Cross Section Through the Pretectal Region of the Midbrain
The pretectal region (B21) situated orally to the superior colliculi represents the
tran-sition from the midbrain to the diencephalon. Hence, the cross section
already contains structures of the diencephalon: dorsally on each side lies the
pulvinar (B22), in the middle the epithalamic
commissure (B23), and
ventrally the mamillary bodies (B24). The pretectal region extends
dor-solaterally with the principal
pretectal nucleus(B25). The
latter is an important relay sta-tion for the pupillary reflex. The fibers of
the optical tract and the fibers of the occipital cortical fields terminate
here. An efferent pathway of the nucleus extends across the epithalamic
commissure to the Edinger – Westphal nucleus (accessory oculomotor nucleus).
Ventral to the aque-duct are the Darkshevich’s
nucleus (B26) and the interstitial nucleus (of Cajal) (B27), the relay stations in the system of the medial longitudinal
fascicle.
Animal
experiments have shown that the interstitial
nucleus of Cajal and the prestitial
nucleus situated further orally are impor-tant relay stations for automatic
motions within the extrapyramidal motor
system. The essential synapses for the rotation of the body around its
longi-tudinal axis lie in the interstitial nucleus, those for raising the head
and upper body in the prestitial nucleus.
B28
Supramamillary commissure.
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