Processing of relational information is a prerequisite underlying a number of higher cognitive faculties. Different brain regions within the frontal cortex have been implicated in supporting this function. The present study aimed at differentiating the roles of two frontal areas - anterior prefrontal cortex (aPFC) and premotor cortex (PMC) - in relational information processing using functional magnetic resonance imaging (fMRI). We tested the assumptions that PMC and aPFC differ as to their respective roles (1) in concrete (action-related) versus abstract relational information processing and (2) in concatenation versus integration of relational information. A reasoning paradigm adapted from Raven's Progressive Matrices was employed, manipulating the number and type of rules governing the matrices and creating an "abstract" and an "action" condition. Results suggest that PMC and aPFC are functionally differentiated by the type, not by the domain of relational processing, with PMC engaged in the sequential concatenation of relations, and aPFC in their integration. These results support hierarchical models of frontal function, while challenging the postulate of domain-specific processing within the frontal lobes.
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