COMPETITION FOR NEUROTROPHIC FACTORS - MATHEMATICAL-ANALYSIS

Neurotrophic factors, particularly the neurotrophin gene family of neu rotrophic factors, are implicated in activity-dependent anatomical pla sticity in the visual cortex and at the neuromuscular junction. Accumu lating evidence implicates neurotrophic factors as possible mediators of activity-dependent competition between afferents, leading to the se gregation of afferents' arbors on the target space. We present a biolo gically plausible mathematical model of competition for neurotrophic f actors. We show that the model leads to anatomical segregation, provid ed that the levels of neurotrophic factors released in an activity-ind ependent manner, or the levels available by exogenous infusion, are be low a critical value, which we derive. Above this critical value, affe rent segregation breaks down. We also show that the model segregates a fferents even in the presence of very highly correlated patterns of af ferent activity. The model is therefore ideally suited for application to the development of ocular dominance columns in the kitten visual c ortex.