2007 年 25 巻 2 号 p. 275-276
We report the development of cortical responses (steady-state visual evoked potentials: VEPs) to radial expansion/contraction. Forty-four 3-4-month-olds and 9 adults viewed moving dots which cyclically (2.085 Hz) alternated between radial expansion (or contraction) and random directional motion. The first harmonic (F1) response in the VEPs must arise from global-motion- sensitive mechanisms. The results indicated that the F1 amplitudes for contraction were significantly larger than those for expansion for the 4-month-olds and the adults but not for the 3-month-olds. These results suggest that the human cortical motion mechanisms have an asymmetrical sensitivity for radial expansion/contraction which develops at around 3 to 4 months of age.