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.
Zago, L., Pesenti, M., Mellet, E., Bricogne, S., Seron, X., Beaudoin, V., Lochon, P., Mazoyer, B., & Mazoyer, N. (1999). Functional anatomy of simple and complex mental calculation using PET. NeuroImage, 9(6 (part. 2)). https://hdl.handle.net/2078.5/159241 (Original work published 1999)