Colored hearing synesthesia: an investigation of neural factors

We studied a 17-year-old boy with colored hearing synesthesia (chromesthesia) using psychophysical and neurophysiologic tests. Specific musical notes consistently evoked the same color hues. Unlike controls, he could make new musical note-color associations in a single trial. Auditory evoked potential studies showed no evidence of abnormal activation. The results in this subject do not favor the notion that chromesthesia was due to aberrant neural transmission in collateral pathways, and support the alternative hypothesis that chromesthesia results from strong cross-modal associative ability.