Pattern reversal evoked potentials: age, sex and hemispheric asymmetry.

Binocular pattern reversal evoked potentials (PREPs) and EEG power were recorded bilaterally from occipital scalp of 50 boys and 50 girls aged 5-14. PREP latency was unaffected by either age or gender. Amplitudes, however, were consistently larger for girls than boys, with differences diminishing by adolescence. Significant electrophysiological asymmetries were also found; larger PREP amplitudes were measured at the right occipital electrode than the left for the two waves investigated. These asymmetries were apparent in both girls and boys across all ages, although they tended to diminish with maturation. EEG alpha asymmetry did not correlate with PREP amplitude asymmetry. PREPs elicited by half-field stimulation of 8 girls aged 9-10 years determined that 'paradoxical lateralization' of the half-field response was the same for both left and right half-fields, thus failing to account for the asymmetry of the full-field binocular response.