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L A Benevento

Publications and source records attributed to L A Benevento.

At least 37 records · Page 2Linked to original sources
PubMed1979

Demonstration of a direct projection from the intralaminar central lateral nucleus to the primary visual cortex.

Orthograde autoradiographic and retrograde horseradish peroxidase (HRP) tracing techniques were used to demonstrate the existence of a direct projection from the central lateral nucleus of the intralaminar complex of the thalamus to the primary visual cortex of the cat. The projection is sparser than the projections from the thalamic non-specific nuclei to other cortical areas of the cat which have been described in the past [9,20,21]. The projection to primary visual cortex is most dense in cortical layers I and VI. It does not appear to have a well-defined topographical organization within this cortical area.

Afferent Pathways↗
PubMed1977

An autoradiographic study of the projections of the pretectum in the rhesus monkey (Macaca mulatta): evidence for sensorimotor links to the thalamus and oculomotor nuclei.

Autordiographic tracing methods were used to determine the differential projections of the pretectal nuclei, in the rhesus monkey, in relation to their inputs. The sublentiform (SL) and olivary (ON) nuclei receive projections from the visual cortex, superior colliculus (SC) and equal bilateral projection from the retina. The nucleus of the posterior commissure (NPC) and its subdivisions do not receive any of these inputs. The projections of the pretectum involve a number of structures within the thalamus and brain stem and there are differences in the projection targets of the pretectal region which receives direct visual input (i.e., SL and ON) and the region which does not (i.e., nucleus of the posterior commissure, NPC). For example, while all pretectal regions project within the pretectum and to the SC, accessory oculomotor nuclei, reticular formation, intralaminar nuclei and hypothalamus, it is only the retinorecipient zone which projects to rostral regions such as the visceral oculomotor nuclei, the lateral pulvinar, the border between the lateral pulvinar and medial pulvinar, the oral pulvinar as well as to the thalamic reticular nucleus, ventral lateral geniculate nucleus, zona incerta and other structures. It is concluded that the retina, SC and cortex which influence the visceral oculomotor nuclei can only do so by virtue of their projections to the pretectum, and that any consideration of accommodative and pupillary reflexes must view the pretectum as an obligatory link through which various structures can influence the intrinsic musculature of the eye. In contrast to the SC, the pretectum does not project to any of the visual relay nuclei of the thalamus, such as the inferior pulvinar, which project to the visual cortices. Instead, the pretectum projects directly to visuomotor, visceromotor and arousal systems.

Animals↗
PubMed1976

The cortical projections of the inferior pulvinar and adjacent lateral pulvinar in the rhesus monkey (Macaca mulatta): an autoradiographic study.

An autoradiographic technique was used to determine superior colliculus (SC) and pulvinar projections in the rhesus monkey. SC projects bilaterally to the inferior pulvinar (PI) while occipital cortex projects to PI and the lateral pulvinar (PL). PI has sustaining, topographical projections to layers IV, III and I of areas 18 and 19 (and VI and I of 17) which agrees with the central representation of the visual hemifield and suggests that there is more than one hemifield representation in prestriate cortex. PL adjacent to PI also projects to the same cortical areas and layers, while the portion of PL extending into the caudal pole of the pulvinar projects to layers IV, III and I of areas 20 and 21. Thus, occipital cortices are associated by cortico-thalamocortical connections and also receive direct lemniscal input via SC-PI and the dorsal lateral geniculate nucleus (DLG), while inferotemporal areas 20 and 21 receive only cortico-thalamocortical connections. It is concluded that Stoffels' principle of lamellation holds and, that one pulvinar subdivision projects to several cortical areas, that adjacent pulvinar subdivisions have overlapping projections to these cortical areas and their layers and that the pulvinar also projects to the same cortical area as DLG but to different layers. These connections are similar to those in lower mammals but not to those in the squirrel monkey and bushbaby.

Animals↗
PubMed1975

The ascending projections of the superior colliculus in the rhesus monkey (Macaca mulatta).

We studied and compared the ipsilateral efferents of the superficial and deep layers of the superior colliculus of the rhesus monkey. Using a stereotaxic method, microelectrodes were inserted through the contralateral hemisphere in order to make electrolytic lesions of the superior colliculus. Large lesions involved all layers of the superior colliculus, while smaller lesions involved either the superficial or the deep layers of the superior colliculus. Following various survival times, the brains were prepared with the Fink-Heimer technique ('67). Following lesions of the superficial layers of the superior colliculus, definite degenerated axonal endings were found in the dorsal and ventral lateral geniculate nuclei, inferior pulvinar, centrointermediate nucleus, magnocellular dorsomedial nucleus, anterior pretectal nucleus and pretectal region. Sparse degenerated axonal endings were found in the limitans nucleus, lateral posterior nucleus and some intralaminar nuclei following lesions of the superficial layers in the rostral portion of the superior colliculus. Following lesions of the deep layers of the superior colliculus, degenerated axonal endings were found in the central gray, magnocellular medial geniculate nucleus, suprageniculate nucleus, limitans nucleus, lateral posterior nucleus, medial and oral pulvinar, nucleus of the accessory optic tract, zona incerta, subdivisions of the ventral lateral and ventral posterior lateral nuclei, ventral posterior inferior nucleus, denosocellular and multiform dorsomedial nuclei, all intralaminar nuclei, inferior colliculus, parabigeminal nucleus, olivary nucleus, reunions nucleus, Forel's Field H and an undefined midbrain nucleus. In general the projections were topographically organized in that the caudal portion of the superior colliculus projected to the rostral portions of thalamic nuclei and the rostral portion of the superior colliculus projected to the caudal portions of thalamic nuclei. All the degeneration patterns seen after lesions of the superficial and deep layers were accounted for by large lesions which involved all layers of the superior colliculus. It is concluded that the superficial and deep layers of the rehesus monkey superior colliculus have different ascending projections. The finding, are related to the organization of visual and multimodal thalamocortical systems in primates and other mammals.

Animals↗
PubMed1975

Stereotaxic coordinates for the Rhesus monkey thalamus and mesencephalon referencing visual afferents and cytoarchitecture.

When using a stereotaxic instrument for visual field stimulation we found that electrode placements in the thalamus and mesencephalon of prone rhesus monkeys with the aid of avaiable atlases showed considerable errors. As these animals are valuable for primate visual system reseach an atlas was constructed with methods that have not been used before for rhesus. In addition, the specific connections from the visual cortices, superior colliculus and retina to the thalamus and mesencephalon are also shown. Anesthetized monkeys of specific body dimensions had a matrix of pins inserted into the brain before fixation. A matrix was used so that the penetrations seen in the sectioned brain could be cross related as a control for accurate measurements of the stereotaxic planes throughout the brain. The surface of the whole brain frozen blocks were photographed on the microtome just before a cut section was taken. These calibrated pictures formed the "floor plan" of the atlas as they represent more accurately the brain geometry than individual sections which are distorted by cutting, staining and mounting. Cytoarchitectural (Nissl stain) and axonal connectional (Fink-Heimer stain) information was transferred and adjusted onto the block pictures from their corresponding stained sections. Follow up experiments showed that the present coordinates are accurate for these monkeys of restricted body dimensions. In addition, referencing visual axonal projections onto the same cytoarchitectural map in stereotaxic coordinates provides an atlas for localizing areas of the thalamus, on a basis other than cytoarchitecture, which receive combinations of visual inputs for further anatomical and physiological studies of the rhesus monkey visual system. The atlas further demonstrates that projections do not necessarily follow the cytoarchitectural definition of an area, but rather redefine the thalamus on the basis of specific axonal connections.

Animals↗