The meaning of weaning: influence of the weaning period on behavioral development in mice.

Maternal care during the first week postpartum has long-term consequences for offspring development in rodents. However, mother-infant interactions continue well beyond this period, with several physiological and behavioral changes occurring between days 18 and 28 PN. In the present study, we investigate the long-term effects on offspring behavior of being weaned at day 21 PN versus day 28 PN. We found that male and female offspring engage in higher initial levels of social interaction if weaned at day 28 PN, as well as sexually dimorphic changes in exploratory behavior. Females who were themselves weaned earlier also appeared to wean their own pups earlier. Sex-specific effects of weaning age were found on levels of oxytocin and vasopressin V1a receptor density in the hypothalamus, central nucleus of the amygdala and nucleus accumbens. These results indicate that altering weaning age in mice may be a useful model for investigating the development of sexual dimorphism in neurobiology and behavior.

EEG functional connectivity in term age extremely low birth weight infants.

OBJECTIVE: The hypothesis is tested that electrocortical functional connectivity (quantified by coherence) of extremely low birth weight (ELBW) infants, measured at term post-menstrual age, has regional differences from that of full term infants. METHODS: 128 lead EEG data were collected during sleep from 8 ELBW infants with normal head ultrasound exams and 8 typically developing full term infants. Regional spectral power and coherence were calculated. RESULTS: No significant regional differences in EEG power were found between infant groups. However, compared to term infants, ELBW infants had significantly reduced interhemispheric coherence (in frontal polar and parietal regions) and intrahemispheric coherence (between frontal polar and parieto-occipital regions) in the 1-12Hz band but increased interhemispheric coherence between occipital regions in the 24-50Hz band. CONCLUSIONS: ELBW infants at term post-menstrual age manifest regional differences in EEG functional connectivity as compared to term infants. SIGNIFICANCE: Distinctive spatial patterns of electrocortical synchrony are found in ELBW infants. These regional patterns may presage regional alterations in the structure of the cortex.