Projections From Octopus Cells of the Posteroventral Cochlear Nucleus to the Ventral Nucleus of the Lateral Lemniscus in Cat and Human
Projections of octopus cells, which are located within the posteroventral cochlear nucleus, to globular cells within the contralateral ventral nucleus of the lateral lemniscus were studied in cat by means of anterograde filling of axons, by immunostaining cells, axons and nerve endings for calretinin, and by single unit electrophysiological record ings within the lateral lemniscus. Injections of biocytin into cut axons of the intermediate acoustic stria resulted in labeling of octopus cells ipsilateral to the injection and of large, complex nerve terminals (endbulbs) within the ventral division of the contralateral ven tral nucleus of the lateral lemniscus. Immunostaining for calretinin showed that octopus cells, their axons and endbulbs within the lateral lemniscus were positive. Single unit recordings within the portion of the lemniscal nucleus that contains endbulbs showed the characteristic electrical signature of cells that receive endbulbs (prepotentials) was asso ciated with cells whose activity in response to acoustic stimulation indicated that their inputs were from octopus cells. Immunostaining of human tissue indicated that octopus cells, their axons and complex endings within the ventral nucleus of the lateral lemniscus were positive for calretinin, which suggests that the projection of octopus cells found in cat is also present in human. Counts of globular cells, the probable recipients of end bulbs, in the ventral nucleus of the lateral lemniscus in human tissue indicated that these cells comprise 38% of the nucleus, as contrasted with 4% in cat. The results suggest that functions subserved by globular cells in this nucleus may play a dominant role in pro cessing acoustic stimuli in the human, whereas cells specialized for processing high fre quency sounds are more dominant in cat.