Functional anatomy of simple and complex mental calculation using PET

Current models of arithmetical cognition assume that adults solve simple arithmetic problems (e.g. 4 x 6) by retrieving an answer from a network of stored declarative associations whereas complex calculations (e.g. 24 x 75) require actual computation. The present study was aimed at separating, in the context of arithmetic, the cerebral areas involved in memory retrieval and those involved in computation