Amnesia for arithmetic facts: a single case study.
We report the case of an anarithmetic patient with a selective deficit of memory for elementary arithmetic facts, who produced, for instance, "25" in answer to "4 x 5." The patient showed good language comprehension and production abilities, had minimal number transcoding difficulties, and mastered normally multidigit arithmetic procedures. She was submitted to a series of calculation, verification, and number classification tasks. The arithmetic deficit was evident in both recognition and recall tasks, was consistent across testing sessions, and did not vary as a function of the format used for presentation of the problems. The patient failed even when only implicit access to arithmetic facts was expected: In a timed addition verification task, she did not show a normal inhibition effect when rejecting addition problems in which the proposed result was the product of the two operands (e.g., "3 + 4 = 12"). We suggest that the deficit resulted from a specific and permanent degradation of some connections and nodes in arithmetic long-term memory.