Infant VEP and preferential looking acuity measured with phase alternating gratings.

Previously, infants' grating acuity was found to be temporally tuned, but adults' grating acuity was not. In infants, acuity was higher for gratings phase alternating at 7.5 and 14 reversals/sec than for stationary gratings and gratings alternating at 2.5 or 23 reversals/sec. Also, when preferential looking (PL) and visually evoked potential (VEP) acuity were estimated with phase alternating gratings (14 reversals/sec), the acuity difference between the two techniques was smaller than that obtained when phase alternating gratings were used to estimate VEP acuity and stationary gratings were used to estimate PL acuity. In the present study, it was determined if PL grating acuity was tuned in older children and if the smaller difference between VEP and PL acuity found when infants were tested with phase alternating gratings was independent of temporal rate. Grating acuity in infants older than 2 yr was found to be not tuned, and the smaller difference between VEP and PL grating acuity in infants when both were measured with phase-alternating gratings was not rate dependent. VEP acuity and PL acuity for phase alternating gratings developed at different rates, converging to nearly equivalent levels by 12 mo of age.