[Numbers, counting and calculating problems in view of cognitive neurology].

The ability to count and calculate is a human-specific skill comprised of understanding numeric values and categories and performing numerical operations; it is an acoustic-verbal symbolic activity that may be expressed in writing and understood by reading. The neuronal bases and precursors of cognitive systems have been supplied to mankind by the process of evolution. Abilities to create symbols (speech, visual letter and number symbols) must have played a decisive role in the emergence of man from the world of primates. Although counting and calculating problems are classified into numerous types, two main forms of dyscalculia have practical importance: the acquired one (the loss of learned knowledge) and the developmental one (the disturbance of the acquisition of arithmetical knowledge).