Syosuke Kawamura

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.

The cerebellar projections to the superior colliculus and pretectum in the cat: An autoradiographic and horseradish peroxidase study

Efferent projections from the cerebellar nuclei to the superior colliculus and the pretectum have been studied using both retrograde and orthograde labeling techniques in the cat. In order to identify what parts of the cerebellar nuclei project to the superior colliculus and the pretectum, the retrograde horseradish labeling technique was employed. In another set of experiments, tritiated amino acids were injected into each of the cerebellar regions from which the cerebello-tectal and cerebello-pretectal projections arise, and the laminar and spatial distributions of orthograde labeling in the superior colliculus and the pretectum were compared. The results showed that the cerebello-tectal projections arise from two different regions of the cerebellar nuclei: the caudal half of the medial nucleus and the ventrolateral part of the posterior interposed nucleus. Fibers arising from the medial nucleus distribute bilaterally in the superficial zone of the intermediate gray layer in the superior colliculus, while those originating from the posterior interposed nucleus terminate contralaterally in the deeper aspect of the intermediate gray layer and in the deep gray and white layers. Although the lateral nucleus does not contribute to the cerebello-tectal projection, it projects profusely to the pretectum contralaterally. The origin of the cerebello-pretectal projection lies in the parvicellular part of the lateral nucleus. Among several pretectal nuclei, the posterior pretectal, the medial pretectal nucleus and the reticular part of the anterior pretectal nucleus receive the cerebellar afferents. The findings of the differential projections from the cerebellum to the superior colliculus and the pretectum suggest that the cerebellum exerts a regulatory influence on visuo-motor and somato-motor transfer in these midbrain structures by differential circuits.

Ascending projections from the nucleus of the brachium of the inferior colliculus in the cat.

SummaryAscending projections from the nucleus of the brachium of the inferior colliculus (NBIC) in the cat were studied by the autoradiographic tracing method. Many fibers from the NBIC ascend ipsilaterally in the lateral tegmentum along the medial border of the brachium of the inferior colliculus. At midbrain levels, fibers from the NBIC end in the superior colliculus, the pretectum, the central gray and the peripeduncular tegmental region bilaterally with ipsilateral predominance. NBIC fibers to the superior colliculus are distributed densely to laminae VI an III throughout the whole rostrocaudal extent of the colliculus. In the pretectum, NBIC fibers terminate in the anterior and medial nuclei and the nucleus of the posterior commissure. NBIC fibers to the dorsal thalamus are distributed largely ipsilaterally. Many NBIC fibers end in the dorsal and medial divisions of the medial geniculate body, but few in the ventral division. The NBIC also sends fibers to the suprageniculate, limitans and lateralis posterior nuclei and the lateral portion of the posterior nuclear complex; these regions of termination of NBIC fibers constitute, as a whole, a single NBIC recipient sector. Additionally, the NBIC sends fibers to the centralis lateralis, medialis dorsalis, paraventricular and subparafascicular nuclei of the thalamus.

Topical organization of the extrageniculate visual system in the cat

Abstract Small electrolytic lesions were made in the superior colliculus of cats. The terminal areas of degenerated fibers from the lesions of the medial and lateral part of the superior colliculus were compared in the pretectum and in the pulvinar complex of the thalamus by utilizing the Nauta and Fink-Heimer technique. The medial part of the superior colliculus projects to the rostral and medial portion of the posterior pretectal nucleus, the nucleus of optic tract, and the dorsal half of the pulvinar complex. The lateral part of the superior colliculus projects to the suboptic and posterior pretectal nuclei and the nucleus of optic tract in the lateral pretectum, and to the ventral half of the pulvinar complex. These tectal projections to the pretectum and the pulvinar complex were compared with the terminal areas of the descending fibers from cortical areas 17 and 18. The results indicated that there is a retinotopic organization in the ascending projections from the superior colliculus in the cat.

A ventral lateral geniculate nucleus projection to the dorsal thalamus and the midbrain in the cat

SummaryRetrograde tracing experiments using horseradish peroxidase (HRP) have been utilized for demonstrating the origin of efferent projections of the ventral lateral geniculate nucleus (LGNv) in the cat. HRP-positive cells identifiable as origins of thalamic projections were found in LGNv after injections of HRP into the lateral central intralaminar nucleus. The labeled cells appeared concentrated in the medial part of the internal division of LGNv, consisting of medium-sized multipolar cells. Contralaterally, fewer labeled cells were present in the corresponding part of LGNv. In the case of injections of HRP into the midbrain (pretectum and superior colliculus), labeled cells in LGNv were distributed almost exclusively in its external division, composed of mainly small cells. Little overlap of the distribution of HRP-positive cells was seen in LGNv between the thalamic and midbrain injection cases.

Topographical origin and ganglion cell type of the retino-pulvinar projection in the cat.

In order to examine the pattern of the retino-pulvinar projection in the cat, the existence of which has been recently demonstrated using autoradiographic fiber tracing technique, a small amount of horseradish peroxidase (HRP) was injected into the lateral part of the pulvinar nucleus at various rostocaudal levels. The retrogradely labeled ganglion cells were analyzed in terms of their topographical location and cell size, as seen inretinal whole mounts. The results were compared with those obtained following injections into the lateral geniculate nucleus. Retrogradely labeled cells were found in the retina bilaterally after injections of HRP into the pulvinar nucleus. Pulvinar injections produced labeling of retinal cells in the nasal half of the retina contralaterally, and in the temporal half ipsilaterally. The labeled cells were diffusely distributed in a retinotopically organized fashion. The representation of the area centralis in the retino-pulvinar projection is displaced rostrally as compared with the retino-geniculate projection. All labeled cells after pulvinar injections were medium to small size and no large cells were encountered.

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.

Direct projections to the pretectum and the midbrain reticular formation from auditory relay nuclei in the lower brainstem of the cat

Direct projections to the pretectum and the midbrain reticular formation from auditory relay nuclei in the lower brainstem were examined by the retrograde and anterograde tracer methods in the cat. After horseradish peroxidase (HRP) injection into the pretectomesencephalic reticular region (Pt-MRF), which includes caudoventral regions of the pretectum and rostrodorsal regions of the midbrain reticular formation, labeled neurons were seen in the dorsal nucleus of the lateral lemniscus (DLL), the pericentral (PC) and external (EN) nuclei of the inferior colliculus (IC), the rostral process of IC (RP) and the nucleus of the brachium of IC (NB); no labeled neurons were found in the main laminated portion of the central nucleus of IC. Subsequently, tritiated leucine was injected into DLL, EN, RP or NB for autoradiographic fiber tracing. After injection into DLL or EN, terminal labeling was confined to the ventral portions of the anterior pretectal nucleus. After injection into RP or NB, heavy terminal labeling was observed in the midbrain reticular formation, extending dorsally into the anterior pretectal nucleus. Thus, 3 sectors are distinguishable in Pt-MRF in terms of termination of fibers from the midbrain auditory relay nuclei; the dorsomedial, intermediate or ventrolateral Pt-MRF sector receives fibers arising from DLL, RP or NB, respectively. Fibers from EN terminate only in the dorsal portion (pretectal regions) of the intermediate sector.

Discontinuous spatial distribution of the tectal afferents from the trigeminal nucleus in the cat

Abstract The use of the autoradiographic fiber tracing method demonstrates that the tectal afferents from the sensory trigeminal nucleus in the cat terminate in the intermediate layers of the superior colliculus (SC) forming several discontinuous patches. Patches are found to distribute contralaterally in the whole area of SC with diameters ranging from 50 to 500 μm. These patches resemble other tectal afferents such as from the retina and substantia nigra as recently reported.

Differential projections to the superior collicular layers from the perihypoglossal nuclei in the cat

The primary objective of the present study is to demonstrate the presence of a projection to the superficial layers of the superior colliculus (SC) from the perihypoglossal nuclei, specifically from the nucleus intercalatus (INT) in the cat. Iontophoretic application of WGA-HRP into the perihypoglossal complex produced orthogradely labeled terminals in the SC contralaterally forming two bands: one is in the superficial gray layer, and the other in the intermediate gray layer. The superficial band was evenly distributed in the upper portion of the superficial gray layers (layers II1-2) and the deeper band existed in the intermediate gray layer (layer IV) being arranged in a discontinuous manner. Injections of the tracer into the superficial layers of the SC yielded retrogradely labeled cells only in the rostral part of the contralateral INT; by contrast, the injection confined to the deep layers produced labeling of cells exclusively in the nucleus prepositus hypoglossi (PH). Thus, the INT and the PH each project separately to the functionally different superficial and intermediate layers of the SC, respectively. On the basis of the present anatomical findings, it is suggested that the perihypoglossal nuclei as a whole contribute not only to the oculomotor but also to the visuosensory regulatory function in the SC.