Reena Murmu

The process of weaning programmes the physiological and neurobehavioural development of various animal species and is thus a critical formative period for adult behaviour. The neural substrates which may underlie these behavioural changes are largely unknown. This study for the first time show that the timing as well as the amount of social contact with family members significantly interferes with the refinement of prefrontal cortical and hippocampal synaptic networks. Studies have quite intensively investigated the critical importance of emotional experience (for instance, time of weaning) at behavioural level. In addition, studies have provided compelling evidence that during development environmental factors (such as social or isolated environment) dynamically modify animal’s behaviour and brain development. Nevertheless, the impact of these two different developmental time windows of emotional experience have never been systematically studied and the neural mechanism remains unk...

The process of weaning programs the neurobehavioral development and therefore provides a critical formative period for adult behavior. However, the neural substrates underlying these behavioral changes are largely unknown. To test the hypothesis that during childhood neuronal networks in the prefrontal cortex are reorganized in response to the timing and extent of social interactions, we analyzed the length, ramification, and spine density of apical and basal dendrites of layer II/III pyramidal neurons in four groups of male rats. (1) Early weaning at postnatal day (PND) 21 + postweaning social rearing (EWS), (2) late weaning at PND 30 + postweaning social rearing (LWS), (3) early weaning + postweaning social isolation (EWI), (4) late weaning + postweaning social isolation (LWI). Compared with late weaned animals, the early weaned animals displayed elevated spine densities on apical and basal dendrites only in the anterior cingulate (ACd), but not in the orbitofrontal cortex (OFC), irrespective of the postweaning housing conditions. For dendritic length and complexity an interaction between the factors weaning and postweaning rearing conditions was observed. In the ACd the EWI animals had longer and more complex apical dendrites compared with all other groups, whereas in the OFC the EWI animals displayed a significant reduction of apical dendritic length and complexity compared with the EWS group. Taken together, our findings show that the timing as well as the amount of social contact with family members significantly affects the refinement of prefrontal cortical synaptic networks, which are essential for emotional and cognitive behavior.