'Hidden lamination' in the dorsal lateral geniculate nucleus: the functional organization of this thalamic region in the rat.

Horseradish peroxidase (HRP) was injected in relatively massive amounts to cover most, or portions, of opercular striate cortex in four macaques. Absence of transcallosal or circumventricular labelling, plus discrete and consistent retrograde labelling in other areas in the four cases, assured the validity and specificity of the observations. Numerous labelled cells in regions directly bordering striate cortex, however, were excluded from the analysis because of the possibility of uptake consequent to physical diffusion. With this exception, all labelled cells were counted at roughly 2-mm intervals for one case with extensive unilateral injection of HRP. Even excluding the closely circumstriate population, the totals indicate that more than 30% of the afferent input to striate cortex arises from nongeniculate sources. Four areas of neocortex together make up about one-fourth of the total afferents: superior temporal sulcus 17.1%; inferior occipital area, 6.1%; intraparietal sulcus, 0.4%; and parahippocampal gyrus, 0.3%. Other areas projecting to striate cortex include claustrum, pulvinar, nucleus paracentralis, raphe system, locus coeruleus, and the nucleus basalis of Meynert. Cells of the latter were particularly striking with their very heavy uptake of HRP, and, even in cases of minimal effective injection, were scattered throughout an extensive area from the posterior edge of the globus pallidus passing rostrally beyond the chiasm and into the nucleus of the diagonal band. On the basis of their distribution and known cholinergic affinity, it is argued that this group also includes the cells labelled in and around lateral hypothalamus and cerebral peduncle, and that as a whole the group constitutes a cholinergic counterpart of the diffusely projecting monoaminergic systems. It seems possible that the basalis projection at first follows a fornical-subcallosal pathway to reach striate cortex via callosoperforant fibers.

Nongeniculate afferents to striate cortex in macaques.

New-world primates such as the marmoset (Callithrix jacchus) show polymorphism for the middle- to long-wavelength sensitive cone pigments. Each X-chromosome carries a gene for only one of three possible pigments. All males are thus dichromats, but some females will be trichromats. We have investigated the responses of cells of the parvocellular (PC) and magnocellular (MC) systems within animals from a single marmoset family. The middle- to long-wavelength pigment of dichromats was identified physiologically. Trichromats could readily be distinguished from dichromats by the presence of a high proportion of red-green opponent PC-cells. The physiological classification of phenotypes was confirmed with genetic analysis. The pattern of inheritance was consistent with current genetic models. In trichromatic females, the properties of cells resembled in detail those of cells from the PC- and MC-pathways of the macaque. In dichromats, cell responses resembled those of trichromats (except for the lack of opponency in PC-cells); PC-cells showed sustained and MC-cells transient responses, with a lower contrast gain for the former type. One difference was that a proportion of PC-cells in dichromats showed strong rod input even at high levels of retinal illuminance. Thus, in trichromatic marmosets the presence of two middle- to long-wave pigments appears to permit the elaboration of all the physiological properties associated with trichromacy.

https://www.jneurosci.org/content/jneuro/15/12/7892.full.pdf

Visual responses in the lateral geniculate nucleus of dichromatic and trichromatic marmosets (Callithrix jacchus)

Young adult squirrel monkeys were subjected to unilateral or bilateral enucleation, and allowed to survive for varying periods of time. Transneuronal degeneration confirms previous studies that the homogeneous parvocellular mass actually has four hidden laminae. Electron microscopic studies show that the retinal (RL) terminals undergo three stages of degenerative changes after enucleation: neurofilamentous hyperplasia; increased electron density; and phagocytosis by glial elements. The time course of these changes is correlated with those of the Glees and the Nauta preparations. The other types of axons remain normal. Three types of neuroglial cells are found in the normal and degenerating LGN: Oligodendrocytes, astrocytes and a phagocytic glial cell type. The oligodendrocytes do not appear to participate actively in phagocytosis. The astrocytes undergo a filamentous hyperplasia during degeneration; they may engulf some degenerating terminals, and contribute to the formation of gliosis. The phagocytic glial cells proliferate during the degenerative process, and actively phagocytose both the dense terminals and the degenerating myelinated axons.

Terminal degeneration and glial reactions in the lateral geniculate nucleus of the squirrel monkey after eye removal.

1Visual responses were recorded from neurones in the magnocellular and parvocellular layers of the lateral geniculate nucleus (LGN) of the thalamus in two species of New World monkeys – the diurnal squirrel monkey (Saimiri sciureus) and the nocturnal owl monkey (Aotus trivirgatis). Recording sites were reconstructed in postmortem tissue and comparisons were made between the response properties of magnocellular and parvocellular neurones.
2Receptive fields were characterized with both white noise and drifting gratings. We found that most of the differences between magnocellular and parvocellular neurones that have been described in the macaque monkey hold for the squirrel monkey and owl monkey. In squirrel monkey and owl monkey, receptive fields of magnocellular neurones were larger than those of parvocellular neurones at similar eccentricities. Although visual responses in the owl monkey were significantly slower than in the squirrel monkey, in both species magnocellular neurones differed from parvocellular neurones in that their responses (1) had higher contrast gains, (2) tended to peak at higher temporal frequencies (but with considerable overlap), (3) had shorter response latencies, and (4) were more transient.
3The strength of a neurone's receptive-field surround was assessed by comparing neuronal responses to gratings of optimal spatial frequency with responses to gratings of low spatial frequency. Using this approach, receptive-field surrounds were found to be equally strong on average for magnocellular and parvocellular neurones.
4Spatial summation, as measured by a null test, was linear for all magnocellular and parvocellular cells tested; that is, Y cells were not observed in either species. Finally, most magnocellular neurones showed a contrast gain control mechanism, although this was not seen for parvocellular neurones.

Visual physiology of the lateral geniculate nucleus in two species of new world monkey: Saimiri sciureus and Aotus trivirgatis.

The parvocellular portion of the lateral geniculate nucleus (LGN) in the squirrel monkey (Saimiri sciureus) is a relatively unlaminated mass of cells . In order to determine whether a concealed laminar structure might exist, one eye was removed in each of three squirrel monkeys . Transneuronal degeneration did not appear prominent in the LGN of the animal which was allowed to survive for six months, but in the two animals which survived for one year six laminae were clearly present. There was transneuronal degeneration in layers 1, 4 and 6 contralateral to the enucleation, and 2, 3 and 5 ipsilaterally . Lack of interlaminar fiber masses prob- ably accounts for the apparent absence of lamination in the normal parvocellular mass . Lamination is a conspicuous feature of

/pdf/lamination-of-the-lateral-geniculate-nucleus-in-the-squirrel-29svhlx3qb.pdf

Lamination of the lateral geniculate nucleus in the squirrel monkey, Saimiri sciureus

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Robert William Doty

Author Tools

Chat about Author

Papers

Lamination of the lateral geniculate nucleus in the squirrel monkey, Saimiri sciureus