Principal Component Analyses and Scalp Distribution of the Auditory P150-250 and N250-550 to Speech Contrasts in Mexican and American Infants Maritza Rivera-Gaxiola, Juan Silva-Pereyra, Lindsay Klarman, and Adrian Garcia-Sierra Institute for Learning and Brain Sciences (I-LABS) and Department of Speech and Hearing Sciences University of Washington, Seattle Lourdes Lara-Ayala and Cesar Cadena-Salazar Autonomous University of Queretaro, Mexico Patricia Kuhl Institute for Learning and Brain Sciences (I-LABS) and Department of Speech and Hearing Sciences University of Washington, Seattle We report a Principal Component Analysis (PCA) and the scalp distribution of the nor- malized peak amplitude values for speech-related auditory Event-related Potentials (ERP) P150-250 and N250-550 in 7-, 11-, and 20-month-old American infants learn- ing English and in 10–13-month-old Mexican infants learning Spanish. After assessing the infant auditory ERP P-N complex using PCA, we evaluated the topographic distri- bution of each of the discriminatory phases to native and non-native CV-syllabic con- trasts used in Spanish and English. We found that the first two Principal Components for each contrast type across ages showing a maximization of differences between the P150-250 and the N250-550 waves, explain more than 70% of the variance. The scalp distributions of the P150-250 and N250-550 components also differed, the P150-250 showing a frontal and anterior temporal distribution, and the N250-550 a more posterior distribution. The older infants showed a broader distribution of DEVELOPMENTAL NEUROPSYCHOLOGY, 31(3), 363–378 Copyright © 2007, Lawrence Erlbaum Associates, Inc. Correspondence should be addressed to Maritza Rivera-Gaxiola, Insitute for Learning and Brain Sciences (I-LABS) and Department of Speech and Hearing Sciences, University of Washington, Box 357988, Seattle, WA 98195. E-mail: rivegaxi@u.washington.edu