Abstract

Acalculia is an acquired disorder of number and/or calculation skills following cerebral damage which affects about 20% of patients with left hemisphere injury. The inability to use numbers can be very incapacitating as it interferes with several everyday activities such as shopping and using bank accounts and telephones. After introducing the main cognitive and anatomical features of the normal number system, this chapter will discuss the main historical and contemporary achievements in the neuropsychology of number cognition. These achievements concern: understanding that the number system is fractionated in distinct subcomponents; characterizing the relation between number and other cognitive skills; defining the role of the brain regions that cause number and calculation disorders or that allow maintenance of residual number skills; and identifying tools for the assessment and the possible rehabilitation of acalculia.