Growth of callosal terminal arbors in primary visual areas of the cat

In kittens ranging in age between postnatal day (P) 5 and P150, callosal axons originating near the 17/18 border were anterogradely labelled with biocytin and reconstructed from serial sections. At the end of the first postnatal week most of the axons begin to invade the cortex near the 17/18 border with multiple branches; some axons already span the grey matter up to layer 1. Branches tend to grow into the grey matter in loose bundles