The habenulo-interpeduncular and mammillothalamic tracts: early developed fiber tracts in the human fetal diencephalon.
OBJECTIVE
The habenulo-interpeduncular (HI) and mammillothalamic (MT) tracts are phylogenetically ancient. The clinical relevance of these tracts has recently received attention. In this work, we map the anatomy the developing HI and MT.


METHODS
To investigate the topographical anatomy of developing fiber tracts in and around the diencephalon, we examined the horizontal, frontal, and sagittal serial paraffin sections of 28 human fetuses at 8-12 weeks of gestation.


RESULTS
In all specimens, eosinophilic early fiber bundles were limited to the bilateral HI and MT tracts in contrast to pale-colored later developing fibers such as the thalamocortical projections and optic tract. The HI and MT tracts ran nearly parallel and sandwiched the thalamus from the dorsal and ventral sides, respectively. The nerve tract course appeared to range from 5-7 mm for the HI tract and 3-5 mm for the MT tract in 15 specimens at 11-12 weeks. The HI tract was embedded in, adjacent to, or distant from the developing parvocellular red nucleus.


CONCLUSIONS
In early human fetuses, HI and MT tracts might be limited pathways for primitive cholinergic fiber connections between the ventral midbrain and epithalamic limbic system.
Department of Neurology, Wonkwang University School of Medicine, Jeonbuk Regional Cardiocerebrovascular Disease Center, Institute of Wonkwang Medical Science, 895, Muwang-ro, Iksan, Jeonbuk, 570-711, Republic of Korea, neurlogy@wonkwang.ac.kr.
Kwang Ho
KH
Cho
Shigemi
S
Mori
Hyung Suk
HS
Jang
Ji Hyun
JH
Kim
Hiroshi
H
Abe
Jose Francisco
JF
Rodriguez-Vazquez
Gen
G
Murakami
D001931:Brain Mapping; D004027:Diencephalon / Q000033:anatomy & histology*; D020392:Entopeduncular Nucleus / Q000033:anatomy & histology* / Q000502:physiology; D005333:Fetus / Q000033:anatomy & histology; D019262:Habenula / Q000033:anatomy & histology* / Q000502:physiology; D006801:Humans; D008326:Mammillary Bodies / Q000033:anatomy & histology* / Q000502:physiology; D009434:Neural Pathways / Q000033:anatomy & histology / Q000502:physiology*; D013788:Thalamus / Q000033:anatomy & histology* / Q000502:physiology