Impacts of environment, nervous system and movements of preterms on body map development: Fetus simulation with spiking neural network

Recent developmental studies have shown the importance of interaction with the environment resulting from fetal spontaneous movements for the formation of body maps in the spinal cord and primary somatosensory area. However, the underlying mechanism as well as the factors which contribute to the development of body maps is largely unknown. Here, we simulated the development of the body map using a human fetus simulation, and investigated the contribution of three factors which often differ in normal fetuses and preterms: (i) developmental environment, (ii) nervous system and (iii) movement patterns. The fetus model has a musculoskeletal body as well as sensory organs for tactile and proprioception, which allows us to simulate sensory feedbacks resulting from interaction with the uterine environment. We simulated the development of body maps by using these sensory feedbacks as inputs to the spinal and somatosensory cortex models, which are spiking neural networks with leaky integrate-and-fire neurons and spike-timing-dependent synaptic plasticity. We showed that the networks under normal fetus conditions can learn body part-specific modular architectures and responses, and have neurons encoding specific postures and double-touch events. In contrast, we found that (i) a change in environment from inside to outside the uterus, (ii) an imbalance between excitation and inhibition of the nervous system and (iii) decrease in variation and complexity of movement patterns each lead to the development of abnormal body maps in terms of function and structure of learned networks. These results suggest that these factors influence or disrupt body map development in preterms and their subsequent cognitive development.