Temporal modulation transfer function of vision by pattern visual evoked potentials in patients with optic neuritis.

To reveal the impairment of the temporal modulation transfer function of vision in patients with optic neuritis, the pattern visual evoked potentials (P-VEPs) were recorded at reversal frequencies ranging from 4 to 24 per second, and the fast Fourier transform (FFT) of VEPs were investigated. In normal subjects, curves of the square root of the power of the FFTs of P-VEPs versus temporal frequency showed the maximum peak at 6 Hz (12 reversals/s). The specific distribution of the power spectrum could be found at each temporal frequency, and the amplitudes of higher harmonic components decreased while a single power spectrum peak became prominent as the temporal frequency increased. In patients with optic neuritis, an abnormality of the power spectrum of steady-state P-VEPs could by detected by estimating the 1st and 2nd harmonic components. The abnormality of the power spectrum of transient P-VEPs could be detected by estimating the higher harmonic components of the power spectrum.