Kahee Niimi

Thalamocortical organization of the auditory system in the cat studied by retrograde axonal transport of horseradish peroxidase.

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Thalamic afferents to the limbic cortex in the cat studied with the method of retrograde axonal transport of horseradish peroxidase

Thalamic afferents to the limbic cortex in the cat were studied with the method of retrograde axonal transport of horseradish peroxidase. The anterior limbic region receives fibers largely from the anteromedial nucleus and partly from the anterodorsal and anteroventral nuclei. There appears to be a dorsoventral organization of cortical projections of the anteromedial nucleus to the anterior limbic region. The cingular area has its main input from the anteroventral and anteromedial nuclei. The lower bank and fundus of the splenial sulcus receive fibers from the anteroventral nucleus, particularly its parvocellular part. The retrosplenial area receives projections from the naterodorsal, anteroventral and anteromedial nuclei. The agranular retrosplenial area (area 30) recieves hardly any fibers from the anterior thalamic nuclei. The postsubicular and presubicular areas receive cortical afferents from the anterodorsal, anteroventral (both magnocellular and parvocellular parts) and anteromedial nuclei. In addition, the limbic cortex receives many fibers from the dorsal lateral, medial pulvinar and lateral pulvinar nuclei, and few fibers from the intralaminar and midline nuclei.

Efferent projections of the head of the caudate nucleus in the cat

Summary The axon degeneration resulting from variously located stereotaxic lesions of the head of the caudate nucleus was studied in the cat by the Nauta-Gygax method. 1. Efferents from the head of the caudate nucleus pass through the globus pallidus and the adjacent portion of the internal capsule. During their course in the globus pallidus many fibers terminate in its medial part and in some cases also in the lateral part. There is a mediolateral organization in the caudatopallidal projections. These projections are also organized in the dorsoventral and probably in the antero-posterior direction. No evidence was found of caudatal efferents ending in the putamen. 2. Fibers having passed through the globus pallidus, together with those directly from the head of the caudate nucleus, descend into the cerebral peduncle to end in the ventromedial portion of the pars reticulata of the substantia nigra at levels rostral to the middle of the superior colliculus. A topical organization of the caudatonigral projections appears to exist in the mediolateral direction, but not in the antero-posterior direction. 3. The dorsolateral part of the head of the caudate nucleus sends fibers to the entopeduncular nucleus. 4. The head of the caudate nucleus projects no fibers to the diffusely projecting thalamic nuclei, the subthalamic nucleus, the red nucleus, the reticular formation of the midbrain or the pontine nuclei.

Cortical Projections of the Pulvinar Nuclear Group of the Thalamus in the Cat; pp. 422–439

Localized stereotaxic lesions wereplaced in the pulvinar nuclear group of the cat thalamus, and the ensuing fiber degeneration was traced to the cerebral cortex by the method of Nauta and Gygax. The m

Cortical projections of the medial geniculate body in the cat

SummaryUnilateral stereotaxic lesions were placed in the medial geniculate body (MGB) in 13 cats, and the ensuing axon degeneration was traced to the cerebral cortex by the method of Nauta and Gygax (1954). The anterior and middle portions of the principal part have heavy projections to the middle ectosylvian gyrus (AI), the lateral bank of the middle suprasylvian sulcus (SF), and the most dorsal parts of the sylvian and the anterior ectosylvian gyri (AII) in an orderly manner anteroposteriorly and dorsoventrally. They also send fibers to the dorsal part of the anterior sylvian gyrus, insular area. The posterior portion of the principal part projects fibers massively to the dorsal part of the posterior ectosylvian gyrus (Ep) and the adjoining part of AI. These projections appear to be organized in both anteroposterior and dorsoventral dimensions. The posterior portion gives off a fair number of fibers to limited caudal parts of AII and of the posterior sylvian gyrus. In addition, the principal part of MGB tends to project sporadic fibers diffusely to AI, AII, Ep, SF and the dorsal part of the insulotemporal region. The magnocelJular part of MGB sends marked projections to AII and the adjacent part of AI in a topical manner in the anteroposterior dimension. Its major portion projects fibers to the insular area. The magnocellular part tends to send scattered fibers to the cortex more extensively toward the temporal pole and the sensory areas than does the principal part.

Thalamic Afferents to the Visual Cortex in the Cat Studied by Retrograde Axonal Transport of Horseradish Peroxidase; pp. 114–126

Thalamic projections to visual areas 17, 18 and 19, neighboring suprasylvian cortex have been studied using the HRP method. Area 17 receives fibers mostly from the main laminae of the dorsal lateral geniculate nucleus (GLd). Area 18 receives inputs mainly from the central and medial interlaminar nuclei (NIC, NIM), and partly from laminae of GLd. Area 19 receives fibers principally from lamina B (C1-C2) and NIM of GLd. In addition, areas 17, 18 and 19 receive a few fibers from extrageniculate thalamic nuclei, particularly the pulvinar and intralaminar nuclei.

Counterstaining of Nauta-Gygax Impregnated Sections with Cresyl Violet

Frozen sections of formalin-fixed brains are impregnated according to the Nauta-Gygax method. After treatment in a 1% Na2S2O3 solution, the sections are washed thoroughly, then bleached for 10–20 sec in a solution prepared by diluting 1 part of a stock solution consisting of: borax, 2 gm; potassium ferricyanide, 2.5 gm; distilled water, 100 ml, with 4 parts of distilled water, washed well, transferred to 1% Na2S2O3, and washed again. The loose sections are placed in Carnoys 6:3:1 fluid for 5 min, then floated onto glass slides which have been coated with 1:1 albumen-glycerol, and drained and dried at room temperature. The bleached sections affixed to the slides are stained 30 min in 0.1% cresyl violet adjusted to pH 3.6–3.8 by adding 10% acetic acid. The sections are differentiated and dehydrated in ascending grades of alcohol and cleared in 2 changes of xylene, and then covered in balsam.

Projections of the medial geniculate nucleus to layer 1 of the auditory cortex in the cat traced with horseradish peroxidase

Thalamic afferents to layer 1 of the auditory cortex in the cat have been studied using retrograde axonal transport of horseradish peroxidase. The magnocellular part of the medial geniculate nucleus sends fibers to layer 1 of the primary and secondary auditory areas and of the dorsal division of the posterior ectosylvian area. The dorsal principal part and the ventromedial portion of the ventral principal part send only a few fibers to layer 1 of these cortical areas.

The laminar arrangement of limbic thalamocortical neurons in the lateropulvinar nuclei of the cat thalamus.

The topical organization of limbic cortical projections of the lateropulvinar nuclei of the thalamus in the cat was studied with the horseradish peroxidase (HRP) technique. The dorsal margins of the dorsal lateral, medial pulvinar and lateral pulvinar nuclei project to the postsubicular and presubicular areas (presubiculum in a wide sense), the most dorsal parts of these nuclei projecting to the retrosplenial area, and the dorsal parts to the cingular area. These three zones of limbic thalamocortical neurons in the lateropulvinar nuclei are arranged in lamination from the surface inward, and may be called presubicular, retrosplenial and cingular zones.

Thalamic projections to the hippocampal formation in the cat

The thalamo-hippocampal projections in the cat were studied by anterograde and retrograde tracing methods. Injections of horseradish peroxidase (HRP) into the hippocampus and dentate gyrus led to retrograde labeling of cells in the nucleus reuniens of the ipsilateral thalamus throughout almost its entire anteroposterior extent. The labeled cells were found mostly in the parvocellular ventral part, but a few cells were labeled in the dorsal part at anterior levels. Anterograde transport following injections of wheat germ agglutinin conjugated to HRP into the nucleus reuniens resulted in terminal labeling in the subicular area, the neighboring parts of the hippocampus (CA1) and the border zone of the dentate gyrus with the hippocampus.