The lateral olfactory tract, the anterior commissure and the cells of the olfactory bulb

Abstract

The respective relations of the cells of the olfactory bulb to the lateral olfactory tract and the anterior commissure were studied in the rabbit by the use of the Nauta and Fink-Heimer techniques. The following observations were made. 1. The origin of the anterior commissure in the bulbar area is limited to the pars rostralis of the anterior olfactory nucleus. In the rabbit this nucleus extends up to the rostral end of the olfactory bulb. 2. The commissural fibers arising in the cucleus olfactorius anterior pars rostralis terminate in the pars externa of the contralateral anterior olfactory nucleus. No interbulbar connection could be demonstrated. 2. The lateral olfactory tract is composed of axons of both mitral and tufted cells of the main olfactory formation. 4. This fiber bundle projects to the olfactory cortex as defined by White and Heimer, with the exception of the medial portion of the nucleus olfactoriusanterior pars dorsalis. The latter nucleus is supplied by fibers which originate in the medial part of the olfactory formation and pass caudally along the medial side of the olfactory peduncle. 5. In contrast to all other portions of the anterior olfactory nucleus the pars rostralis receives no afferents from the main olfactory formation. 6. The synaptic distribution of the tufted cell axons in the olfactory cortex appears to be considerably more limited than that of the mitral cell axons. 7. No areal localization could be detected in the projection of the olfactory bulb via the lateral olfactory tract to the ipsilateral forebrain regions. This appears to apply to the projections of the mitral cells as well as to those of the tufted cells.