| Objective:Language, which is a human-specific tool for daily communication, may affect reading, learning, intelligence, emotional and social skills development in children. This study was designed to explore the underlying mechanisms relating to the early language development through the aspects of auditory, memory and social factors:1. To examine the developmental trajectory of auditory pathway and central auditory temporal processing ability in term infants in the first year of life.2. To study the language development in early infancy, and evaluate the correlation between central auditory temporal processing, mother intelligence quotient (IQ), family social-economic status (SES) and early language development.3. To investigate the early development of auditory recognition memory.Method:A total of126infants with gestational age (GA) between37and41week were enrolled at6-week-old,107infants attended9-month follow-up measurements. All infants were divided by sex and GA:male and female; early term group (37-38weeks GA) and term group (39-41weeks GA). Regular auditory brainstem response (ABR) and forward masking test were conducted at6weeks and9months old; scores of Chinese Communicative Development Inventory-Putonghua version (CCDI-P) in infants, Raven's Standard Progressive Matrices (SPM) in mothers and family socio-economic status questionnaire were obtained at9months; event-related potential (ERP) was performed in456-week-old infants and492-month-old infants, respectively. Main parameters or scores for evaluation are as follows:1. ABR variables:Peak latencies (PL) and amplitudes (Amp) for waves â… , â…¢ and â…¤, and interpeak latencies for wave â… -â…¢,â…¢-â…¤ and â… -â…¤ in regular ABR test; wave â…¤ latency and amplitude elicited by the probe in forward masking test.2. CCDI-P:scores for subtests of phrases understood, gestures, words understood and words produced; CDI composite (consisting of phrases understood, gestures and words produced) and CDI total score (consisting of phrases understood, gestures, words understood and words produced).3. Raven's Standard Progressive Matrices (SPM):IQ.4. Family Socio-economic Status Questionnaire:SES index.5. ERP measurements:latency and amplitude for P2, average amplitude for P750, NSW and PSW.Results:1. In regular ABR test, consistent sex effects were found at both6weeks and9months. Males showed longer peak latencies for waves â…¢ and â…¤ and â… -â…¢, â…¢-â…¤ and â… -â…¤ intervals (p<0.05). In addition, lower amplitudes for waves â… , â…¢ and â…¤ were found in males at6weeks (p<0.05). Infants in the early term group had longer wave â…¢ and â…¤ latencies and â… -â…¤ interval than that of term peers at6weeks and9months (p<0.05). In forward masking test, wave â…¤ latency shorted and amplitude increased with the masker-probe intervals at both ages, the latency also decreased and amplitude increased with the increasing of age(all p<0.01). Males demonstrated longer wave â…¤ latencies in all masker conditions at both ages (p<0.01) and lower wave â…¤ amplitude at6weeks (p<0.05). Infants in the early term group showed significantly longer wave â…¤ latencies in all conditions at6weeks (p<0.01) and longer wave â…¤ latencies in64ms and16ms conditions at9months (p<0.05,p<0.1).2. Compared to females, males showed significantly lower scores for phrases understood, gestures and CDI composite (p<0.05). Infants in early term group had lower scores for words understood and CDI total score (p<0.05). Infants had shorter wave â…¤ latency of the64ms condition at9months had higher scores for phrases understood (p<0.01), words understood, CDI composite and CDI total score (all p<0.05). Controlling for wave â…¤ latency of the64ms condition at9months, sex and GA effects on CCDI-P scores were all disappeared(p>0.05). Pearson correlation and linear regression were used and indicated that the wave â…¤ latency of the64ms condition at9months was the best predictor of scores for phrases understood, words understood, CDI composite and CDI total score, regression equations for CCDI-P scores were established as follows:Y1=11.105-1.633X; Y2=157.313-18.706X; Y3=25.431-3.437X; Y4=182.743-22.143X. In addition, infants from lower SES families showed lower scores for words understood and CDI total score than those from higher SES families(p<0.05). Infants with lower maternal education level had lower scores for words understood and CDI total score (p<0.05). Maternal IQ, parents'age and paternal education have no correlation ship with children's language development.3. At6weeks, P2amplitude elicited by the maternal voice was greater than that by stranger's voice at middle frontal, right front-central and central electrode locations (all p<0.05), no significant differences were found for P2latency for the two stimulus types; at2months, P2amplitude elicited by maternal voice was greater only at midline electrode locations (p<0.05), and P2latency elicited by maternal voice was slightly longer than that by stranger's voice (p<0.1). There were no significant differences in average amplitude of the P750between two stimuli at6weeks, however the average amplitude of the P750elicited by the stranger's voice was greater than that by maternal voice at left electrode locations at2months(p<0.05). The NSW elicited by the stranger's voice was more negative than that by the maternal voice in both groups (p<0.01, p<0.05).6-week-old Infants did not elicited PSW by the stranger's voice, and2-month-old infants elicited PSW by the stranger's voice at right temporal hemisphere (p<0.05).Conclusion:1. Sex and GA affect developmental trajectory of auditory pathway and auditory temporal processing in term infants. Females showed more advanced development of the auditory brainstem than males, infants of37-38weeks GA had less mature auditory development than those with39-41weeks GA.2. Sex and GA affect early language development, females and infants with39-41weeks GA had more advanced language development. Auditory temporal processing is one of the most important biological factors affecting language development; family SES, especially for the maternal education also plays an important role in early language development.3. Infants can distinguish familiar auditory stimuli and detect novel stimuli at6weeks and2months, older infants might engage in more processing of the word than younger infants, indicating a result of maturation;2-month-old infants rather than those with6-week-old have the capacity to encode novel stimuli, indicating memory updating. |
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