title: The maturation of auditory responses in infants and young children: a cross-sectional study from 6 to 59 months.
abstract: BACKGROUND
  An understanding of the maturation of auditory cortex responses in typically developing infants and toddlers is needed to later identify auditory processing abnormalities in infants at risk for neurodevelopmental disorders. The availability of infant and young child magnetoencephalography (MEG) systems may now provide near optimal assessment of left and right hemisphere auditory neuromagnetic responses in young populations. To assess the performance of a novel whole-head infant MEG system, a cross-sectional study examined the maturation of left and right auditory cortex responses in children 6- to 59-months of age.
  
  
  METHODS
  Blocks of 1000 Hz (1st and 3rd blocks) and 500 Hz tones (2nd block) were presented while MEG data were recorded using an infant/young child biomagnetometer (Artemis 123). Data were obtained from 29 children (11 males; 6- to 59-months). Latency measures were obtained for the first positive-to-negative evoked response waveform complex in each hemisphere. Latency and age associations as well as frequency and hemisphere latency differences were examined. For the 1000 Hz tone, measures of reliability were computed.
  
  
  RESULTS
  For the first response-a response with a "P2m" topography-latencies decreased as a function of age. For the second response-a response with a "N2m" topography-no N2m latency and age relationships were observed. A main effect of tone frequency showed earlier P2m responses for 1st 1000 Hz (150 ms) and 2nd 1000 Hz (148 ms) vs. 500 Hz tones (162 ms). A significant main effect of hemisphere showed earlier N2m responses for 2nd 1000 Hz (226 ms) vs. 1st 1000 Hz (241 ms) vs. 500 Hz tones (265 ms). P2m and N2m interclass correlation coefficient latency findings were as follows: left P2m (0.72, p < 0.001), right P2m (0.84, p < 0.001), left N2m (0.77, p < 0.001), and right N2m (0.77,p < 0.01).
  
  
  CONCLUSIONS
  Findings of strong age and latency associations, sensitivity to tone frequency, and good test-retest reliability support the viability of longitudinal infant MEG studies that include younger as well as older participants as well as studies examining auditory processing abnormalities in infants at risk for neurodevelopmental disorders.
authors.affiliation: Lurie Family Foundations MEG Imaging Center, Department of Radiology, Children's Hospital of Philadelphia Philadelphia, PA, USA.
authors.forename: J Christopher
authors.initials: JC
authors.lastname: Edgar
authors.affiliation: Lurie Family Foundations MEG Imaging Center, Department of Radiology, Children's Hospital of Philadelphia Philadelphia, PA, USA.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Murray
authors.affiliation: Lurie Family Foundations MEG Imaging Center, Department of Radiology, Children's Hospital of Philadelphia Philadelphia, PA, USA.
authors.forename: Emily S
authors.initials: ES
authors.lastname: Kuschner
authors.affiliation: Tristan Technologies, Inc. San Diego, CA, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Pratt
authors.affiliation: Tristan Technologies, Inc. San Diego, CA, USA.
authors.forename: Douglas N
authors.initials: DN
authors.lastname: Paulson
authors.affiliation: Lurie Family Foundations MEG Imaging Center, Department of Radiology, Children's Hospital of Philadelphia Philadelphia, PA, USA.
authors.forename: John
authors.initials: J
authors.lastname: Dell
authors.affiliation: Lurie Family Foundations MEG Imaging Center, Department of Radiology, Children's Hospital of Philadelphia Philadelphia, PA, USA.
authors.forename: Rachel
authors.initials: R
authors.lastname: Golembski
authors.affiliation: Lurie Family Foundations MEG Imaging Center, Department of Radiology, Children's Hospital of Philadelphia Philadelphia, PA, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Lam
authors.affiliation: Lurie Family Foundations MEG Imaging Center, Department of Radiology, Children's Hospital of Philadelphia Philadelphia, PA, USA.
authors.forename: Luke
authors.initials: L
authors.lastname: Bloy
authors.affiliation: Lurie Family Foundations MEG Imaging Center, Department of Radiology, Children's Hospital of Philadelphia Philadelphia, PA, USA.
authors.forename: William
authors.initials: W
authors.lastname: Gaetz
authors.affiliation: Lurie Family Foundations MEG Imaging Center, Department of Radiology, Children's Hospital of Philadelphia Philadelphia, PA, USA.
authors.forename: Timothy P L
authors.initials: TP
authors.lastname: Roberts
keywords: auditory; infant; magnetoencephalography; young child