br Conflict of interest br Acknowledgement

Conflict of interest
Acknowledgement Support for manuscript preparation was provided by grants from the National Institutes of Health (MH094633, MH103627) to Koraly Pérez-Edgar.
Introduction
Materials and methods
Results
Discussion We investigated the impact of music training on the maturation of central auditory processes by assessing auditory event related potentials and behavioral responses in children ages 6–7, prior to their participation in music training and two years after the start of training. We report two main findings: (1) In the passive pitch perception task, a decrease in P1 amplitude and an increase in the incidence of an identifiable N1 component as well as an increase in the N1/P1 ratio from baseline to year two were observed in the music group; none of these dna stain effects had emerged to the same extent in the age-matched comparison groups. Moreover, a decrease in latency of the P1 peak was present when comparing music and sports groups. (2) In the active pitch discrimination task, children involved with music training detected deviations in pitch more accurately and showed larger P3 component amplitude in response to such changes. Next, we discuss each of these results separately and in relation to previous findings. The P1 component is the most reliably measured component of auditory evoked potentials in children and has a fronto-central distribution (Ponton et al., 2000). Its latency decreases systematically with increasing age (Cunningham et al., 2000; Sharma et al., 1997; Wunderlich and Cone-Wesson, 2006) from peak latency of 85–95ms in 5–6year olds to 40–60ms in 18–20 years old adults. This decline in P1 latency is known to be related to the ongoing increases in neural transmission speed as a result of developmental changes in myelination of underlying neural generators. Furthermore, increases in synaptic synchronization contributes to the speed of neural transmission during development (Huttenlocher, 1979; Wunderlich and Cone-Wesson, 2006). The P1 amplitude decreases with age as well, a phenomenon likely related to the emergence of N1 component and the development of underlying P1 generators (Čeponieneet al., 2002). The most robust differential findings between groups were observed on the P1 component elicited by the piano tones in the passive task. We observed a decrease in P1 amplitude and latency that was largest in the music group compared to age-matched comparison groups after two years of training. In addition, focusing just on the year 2 data, the music group showed the smallest amplitude of P1 compared to both no-training and sports group, in combination with the accelerated development of the N1 component. These findings indicate that the pattern of auditory cortical processing was associated with faster maturation in the music group, likely related to more active sustained engagement of auditory neural circuitry (Trainor et al., 2012). This may be an indication that underlying processes of developmental myelination proceeded faster as a result of musical experience, a possibility we hope to address in our ongoing structural MRI studies of these same groups. Of note, Shahin et al., 2004, using a similar paradigm, showed larger P1 amplitude in children trained for one year with music using the Suzuki method relative to non-music trained children. Although our findings, at the first glance appear contrary to theirs, few points are important to consider when comparing these results: First, the children participants in the Shahin et al. study were on average 5–6 years old and were assessed cross-sectionally at this one time point, not over time so as to interact with the development of the P1. Secondly, the morphological changes of the P1 peak (decreasing amplitude and latency in combination with the developing N1 peak) has been noted to take shape more prominently after age 7 (McArthur and Bishop, 2002; Ponton et al., 2000). Lastly, several recent studies (Kraus and Anderson, 2014; Slater et al., 2014) have shown that effects of music training, specifically at the neural level, are not noticeable until at least after two years of training and children in the Shahin et al. study were assessed at only one year after music training. Therefore our results of experience related plasticity of P1 amplitude and latency in the expected direction of development are in concordance with previous findings. It may well be the case that early music training increases the amplitude of the P1 component at age 4–5 as this is the predominant neural response to auditory input at that stage of brain development, but that as training proceeds, between the ages of 6–9, it tends to favor the transition of the P1 to the more fully developed P1-N1 complex as observed in the present data.