs evolves around neural overlap between concurrent tasks. Recent evidence suggests training-related reductions in representational overlap in fronto-parietal brain regions predict multitasking improvements. Cognitive theories assume that overlap of task representations may be associated with between-task crosstalk.
Recently, modality-based crosstalk between the stimulus modality in one task and sensory action consequences in the concurrent task was suggested to affect multitasking costs. Increased costs for certain modality mappings were shown consistently, even when both tasks use non-overlapping stimulus and response modalities.
Whether modality-based crosstalk emerges from representational overlap in general multitasking or modality-specific regions is unknown. This functional imaging study investigates neural overlap in multitasking performance, focusing on modality compatibility by employing multivariate pattern analysis and modality-specific practice interventions in three groups (total N = 54) consisting of healthy young adults (18-30 years old, mean age 22.5). We observed differences between modality-compatible and modality-incompatible single-task representations, specifically in the auditory cortex but not in fronto-parietal regions. Notably, improved auditory decoding accuracy related to modality-incompatible tasks was predictive of performance gains in the corresponding dual task along with complete elimination of the modality-specific dual-task costs. This predictive relationship was evident only in the group practicing modality-incompatible mappings, suggesting that specific training on tasks with modality overlap influenced both neural representations and subsequent multitasking performance.
This study contributes to integrating cognitive theory with neuroscience about the role of task representation for dual-task interference.