Schematic representation in horizontal (A) and coronal (B) planes of the chemorepulsive and chemoattractive factors that influence the formation of the lateral olfactory tract. The olfactory epithelium (OE) would released a repulsive factor (violet circles), probably Sema IV, forcing LOT axons (red) to leave the olfactory bulb. An unidentified factor (green circles) produced by the septum (S) would prevent LOT axons to cross the midline. In addition, LOT axons would grow very superficially, being attracted by Sema A (orange circles) secreted by the mesenchyme precursor of the frontal bone (gray).