The vestibular nuclei in the domestic hen

Summary Stereotaxic injections of small quantities of horseradish peroxidase (HRP) are made in the vestibular complex in the hen and the labelled cells due to retrograde transport of the tracer enzyme are studied, especially in the vestibular complex but also in other parts of the brain stem. The superior vestibular nucleus sends commissural fibres to the superior, medial, and descending nuclei and to Deiters' complex. The cell group A projects to the contralateral superior nucleus and to the Deiters' complex. The medial nucleus projects to the contralateral superior and descending nuclei, Deiters' complex, as well as strongly to the medial nucleus. The descending nucleus projects commissurally to the superior nucleus, the medial nucleus and the Deiters' complex, as well as heavily to the descending nucleus. The nucleus Deiters ventralis, the nucleus Deiters dorsalis, the cell group B and the tangential nucleus do not project to any other vestibular nuclei. Furthermore, the medial nucleus projects to the superior and descending nuclei and the Deiters' complex on the same side. The descending nucleus projects to the superior and medial nuclei on the same side. Finally, the superior nucleus, the medial nucleus, the descending nucleus, and the Deiters' complex receive fibres from the ipsilateral nucleus of Darkschewitsch and the nucleus ectomammillaris, as well as bilaterally from the pontine but mainly from the bulbar reticular formation.