Concept combination with logical connectives

A defining trait of cognition is the capacity to combine information into compound concepts. This ability relies, among others, on the logical connectives 'and', 'or' and 'if-then'. Simple sentences, such as 'there is a fork on the table' (A) or 'there is a knife' (B), can be combined in different ways using different connectives. No evidence is available to date on how and where the brain represents different concept combinations produced by different connectives, and how these are evaluated against new facts. Here, participants learned associations between graphic cues and conjunctive (A and B), disjunctive (A or B) or conditional (If A then B) sentences. During fMRI scanning, a cue was presented, followed by a delay, during which participants had to represent the sentence associated to the cue; finally, a visual scene had to be evaluated for compatibility with the sentence. Two participant groups were recruited so that conditionals (If A then B) were interpreted in either of two alternative ways (thus, same form, different semantics). Multivariate decoding applied to the delay period revealed that the active sentence was encoded in left inferior frontal gyrus (BA44). During the delay, no difference was found between participant groups. During the target phase, we found higher activations in rostral regions of left inferior frontal cortex (BA47), for disjunctions and conditionals relative to conjunctions. Activation of BA47 was modulated by the interpretation of conditionals. We suggest BA44 represents the surface form of a compound sentence, while BA47 is involved in deriving its logical consequences.