MORPHOMETRIC ANALYSIS OF THE VESTIBULAR COMPLEX IN THE RAT

The characteristics of the four major vestibular nuclei and accessory cell groups in the rat have been studied in serially cut horizontal se ctions. Camera lucida drawings of the vestibular nuclei and their neur ons were made in these sections and subjected to a computerized image analysis. The dimensions (volume and length) and the number of cells o f each vestibular nucleus were obtained, as well as morphometric param eters of their neurons (cross-sectional area, maximum and minimum diam eter, and shape). These parameters were statistically analyzed by comp aring the cell population from different nuclei and different parts of each nucleus. Of the major nuclei, the medial, which is the largest, has the greatest number of cells, its neurons being the smallest of al l the nuclei, with the size of cells decreasing in a rostrocaudal dire ction. In contrast, the lateral nucleus contains the fewest cells but also the largest ones. Neurons of the superior and descending nuclei a re of an intermediate size and number, with a rostrocaudal decrease in the size of the descending nucleus cells. In addition, minor nuclei a re identified and described in their relationship to the other structu res in the brain stem. The relevant aspects of the anatomical informat ion in regard to functional roles are reviewed.