Tracking task-specific activity in dual-task condition with ultrafast fMRI resolves the neural locus of a central bottleneck of information processing

Poster Session F - Tuesday, April 16, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Qiuhai Yue^1,2, Allen T. Newton³, René Marois^1,4,5; ¹Vanderbilt University, ²Shenzhen University, ³Vanderbilt University Medical Center, ⁴Vanderbilt Vision Research Center, ⁵Vanderbilt Brain Institute

Pashler (1984) showed that our ability to perform two attention-demanding tasks at the same time is limited by a central amodal stage of information processing, resulting in the postponement of the second task until central processing of the first one is completed. The neural locus of this central bottleneck has remained elusive because of the intractability of distinguishing task-specific information under dual-task conditions as each task processes through the brain. Here we show the feasibility of using ultra-fast (199ms TR), high-field fMRI (7T) with MVPA to distinguish the brain activity of two arbitrary sensorimotor response selection tasks – each involving 8-alternative discriminations resulting in single-task RTs of over 1 second – as participants (n=26) performed the tasks when they were overlapping (300ms SOA) or not (1500ms SOA). The behavioral results revealed a psychological refractory period (PRP) exceeding 500ms at the short vs long SOA. Using univariate and multivariate fMRI analyses, we traced the flow of information processing of each task through sensory, central amodal, and motor areas. We observed postponement of Task 2 activity of the duration of the PRP at short but not long SOA in a subset of amodal fronto-parietal areas while earlier sensory stages were unhindered. These results provide direct neural evidence for serial queuing of central information processing under overlapping dual-task conditions and identify the neural substrates of the central bottleneck. The findings also demonstrate the feasibility of using ultra-fast fMRI and multivariate analyses to track the flow of information processing in the human brain.

Topic Area: ATTENTION: Other