H. Künzle

Bilateral projections from precentral motor cortex to the putamen and other parts of the basal ganglia. An autoradiographic study inMacaca fascicularis

By tracing radioactively labeled proteins transported by axonal flow, projections from area 4 to the ipsi- and contralateral neostriatum and claustrum were demonstrated in 7 monkeys. A reversed topographic organization was found on both sides for the corticoneostriatal and corticoclaustral projections. The most extensive terminal field could be observed in the putamen. In contrast, very few area 4 efferents seemed to terminate in the caudate nucleus. This suggests differential functions for the two striatal components in sensorimotor mechanisms. These unexpected results give further evidence for the superior sensitivity of the autoradiographic technique, although the limitations of the new method in delineating the injection field were noted.

An autoradiographic analysis of the efferent connections from premotor and adjacent prefrontal regions (Areas 6 and 9) in Macaca fascicularis..

The efferent connections from area 6 and adjacent regions of area 9 were investigated in 9 adult monkeys (Macaca fascicularis) using the autoradiographic technique. Injection fields throughout these regions projected ipsilaterally to area 7 in the parietal lobe, n. caudatus, claustrum, n. ventralis anterior, n. parafascicularis, n. medialis dorsalis, n. reticularis thalami, colliculus superior, griseum centralis, griseum pontis and n. reticularis tegmenti pontis. The dorsolateral and medial aspects of areas 6 and 9 projected to the caudal cingulate gyrus, n. ventralis lateralis pars caudalis and n. interstitialis of Cajal. Axons originating in the ventrolateral cortex of areas 6 and 9 terminated in the orbital cortex. Projections arising from area 6 were traced to area 4, into the ventral bank of the rostral cingulate sulcus, to putamen, n. centralis superior lateralis, area X and its caudal continuation within n. ventralis posterior lateralis pars oralis, to n. ruber pars parvocellularis as well as the bulbar reticular formation. Adjacent prefrontal areas projected to the medial aspect of area 24, to areas 19, 20, 21 and 49/27 and to parts of the lateral thalamic nuclear group. This prefrontal projection pattern was in many respects also seen in cases injected into the dorsolateral portion of area 6, while its medial and ventrolateral subdivisions showed additional projections to n. ventralis medialis, the medial parts of centrum medianum as well as spinal and prorhinal projections, respectively.Furthermore, extensive bilateral connections were found within the frontal lobe, to basal ganglia, n. parafascicularis, n. centralis thalami, n. ruber, griseum pontis, n. reticularis tegmenti pontis, bulbar reticular formation and, more selectively, to colliculus superior and n. medialis dorsalis. Evidence was also presented for direct prefrontal connections to amygdala and corticonigral projections arising from areas 6 and 9. The results are discussed with respect to the intermediate position of area 6 between primary motor and prefrontal cortex as well as to differences of projection patterns within area 6 itself and, in particular, the supplementary motor area.

Projections of the precentral motor cortex and other cortical areas of the frontal lobe to the subthalamic nucleus in the monkey

SummaryCorticofugal projections were examined by means of the autoradiographic tracer method in 21 macaca fascicularis. The labeled material was injected into the main body representation areas of the precentral motor cortex and into various regions of Brodmanns areas 6, 8 and 9 of the frontal lobe. The ipsilateral subthalamic nucleus receives a moderately strong and somato-topically organized projection from Woolseys precentral motor cortex. This projection is mainly restricted to the lateral moiety. The remaining nucleus is occupied by less intensive projections from premotor and prefrontal areas. It is concluded that the subthalamic nucleus is a convergence site of pallidal and corticomotor and frontal projections. Cortical afferents may exert an influence on the pallido-subthalamic-pallidal inhibitory feedback loop.

Projections from the primary somatosensory cortex to basal ganglia and thalamus in the monkey

SummaryRadioactive amino acids were injected into the postcentral cortex (areas 3, 1 and 2) in 6 monkeys (Macaca fascicularis). Fibers were traced to the ipsilateral putamen, to Olszewskis n. ventralis posterior lateralis pars caudalis, n. ventralis posterior medialis and inferior, to n. pulvinaris oralis, n. suprageniculatus and corpus geniculatum mediale pars magnocellularis. Furthermore, there were faint postcentral projections to claustrum, n. caudatus, n. centralis lateralis, n. centrum medianum, zona incerta and with respect to the postcentral face region to n.medialis dorsalis pars multiformis.Discrepancies with earlier findings were discussed and comparison was made between pre- and postcentral target regions.

Projections of precentral and premotor cortex to the red nucleus and other midbrain areas in Macaca fascicularis.

SummaryMidbrain projections from the precentral and premotor cortex were studied autoradiographically in seven macaques. Earlier findings of Kuypers and Lawrence (1967) based on silver impregnated axonal degeneration were largely confirmed and partly extended. Laminar projections into the parvocellular red nucleus were found bilaterally from the somatotopic representation areas of the precentral cortex and three main divisions of premotor cortex (ventral, dorsal, and medial). The heaviest contralateral projection was recorded from the medial hemispheric aspects of area 6 (partly identical with the supplementary motor cortex). Homolateral projections were found from the limb areas of the precentral motor cortex to the magnocellular portion of the red nucleus and direct evidence for the overlap between corticorubral projections and corresponding areas of origin of the rubrospinal tract was obtained. Other projections concerned N. Darkschewitsch, N. Edinger-Westphal, suprarubral and dorsal mesencephalic reticular formation and adjacent lateral periaqueductal grey, substantia nigra, pretectal region, superior colliculus and N. tegmenti pedunculo-pontinus.

Characterization of the pigeon isthmo-tectal pathway by selective uptake and retrograde movement of radioactive compounds and by Golgi-like horseradish peroxidase labeling.

Abstract Autoradiographs of the pigeon optic lobe were prepared after injection of various tritiated amino acids or choline in the optic tectum or in the subtectal nucleus isthmi, pars parvocellularis (Ipc). Horseradish peroxidase (HRP) was also injected into Ipc. A topographically organized reciprocal connection was observed between the tectum and Ipc. The tectal-Ipc pathway had cell bodies lying in sublayer IIi. The acetylcholinesterase staining disappeared topographically in Ipc after tectal lesion. The Ipc-tectal fibers project mainly upon the superficial sublayers IId and IIb. These terminals, filled with HRP, were seen at the electron microscopic level to contain mainly round vesicles and primarily to contact horizontally running structures. In the lateral and caudal part of the tectum the application of [ 3 H]glycine, [ 3 H]serine, [ 3 H]α-alanine or [ 3 H]choline was followed by labelling of the cell bodies in Ipc, while the injection of all the other amino acids tested lead only to neuropil labeling. [ 3 H]Glycine application to the superficial sublayers of the optic tectum was a necessary condition for the appearance of label within Ipc neurons. Rostral tectal injections of [ 3 H]GABA, but not [ 3 H]glycine, resulted in a labeling of rostral-Ipc somata. Glycine injected directly into Ipc was accumulated by neurons while little uptake of GABA or DABA was seen except for a small number of profiles within rostral regions of the nucleus. It is suggested that glycine and GABA, as putative neurotransmitters, are picked up by the Ipc-tectal terminals and that the label is transported retrogradely to the cell bodies. It is further proposed that glycine or a glycine related transmitter is active within portions of the Ipc-tectal pathway while rostrally located neurons of the subtectal nucleus are chemically differentiated and use GABA as their neurotransmitter.

Autoradiographic tracing of the cerebellar projections from the lateral reticular nucleus in the cat

SummaryThe autoradiographic technique was used for tracing the efferent fibers from the lateral reticular nucleus (LRN) in cats. The terminal fields lie within the granular layer of both the ipsi- and the contralateral cerebellar cortex. The projections are symmetrical, but more pronounced on the ipsilateral side. The main portion of LRN projects to lobuli I–V, to the rostral part of lobulus VI, the most caudal part of lobulus VII, to lobulus VIII, as well as to lobulus simplex, the medial parts of the lobulus ansiformis and to the lobulus paramedianus.Medio-laterally arranged bands of dense mossy fiber terminations, directed rostro-caudally, lend support to an organized projection of the lateral reticulocerebellar fibers and further evidence for a division of the cerebellar cortex into longitudinal zones (Voogd et al., 1967, 1969). Evidence for a cerebellar re-representation of the LRN spinal segmental arrangement is not obvious, although it can not be excluded. The fibers to the contralateral side seem to mainly follow the course of the olivo-cerebellar fibers, crossing at brain stem levels. Following the general criteria for the identification of a terminal field, few, if any, fibers can be traced to the cerebellar nuclei and to regions outside the cerebellum.

Differential labeling in neuronal tracing with wheat germ agglutinin

Abstract Special labeling phenomena were observed following the injection of [ 125 I]wheat germ agglutinin (WGA) into the turtle cerebellar cortex and into the eye of turtles and pigeons. In addition to the usual bidirectional labeling WGA was transported transneuronally in anterograde-anterograde and also in anterograde-retrograde direction. Very striking was the finding of two pathways which, in contrast to horseradish peroxidase, essentially failed to be labeled with WGA.

Iontophoretic and Autoradiographic Studies on the Role of Proline in Nervous Transmission

SummaryIontophoretic experiments with the aid of multibarreled micropipettes demonstrate a reversible depressant effect ofl-proline on the spontaneous discharge of Purkinje cells in the cat cerebellar cortex. The failure of a specific interaction with strychnine and bicuculline leads to the conclusion that proline acts neither on receptors for “glycine-like” nor on receptors for “GABA-like” amino acids. Autoradiographic investigations reveal a differential distribution of radioactivity after injection of3H-leucine and3H-proline into the cerebellar cortex. After leucine injection, high grain density can be observed over Stellate, Basket, Golgi and especially Purkinje cells. In contrast after application of3H-proline, the silver grains are concentrated primarily in the tissue adjacent to the Purkinje cells, mainly in the supraganglionic region and between these faintly labelled cerebellar cells. These results suggest the possibility that proline is involved in inhibitory neurotransmission.

Increased projection of ascending dorsal root fibers to vestibular nuclei after hemilabyrinthectomy in the frog

SummaryThe projections from brachial, ascending dorsal root fibers were studied autoradiographically in controls and chronically (four months) hemilabyrinthectomized frogs. Comparison showed that projections into the partially denervated vestibular nuclear complex of chronically hemilabyrinthectomized animals were far more dense than in control animals. In the cerebellar granular layer, no obvious difference in the extent of dorsal root projections was observed between both groups of animals. Cerebellar areas such as the auricular lobe and the dorsal rim, which normally receive many terminals from vestibular but not from dorsal root afferents, were not invaded by dorsal root fibers in chronically hemilabyrinthectomized frogs.