PURPOSE: The authors examined the development of lateral interactions between neurons in the human visual system through the use of visual evoked potentials (VEPs) elicited by windmill-dartboard stimuli. Previously, these VEPs have revealed two distinct types of lateral interactions (short-range and long-range) in adults. This study aims to track the development of these interactions in the first 6 months of life. METHOD: Windmill-dartboard stimuli were generated by a computer-controlled visual stimulator and presented on an oscilloscope display. VEPs to these stimuli were obtained from a group of human infants between 14 days and 6 months of age and from a group of adults who served as a basis for comparison. Fourier analysis was used to retrieve amplitude and phase measures of the relevant frequency components of the response. RESULTS: Amplitude measures of the VEP components elicited by the windmill-dartboard stimulus showed that the attenuation of the second harmonic frequency component (reflecting long-range lateral interactions) was essentially adultlike at all temporal frequencies for the majority of infants. In contrast, the amplitude of the fundamental frequency component (thought to reflect short-range lateral interactions) exhibited a low-pass temporal tuning function in infants that differed dramatically from adults. Additional immaturities were observable in the phase of the fundamental component of the infant VEPs. CONCLUSIONS: Evidence for the presence of some degree of lateral interaction was seen in even the youngest infant. Long-range lateral interactions appear to mature rapidly in infancy, whereas short-range lateral interactions show a much longer developmental time-course, and their properties are dependent on temporal frequency.
PURPOSE: The authors examined the development of lateral interactions between neurons in the human visual system through the use of visual evoked potentials (VEPs) elicited by windmill-dartboard stimuli. Previously, these VEPs have revealed two distinct types of lateral interactions (short-range and long-range) in adults. This study aims to track the development of these interactions in the first 6 months of life. METHOD:Windmill-dartboard stimuli were generated by a computer-controlled visual stimulator and presented on an oscilloscope display. VEPs to these stimuli were obtained from a group of humaninfants between 14 days and 6 months of age and from a group of adults who served as a basis for comparison. Fourier analysis was used to retrieve amplitude and phase measures of the relevant frequency components of the response. RESULTS: Amplitude measures of the VEP components elicited by the windmill-dartboard stimulus showed that the attenuation of the second harmonic frequency component (reflecting long-range lateral interactions) was essentially adultlike at all temporal frequencies for the majority of infants. In contrast, the amplitude of the fundamental frequency component (thought to reflect short-range lateral interactions) exhibited a low-pass temporal tuning function in infants that differed dramatically from adults. Additional immaturities were observable in the phase of the fundamental component of the infant VEPs. CONCLUSIONS: Evidence for the presence of some degree of lateral interaction was seen in even the youngest infant. Long-range lateral interactions appear to mature rapidly in infancy, whereas short-range lateral interactions show a much longer developmental time-course, and their properties are dependent on temporal frequency.