Context Free and Context-Dependent Conceptual Representation in the Brain

Abstract

How concepts are coded in the brain is a core issue in cognitive neuroscience. Studies have focused on how individual concepts are processed, but how conceptual representation changes to suit the context is unclear. We parametrically manipulated the association strength between words, presented in pairs one word at a time using a slow event-related fMRI design. We combined representational similarity analysis and computational linguistics to probe the neurocomputational content of these trials. Individual word meaning was maintained in lateral and medial temporal and medial parietal cortex (areas associated with heteromodal representation) when items were judged to be unrelated, but not when a linking context was retrieved. Context-dependent meaning was represented in left lateral prefrontal and premotor cortex and pre-supplementary motor area (regions associated with semantic control). Moreover, neural representation of context-dependent meaning was affected by the association strength in left lateral prefrontal cortex (LIFG) and anterior temporal lobe (ATL) to different degrees: ATL supported combined meanings more for strong associations; in contrast, LIFG supported combined meanings across trials, even when more control was required. These findings indicate that the semantic store in ATL amplifies long-term semantic associations when these are retrieved but does not directly capture short-term non-dominant associations.