Frontal auditory-evoked potential augmenting-reducing and urinary homovanillic acid.

Relationships between augmenting-reducing (Aug/Red) in auditory modality and dopaminergic metabolism were investigated in young adults with respect to sex. The slope values of evoked potential amplitude changes with increasing intensities were used to evaluate Aug/Red both at Cz and Fz for each of the five components: P1, N1, P2, P1N1, N1P2. The greatest slopes (Aug) were found in females. Individual differences in dopaminergic metabolism were estimated by assaying free and conjugated forms of homovanillic acid (HVA) in urines. HVA excretion rates were significantly more variable in males than in females. Relationships between Aug/Red and HVA levels were only found in males. The lower the Aug/Red slopes recorded at Fz site for the N1 component (weak augmenter or reducer responses), the higher the urinary HVA level and particularly the conjugated forms of HVA. These results are of interest for further applications in psychopathology.