COMPETITION FOR NEUROTROPHIC FACTORS - OCULAR DOMINANCE COLUMNS

Activity-dependent competition between afferents in the primary visual cortex of many mammals is a quintessential feature of neuronal develo pment. From both experimental and theoretical perspectives, understand ing the mechanisms underlying competition is a significant challenge. Recent experimental work suggests that geniculocortical afferents migh t compete for retrograde neurotrophic factors. We show that a mathemat ically well-characterized model of retrograde neurotrophic interaction s, in which the afferent uptake of neurotrophic factors is activity-de pendent and in which the average level of uptake determines the comple xity of the axonal arbors of afferents, permits the anatomical segrega tion of geniculocortical afferents into ocular dominance columns. The model induces segregation provided that the levels of neurotrophic fac tors available either by activity-independent release from cortical ce lls or by exogenous cortical infusion are not too high; otherwise segr egation breaks down. We show that the model exhibits changes in ocular dominance column periodicity in response to changes in interocular im age correlations and that the model predicts that changes in intraocul ar image correlations should also affect columnar periodicity.