In the first half of the project, we were able to successfully develop the proposed genomic bottleneck approach, we call Neural Developmental Programs (NDPs). This approach is able to grow a fully functioning neural network from a single seed "neuron". Inspired by biological development, the NDP allows networks to self-assemble and evolve solely based on local communication between its components. Unlike conventional AI, which requires extensive manual design, these networks can adapt their shape and structure dynamically, making them more robust.
During the development of the NDP, we identified a key challenge: ensuring phenotypic complexity requires maintaining neuronal diversity, but this diversity comes at the cost of optimization stability. To address this, we introduce two mechanisms: (a) equipping neurons with an intrinsic state inherited upon neurogenesis; (b) lateral inhibition, a mechanism inspired by biological growth, which controls the pace of growth, helping diversity persist. We show that both mechanisms contribute to neuronal diversity and that, equipped with them, NDPs achieve comparable results to existing direct and developmental encodings in complex locomotion tasks.
A significant limitation of most current AI models is that they are trained once and then remain fixed, limiting their ability to handle new challenges. This is in stark contrast to biological neural networks that are characterized by their high degree of plasticity, a core property that enables the remarkable adaptability of natural organisms. Building on the NDP, we were able to develop a class of self-organizing neural networks capable of synaptic and structural plasticity in an activity and reward-dependent manner which we call Lifelong Neural Developmental Program (LNDP). Our results demonstrate the ability of the model to learn from experiences in different control tasks starting from randomly connected or empty networks. We further show that structural plasticity is advantageous in environments necessitating fast adaptation or with non-stationary rewards.