Decoding cognitive control in the parietal cortex

Abstract

We have previously reported evidence for a transient reconfiguration signal in the medial superior parietal lobule (mSPL/precuneus) that is time-locked to the initiation of shifts of attention within several perceptual domains, (e.g., attention shifts between spatial locations, features, objects or sensory modalities; Yantis et al., 2002; Liu et al., 2004; Serences et al., 2004, Shomstein & Yantis, 2004). Independently, studies of task-switching have revealed a frontoparietal cortical network exhibiting transient activity during switches between two categorization tasks (e.g., Braver et al., 2003). Here we investigated the neural basis of cognitive control during task-switching and spatial attention shifting within the same paradigm. Subjects directed covert attention to one of two rapid serial visual presentation (RSVP) streams displayed to the left and right of fixation, and were prepared to perform one of two digit categorization tasks (high/low or even/odd). Each stream contained mostly filler distractor items along with occasional cues and digit targets. Four types of cues instructed subjects to shift or hold spatial attention or to switch or hold their categorization task. Using the standard univariate GLM, we observed a transient reconfiguration signal evoked by both attention shift and task switch cues in a common region of mSPL/precuneus. We then applied multivoxel pattern classification (linear support vector machine) to determine whether this apparently domain-independent signal differs for the two domains of cognitive control. The multivoxel patterns of activity within this region did predict which type of shift was being executed on an individual trial basis. The multivariate analysis reveals that although this region is recruited for shifts in multiple domains, domain-specific spatial patterns of activity are associated with different acts of control.