Word Puzzles Produce Distinct Patterns of Activation in the Ventrolateral Prefrontal Cortex and Anterior Cingulate Cortex

This research reports two studies that use word puzzles that required participants to find a word that satisfied a set of constraints. The first experiment used a remote associates tasks where participants had to find a word that would form a compound word with three other words. The second experiment required participants to complete a word fragment with an associate of another word. Both tasks produced distinct patterns of activity in the ventrolateral prefrontal cortex (VLPFC) and the anterior cingulate cortex (ACC). In both experiments activity in the VLPFC continued only as long as the participants were trying to retrieve the solution and disengaged as soon as the solution was obtained, while activation in the ACC increased upon the retrieval of a solution reflecting the need to process that solution. An ACT-R model was fit to the data of the second experiment. This theory attributes the activity in VLPFC to retrieval operations and the activity to ACC to setting of control states or subgoals. The data confirm these interpretations over alternative interpretations that have been offered in the literature for the function of these two regions.