title: Divided versus selective attention: evidence for common processing mechanisms.
abstract: The current study revisited the question of whether there are brain mechanisms specific to divided attention that differ from those used in selective attention. Increased neuronal activity required to simultaneously process two stimulus dimensions as compared with each separate dimension has often been observed, but rarely has activity induced by a divided attention condition exceeded the sum of activity induced by the component tasks. Healthy participants performed a selective-divided attention paradigm while undergoing functional Magnetic Resonance Imaging (fMRI). The task required participants to make a same-different judgment about either one of two simultaneously presented stimulus dimensions, or about both dimensions. Performance accuracy was equated between tasks by dynamically adjusting the stimulus display time. Blood Oxygenation Level Dependent (BOLD) signal differences between tasks were identified by whole-brain voxel-wise comparisons and by region-specific analyses of all areas modulated by the divided attention task (DIV). No region displayed greater activation or deactivation by DIV than the sum of signal change by the two selective attention tasks. Instead, regional activity followed the tasks' processing demands as reflected by reaction time. Only a left cerebellar region displayed a correlation between participants' BOLD signal intensity and reaction time that was selective for DIV. The correlation was positive, reflecting slower responding with greater activation. Overall, the findings do not support the existence of functional brain activity specific to DIV. Increased activity appears to reflect additional processing demands by introducing a secondary task, but those demands do not appear to qualitatively differ from processes of selective attention.
authors.affiliation: NIH/National Institute on Drug Abuse-IRP, Neuroimaging Research Branch, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA. britta.hahn@gmail.com
authors.forename: Britta
authors.initials: B
authors.lastname: Hahn
authors.forename: Frank A
authors.initials: FA
authors.lastname: Wolkenberg
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Ross
authors.forename: Carol S
authors.initials: CS
authors.lastname: Myers
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Heishman
authors.forename: Dan J
authors.initials: DJ
authors.lastname: Stein
authors.forename: Pradeep K
authors.initials: PK
authors.lastname: Kurup
authors.forename: Elliot A
authors.initials: EA
authors.lastname: Stein
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D002755:Choice Behavior / Q000502:physiology*; D005260:Female; D005364:Field Dependence-Independence; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D008606:Mental Processes / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D012016:Reference Values