The olfactory peduncle and
olfactory bulb lie in the
olfactory sulcus a
sulcus formed by the
medial orbital gyrus on the inferior surface of each
frontal lobe. The olfactory peduncles lie in the sulci which run closely parallel to the midline. Fibers of the olfactory peduncle appear to end in the antero-lateral part of the
olfactory tubercle, the dorsal and external parts of the
anterior olfactory nucleus, the frontal and temporal parts of the
prepyriform area, the cortico-medial group of
amygdala nuclei and the
nucleus of the stria terminalis. The olfactory peduncle divides posteriorly into three main branches: the medial, intermediate and lateral striae. The olfactory peduncle thus terminates in a triangular structure called the
olfactory trigone. Caudal to these elements is the
anterior perforated substance, the anterior part of which is marked by the relief of the
olfactory tubercle. Finally, projections from the olfactory peduncle to the anterior olfactory nucleus are sometimes grouped together under the name of
superior olfactory stria. The terms olfactory tubercle and olfactory trigone are commonly confused in the literature.
Medial olfactory stria The
medial olfactory stria is classically described as running medially behind the
parolfactory area (hence its name) and terminating in the
subcallosal gyrus. However, this description has been rejected for some fifty years. The medial olfactory stria is now described as terminating much more medially, in the ventral
tenia tecta.
Intermediate olfactory stria The
intermediate olfactory stria is the branch (or branches) extending from the medial or lateral olfactory striae to the olfactory tubercle and anterior perforated substance. Trolard's term "pectineal formation " is used to refer to multiple intermediate striae extending from the lateral olfactory stria.
Lateral olfactory stria The
lateral olfactory stria is directed across the lateral part of the anterior perforated substance and then bends abruptly medially toward the
uncus of the
parahippocampal gyrus. ==Clinical significance==