OBJECTIVE: In this study, we examined the effects of Mozart's music on spatial-reasoning ability by near-infrared spectroscopy (NIRS). METHODS: The subjects comprised five males and five females (aged 25-35 years). They were administered the seven original core subtests of the Japanese version of the Tanaka B-type intelligence test, which includes a spatial-reasoning subtest. We used three different music conditions: Mozart's sonata (K. 448), Beethoven and a silent control condition. Moreover, we used optical topography to assess the effects of music on brain function with a spatial-reasoning subtest. RESULTS: We found that exposure to Mozart's sonata enhanced cognitive performance in intelligence tests when compared with results obtained upon exposure to Beethoven or silence. In addition to the expected temporal cortex activation, we report dramatic results revealing differences in activation in the dorsolateral prefrontal cortex and the occipital cortex, both of which are expected to be important for spatial-temporal reasoning [emphasis added]. DISCUSSION: We suggest the possibility of a direct priming effect being responsible for preferential activation, and open the door to understanding the potential effects of Mozart's music.