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M F Huerta

Publications and source records attributed to M F Huerta.

30 records · Page 2Linked to original sources
PubMed1983

Studies of the principal sensory and spinal trigeminal nuclei of the rat: projections to the superior colliculus, inferior olive, and cerebellum.

We have analyzed the connections between the sensory trigeminal nuclei and two major sensorimotor areas (i.e., the superior colliculus and crura I and II of the cerebellar cortex) in which tactile input from peri-oral and other facial regions is a prominent feature. Following injections of horseradish peroxidase into the superior colliculus, retrogradely labeled cells occupy the ventral one-third of the contralateral principal sensory and spinal trigeminal nucleus; trigeminocollicular neurons are especially numerous within the subnucleus interpolaris (Svi). Injections of either 3H-proline or horseradish peroxidase (HRP) into the Svi reveal that trigeminocollicular axons reach the rostral two-thirds to three-quarters of the contralateral superior colliculus, where they distribute in a nonuniform, patchy manner within layers IV-VI. In addition to demonstrating the trigeminocollicular projection, anterograde and retrograde transport studies of the Svi also reveal a trigeminoolivary projection which terminates primarily within the contralateral rostral dorsal accessory (DAO) and adjacent principal (PO) olives; some of the Svi neurons innervate both the superior colliculus and the DAO-PO via axon collaterals. Data from a final set of retrograde tracing experiments show that the trigeminorecipient zone of the DAO-PO contains neurons which project to crura I and/or II of the cerebellar cortex. Of the various submodalities conveyed by the trigeminal system, it is likely that the trigeminal connections we have demonstrated are carrying tactile information. This is indicated by the fact that responses to tactile stimulation of the face have been reported for cells in (1) the deeper collicular layers, (2) the trigeminorecipient zone of the DAO-PO, and (3) cerebellar targets of this zone, crura I and II. All data are discussed in the context of the anatomical and physiological literature.

Afferent Pathways↗
PubMed1983

The geniculostriate projection in the grey squirrel: preliminary autoradiographic data.

Anterograde autoradiographic experiments reveal connectional specificity between the dorsal lateral geniculate (LGN) laminae and striate cortical layers in a rodent, the gray squirrel (Sciurus carolinensis). Our data indicate that although the geniculostriate projection does not segregate right and left eye information within layer IV, geniculate projections to this layer are tightly organized such that particular cortical substrata receive input from specific LGN layer(s). Preliminary data suggest that geniculate layers 1 and 2 of the LGN project to a central zone of layer IV. In contrast, the layer 3 complex projects densely to a dorsal and ventral tier in layer IV, as well as to layer VI and the supragranular laminae. It is speculated that the input to supragranular layers arises from cells within layer 3c. which in turn, have been shown to receive input from the stratum griseum superficiale of the superior colliculus. It is argued that this tecto-geniculo-supragranular cortical pathway might convey W-cell information, as has been suggested for other species.

Animals↗
PubMed1983

Sublamination within the superficial gray layer of the squirrel monkey: an analysis of the tectopulvinar projection using anterograde and retrograde transport methods.

Anterograde and retrograde tracing methods have been used to analyze the cells of origin and the axonal distribution of the tectopulvinar projection in the squirrel monkey. Our most interesting finding is that tectopulvinar neurons occupy a cytoarchitecturally distinct sublamina of the stratum griseum superficiale (SGS) called the lower SGS (SGSL). The distinction between the SGSL and the upper SGS (SGSU) is further indicated by the findings of others that the SGSL receives different amounts of retinal and cortical input compared to the SGSU. Previous physiological studies have also shown that cells in the SGSL possess different response characteristics than those in the SGSU. Differences in cytoarchitecture, afferent and efferent connections, and physiological properties of the SGSL versus the SGSU indicate that sublaminae are the anatomical mechanism which enables different information channels to maintain some degree of autonomy within the SGS, and at the same time use the same topographic map within this layer.

Animals↗
PubMed1983

The projections of the lateral geniculate nucleus of the squirrel monkey: studies of the interlaminar zones and the S layers.

Anterograde and retrograde tracing techniques were used to reveal that axons arising from neurons within the interlaminar zones and the S layers of the lateral geniculate nucleus of the squirrel monkey terminate within the supragranular layers of area 17. Specifically, our data indicate that the axons of the neurons housed within the S layers end in a patchlike fashion in cortical layers IIIa and IIIb, while neurons in the interlaminar zones project primarily to layer I. Both pathways may convey W-cell information from the retina and the superior colliculus to the striate cortex.

Animals↗
PubMed1982

Projections of the superior colliculus to the supraspinal nucleus and the cervical spinal cord gray of the cat.

Anterograde transport experiments reveal two novel findings regarding the distribution of descending tectofugal axons. First, such axons project to the supraspinal nucleus of the caudal medulla; this nucleus is known to project to the upper cervical spinal cord gray. Second, some tectospinal axons ramify within Rexed's lamina IX of the first 5 cervical spinal cord segments. This zone contains motoneurons which innervate neck musculature. Retrograde data reveal that tectospinal neurons occur in clusters within the intermediate and deep gray layers. A close relationship between the clusters of tectospinal neurons and a modular type of connectional organization of the intermediate and deep gray layers is suggested.

Animals↗
PubMed1982

The projection from the nucleus of the posterior commissure to the superior colliculus of the cat: patch-like endings within the intermediate and deep grey layers.

The nucleus of the posterior commissure projects to the intermediate (SGI) and deep (SGP) grey layers of the ipsilateral superior colliculus throughout its rostral-caudal dimension. This projection terminates in a patchy, discontinuous, manner. The patches form a tier in the dorsal half of SGI, and are smaller medially than laterally. These results are discussed in relation to other patchy projections to SGI and in relation to a possible modular organization of the superior colliculus.

Animals↗
PubMed1981

The trigeminocollicular projection in the cat: patch-like endings within the intermediate gray.

We have used two neuroanatomical tracing techniques to study the trigeminocollicular projection in the cat. In one series of experiments we injected [3H]proline into the alaminar division of the spinal trigeminal nucleus and analyzed the distribution and pattern of anterogradely transported label within the superior colliculus. These autoradiographic data reveal that the trigeminocollicular projection: (1) is primarily contralateral; (2) reaches only the rostral 60-70% of the colliculus; and (3) terminates in a discontinuous, patch-like tier within the middle of the dorsal-ventral axis of the stratum griseum intermediale (SGI). The patches of label measure approximately 330 micrometer in the medial-lateral dimension and 250 micrometer in the dorsal-ventral extent. There seems to be an alignment of the patches in the rostral-caudal direction, suggesting that the trigeminal input forms longitudinal columns in the colliculus. Anterogradely transported protein is also present within the stratum griseum profundum (SGP). In contrast to the patch-like pattern present in the SGI, label in the SGP is more diffusely distributed. In a second series of experiments we injected horseradish peroxidase-wheat germ agglutinin (HRP-WGA) into the spinal trigeminal nucleus. While the distribution and pattern of the contralateral trigeminocollicular axons is similar to that in the autoradiographic experiments, patches of anterogradely transported HRP-WGA are also present within the ipsilateral SGI and SGP. Furthermore, the HRP-WGA data reveal groups of retrogradely labeled collicular neurons which lie in intimate association with the patches of anterogradely transported tracer. Our findings are discussed in relation to other collicular afferents which terminate in a patch-like manner within the SGI. We hypothesize that the colliculus contains many vertically oriented modules. Each module consists of tectopetal axon terminals -- arranged in sandwich fashion -- and functionally related collicular (tectofugal) neurons.

Afferent Pathways↗
PubMed1980

Ascending pathways from the monkey superior colliculus: an autoradiographic analysis.

The autoradiographic tracing method has been used to analyze the distribution of ascending tectofugal pathways in the rhesus monkey. Our findings show that axons which arise from deep collicular neurons terminate within several dorsal thalamic nuclei which in turn project upon the frontal eye fields (area 8) and the inferior parietal lobule (area 7). Both of these cortical areas are functionally quite similar to the deep colliculus, and we suggest that ascending channels from the deep tectum must account, at least in part, for these functional similarities. The present autoradiographs reveal projections to several nuclear zones previously not identified as deep collicular targets in the monkey. Such targets include the visceral cell columns of the oculomotor complex, the rostral interstitial nucleus of the medial longitudinal fasciculus, and the magnocellular division of the ventral anterior nucleus. Deep tectal input also has been shown to terminate quite extensively within the paralamellar region of the mediodorsal nucleus and in the parafascicular nucleus; very little input to the central lateral and centromedian nuclei was observed. Radioisotope injections restricted to the superficial layers reveal dense projections to the parabigeminal nucleus, the pretectum, the inferior and lateral pulvinar nuclei, and to the ventral and dorsal lateral geniculate nuclei. Transported protein within the dorsal lateral geniculate nucleus occupied the "S" layers and the interlaminar zones.

Animals↗
PubMed1979

The precise origin of the tectospinal pathway in three common laboratory animals: a study using the horseradish peroxidase method.

The horseradish peroxidase tracing method has been used to study the cells of origin of the tectospinal projections in the opossum, the tree shrew, and the cat. The present data show that only those collicular neurons which occupy the deep (ventral to the stratum opticum) tectal laminae send axons to the cervical spinal cord. In particular, layer IV contains the greatest number of spinal projecting neurons. Our results also reveal that while only the large sized collicular neurons project upon the cervical spinal cord in the opossum and the tree shrew, neurons comprising several different size categories do so in the cat. We thus suggest that several different descending channels exist over which the superior colliculus can influence the neck musculature in the cat.

Animals↗
PubMed1978

Patterns of retinal terminations and laminar organization of the lateral geniculate nucleus of primates.

Autoradiographic tracing procedures have been used to study the organization of retinogeniculate axons in seven primates, i.e., four species of New World monkeys, one species of Old World monkeys and two species of prosimians. These data suggest that the basic primate pattern of geniculate lamination consists of two parvocellular layers, two magnocellular layers, and two poorly developed and highly variable superficial (S) layers which are ventrally located. Ocular input to each member of each of the three pairs differs. In the macaque, the squirrel, and the saki monkey, the parvocellular layers subdivide and interdigitate into four leaflets so as to give the appearance of four parvocellular "layers." These leaflets are much less extensive in the owl and marmoset monkeys. In some individual macaque monkeys, there is further splitting of the parvocellular leaflets into subleaflets, giving the appearance of six parvocellular "layers." The prosimians (galago and slow loris) have two additional layers that are not found in pithecoid primates, and only one superficial layer is apparent. The two additional layers are termed "koniocellular" since they consist of very small cells. Finally, New and Old World monkeys have both ipsilateral and contralateral retinal input to the interlaminar zones. We conclude that the basic pattern of lateral geniculate organization is six layers, but not the traditional six. Prosimians have evolved two additional layers, the koniocellular layers, and have possibly lost one superficial layer. Both New World and Old World monkeys have elaborated the parvocellular layers by forming leaflets to varying extents. With the possible exception of the single S layer in prosimians, layers form pairs that are similar in cell types, but different in ocular input.

Animals↗
PubMedDate not supplied

A variant of the mammalian somatotopic map in a bat.

Two ordered representations of the body surface, S-I and S-II, have been described on the cortical surface of the brains of a variety of mammals; additional separate topographical maps have been found in the somatosensory cortex of the cat and monkey. Except for minor variations in the placement of the body parts, the basic somatotopy of the maps is remarkably consistent across species. As the reasons for this consistency and the minor variations are unclear, we examined the somatotopy of the bat, whose body plan has been modified extensively so that the forelimb can be used for flight. We report here that in both S-I and S-II of the grey-headed flying fox, not only is the representation of the distal forelimb displaced from its usual position on the map, but the digits are directed caudally instead of rostrally as they are in all other mammals studied. The variant somatotopy appears to reflect the postural differences between flying and walking mammals, supporting the notion that topographical maps may have functional significance apart from their point-to-point connections with the sensory periphery.

Animals↗