Origin of the fornix system in the squirrel monkey

doi:10.1016/0006-8993(79)91069-2

Brain Research

Volume 160, Issue 3, 19 January 1979, Pages 401-411

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Summary

With the use of the horseradish peroxidase retrograde axonal transport technique this experiment attempted to identify the cell bodies of origin whose axons supply the septal area, mammillary bodies and the anterior thalamic complex in the squirrel monkey. It was noted that axons which innervate the anterior thalamic complex arise predominantly from the deepest cell layer of both the retrosplenial cortex and adjoining portions of subicular cortex. Hippocampal afferents to the mammillary bodies arise principally from all cell layers of the subiculum proper and to a lesser extent from the presubiculum. Afferents which innervate the septal area originate from all cell fields of the cornu Ammonis and adjacent prosubicular cortex. It was further noted that axons which are distributed to caudal levels of the septum probably arise from both the cornu Ammonis and adjacent prosubiculum, whereas axons which innervate more rostral levels of septum originate exclusively from the prosubicular cortex.

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Fibers of the fornix terminate mostly in the mamillary nuclei, medial, and lateral hypothalamus and in septal area in rats (Guillery, 1955; Powell et al., 1957; Swanson and Cowan, 1977; Canteras and Swanson, 1992; Kishi et al., 2000) and monkeys (Valenstein and Nauta, 1959). Fibers deriving from the hippocampus target mostly the septal area in rats (Saper, 2004), while mamillary bodies receive afferents from the subiculum and partially from the presubiculum in rats and primates (Swanson and Cowan, 1975; Krayniak et al., 1979). In addition to hypothalamic afferent fibers forming the vast majority of the fornix, some neurons, predominantly from the preoptic area, terminate in the hippocampal formation via the fornix (Saper, 2004).
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Lamina separation was then found for the comparable efferents in the monkey brain. Thus, the hippocampal projections to the anterior thalamic nuclei arise almost exclusively from polymorphic cells in the deepest cell layer of the subiculum (Aggleton et al., 1986a; Krayniak et al., 1979). Using the nomenclature of Lorente de Nó (1934), these projections arise from layer IV of the proximal subiculum (prosubiculum) and from layers IV and V of the rest of the subiculum.
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Origin of the fornix system in the squirrel monkey

Summary

Neurosci. Lett.

Brain Research

Brain Research

Exp. Neurol.

Brain Research

Brain Research

Neuroanatomical and electrophysiological studies of the subicular complex

Anat. Rec.