Terminal Accessory Optic Nucleus Research Articles

Projections from visual areas of the cerebral cortex to pretectal nuclear complex, terminal accessory optic nuclei, and superior colliculus in macaque monkey.

The purpose of this study was to analyze the projections from visually related areas of the cerebral cortex of rhesus monkey to subcortical nuclei involved in eye-movement control; i.e., the pretectal nuclear complex, the terminal nuclei of the accessory optic system (AOS), and the superior colliculus (SC). The anterograde tracer 3H-leucine was pressure injected bilaterally into the cortex of six monkeys (for a total of 12 cases) involving the primary visual cortex (area 17); the medial prestriate cortex (medial 18/19); dorsomedial area 19; the caudal portion of the cortex of the superior temporal sulcus, upper bank (cytoarchitectural area OAa) and lower bank (area PGa); the lower bank of the caudal lateral intraparietal sulcus (area POa); and the inferior parietal lobule (area 7). The results revealed that the pretectal nucleus of the optic tract received inputs from medial prestriate cortex, dorsomedial part of area 19, OAa, and PGa. The posterior pretectal nucleus received sparse projections from area 7 and the cortex lining the intraparietal sulcus (dorsomedial part of area 19 and POa). The pretectal olivary nucleus was targeted by neurons in cortex of dorsomedial area 19, and the anterior pretectal nucleus was targeted by neurons in both dorsomedial 19 and area 7. The nuclei of the AOS (dorsal terminal; lateral terminal; and interstitial nuclei of the superior fasciculus, posterior and medial fibers) received projections exclusively from areas OAa and PGa. Furthermore, in one case with PGa injection, the medial terminal nucleus, dorsal portion, was also labeled. The visual cortical areas studied projected differentially upon the SC laminae. The primary visual area 17 projected only to the superficial laminae, i.e., stratum zonale (SZ), stratum griseum superficiale (SGS), and stratum opticum (SO). On the other hand, the medial portion of the prestriate cortex and caudal OAa and PGa targeted the superficial and intermediate laminae, i.e., SZ, SGS, SO, and stratum griseum intermediale (SGI), whereas caudal area POa projected primarily to the intermediate layer SGI. Rostral area 7 (mainly 7b) neurons terminated in the stratum album intermediale (SAI); no SC terminals were found in a case in which caudal area 7 (mainly 7a) was injected.

Projections of the lateral terminal accessory optic nucleus of the common marmoset (Callithrix jacchus)

The connections of the lateral terminal nucleus (LTN) of the accessory optic system (AOS) of the marmoset monkey were studied with anterograde 3H-amino acid light autoradiography and horseradish peroxidase retrograde labeling techniques. Results show a first and largest LTN projection to the pretectal and AOS nuclei including the ipsilateral nucleus of the optic tract, dorsal terminal nucleus, and interstitial nucleus of the superior fasciculus (posterior fibers); smaller contralateral projections are to the olivary pretectal nucleus, dorsal terminal nucleus, and LTN. A second, major bundle produces moderate-to-heavy labeling in all ipsilateral, accessory oculomotor nuclei (nucleus of posterior commissure, interstitial nucleus of Cajal, nucleus of Darkschewitsch) and nucleus of Bechterew; some of the fibers are distributed above the caudal oculomotor complex within the supraoculomotor periaqueductal gray. A third projection is ipsilateral to the pontine and mesencephalic reticular formations, nucleus reticularis tegmenti pontis and basilar pontine complex (dorsolateral nucleus only), dorsal parts of the medial terminal accessory optic nucleus, ventral tegmental area of Tsai, and rostral interstitial nucleus of the medial longitudinal fasciculus. Lastly, there are two long descending bundles: (1) one travels within the medial longitudinal fasciculus to terminate in the dorsal cap (ipsilateral >> contralateral) and medial accessory olive (ipsilateral only) of the inferior olivary complex. (2) The second soon splits, sending axons within the ipsilateral and contralateral brachium conjunctivum and is distributed to the superior and medial vestibular nuclei. The present findings are in general agreement with the documented connections of LTN with brainstem oculomotor centers in other species. In addition, there are unique connections in marmoset monkey that may have developed to serve the more complex oculomotor behavior of nonhuman primates.

GABAergic and non-GABAergic projections of accessory optic nuclei, including the visual tegmental relay zone, to the nucleus of the optic tract and dorsal terminal accessory optic nucleus in rat.

This study examines the non-gamma-amino butyric acid (GABA)ergic (group I neurons) and GABAergic neurons (group II neurons) of the accessory optic system projecting to the nucleus of the optic tract (NOT)/dorsal terminal nucleus (DTN) of the accessory optic system in rat. These nuclei include the dorsal (MTNd) and ventral (MTNv) divisions of the medial terminal nucleus, the lateral terminal nucleus, the interstitial nucleus of the superior fasciculus, the posterior fibers, and the visual tegmental relay zone. GABAergic neurons of these nuclei that do not target the NOT/DTN (group III neurons) have also been observed. The fluorescent retrograde tracer fluoro-gold was injected into the pretectum, targeting the NOT/DTN and the tissue prepared immunocytochemically to reveal neurons containing the neurotransmitter GABA. Three groups of neurons (groups I, II, and III neurons) were examined in terms of their distribution, density, and percentage present. Group I neurons are single-labeled with fluoro-gold and represent non-GABAergic neurons projecting to the NOT/DTN. These neurons are of the highest density in the lateral terminal nucleus (204 neurons/mm2). Their densities are also substantial in the MTNv (120 neurons/mm2), interstitial nucleus of the superior fasciculus, posterior fibers (96 neurons/mm2), and visual tegmental relay zone (93 neurons/mm2). Group II neurons are double-labeled with fluoro-gold and GABA. They form a system of GABAergic neurons projecting to the NOT/DTN, which are exceedingly dense in the MTNd (78 neurons/mm2) but are also dense in both the visual tegmental relay zone (49 neurons/mm2) and MTNv (33 neurons/mm2). Group III neurons are GABAergic neurons that do not target the NOT/DTN but must project to other brain nuclei and/or be interneurons. These are of extremely high concentration in the visual tegmental relay zone (316 neurons/mm2) and are also of substantial densities in the MTNd (77 neurons/mm2), lateral terminal nucleus (72 neurons/mm2), and MTNv (44 neurons/mm2). The MTNd has the highest percentage of GABAergic neurons projecting to the NOT/DTN (72%). GABAergic neurons also form significant percentages of the projections to the NOT/DTN from the visual tegmental relay zone (34%) and MTNv (21%). The percentage of the total GABAergic neurons that project to the NOT/DTN is the highest in the MTNd (50%) and MTNv (42%). The described GABAergic afferents to the NOT/DTN may function to process information concerned with the compensation for retinal slip.

Correlation between amount of retinal afferents to the pretectal nucleus of the optic tract and dorsal terminal accessory optic nucleus and performance of horizontal optokinetic reflex in rat

Intraocular kainic acid injection in Long-Evans rats induces loss of retinal afferents to subcortical visual centers as assessed by the axoplasmic transport of [14C]valine. The optical terminal fields of the pretectal nucleus of the optic tract (NOT), superior colliculus and accessory optic system (AOS) nuclei appear particularly affected. Since NOT and the AOS dorsal terminal nucleus (DTN) represent the first relay station of the visuomotor pathway mediating horizontal optokinetic nystagmus (HOKR), we have studied the characteristics of HOKR after various degrees of retinal deafferentation of these nuclei induced by intraocular KA injection. Taking advantage of the arrangement of the primary optic projections to NOT-DTN, that in rats are almost entirely crossed, in each animal, monocular HOKR induced by stimulation of the injected eye was compared to monocular HOKR elicited by stimulation of the intact, ipsilateral eye. Following NOT-DTN optic denervation, HOKR gain always worsened, and in a way, that the greater the deficits of retinal afferents, the greater the HOKR inability to compensate for visual motion. Furthermore, for any given retinal denervation the higher the stimulus velocity, the greater the HOKR deficit. While the correlation between HOKR gain and the amount of retinal afferents to NOT-DTN would seem to indicate a functional homogeneity of the retinal ganglion cells sending axons to these nuclei, the finding that the extent of HOKR impairment also varied with velocity might not support the above view.

Preoccipital cortex receives a differential input from the frontal eye field and projects to the pretectal olivary nucleus and other visuomotor-related structures in the rhesus monkey

The bidirectional axonal transport capabilities of the horseradish peroxidase (HRP) technique facilitated the study of the frontal-eye-field (FEF) input and pretectal output of two regions of extrastriate preoccipital cortex (POC). Following horseradish peroxidase (HRP) gel implants into the middle and dorsal POC in two rhesus monkeys, the middle POC implant demonstrated retrograde frontal cortical labeling largely restricted to the inferior frontal eye field (iFEF) and adjacent inferior prefrontal convexity, whereas the dorsal POC implant showed labeling in the caudal ventral bank of the superior ramus of the arcuate sulcus (sas) and middle-to-dorsal region of the rostral bank of the concavity of the arcuate sulcus (dorsal FEF). Prominent anterogradely labeled efferent preoccipital projections were observed to the ipsilateral pretectal olivary nucleus (PON) and to a lesser extent the anterior pretectal nucleus. Although the middle POC case had heavier projections to the lateral PON, the dorsal case projected more heavily to the medial PON. In addition, both implants demonstrated subcortical connections with the lateral and dorsal inferior pulvinar nuclei, central superior lateral thalamic intralaminar nucleus, caudate nucleus, and middle-to-ventral claustrum. However, while the middle POC implant had efferent projections to the superficial superior colliculus (SC), pregeniculate nucleus (PGN), lateral terminal accessory optic nucleus (LTN), and dorsolateral pontine nucleus (DLPN), resembling those previously reported for the middle temporal (MT) visual area (Maunsell & Van Essen, 1982; Ungerleider et al., 1984), the dorsal implant had projections to the lateral intermediate SC, zona incerta (ZI), PGN, a notably lesser projection to the LTN, and basilar pontine projections to the lateral and lateral dorsal pontine subnuclei (not including the extreme dorsolateral DLPN). These preliminary results suggest that the preoccipital cortex, which reportedly functions in pupillary constriction, accommodation, and convergence, entertains connections with the PON and other visuomotor-related structures, and thus could act as an intermediary in the pathway between the iFEF and PON, and provide a possible explanation for pupillary effects that occur with stimulation of the FEF (Jampel, 1960) and within the contex of other oculomotor activities. The findings shed light on certain differences in connections of middle vs. dorsal POC with visuomotor-related nuclei, and appear to suggest that the middle region, which receives input from the iFEF, has greater access to the optokinetic (OKN) system by virtue of its projection to the LTN, and to the smooth-pursuit system b

Correlation between retinal afferent distribution, neuronal size, and functional activity in the guinea pig medial terminal accessory optic nucleus

The intrinsic morpho-functional organization of the medial terminal nucleus of the accessory optic system was investigated in the guinea pig. The distribution of the retinal afferents, as assessed by the axoplasmic transport of 14C-valine, showed a remarkable asymmetry within the nucleus. Thus, while the retinal terminal field covered the entire medial terminal nucleus, by far the largest density of labeled retinofugal axon terminals was found within its dorsal division. In this same portion of the nucleus, we found the greatest density of large cells and the maximum intensity of functional activation, this latter as estimated by the increase in metabolic activity of neurons using the 14C-2-deoxyglucose autoradiographic method in the vertical and horizontal whole-field movement in the visual field.

Ultrastructural organization of the retino‐pretecto‐olivary pathway in the rabbit: A combined WGA‐HRP tracing and gaba immunocytochemical study

The ultrastructural organization of the pretecto-olivary projection neurons within the nucleus of the optic tract and dorsal terminal accessory optic nucleus of rabbits was studied by using anti-GABA immunolabelling and retrograde transport of WGA-HRP. GABA-like immunoreactivity was determined with a postembedding colloidal gold technique. WGA-HRP was injected in the dorsal cap of the inferior olive. The WGA-HRP-labelled neurons were incubated with gold-substituted silver peroxidase. Neurons projecting to the inferior olive had large to medium-sized cell bodies and were GABA negative. In the nucleus of the optic tract, projection neurons are found in the rostral parts, while the majority of the local GABAergic interneurons are mainly found in the caudal parts. In the dorsal terminal nucleus both types of neurons are intermingled. The projection neurons were frequently in synaptic contact by GABAergic terminals. These neurons also receive retinal afferents indicating the existence of a two-step synaptic connection from the retina to the inferior olive. It is suggested that this class of projection neurons forms the "direction-selective" neurons that can be antidromically stimulated from the inferior olive. The GABAergic terminals on the identified projection neurons are of axonal origin (F-terminals), whereas presynaptic dendrites of interneurons (P-terminals) were seldom observed to be in synaptic contact with retrogradely labelled profiles. The strong input of GABA on direction-selective neurons indicates that GABA is directly involved in modulating retinal signals to the inferior olive.

Neurons of the medial terminal accessory optic nucleus of the rat are poorly collateralized

The vast majority of neurons of the rat medial terminal nucleus (MTN) project to the nucleus of the optic tract (NOT), but the MTN also projects to a lesser degree upon a number of other brainstem nuclei controlling optokinetic nystagmus. Because of the diversity of targets of the MTN, it is possible that individual neurons have branched axons that project to two or more brainstem nuclei. The possibility that axons of MTN-NOT neurons collateralize to innervate other MTN targets is examined in the rat with the fluorescent, double-labeling, retrograde tracer technique. Fluoro-Gold was injected into the NOT while Fast Blue was simultaneously injected into each of five other known targets of the MTN: the supraoculomotor-periaqueductal gray; the dorsal cap of the inferior olive; the visual tegmental relay zone; the dorsolateral nucleus of the basal pons; and the superior/lateral vestibular nuclei. Brainstem sections were processed for fluorescence microscopy and the MTN was examined for single- and double-labeled neurons. Results show that virtually all neurons of the MTN (greater than 97.5%), together with neurons in the visual tegmental relay zone immediately surrounding the MTNd, are single-labeled in all paired injections involving the NOT and the other target nuclei. It was found that about 69% of MTN neurons project exclusively to the NOT, 5-10% project to each one of the other nuclei, and 3% of MTN neurons project to more than one target. Based upon cell counts from the fluorescent material, and previous analysis of Nissl-stained serial sections, the findings show that virtually all MTN neurons are projection neurons. It was concluded that the MTN is comprised of independent projection systems, possibly involved in different aspects of generating optokinetic nystagmus.

Nonretinal projections to the medial terminal accessory optic nucleus in rabbit and rat: a retrograde and anterograde transport study.

The distribution and density of the nonretinal projections to the rabbit medial terminal accessory optic nucleus (MTN) have been studied after injections of horseradish peroxidase (HRP) into the MTN in seven rabbits, and confirmation for the presence of certain of these projections has been made in the rabbit or rat by utilizing anterograde transport of tritiated leucine or leucine/proline after appropriate injections into cerebral cortical areas and brainstem nuclei. In seven cases studied by the retrograde axonal transport method, HRP-labeled neurons have been identified: (A) In four visual or preoculomotor nuclei in which available autoradiographic brain series have confirmed the presence of projections to the MTN: (1) The nucleus of the optic tract/dorsal terminal accessory optic nucleus, (2) the interstitial nucleus of the superior fasciculus (posterior fibers), (3) the periaqueductal gray (including its supraoculomotor portion), and (4) the medial division of the deep mesencephalic nucleus. (B) Within the ventral lateral geniculate nucleus, from which a projection to the MTN has been confirmed autoradiographically in the rat by other workers. (C) In brainstem nuclei and cerebral cortical areas in which available autoradiographic brain series fail to confirm the presence of afferents to the MTN: (1) The nucleus reticularis pontis, pars oralis and pars caudalis, (2) the intermediate interstitial nucleus of the medial longitudinal fasciculus, (3) the nucleus raphe pontis, and (4) five cerebral cortical areas (the area retrosplenialis granularis dorsalis, the striate area, the parietal area 3, the subicular cortex, and the regio praecentralis granularis). Finally, we report retrograde labeling which, on the basis of published connectional data, we believe to result from the spread to and uptake from axons en passant. The false-positive labeling in this category is likely to result from spread of HRP into ventral tegmental nuclei or tracts adjacent to the MTN. Thus, as a result, in the medulla and pons, labeled neurons are found in the medial, lateral, and superior vestibular nuclei, the medullary reticular formation including the nucleus reticularis gigantocellularis, the lateral reticular nucleus, the nucleus raphe magnus, the spinal nucleus of V, the nucleus gracilis/nucleus cuneatus, the dorsal and ventral divisions of the parabrachial nucleus, the central pontine gray, the nucleus K of Meessen and Olszewski, and the dorsal nucleus of the lateral lemniscus.(ABSTRACT TRUNCATED AT 400 WORDS)

GABAergic neurons comprise a major cell type in rodent visual relay nuclei: an immunocytochemical study of pretectal and accessory optic nuclei.

The enzyme glutamic acid decarboxylase (GAD) has been localized in sections of rodent brains (gerbil, rat) using conventional immunocytochemical techniques. Our findings demonstrate that large numbers of GAD-positive neurons and axon terminals (puncta) are present in the visual relay nuclei of the pretectum and the accessory optic system. The areas of highest density of these neurons are in the nucleus of the optic tract (NOT) of the pretectum, the dorsal and lateral terminal accessory optic nuclei (DTN, LTN), the ventral and dorsal subdivisions of the medial terminal accessory optic nucleus (MTNv, MTNd), and the interstitial nucleus of the posterior fibers of the superior fasciculus (inSFp). The findings indicate that 27% of the NOT neurons are GAD-positive and that these neurons are distributed over all of the NOT except the most superficial portion of the NOT caudally. The GAD-positive neurons of the NOT are statistically smaller (65.9 microns2) than the total population of neurons of the NOT (84.3 microns2) but are otherwise indistinguishable in shape from the total neuron population. The other visual relay nuclei that have been analyzed (DTN, LTN, MTNv, MTNd, inSFp) are similar in that from 21% to 31% of their neurons are GAD-positive; these neurons are smaller in diameter and are more spherical than the total populations of neurons. The data further show that a large proportion of the neurons in these visual relay nuclei are contacted by GAD-positive axon terminals. It is estimated that approximately one-half of the neurons of the NOT and the terminal accessory optic nuclei receive a strong GABAergic input and have been called "GAD-recipient neurons". Further, the morphology of the GAD-positive neurons combined with their similar distribution to the GAD-recipient neurons suggest that many of these neurons are acting as GABAergic, local circuit neurons. On the other hand, the large number of GAD-positive neurons in the NOT and MTN (20-30%) in relation to estimates of projection neurons (75%) presents the possibility that some may in fact be projection neurons. The overall findings provide morphological evidence which supports the general conclusion that GABAergic neurons play a significant role in modulating the output of the visually related NOT and terminal accessory optic nuclei.

Projections of medial terminal accessory optic nucleus, ventral tegmental nuclei, and substantia nigra of rabbit and rat as studied by retrograde axonal transport of horseradish peroxidase.

Projections of the medial terminal nucleus (MTN) of the accessory optic system, the ventral tegmental area of Tsai, and the substantia nigra of the rabbit and the rat have been studied by the method of retrograde axonal transport of horseradish peroxidase. The data show that MTN projections are remarkably similar in the rabbit and rat. The MTN projects heavily to the ipsilateral nucleus of the optic tract and dorsal terminal nucleus of the accessory optic system and to a portion of the contralateral ventral tegmental area of Tsai that we have termed the visual tegmental relay zone (VTRZ). Further, the MTN sends projections to the ipsilateral mesencephalic (deep mesencephalic nucleus, pars medialis) and pontine (nucleus reticularis pontis oralis) reticular formations; the contralateral dorsolateral division of the basal pontine complex; the superior and lateral vestibular nuclei (contralateral in rat; bilateral in rabbit); and the ipsi- and contralateral interstitial nucleus of Cajal, nucleus of Darkschewitsch, and supraoculomotor-periaqueductal gray. The findings also indicate that the MTN has a small bilateral, but mainly ipsilateral, projection to the dorsal cap, its ventrolateral outgrowth, and the B division of the inferior olivary complex. This study further reveals that ventral tegmental nuclei (n. parabrachialis pigmentosus and n. paranigralis) and subdivisions of the substantia nigra (pars compacta and pars reticulata) project to many brain stem targets of the MTN. Thus, the VTRZ projections are similar to those of the MTN in both distribution and density except that the VTRZ projection to the inferior olive is substantially stronger. The nucleus parabrachialis pigmentosus sends a small contralateral projection to the VTRZ and a moderate-sized bilateral projection to the supraoculomotor-periaqueductal gray. The nucleus paranigralis sends a moderate number of axons to the ipsilateral deep mesencephalic nucleus, pars medialis, and the nucleus reticularis pontis oralis and provides a strong bilateral projection to the supraoculomotor-periaqueductal gray. The pars compacta of the substantia nigra provides a sparse input to the ipsilateral deep mesencephalic nucleus, pars medialis, and nucleus reticularis pontis oralis, and to the contralateral VTRZ and sends a moderate number of axons, bilaterally, to the supraoculomotor-periaqueductal gray. The pars reticulata of the substantia nigra sends an ipsiateral projection of moderate size to the intermediate and deep layers of the superior colliculus, sparse ipsilateral projections to the deep mesencephalic nucleus, pars medialis, and nucleus reticularis pontis oralis, and a sparse bilateral projection to

Cortical visual areas of the cat project differentially onto the nuclei of the accessory optic system

Cortical projections to the nuclei of the cat's accessory optic system were demonstrated by anterograde transport and degeneration methods. Areas 21a, 21b, AMLS and PMLS were found to project to the medial, lateral and dorsal terminal accessory optic nuclei. Selective projections from area PLLS to the lateral terminal nucleus and from areas 17 and 18 to the medial terminal nucleus were noted. No terminal labeling was detected following injections of areas ALLS, DLS, 20a, 20b, 19, 7 or the splenial visual area. The accessory optic system has been implicated in the control of optokinetic nystagmus. Additional evidence supports a role for ipsilateral visual cortical projections in mediating optokinetic pursuit in the naso-temporal direction under monocular conditions 16, 55. Thus the visual cortical projections we describe may partially underlie the observed functional laterality of monocularly elicited optokinetic pursuit in the cat. The present results further indicate that suprasylvian areas AMLS, PMLS and 21 are the cortical regions primarily responsible for descending visual influences on the cat's accessory optic nuclei.

The accessory optic fiber system of the golden hamster with special reference to retinohypothalamic projection.

The hamster accessory optic fiber system has been investigated with the use of de Olmos-Ingram and Fink-Heimer silver methods following the production of unilateral ocular enucleation. It was found that this fiber system consists of both crossed and uncrossed inferior and superior fasciculi. The fibers of the inferior fasciculus (anterior accessory optic tract) run along the medial edge of the cerebral peduncle and terminate within the medial terminal nucleus of the accessory optic system. The fibers of the superior fasciculus (posterior accessory optic tract) leave the main optic tract, pass superficially over the medial geniculate nucleus and the cerebral peduncle; they synapse within the dorsal, the lateral and the medial terminal accessory optic nuclei. The presence of a retinohypothalamic tract could not be confirmed.

The primary optic projections in pigmented and albino guinea pigs: an experimental degeneration study

Summary An eye was enucleated in each of 6 pigmented and 6 albino guinea pigs. Six to 8 days later the animals were killed and their brains were prepared by the Nauta and Nissl methods in order to study the course and terminal distribution of the degenerating optic fibers. Several major differences were demonstrated between the pigmented and albino guinea pigs in the terminal distribution of the crossed and uncrossed optic fibers. First, it was shown that in the pigmented animals the ventral and dorsal lateral geniculate nuclei, the nucleus tractus opticus, the nuclei praetectalis anterior and posterior, and the superior colliculus all receive inputs from both retinae; whereas in the albino animals these same nuclei could be found to receive organized inputs only from the contralateral retina. Second, it was found that the pattern of the contralateral retinal input to the ventral and dorsal lateral geniculate nuclei, but not to the pretectal nuclei, the superior colliculus and the terminal accessory optic nuclei, differs between the two strains of animals. In both the pigmented and albino guinea pigs it was shown that the accessory optic system is composed entirely of crossed optic fibers and consists of two fiber groups (inferior and superior fasciculi) and 3 terminal nuclei (dorsal, lateral and medial terminal nuclei). It was also shown that in both strains of animals the degenerating optic fibers that lie in and adjacent to the ventral and dorsal lateral geniculate nuclei and the pretectal nuclei course within two distinct fiber systems oriented perpendicularly to each other.