What you set is not what you see: unconscious activation of cognitive control.

Editor's Note: These short reviews of a recent paper in the Journal, written exclusively by graduate students or postdoctoral fellows, are intended to mimic the journal clubs that exist in your own departments or institutions. For more information on the format and purpose of the Journal Club, please see Cognitive control can prevent purely stimulus-driven or reflexive processing from dominating neural representation, thought, and behavior. This top-down cognitive control instead allows for goal-driven attentional selection and task-relevant behavior. Consciousness is often assumed to be intrinsic to these high-level control functions sitting atop a processing hierarchy in the prefrontal cortex (PFC). However, in a recent The Journal of Neu-roscience article, Lau and Passingham (2007) present new evidence that questions this assumption. Preparation for an upcoming task is an important element of cognitive control. Before execution, neural activity increases in cortical regions that process information relevant to the upcoming task. For example, cues indicating an upcoming color task initiate activation of visual areas that process color information (Wylie et al., 2006). This finding suggests that task-set preparation may use mechanisms similar to those in the biased-competition model of attention (Desimone and Dun-can, 1995), in which selective attention modulates lower visual area processing via top-down biasing. Extending the concept of biased competition outside the visual domain, cortical regions associated with task processing may also receive top-down modulation. The PFC is considered as the source of both attentional and task-set control signals. Preparing for a specific task can result in task-specific processing of even unseen stimuli. Naccache et al. (2002) engaged participants in a number judgment task. A masked number prime was presented before the target number for which the task was intended. Even when the masked number was unable to be seen, priming was observed, showing that semantic analysis and response generation occur even for a stimulus that does not enter conscious awareness. Lau and Passing-ham (2007) take this one step further and illustrate how unseen cues can interfere with task-set control. The design of Lau and Passingham (2007) takes advantage of metacontrast masking, as well as two tasks that involve discrete brain regions, specifically left inferior frontal cortex and middle temporal gyrus for semantic judgments and left ventral premotor area for phonological judgments (Sakai and Passingham, 2006). Metacontrast masking occurs when an object is rendered invisible by a subsequently presented mask containing adjacent contours. The metacontrast masking used by Lau and Passingham …