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Kimron Shapiro, Zhao Fan, Suresh Muthukumaraswamy, Krish Singh; The role of a sustained left parietal-occipital component in the serial chaining of two cognitive operations. Journal of Vision 2009;9(8):91. doi: 10.1167/9.8.91.
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A fundamental process in human cognition is to accomplish chained sequential operations in which a second task requires an input from the preceding one. In Experiment 1, we required participants in a novel spatial PRP-type task to respond as quickly as possible to two sequential visual tasks, which were either chained or independent. The results revealed RTs for the Chained condition were larger than RTs for the Independent condition across 5 levels of SOA. In Experiment 2, participants performed the same task (100ms SOA only) while magnetoencephalographic (MEG) signals were recorded simultaneously. Half of the trials contained only the first task (single-task trials) while the other half contained both tasks (dual-task trials). The independent condition also included two sub-conditions where the cue and target were either spatially congruent (same side) or incongruent (different side). The event-related field data suggest that a sustained posterior component (SPC) beginning 0.3s and lasting for 700 ms after Task 2 onset is linked with the chained processing of two cognitive operations. Multiple-channel comparisons reveal this component originated from occipito-parietal areas, primarily in the left hemisphere. The SPC did not appear in two other contrasts suggesting it is linked with chained processing rather than task difficulty or attention switching. Additional time-frequency analyses confirmed a larger event-related desynchronization (power decrease) for the Chained condition between 0.3s to 1.1s after Task 2 onset in the frequency band of 0 to 22Hz. We suggest the left SPC may be linked with the serial processing requirement involved in decision-making and response selection.
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