Lateroposterior Nucleus Research Articles

On the organization of the retino-tecto-thalamo-telencephalic pathways in a Chilean rodent; the Octodon degus

After performing eye enucleations or restricted lesions in the superior colliculus or the pulvinar nucleus, the degeneration patterns provoked by these procedures were analyzed by means of the Nissl and the Fink-Heimer methods in 30 specimens of Octodon degus. The pulvinar or lateroposterior nucleus can be subdivided into 3 regions (rostrolateral, rostromedial and caudal), on the basis of cytoarchitecture, tectofugal afferent and efferent connections to the cerebral cortex. In addition, this nucleus projects to the ipsilateral tail of the caudate nucleus and to the nucleus lateralis dorsalis of the thalamus, which has been shown to project over the cingulate cortex in this animal. These findings support the possibility that the pulvinar may have an important role in visuo-limbic interactions, by way of its connections with the nucleus lateralis dorsalis. Another highly interesting finding from the phylogenetic point of view is that the organization of the pulvinar in the Octodon degus is remarkably similar to that organization of the retino-tecto-thalamo-cortical pathways described in the grey squirrel and in the tree shrew is strikingly similar to those found in the Octodon degus, a semi-fossorial South American rodent that has evolved in isolation from the two former species for about 40 million years, makes it impossible to explain the organization of this pathway by advocating convergent evolution, due to environmental pressures determined by arboreal life, as postulated by Kaas et al. 39.

A description of the dorsal thalamus of the marsupial native cat, Dasyurus viverrinus (Dasyuridae).

The nuclear architecture of the dorsal thalamus in the marsupial native cat, Dasyurus viverrinus, is described. The nine midline and intralaminar nuclei comprise a large and prominent part of the thalamus. The lateroposterior nucleus is clearly divided into medial and lateral divisions. A ventroanterior nucleus is distinguished from the ventrolateral nucleus, and the ventroposterior complex is divided into cytoarchitecturally distinctive medial and lateral divisions. There is a large posterior nucleus. The medial geniculate nucleus displays an external or principal division and an internal division. The dorsal lateral geniculate nucleus has three cell laminae. Though the dasyurus thalamus presents features that are intermediate between those displayed by the American opossum, Didelphis virginiana, and the Australian brush-tailed possum, Trichosurus vulpecula, overall the two Australian forms resemble each other more closely than either resembles the American from.

A horseradish peroxidase study of the projections from the latero-posterior nucleus to three lateral peristriate areas in the rat

A horseradish peroxidase study of the projections from the latero-posterior nucleus to three lateral peristriate areas in the rat

Thalamocortical projections to the temporal and parietal association cortices in the rat

Thalamic projections to the parietal cortex were studied with the Nissl technique and thalamic projections to the temporal cortex were studied with both Nissl and horseradish peroxidase techniques. Results indicated that the parietal cortex receives projections from the lateral thalamic nucleus, pars principalis while the temporal cortex receives projections from the latero-posterior nucleus. It was suggested that the temporal cortex may be homologous to the primate posterior association cortex receiving projections from the pulvinar.

Thalamic projections to visually responsive regions of parietal cortex

Thalamic efferents to visually responsive regions of parietal cortex of the cat were investigated by experimental retrograde tracing techniques. Two classes of photically evoked potentials recorded from the middle suprasylvian gyrus could be distinguished on the basis of waveform and latency. Type 1 responses were recorded from the Clare-Bishop area at the lateral border of the suprasylvian gyrus and Type 2 responses were recorded from association response areas on the crown of the suprasylvian gyrus. Studies of retrograde degeneration in kittens and adult cats and retrograde transport of intracortically injected horseradish peroxidase indicate that afferents to the electrophysiologically identified Clare-Bishop area originate in the lateroposterior nucleus, the posterior nucleus, and the medial interlaminar nucleus of the lateral geniculate body. Afferents to electrophysiologically identified association response areas originate in the lateroposterior nucleus, ventroanterior nucleus, the pulvinar, the laterodorsal nucleus, and the central lateral nucleus. Studies of orthograde degeneration following placement of parietal lesions indicate a close reciprocity of corticothalamic and thalamocortical projections.

Relation of the visual field to the lateral geniculate body of the albino rat.

Relation of the visual field to the lateral geniculate body of the albino rat.

PROJECTION OF THE RETINA ON TO STRIATE AND PRESTRIATE CORTEX IN THE SQUIRREL MONKEY, SAIMIRI SCIUREUS.

PROJECTION OF THE RETINA ON TO STRIATE AND PRESTRIATE CORTEX IN THE SQUIRREL MONKEY, SAIMIRI SCIUREUS.