Hypercalculia in savant syndrome: central executive failure?

Background: The existence of outstanding cognitive talent in mentally retarded subjects persists as a challenge to present knowledge. We report the case of a 16-year-old male patient with exceptional mental calculation abilities and moderate mental retardation.

Methods: The patient was clinically evaluated. Data from standard magnetic resonance imaging (MRI) and two 99mTc-ethyl cysteine dimer (ECD)-single photon emission computer tomography (SPECT) (in resting condition and performing a mental calculation task) studies were analyzed.

Results: Main neurologic findings were brachycephalia, right-side neurologic soft signs, obsessive personality profile, low color-word interference effect in Stroop test, and diffuse increased cerebral blood flow during calculation task in 99mTc-ECD SPECT. MRI showed anatomical temporal plane inverse asymmetry.

Conclusions: Evidence appears to support the hypothesis that savant skill is related to excessive and erroneous use of cognitive processing resources instigated by probable failure in central executive control mechanisms.