Examples from the Web for brainwork
Beauty can't amuse you, but brainwork—reading, writing, thinking—can.
Extremely clever at any form of brainwork, she was gauche and brusque in her manners, and totally lacking in perception.The Girls of St. Cyprian's|Angela Brazil
I may have brainwork to do, or something important to think about There is no comparison.The Beth Book|Sarah Grand
No amount of brainwork has conjured any sense from Iffley, and the etymology has been placed on the shelf as “unknown”.Archaic England|Harold Bayley