TEMPORAL FREQUENCY RESPONSIVITY SHOWS MULTIPLE MATURATIONAL PHASES - STATE-DEPENDENT VISUAL-EVOKED POTENTIAL LUMINANCE FLICKER FUSION FROM BIRTH TO 9 MONTHS

Maturation of temporal resolution was investigated in a visual evoked potential study in 77 infants from birth to 9 months of age. Luminance evoked potential measures in response to homogeneous sinusoidal flickering light (1-64 Hz) were recorded under behavioral state-defined conditions. Behavioral state was determined by direct observation and by polygraphic recording of the electroencephalogram (EEG), eye movements (EOG), muscle activity (EMG), heart rate (ECG), and respiration. Temporal-frequency functions of the amplitude of the fundamental response across the temporal-frequency range were recorded during sleep and wakefulness. The highest temporal-frequency response recorded during wakefulness was accepted as a measure for inclusion in a growth function of temporal-frequency responsiveness. The resulting temporal resolution frequency vs. age function showed three separate maturational phases. Maturational phases were defined as (1) an initial slow phase from 1-32 days postnatal during which maturation of temporal vision is unremarkable; (2) an intermediate rapid phase of improvement from age 26 to 170 days; and (3) an overlapping but final slow phase from 151 to at least 270 days during which adult-like flicker resolution is approximated. This study suggests that the multiple maturational phases of the infant's responses to flickering light are due to maturational differences, which correspond with maturation of structural factors of brain function. Finally, across the age span tested, high-frequency responsivity was influenced significantly by the degree of infant arousal.