The organisation of conceptual knowledge in the brain: The future's past and some future directions.

We review the development and current status of theories of the organisation and representation of conceptual knowledge in the human brain. The currently known facts from optic aphasia, category-specific semantic deficits, and functional neuroimaging are consistent with a framework in which the first-order constraint on the organisation of conceptual knowledge is domain. Data from functional neuroimaging suggests additionally a framework characterised by both domain- and modality-specific constraints. Work in congenital disorders and in apraxia indicate that the content of conceptual knowledge is not exhausted by modality-specific input/output processes. It is concluded that future empirical and theoretical work on the organisation and representation of conceptual knowledge will profit from a reorientation of the problem from the organisation of distinct processing systems to the content of information represented internal to such systems.