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Shinyoung Jung, Suk Won Han*; Frontoparietal cortex encodes task set only when it is needed. Journal of Vision 2018;18(10):981. doi: 10.1167/18.10.981.
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The present study investigated how the frontoparietal network of the human brain is engaged when a task set is formulated, maintained, and executed. In an fMRI experiment, participants performed a cued-switching task. The target stimulus was created by superimposing an image of a face and an image of a building. At the beginning of each trial, a cue, indicating whether the face or the building should be attended, was presented. In the face task trials, participants performed the gender identification task (male/female), while in the building task trials, the building structure discrimination (1 story/ 2 story) was performed. The cue and target presentations were separated by jittered intervals (4, 8, or 12 secs). Importantly, we intended to include long intervals (8 or 12 secs) to separately examine cue- and target-evoked activities. As results, the frontoparietal regions (lateral prefrontal cortex and intraparietal sulcus) showed transient responses at the onsets of the cue and target. Notably, we found no evidence that the cue evokes sustained activation, preparing for the target presentation. Subsequent multivariate pattern analysis (MVPA) revealed that the two tasks elicited differential activation patterns from the frontoparietal regions. However, the task sets were able to be decoded only from target-evoked activation, p's < .05. The cue-evoked activity did not encode any task information. These findings challenge the predominant account that task cues evoke sustained activation, encoding task representations. Instead, we suggest that the coding of task sets in the frontoparietal regions becomes apparent at the moment when the task rule should be applied (target onset). This supports the adaptive coding model of the human brain, suggesting that the frontoparietal regions' task coding is determined by task demands (Woolgar, Hampshire, Thompson, & Duncan, 2011).
Meeting abstract presented at VSS 2018
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