Infant eye movement asymmetries: Temporal-nasal asymmetry is reversed at isoluminance in 2-month-olds

Tested monocularly with luminance-modulated stimuli, young infants classically show a directional asymmetry of eye movements: optokinetic nystagmus (OKN) and OKN-like eye movements are more reliably elicited by temporo-nasally- (T-N) than by naso-temporally- (N-T) directed stimuli. In the present experiment, 2-month-old infants were tested with isoluminant red-green gratings. A reverse asymmetry was found: at isoluminance, directionally appropriate eye movements were more readily elicited by N-T- than by T-N-directed stimuli. The results suggest the presence of a reverse asymmetry in the ensemble of direction-selective neurons that controls young infants' immature eye movements in response to isoluminant stimuli.