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.