Telencephalon of the teleost Macropodus: experimental localization of secondary olfactory areas and of components of the lateral forebrain bundle

Abstract

Connections of the telencephalic hemisphere were experimentally examined to facilitate investigations of the functions of this major brain area in teleosts. The distribution of afferent olfactory tract fibers was traced using a degeneration method and autoradiographic localization of axonally transported protein. Afferents terminate predominantly ipsilaterally in the medial, lateral, and posterior zones of the hemisphere and in the nucleus posterior tuberis of the diencephalon. Afferents also project to the contralateral olfactory bulb through the commissure of Goldstein. The results of similar experiments in five other teleosts are briefly reviewed. Evidence of retrograde transport of tritiated proline or metabolite is also discussed. Components of the lateral forebrain bundle originating in the extreme rostral end of the dorsal zone of the hemisphere were traced to: (1) the corresponding zone of the contralateral hemisphere; (2) nucleus entopenduncularis; and (3) the extreme ventral part of the posterior zone of the diencephalon. The anatomical findings are discussed in relation to previous experiments in Macropodus dealing with the location of brain areas which concentrate sex steroids and with the effects of brain lesions on reproductive behavior in the male.