No abstract

The sciurid retina projects to the contralateral superior colliculus, pretectal complex, ventral nucleus of the lateral geniculate body and to five distinct zones in the dorsal nucleus of the lateral geniculate. Ipsilateral projections are distributed to the same targets except the superior colliculus. Zones of terminal debris as identified by the Fink-Heimer method do not develop uniformly; instead some structures become argyrophyllic before others do so that an injudicious choice of survival times may produce misleading data.The topography of the retinal mosaic is preserved in all its projections except those to the accessory optic system. In the cases of the superior colliculus, ventral nucleus of the lateral geniculate body and the anterior pretectal nucleus, these retinal projections are in perfect register with other afferent connections which are also retinotopically organized. An enormous proportion of the cells in the dorsal nucleus of the lateral geniculate body are connected with the overlapping portions of the retina; only a very small part of this structure receives input from the much larger nonoverlapping retinal quadrants.

The sciurid retina projects to the contralateral superior colliculus, pretectal complex, ventral nucleus of the lateral geniculate body and to five distinct zones in the dorsal nucleus of the lateral geniculate. Ipsilateral projections are distributed to the same targets except the superior colliculus. Zones of terminal debris as identified by the Fink-Heimer method do not develop uniformly; instead some structures become argyrophyllic before others do so that an injudicious choice of survival times may produce misleading data.The topography of the retinal mosaic is preserved in all its projections except those to the accessory optic system. In the cases of the superior colliculus, ventral nucleus of the lateral geniculate body and the anterior pretectal nucleus, these retinal projections are in perfect register with other afferent connections which are also retinotopically organized. An enormous proportion of the cells in the dorsal nucleus of the lateral geniculate body are connected with the overlapping portions of the retina; only a very small part of this structure receives input from the much larger nonoverlapping retinal quadrants.

The effects on taste aversion learning of lesions in a variety of brain areas known to alter taste avoidance and/or shock avoidance behavior were examined in 72 adult male rats. Bilateral lesions of the medial frontal cortex, orbital or sulcal frontal cortex, cingulate cortex, caudate nucleus. medial thalamus, or hippocampus failed to significantly alter taste aversion learning, while bilateral lesions to the amygdala impaired this learning. Lesions to the septum produced equivocal results. There does not appear at present to be a general conceptual framework that can account for the data described here as well as do previous studies in the literature.

The neuroanatomical organization of the visual system in the tree shrew has been described. A cytoarchitectonic description of the components of this system as seen in Nissl stained material has been provided; an experimental neuroanatomical description of the efferent connections of the striate cortex, the superior colliculus, and the retina as identified by the reduced silver methods of Fink and Heimer [1967] was also undertaken.