A model of ocular dominance column development by competition for trophic factor: Effects of excess trophic factor with monocular deprivation and effects of antagonist of trophic factor

Recent experimental evidence has implicated neurotrophic factors (NTs) in t he competitive process believed to drive the development of ocular dominanc e (OD) columns. Application of excess amounts of particular NTs can prevent the segregation process, suggesting that they could be the substance for w hich geniculocortical afferents compete during development. We have previou sly presented a model that accounts for normal OD development as well as th e prevention of that development with excess NT. The model uses a Hebbian l earning rule in combination with competition for a limiting supply of corti cal trophic factor to drive OD segregation, without any weight normalizatio n procedures. Subsequent experimental evidence has further suggested that NTs may be caus ally involved in the competitive process. Application of NT antagonist can prevent OD columns by causing inputs from both eyes to be eliminated, sugge sting that NTs may be the substance for which geniculocortical afferents co mpete. Also, excess NT can mitigate the shift to the open eye normally caus ed by monocular deprivation (MD). In this article, we show that the current model can account for these subsequent experiments. We show that deprivati on of NT causes inputs from both eyes to decay and that excess NT can mitig ate the shift to the open eye normally seen with MD. We then present predic tions of the model concerning the effects of NT on the length of the critic al period during which MD is effective. The model presents a novel mechanis m for competition between neural populations inspired by particular biologi cal evidence. It accounts for three specific experimental results, and prov ides several testable predictions.