title: The maturational process of the auditory system in the first year of life characterized by brainstem auditory evoked potentials.
abstract: The study of brainstem auditory evoked potentials (BAEP) allows obtaining the electrophysiological activity generated in the cochlear nerve to the inferior colliculus. In the first months of life, a period of greater neuronal plasticity, important changes are observed in the absolute latency and inter-peak intervals of BAEP, which occur up to the completion of the maturational process, around 18 months of life in full-term newborns, when the response is similar to that of adults.
  
  
  OBJECTIVE
  The goal of this study was to establish normal values of absolute latencies for waves I, III and V and inter-peak intervals I-III, III-V and I-V of the BAEP performed in full-term infants attending the Infant Hearing Health Program of the Speech-Language Pathology and Audiology Course at Bauru School of Dentistry, Brazil, with no risk history for hearing impairment.
  
  
  METHODS
  The stimulation parameters were: rarefaction click stimulus presented by the 3ª insertion phone, intensity of 80 dBnHL and a rate of 21.1 c/s, band-pass filter of 30 and 3,000 Hz and average of 2,000 stimuli. A sample of 86 infants was first divided according to their gestational age in preterm (n=12) and full-term (n=74), and then according to their chronological age in three periods: P1: 0 to 29 days (n=46), P2: 30 days to 5 months 29 days (n=28) and P3: above 6 months (n= 12).
  
  
  RESULTS
  The absolute latency of wave I was similar to that of adults, generally in the 1st month of life, demonstrating a complete process maturity of the auditory nerve. For waves III and V, there was a gradual decrease of absolute latencies with age, characterizing the maturation of axons and synaptic mechanisms in the brainstem level.
  
  
  CONCLUSIONS
  Age proved to be a determining factor in the absolute latency of the BAEP components, especially those generated in the brainstem, in the first year of life.
authors.affiliation: Department of Speech-Language Pathology and Audiology, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.
authors.forename: Raquel Beltrão
authors.initials: RB
authors.lastname: Amorim
authors.forename: Raquel Sampaio
authors.initials: RS
authors.lastname: Agostinho-Pesse
authors.forename: Kátia de Freitas
authors.initials: Kde F
authors.lastname: Alvarenga
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D001307:Auditory Perception / Q000502:physiology*; D003056:Cochlear Nerve / Q000254:growth & development; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D011930:Reaction Time; D013997:Time Factors