epinastine hydrochloride A second negativity that has been e

A second negativity that epinastine hydrochloride has been elicited from deviant stimuli in passive auditory oddball experiments is late discriminative negativity (LDN). This negative component appears after MMN and peaks at approximately 400–430ms in response to changes in speech stimuli for both children and young adults (Korpilahti et al., 1995; Čeponienė, et al., 2003; Čeponienė et al., 2004; Kraus et al., 1993). Compared with MMN, LDN was stably observed in children aged 2–3 years exposed to changes in the fundamental frequency, duration, intensity, and source in complex tones pattern (Putkinen et al., 2012). On the basis of a combination of the mismatch responses (MMR) patterns from age groups and two speech contrasts with different discriminative difficulty, Liu et al. (2014) demonstrated that the emergence of mismatch responses (MMN, p-MMR, and LDN) may indicate the neural discriminative processing of speech features. At the beginning stage of speech discrimination development, an enhancement in p-MMR might reflect involuntary attention orientation, when children fail to analyze the acoustic difference between two speech stimuli and regard the deviant sound as a novel stimulus. When entering the advanced level, children begin to process the sound structures, as reflected by the emergence of LDN and its latency change. Finally, children develop the automatic processing to discriminate between the subtle acoustic differences in their speech inventory that adults possess. The study has clearly established the utility of using the converging patterns of MMR measures as research tools to understand the nature of developmental disorders involving speech and language impairments, particularly in situations where behavioral responses cannot be readily elicited. For Mandarin-speaking children, the ability to discriminate lexical tones is critical for language development. A Mandarin syllable may be composed of four possible elements. Tone and vowels serve as the compulsory units, and consonants are optional units occurring in either the initial or final position. Mandarin Chinese has four tones: T1 ([ma1] means “mother”), T2 ([ma2] means “hemp”), T3 ([ma3] means “horse”), and T4 ([ma4] means “scold”). T1 through T4 can be described phonetically as high level, high rising, low falling and rising, and high falling, respectively. Among the four tones, T2 is acoustically similar to T3; the two tones only differ in the turning time point of the pitch contour. Studies have confirmed that T2 and T3 constitute the most confusing tone pair for children and second language learners (Wong et al., 2005; Chandrasekaran et al., 2007; Tsao, 2008). Behavioral and ERP studies have demonstrated that lexical tone perception abilities develop quickly in infancy and continue to be fine-tuned in childhood. Cheng et al. (2013) used a two-deviant MMN paradigm and demonstrated that the T1/T3 pair elicited a left frontal-distributed p-MMR in newborns, whereas cytosine elicited an adult-like MMN in 6-month-old infants. However, the T2/T3 pair did not elicit any MMRs in newborns and elicited a p-MMR in 6-month-old infants only when they were awake. The p-MMR switched to the adult-like MMN as the infants grew, but the trajectory of the polarity transition depended on the degree of deviance. Lee et al. (2012) also reported that the T1/T3 pair elicited adult-like MMNs between 150 and 300ms in 4-, 5-, and 6-year-old children, but T2/T3 elicited only p-MMRs in the 5- and 6-year-old groups. Liu et al. (2013) used AX phonetic discrimination tasks to explore the developmental changes of speech discrimination abilities in Mandarin-speaking children of preschool and school age. Results indicated that accuracy in discriminating the T2/T3 pair increased with age, reaching nearly 90% at 8 years. In addition, the regression model showed that lexical tone discrimination sensitivity contributed to the variance of PPVT scores, suggesting that lexical tone perception plays an essential role in word comprehension development in Mandarin-speaking children.