title: Brain activations during bimodal dual tasks depend on the nature and combination of component tasks.
abstract: We used functional magnetic resonance imaging to investigate brain activations during nine different dual tasks in which the participants were required to simultaneously attend to concurrent streams of spoken syllables and written letters. They performed a phonological, spatial or "simple" (speaker-gender or font-shade) discrimination task within each modality. We expected to find activations associated specifically with dual tasking especially in the frontal and parietal cortices. However, no brain areas showed systematic dual task enhancements common for all dual tasks. Further analysis revealed that dual tasks including component tasks that were according to Baddeley's model "modality atypical," that is, the auditory spatial task or the visual phonological task, were not associated with enhanced frontal activity. In contrast, for other dual tasks, activity specifically associated with dual tasking was found in the left or bilateral frontal cortices. Enhanced activation in parietal areas, however, appeared not to be specifically associated with dual tasking per se, but rather with intermodal attention switching. We also expected effects of dual tasking in left frontal supramodal phonological processing areas when both component tasks required phonological processing and in right parietal supramodal spatial processing areas when both tasks required spatial processing. However, no such effects were found during these dual tasks compared with their component tasks performed separately. Taken together, the current results indicate that activations during dual tasks depend in a complex manner on specific demands of component tasks.
authors.affiliation: Division of Cognitive Psychology and Neuropsychology, Institute of Behavioural Sciences, University of Helsinki Helsinki, Finland ; Advanced Magnetic Imaging Centre, Aalto University School of Science and Technology Espoo, Finland.
authors.forename: Emma
authors.initials: E
authors.lastname: Salo
authors.affiliation: Division of Cognitive Psychology and Neuropsychology, Institute of Behavioural Sciences, University of Helsinki Helsinki, Finland.
authors.forename: Teemu
authors.initials: T
authors.lastname: Rinne
authors.affiliation: Helsinki Medical Imaging Center, Helsinki University Central Hospital Helsinki, Finland.
authors.forename: Oili
authors.initials: O
authors.lastname: Salonen
authors.affiliation: Division of Cognitive Psychology and Neuropsychology, Institute of Behavioural Sciences, University of Helsinki Helsinki, Finland ; Helsinki Collegium for Advanced Studies, University of Helsinki Helsinki, Finland ; Swedish Collegium for Advanced Study Uppsala, Sweden.
authors.forename: Kimmo
authors.initials: K
authors.lastname: Alho
keywords: divided attention; dual task; fMRI; phonological processing; spatial processing