Fig. 3-1. Basal view of cerebral hemispheres showing the olfactory system. Lesions of the trigone, tract, bulb, olfactory filaments (schematically represented by dots on olfactory bulb) and olfactory epithelium cause unilateral loss of olfaction. Unilateral lesions of the lateral stria or olfactory cortex do not cause loss of olfaction because of the bilateral temporal lobe distribution of each olfactory apparatus through the anterior stria and anterior commissure.