Modelling aIN axon growth and positional effects on axon turning angles. (a) aIN descending axons generated by a simple random growth model (red) fit the distribution of real descending axons (blue, to right) but model ascending axons do not match real ascending axons. (b,c) Real aIN ascending axon turning angles depend on the current growth angle and dorso-ventral (d-v) position. (d) In a model where growth angle depends on dorso-ventral position, generated aIN axons (red) match real axons (blue) closely. (e,f) Turning angles of modelled axons significantly match dependence of real axons on current angle and dorso-ventral position.