S. Tobimatsu et al., EFFECT OF SPATIAL-FREQUENCY ON TRANSIENT AND STEADY-STATE VEPS - STIMULATION WITH CHECKERBOARD, SQUARE-WAVE GRATING AND SINUSOIDAL GRATING PATTERNS, Journal of the neurological sciences, 118(1), 1993, pp. 17-24
We recorded VEPs to the alternation of checkerboard, square-wave grati
ng and sinusoidal grating patterns to evaluate the contribution of the
fundamental spatial frequency and higher harmonic components in 12 no
rmal subjects. Their fundamental spatial frequencies were equated and
ranged from 0.5 to 8.0 c/deg. Both the transient VEP (T-VEP) and stead
y-state VEP (S-VEP) were obtained. The latency and amplitude of P100 o
f T-VEPs were measured. S-VEPs were Fourier analyzed, and phase and am
plitude of the second harmonic response were measured. The mean P100 l
atency and the mean phase had a U-shaped function with a peak at a fun
damental spatial frequency of 2.0 c/deg irrespective of the stimulus p
atterns, while the mean P100 amplitude and the mean amplitude of S-VEP
s did not show such spatial selectivity. At low and medium spatial fre
quencies, differences in P100 latency, phase and amplitude between pat
tern types were more pronounced. However, this difference became insig
nificant at high spatial frequencies. These results indicate that VEP
responses are predominantly determined by the fundamental spatial freq
uency, and that the contribution of higher harmonics to VEP responses
is not negligible. Our results are consistent with the concept that th
e human visual system may use spatial frequency-domain information.