During the first 2 weeks of postnatal development, numerous GATA3-expressing cells were found in the intergeniculate leaf, ventral lateral geniculate nucleus, pretectal nucleus, nucleus of the posterior commissure, superior colliculus, inferior colliculus, periaqueductal grey, substantia nigra and raphe nuclei.
In both postnatal and adult brains, ERRbeta immunoreactive fibers were distributed in a pattern which perfectly matched the retinal efferent projections: optic tract, supraoptic commissure, hypothalamic suprachiasmatic nucleus, ventral and dorsal geniculate nuclei, pretectal nuclei, and superior colliculus.
It is now common knowledge that the total surgical section of the corpus callosum (CC) and of the other forebrain commissures prevents interhemispheric transfer (IT) of a host of mental functions. We tested the possibility that the residual IT is mediated by the collicular commissure interconnecting the two sides of the superior colliculus (SC).
Thus, the highest density of cell bodies containing d-glutamate was observed in the dorsal raphe nucleus, the ventral part of the mesencephalic central gray, the superior colliculus, above the posterior commissure, and in the subparafascicular thalamic nucleus.
The main areas shown to project to the optic tectum were the following: the caudoventral part of the medial pallium, the area of the ventral thalamus and dorsal thalamus, the nucleus of the posterior commissure, the torus semicircularis, the mesencephalic M5 nucleus of Schober, the mesencephalic reticular area, the ishtmic area, and the octavolateral nuclei.
Following tectal injections, backfilled diencephalic cells were found bilaterally in: prethalamic eminence, ventral geniculate nucleus, periventricular prethalamic nucleus, periventricular pretectal nucleus, precommissural nucleus, magnocellular and parvocellular nuclei of the posterior commissure and pretectal nucleus; and ipsilaterally in: nucleus of Bellonci, periventricular thalamic nucleus, nucleus of the tuberculum posterior, and the subpretectal tegmentum, as well as in the pineal organ.
The subcommissural organ (SCO) is an ependymal differentiation located in the dorsal midline of the caudal diencephalon under the posterior commissure.
The development of the corpus callosum (CC) and the anterior commissure (CA) is well known in a wide variety of species. No study, however, has described the development of the commissure of the superior colliculus (CSC) from embryonic state to adulthood in mammals. In this study, by using the lipophylic tracer DiI, we investigated the ontogeny of this mesencephalic commissure in the hamster at various ages.
The region of interest was located just lateral to the posterior commissure and extended caudally to the level of the superior colliculus.
These structures included the neocortex, hippocampus, amygdala, olfactory bulbs, basal forebrain and septum, caudate-putamen, globus pallidus, thalamus, hypothalamus, central gray, superior colliculi, inferior colliculi, the rest of midbrain, cerebellum, brainstem, corpus callosum/external capsule, internal capsule, anterior commissure, fimbria, and ventricles.
From neurological and anatomical investigation we report that these irrepressible saccades were caused by a discrete cerebrovascular accident that involved the rostral superior colliculus along with its commissure, and with minor invasion of periaqueductal gray and adjacent mesencephalic reticular formation.
The main sources of input to nucleus reuniens were from the orbitomedial, insular, ectorhinal, perirhinal, and retrosplenial cortices; CA1/subiculum of hippocampus; claustrum, tania tecta, lateral septum, substantia innominata, and medial and lateral preoptic nuclei of the basal forebrain; medial nucleus of amygdala; paraventricular and lateral geniculate nuclei of the thalamus; zona incerta; anterior, ventromedial, lateral, posterior, supramammillary, and dorsal premammillary nuclei of the hypothalamus; and ventral tegmental area, periaqueductal gray, medial and posterior pretectal nuclei, superior colliculus, precommissural/commissural nuclei, nucleus of the posterior commissure, parabrachial nucleus, laterodorsal and pedunculopontine tegmental nuclei, nucleus incertus, and dorsal and median raphe nuclei of the brainstem.
Preoptic structures (suprachiasmatic and preoptic nuclei) projected mainly to the anteromedial tectal zone, whereas thalamic (ventral and dorsal) and pretectal (central, superficial, and posterior commissure) nuclei projected to all divisions of the tectum.
Other retrogradely labeled neurons were found ipsilateral to the injection site, in the pretectum, the ventral tegmentum, the dorsal nucleus of the posterior commissure and the lateral habenular nucleus. Anterogradely labeled fibers projected from BON following three paths, a lateral bundle to the ipsilateral dorsal midbrain, an intermediate bundle to the ipsilateral pretectal area or the posterior commissure and a ventral fiber bundle to the tegmentum bilaterally. Fibers that coursed via the intermediate bundle to the posterior commissure were also seen reaching the contralateral pretectal area and the contralateral BON.
the lateral olfactory tract, olfactory and temporal limb of the anterior commissure, corpus callosum, stria terminalis, globus pallidus, fornix, mammillothalamic tract, solitary tract, and spinal tract of the trigeminal nerve.
At 4 d, higher order neurons were revealed in trigeminal, auditory, vestibular, and deep cerebellar nuclei (medial, interpositus, and lateral), oculomotor and visual-related structures (Darkschewitsch, nucleus of the posterior commissure, deep layers of superior colliculus, and pretectal area), lateral hypothalamus, and cerebral cortex (particularly in parietal areas).
After BDA injections into nucleus rotundus, retrogradely labelled neurons were observed consistently within the following neuronal groups in the midbrain and the diencephalon: (i) the stratum griseum centrale of the optic tectum; (ii) the nucleus subpretectalis in the pretectum; (iii) the nucleus ansa lenticularis posterior, the posterior nucleus of the ventral supraoptic commissure, and the posteroventral nucleus, in the dorsal thalamus and (iv) the lateral suprachiasmatic nucleus and part of the reticular complex in the ventral thalamus.
Degeneration of nerve fibers was brought about by transectioning the optic tract, the tectothalamic and tectoisthmic tracts, the postoptic commissure or the radial nerve.
The developing mesencephalic trigeminal nucleus (nucleus of the fifth cranial nerve; Mes5) is composed of four neuron populations: 1) the medial group, located at the tectal commissure; 2) the lateral group distributed along the optic tectum hemispheres; 3) a group outside the neural tube; and 4) a population located at the posterior commissure.
The primary components of the mammalian subcortical visual system are the superior colliculus, nucleus of the optic tract, anterior and posterior pretectal nuclei, nucleus of the posterior commissure, and an area within the mesopontine reticular formation that includes parts of the cuneiform, subcuneiform and pedunculopontine nuclei.
Smaller numbers of cells were located in the periaqueductal gray matter, nucleus annularis, and magnocellular nucleus of the posterior commissure. Dorsomedial injections in the ventral horn near the ventral commissure labeled only a subset of these projections, including cells in the mesencephalic reticular formation adjacent to the INC and in the nucleus annularis.
The superior colliculi on either side are interconnected via the intercollicular commissure, which has been proposed to play a role in visual transfer and gaze orienting.
Visual information from the blind hemifield can thus gain access to the brain and could potentially reach the contralateral cerebral cortex through the midbrain commissure and possibly through thalamic commissural cells..
Cats rendered hemianopic by a unilateral visual cortical ablation can recover the visual orienting response in the hemianopic visual field following disruption of the caudal non-tectotectal containing half of the commissure of the superior colliculus. In these cats, subsequent transection of the commissure of the superior colliculus does lead to the recovery. We hypothesize that another projection through the caudal commissure of the superior colliculus, from the pedunculopontine nucleus, is involved in the recovery effect.Visual orienting behavior was recorded before and after ibotenic acid lesions made in the pedunculopontine nucleus region contralateral to a visual cortical ablation in 16 cats.
It has been shown that visual awareness in the blind hemifield of hemianopic cats that have undergone unilateral ablations of visual cortex can be restored by sectioning the commissure of the superior colliculus or by destroying a portion of the substantia nigra contralateral to the cortical lesion (the Sprague effect). These oscillatory activities are normally partially suppressed by the inhibitory, GABAergic contralateral nigrotectal projection, and the destruction of the substantia nigra, or the sectioning of the collicular commissure, disinhibits the collicular neurons, causing an increase in the extent of oscillatory activity and/or synchronization between activities at different sites.
fixation neurons, may establish excitatory connections with cells in the contralateral SC through the collicular commissure.
Therefore, axonal regeneration was assessed following complete transection of the commissure in AP5/CNQX-treated IC cultures from P12 animals. These data show that neuron survival is not sufficient to permit axon regeneration at P12, and suggest that P12 lesion sites manufacture a prohibitive substrate since process outgrowth is blocked specifically at the commissure transection..
The model includes ascending connections from both lateral and medial superior olives (LSO and MSO) as well connections from interneurons in the DNLL and connections from the contralateral DNLL through the commissure of Probst. In addition, we examine the effects of the MSO and the commissure of Probst on DNLL output.
Fibers that interconnect both tecta coursed through the tectal commissure. The tectal commissure was composed of at least two distinct bundles of axons, which differed in their dorsoventral location, fiber diameter, and projection targets.
After tracer injections aimed at the red nucleus, retrograde labeling was found in the reticular thalamus, the subthalamus, the nucleus of the posterior commissure, as well as in two retinorecipient nuclei, namely, the ventral lateral and pretectal geniculate nuclei, where labeled cells are especially abundant.
Notably, the PRC presents a projection pattern that resembles in many ways the pattern described previously for the rostral dorsolateral PAG in addition to projections to a number of targets that also are innervated by neighboring pretectal nuclei, including the rostrodorsomedial part of the lateral dorsal thalamic nucleus, the ventral part of the lateral geniculate complex, the medial pretectal nucleus, the nucleus of the posterior commissure, and the ventrolateral part of the subcuneiform reticular nucleus.
Hemisectioning the tegmentum close to the anterior border of the isthmic nucleus, transection of the caudal tectal commissure and decussatio veli, or electrical lesioning of the anterodorsal tegmental nucleus all resulted in a moderate decrease in the density of GABA-positive fibers.
The target areas are the preoptic area, thalamus, area pretectalis, nucleus of posterior commissure, optic tectum, and nuclei of the accessory optic tract.
NTT4 is detected beginning at E18 in various parts of the rat brain, including the cerebral cortex, fimbria hippocampi, fornix, lateral lemniscus, anterior commissure, and spinal cord.
The presence of a commissure connecting the two superior colliculi suggests they do not act independently, but the function of the tectotectal connection has never been firmly identified.
The embryo demonstrated substantial labeling in neurons of the caudate putamen, bed nucleus of the stria terminalis, preoptic area, lateral hypothalamic area, paraventricular thalamic nucleus, ventromedial hypothalamic nucleus, magnocellular nucleus posterior commissure, and periaqueductal central gray.
It was conceivable that the PAG lesion might be contributory to fatigable blepharoptosis (pseudomyasthenia) and supranuclear upward gaze palsy in the present case, because the PAG controls levator palpebrae neurons of central caudal nucleus in oculomotor nucleus complex and receives afferents from the limbic system., reticular formation and posterior commissure..
Clustering of intensely positive neurons was observed in discrete areas including the main and accessory olfactory bulbs, the islands of Calleja, the amygdala, the paraventricular nucleus of the thalamus, several hypothalamic nuclei, the lateral geniculate nucleus, the magnocellular nucleus of the posterior commissure, the superior and inferior colliculi, the laterodorsal and pedunculopontine tegmental nuclei, the nucleus of the trapezoid body, the nucleus of the solitary tract and the cerebellum.
Visual orientation can be restored to the blind hemifield by transection of the commissure of the superior colliculus or by destruction of the superior colliculus (SC) or the substantia nigra pars reticulata (SNpr) contralateral to the cortical lesion.
A third group of cadherin-8-positive gray matter structures has functional connections with the cerebellum (superior colliculus, anterior pretectal nucleus, red nucleus, nucleus of posterior commissure, inferior olive, pontine, pontine reticular, and vestibular nuclei).
Stronger projections originate in the lateral preoptic area, the zona incerta, the nucleus of the posterior commissure and some other thalamic areas, the lateral substantia nigra, the deep layers of the superior colliculus, the dorsal and lateral central gray, the deep mesencephalic nucleus, the paralemniscal zone, the intercollicular nucleus, the external cortex of the inferior colliculus, the oral and caudal pontine reticular nucleus, the deep cerebellar nuclei, the gigantocellular and lateral paragigantocellular reticular nuclei, the prepositus hypoglossal nucleus, the spinal trigeminal nuclei, and the intermediate layers of the spinal cord. Moderate projections were seen to diencephalic reticular areas, the zona incerta, the nucleus of the posterior commissure, and to various other thalamic areas.
Transection of the ventral rhombencephalic commissure enhanced dorsal light response; negative phototaxis was retained with smaller turning angles than normal.
Three regions were found to evoke the accommodation response: the posterolateral pretectum, including the nucleus of the optic tract and the posterior pretectal nucleus; the posteromedial pretectum, including the nucleus of the posterior commissure (NPC) and adjacent commissural fibers; and the MRF area dorsolateral to the oculomotor nucleus.
Beginning in week 22, there is development of commissural axons (dorsal commissure of the lateral lemniscus and commissure of the inferior colliculus) and descending projections (descending collicular axons and olivocochlear bundle).
The two hemispheres are connected by fibers decussating in the anterior commissure.
The study also investigated the effect of monocular enucleation plus simultaneous transection of the intercollicular commissure (a recognised pathway for communication between the colliculi). Similarly, in the group in which the collicular commissure had been severed at the time of monocular enucleation, the auditory responses were also disrupted in the colliculus contralateral to the enucleation. Thus, severing the intercollicular commissure at the time of monocular enucleation protected the map of auditory space in the ipsilateral colliculus..
Faint projections were demonstrated to the nucleus of the posterior commissure and the nucleus of Darkschewitsch.
Pathways to the contralateral brain stem were via the commissure posterior, ventral supraoptic decussation, and the predorsal bundle.
Following the injection of biocytin, in the ascending projections, labeled terminals were seen mainly in the caudal portion of the nucleus of the optic tract, the nucleus of the posterior commissure, the posterior pretectal nucleus, the olivary pretectal nucleus, the mesencephalic reticular formation at the level of the oculomotor nucleus, and the lateral posterior nucleus of the thalamus on the ipsilateral side. Following the injection of muscimol into the pretectum, including the nucleus of the optic tract, the posterior pretectal nucleus, and the nucleus of the posterior commissure, accommodative responses evoked by microstimulation of the superior colliculus were reduced to 33-55% of the value before the injections. These findings suggest that the accommodation area in the superior colliculus projects to the oculomotor nucleus through the ipsilateral pretectal area, especially the nucleus of the optic tract, the nucleus of posterior commissure, and the posterior pretectal nucleus, and also projects to the pupilloconstriction area (the olivary pretectal nucleus), the vergence-related area (the mesencephalic reticular formation), and the active visual fixation-related area (the nucleus raphe interpositus)..
The intertectal commissure is an important pathway that interconnects directly the two sides of the optic tectum. Retrogradely labelled neurons were best obtained by depositing HRP directly within the compact commissure at the midline. Axons labelled from the tectum did not enter the posterior commissure nor the intervening commissural region related to the griseum tectale..
Some of these dendrites extend contralaterally through the commissure of the OT.
Three projection systems of the NIC were distinguished: commissural (through the posterior commissure), descending, and ascending. The posterior commissure system gave rise to dense terminal fields in the contralateral NIC, the oculomotor nucleus, and the trochlear nucleus.
In several species including monkey, cat and hamster, the paired colliculi are connected by a commissure.
These lesions also destroyed axons in the commissure of the superior colliculus (CS). We conclude that unilateral loss of collicular cell function and the presence of fibers coursing through the commissure of the superior colliculus are both necessary for the prolonged deficit in visual orienting behavior.
Phosphorothioate-modified AS oligos caused navigational errors in both the optic projection (OP) and the intertectal commissure (ITC).
Some labelled axons were seen coursing to the contralateral side through the posterior commissure and the decussation of the superior cerebellar peduncle.
Correlation of myelin-stained or cryotomic sections of human brain with inversion-recovery MR images can display the cerebral commissures as white-matter tracts (in hypersignal on MRI), crossing the mid-line. MRI shows routinely in three orthogonal planes a) the corpus callosum stretched above the supra-tentorial ventricles, it's four portions (rostrum, genu, body and splenium) and connections with the Deep Grey Nuclei b) the fornix, intralimbic commissure joining anteriorly the mammillary bodies (through it's columns) to the alveus posteriorly and inferiorly (via it's two crura), arcing around the thalamus and lying over the hippocampus and the dentate gyrus as shown on the frontal sections c) the anterior commissure, white-matter tract connecting the two temporal lobes. In axial view, the anterior commissure has the shape of bicycle handlebars, coursing posteriorly, inferiorly and laterally behind the head of the caudate nucleus and passes into the lateral nucleus of the globus pallidus into the inferior and middle temporal gyri. Because the anterior commissure is easily recognisable in all planes, it's appears to be a important landmark for identification of the lateral and medial nuclei of the globus pallidus on axial and sagittal planes d) at least, the posterior commissure, anterior margin of the pineal region, closely related to the superior colliculi, acquire a major importance in the AC-PC line delineation becoming a reference landmark for stereotatical procedures..
The leading retinal growth cones, typically 4-10 in number, advanced alongside the tract of the postoptic commissure but rarely sent filopodia into it and never wrapped its axons.
In addition, a few stained neurons were scattered in the nucleus of the posterior commissure and in nucleus pretectalis superficialis pars magnocellularis.
Cytochrome P450 oxidoreductase was also detected in the nucleus of the posterior commissure, superior colliculus, intermediate gray layer, periaqueductal gray and in the molecular, Purkinje and granular layers of the cerebellum.
the nucleus of posterior commissure (NPC), the nucleus of Darkschewitsch (NDK) and the interstitial nucleus of Cajal (INC) and the putative neurotransmitters subserving this pathway have been studied in adult rats.
Fibers cross the midline in the supraoptic commissure by E12, other arrive in the lateral geniculate region, and a branch of the MFB extends toward the mammillary area. At E13, a periventricular medial thalamic branch of the MFB is seen, axons appear in the supramammillary commissure, and a fine fasciculus between the medial thalamus and intergeniculate leaflet is visible.
A high concentration of tenascin was found in areas bordering the developing visual pathway, such as the optic disc, the outer surface of the optic nerve, and the supraoptic commissure.
For example, the neuropil of several thalamic nuclei (i.e., dorsal lateral geniculate nucleus, lateral posterior nucleus, ventroposterior nucleus), cerebral cortex, upper layers of the superior colliculus and matrix zones of the neostriatum, were strongly immunoreactive, while the anterior commissure, corpus callosum, optic tract and internal capsule were devoid of staining.
On the other hand, CaM mRNA was colocalized with the AC and GC mRNA, but its distribution was more abundant and specific for neuronal cells, since there was little hybridization signal with CaM probe in neuronal fiber regions such as the corpus callosum and the anterior commissure.
In addition, NAALADase-IR was observed in some NAAG-containing fiber tracts including the corpus callosum, fornix, habenular commissure, solitary tract, stria medularis, and stria terminalis.
Labeled neurons in the amygdala, colliculus superior and mesencephalic trigeminal nucleus were only found following cervical injections; all other mentioned areas and the posterior commissure complex projected to, at least, midthoracic level..
The medial pallium receives projections from fewer centers in the contralateral hemisphere, which include the medial septal nucleus, the pars medialis of the amygdala, the bed nucleus of the pallial commissure and the medial pallium. The medial pallium projects ipsilaterally to all telencephalic nuclei, with the exception of a large part of the corpus striatum, and contralaterally to the medial septal nucleus, the olfactory tubercle, amygdala, medial pallium and bed nucleus of the pallial commissure.
Psychol., 91 (1977) 975-988), post-lesioning CI disruption was observed in some of the mesencephalic lesion cases involving the posterior commissure, PAG and/or accessory oculomotor nuclei.
Cells projecting into the commissure of the cat's superior colliculus were identified during extracellular recording by antidromic activation.
Conventional retrograde and orthograde axonal transport tract-tracing techniques were used in cats to explore the auditory decussations and commissures in the upper pons and midbrain. Three of the 8 decussations (from the dorsal nucleus of the lateral lemniscus to the contralateral dorsal nucleus of the lateral lemniscus, from the dorsal nucleus of the lateral lemniscus to the contralateral inferior colliculus, from the sagulum to the contralateral sagulum) reach their targets via the commissure of Probst. The remaining 5 decussations (from the inferior colliculus to the contralateral inferior colliculus or medial geniculate, from the intermediate nucleus of the lateral lemniscus to the contralateral medial geniculate, from the sagulum to the contralateral inferior colliculus or medial geniculate) reach their targets via the commissure of the inferior colliculus. The results also suggest that the commissure of Probst is not a general avenue for decussating auditory fibers of the lateral lemniscus but is instead a specific avenue only for fibers from the dorsal nucleus of the lateral lemniscus and sagulum.
In the midbrain, labeled terminals were found in the rostral interstitial nucleus of the medial longitudinal fasciculus, a medial part of Forel's H-field, the periaqueductal gray, the posterior commissure nucleus, and the superior colliculus of the contralateral side.
Influence of the midbrain in facilitating focal vision is shown by the restoration of form discriminations after section of the superior collicular commissure.
Retinal axons grow through one of these tracts, the tract of the post-optic commissure (tPOC).
A few fibers in the contralateral medial optic tract redecussate via the posterior commissure to reach the ipsilateral periventricular pretectum.
Low but detectable densities of endothelin binding sites were found in medial geniculate nucleus, fields of Ammon's horn, caudate-putamen, globus pallidus, entopeduncular nucleus, substantia nigra, anterior commissure, internal capsule, anterior pituitary, median preoptic nucleus, septohypothalamic nucleus, superior colliculus and area postrema.
The periventricular bundle bifurcates at the level of the posterior commissure to form hypothalamic and thalamic components which distribute to the anterior pretectal region, lateral habenulae, and nuclei of the posterior commissure, the majority of the intralaminar and midline thalamic nuclei, and to almost all of the hypothalamus.
They appeared also in the central mesencephalic reticular formation (cMRF), the periaqueductal gray (PAG), the posterior commissure nucleus, and the superior colliculus.
While the heaviest anterogradely labeled ascending projections were observed to the contralateral ventral posterolateral nucleus of the thalamus, pars oralis (VPLo), efferent projections were also observed to the contralateral ventrolateral thalamic nucleus (VLc) and central lateral (CL) nucleus of the thalamic intralaminar complex, magnocellular (and to a lesser extent parvicellular) red nucleus, nucleus of Darkschewitsch, zona incerta, nucleus of the posterior commissure, lateral intermediate layer and deep layer of the superior colliculus, dorsolateral periaqueductal gray, contralateral nucleus reticularis tegmenti pontis and basilar pontine nuclei (especially dorsal and peduncular), and dorsal (DAO) and medial (MAO) accessory olivary nuclei, ipsilateral lateral (external) cuneate nucleus (LCN) and lateral reticular nucleus (LRN), and to a lesser extent the caudal medial vestibular nucleus (MVN) and caudal nucleus prepositus hypoglossi (NPH), and dorsal medullary raphe.
These areas include zona incerta, nucleus of the posterior commissure, anterior and posterior pretectal nuclei, nucleus of the optic tract, superior colliculus, cuneiform nucleus, subcuneiform area, substantia nigra pars reticulata and pars lateralis, periparabigeminal area, external nucleus of the inferior colliculus, the area ventral to the external nucleus of the inferior colliculus, mesencephalic reticular formation, dorsal and ventral nuclei of the lateral lemniscus, and the perihypoglossal nucleus.
At this age, there were also many immunoreactive fibers that crossed from one side of the brainstem to the other in the commissure of the superior colliculus. By this age, only a very few immunoreactive fibers were present in the commissure of the superior colliculus.
Inputs to LDTg were found from frontal cortex, diagonal band, preoptic areas, lateral hypothalamus, lateral mamillary nucleus, lateral habenula; the interpeduncular nucleus, ventral tegmental area, substantia nigra and retrorubral fields; the medial terminal nucleus, interstitial nucleus, supraoculomotor central grey, medial pretectum, nucleus of the posterior commissure, paramedian pontine reticular formation, paraabducens and paratrochlear region; the parabrachial nuclei and nucleus of the tractus solitarius. A number of brainstem structures apparently associated with visual functions were also innervated, mainly the superior colliculus, medial pretectum, medial terminal nucleus, paramedian pontine reticular formation, inferior olive, supraoculomotor, paraabducens and supragenual regions, prepositus hypoglossi and nucleus of the posterior commissure.
Lesser projections were observed to the intermediate layer of the superior colliculus, nucleus of the posterior commissure, and prerubral field.
Transection of non-tectotectal fibers in the caudal one-half of the commissure of the superior colliculus restores visual orienting to a cat previously rendered hemianopic by a large unilateral visual cortical lesion. One cat was normal (control), and the other (experimental) had previously received a caudal transection of the collicular commissure. Quantitative comparison of the retrograde labeling in collicular afferents revealed that a number of mesencephalic regions contain neurons that project to the colliculus via the caudal collicular commissure. In the behavioral experiments, we attempted to replicate the Sprague effect by destroying the neurons giving rise to the axons in the caudal collicular commissure.
The anterior commissure appears in stage 23. The dentate nucleus, as well as the inferior and superior cerebellar peduncles and some of the cerebellar commissures, are present.
The ipsilateral PrV-SC projection appeared to arise mainly from axons that recrossed the midline at the level of the SC commissure.
Many of the same nuclei contained double-labeled neurons following collicular injections, but in addition, double-stained cells were found in the primary visual cortex, lateral dorsal and lateral posterior thalamic nuclei, nucleus of the posterior commissure, ventral lateral geniculate nucleus, dorsal column nuclei and several additional pretectal nuclei.
Transection of the commissure of the superior colliculus restores visual orientation behavior to a cat previously rendered hemianopic by a unilateral visual cortical lesion (the Sprague effect). Using two methods, we asked whether this recovery resulted from the severing of the tectotectal component of the commissure or whether the destruction of some other connection was responsible. First, we transected either the rostral or the caudal one-half of the tectal commissure in hemianopic cats. If destruction of tectotectal fibers is responsible for the Sprague effect, then only rostral transections should produce the recovery since nearly all tectotectal connections lie in the rostral one-half of the commissure. This lesion eliminated the contralateral tectotectal pathway from the contralateral colliculus but left other fibers (originating elsewhere but coursing through the commissure) largely intact. These ibotenic acid lesions failed to produce the recovery; but when the caudal portion of the tectal commissure was subsequently transected in the same animals, the recovery was observed. The results of both experiments support the conclusion that the transection of a nontectotectal component of the commissure of the superior colliculus is responsible for the recovery of visual orientation behavior in a cortically blind cat..
Other afferents, which were thought to have been labeled through spread of HRP into the medial longitudinal fasciculus (MLF), adjacent paramedian pontine reticular formation, or uptake by transected fibers descending to the inferior olive, included the nucleus of Darkschewitsch, interstitial nucleus of Cajal, zona incerta, prerubral fields of Forel, deep superior colliculus, nucleus of the posterior commissure, nucleus cuneiformis, ventral periaqueductal gray, vestibular complex, perihypoglossal complex, and deep cerebellar nuclei.
Combined section of the minor and horizontal commissure was then performed in animals trained on the colour problem, and transection of the posterior commissure in fish which had acquired the shape task.
An additional case proved that this projection courses through the ventral supraoptic commissure.
The dimesencephalic borderline passes through the commissural fibres in the roof: the rostral part of the commissure is the posterior commissure, the caudal part, the commissure of the superior colliculi.
Apart from the commissure of the superior colliculi, which began to appear in advanced embryos of stage 14, fibres of the posterior commissure are now present in some specimens.
Smaller and sparser collections of stained cell bodies could be found in the ventromedial hypothalamus, the posterior pretectal nucleus, the nucleus of the posterior commissure, the peripeduncular nucleus, the periaqueductal central gray, the contralateral anterior pretectal nucleus, and the locus coeruleus.
In 2 of these 4 monkeys whose lesions were localized in the lateral portions of the pretectum, rapid rise in OKN velocity remained unchanged, whereas in the remaining two whose lesions were large enough to extend into the medial portions of the pretectum near the nucleus of the posterior commissure, rapid rise in OKN velocity was reduced.
In young adult Xenopus laevis frogs the axons of isthmic neurons projecting to the contralateral tectum were severed at the postoptic commissure and the survival of such neurons was studied between 2 and 26 weeks after the operation.
Some cells could be anti- and/or orthodromically activated by a stimulating electrode placed at the intercollicular commissure.
The earliest degeneration was observed at day 1 in the intermediate and ventral divisions of the lateral septal nucleus, followed by development of degeneration on days 2-4 in neuron populations including the septohippocampal nucleus, septohypothalamic nucleus, anterior olfactory nucleus, bed nucleus of the stria terminalis, endopiriform nucleus, parafascicular nucleus, superior colliculus, interstitial nucleus of the posterior commissure, inferior colliculus, pontine nuclei, raphe nuclei, pars caudalis of the spinal trigeminal nucleus, the caudal aspect of nucleus tractus solitarius, dorsal vagal motor nucleus, granule cells in the dentate gyrus, pyramidal cells in CA fields of the hippocampus, and of neurons in the subiculum, pyriform cortex, entorhinal cortex and neocortex (mainly layer Vb and VI).
In the pretectal region, labeled terminal patches were consistently found in the nucleus limitans of the posterior thalamus, but we could not determine if label in the nucleus of the pretectal area and dorsal parts of the nucleus of the posterior commissure marked axon terminals or fibers of passage.
Transplant-derived astrocytes were found on the glia limitans along the entire circumference of the brain, in the hippocampal commissure, corpus callosum, internal capsule, entopeduncular nucleus, habenular commissure, brachium of the superior colliculus, optic tract, optic chiasm, and sensory root of the trigeminal nerve.
Each type of afferent source was also seen in the nucleus of the posterior commissure and the posterior ventral lateral hypothalamic area.
commissures include the supramamillary, that of the superior colliculi, and (in some embryos) the first fibres of the posterior commissure.
As well as the strong ipsilateral projection, there was a much weaker contralateral one which crossed the midline in the tectal commissure.
The deep laminae were mainly connected with auditory, somatosensory and reticular regions of the brain, including the inferior colliculus, zona incerta, substantia nigra, mesencephalic central grey, pontine nuclei, spinal trigeminal nucleus, nucleus of the posterior commissure, thalamic reticular nucleus, raphe nuclei, lateral vestibular nucleus, the lateral superficial reticular formation of the medulla, the mesencephalic reticular formation, nucleus gracilis and the cervical spinal cord.
In selected animals, 3 days before the intended sacrifice, the postoptic commissure was transected and the cut isthmotectal fibres filled with horseradish peroxidase (HRP).
Other labeled cells following injections in the rostral and medial portions of the lateral dorsal nucleus are seen contralaterally in the medial pretectal region and nucleus of the posterior commissure, and bilaterally in the rostral tips of laminae IV and V of the superior colliculus.
No specific binding of M-[ 125I]vasoactive intestinal peptide was observed in white matter tracts such as corpus callosum, anterior commissure, medial forebrain bundle and fornix.
Retrogradely labeled cells were observed in numerous oculomotor-related structures, including the prerubral field (rostral interstitial nucleus of the medial longitudinal fasciculus), nucleus of Darkschewitsch, nucleus of the posterior commissure, deep superior colliculus, supraoculomotor ventral periaqueductal gray, contralateral paramedian pontine reticular formation, pontine raphe and dorsal medial pontine tegmentum medial to the abducens nucleus (purported to contain omnipause neurons), cell group Y, and the perihypoglossal complex (nucleus prepositus hypoglossi).
In one group we made midline lesions of the ansulate commissure, through which run the major crossed descending projections from both tectal lobes. In the case of ansulate commissure section, mirrored orienting responses were observed for tactile stimuli as well.
Birds submitted to visual Wulst ablation or supraoptic commissure lesion performed in much the same way. In contrast, when the tectal and posterior commissures were lesioned, pigeons failed to show interocular transfer of that learning process..
After a localized lesion was made within the posterior commissure, dense degenerated terminals were distributed in the most rostral part of the nucleus pretectalis posterior, the nucleus of posterior commissure, the interstitial nucleus of Cajal, and the central tegmental field. Following an HRP (dissolved in 5% alkyl-phenol ethylene oxide) injection into the unilateral area pretectalis where fibers of the posterior commissure fan out, retrogradely labeled cells were observed in all of the above described (posterior commissural fiber recipient) regions of the pretectal and neighboring structures, with the exception of the somatic cell columns of the oculomotor nucleus and the trochlear nucleus. The findings were discussed with special reference to the pupilloconstrictory pathway via the posterior commissure..
Crossed projections were observed to pass through the supraoptic decussation and the posterior commissure, however only the contralateral n.
In all four species, the retinal fibres terminate bilaterally in the suprachiasmatic nucleus, dorsolateral optic nucleus of the thalamus and the optic nucleus of the posterior commissure; a bilateral retinotectal projection was only found in E.
There was also a much sparser contralateral descending projection that crossed midline in the tectal commissure, and sent terminals to the contralateral cuneiform area and adjoining regions.
The frontal eye field also projects to the ipsilateral pretectal nuclei, subthalamic nucleus, nucleus of the posterior commissure, superior colliculus (especially layer four), zona incerta, rostral interstitial nucleus of the medial longitudinal fasciculus, nucleus Darkschewitsch, dorsomedial parvocellular red nucleus, interstitial nucleus of Cajal, basilar pontine nuclei, and bilaterally to the paramedian pontine reticular formation and the nucleus reticularis tegmenti pontis.
Different branches of this system innervate the midbrain (superior colliculus, interstitial magnocellular nucleus of the posterior commissure, and anterior pretectal nucleus), the diencephalon (lateral habenular nucleus, parafascicular, anteroventral, anterodorsal, mediodorsal, and intralaminar thalamic nuclei), and the telencephalon (lateral septum and medial prefrontal cortex).
In the spinal cord cells were found in the substantia gelatinosa at all levels, the dorsolateral funiculus and dorsal gray commissure in lumbosacral cord. The presence of neuropeptide Y immunoreactive fibres in tracts such as the corpus callosum, anterior commissure, lateral olfactory tract, fimbria, medial corticohypothalamic tract, medial forebrain bundle, stria terminalis, dorsal periventricular bundle and other periventricular areas, indicated that in addition to the localisation of neuropeptide Y-like peptide(s) in interneurons in the forebrain, neuropeptide Y may be found in long neuronal pathways throughout the brain..
Additional terminals were observed bilaterally in the nuclei of the posterior commissure and pretectal areas at the midbrain-diencephalic junction.
Afferents project bilaterally from the parabigeminal nuclei, the nucleus of the optic tract, the posterior pretectal region, the dorsal part of the lateral posterior-pulvinar complex and the ventral nucleus of the lateral lemniscus; and ipsilaterally from the substantia nigra pars reticulata, the pars lateralis of the ventral lateral geniculate nucleus, the intergeniculate leaflet, the zona incerta, the olivary pretectal nucleus, the nucleus of the posterior commissure, the lateral thalamus, Forel's field H2, and the ventromedial hypothalamus. Collicular efferents terminate ipsilaterally in the anterior, posterior and olivary pretectal nuclei, the nuclei of the optic tract and posterior commissure, the ventrolateral part of the dorsal lateral geniculate nucleus, the pars lateralis of the ventral lateral geniculate nucleus, the intergeniculate leaflet, and the zona incerta; and bilaterally in the parabigeminal nuclei and lateral posterior-pulvinar complex (chiefly its dorsal part).
Results indicate that the NRTP receives afferents from visual relay nuclei, including the nucleus of optic tract, the superior colliculus, and the ventral lateral geniculate nucleus; oculomotor-associated structures including the zona incerta, the H1 and H2 fields of Forel, the nucleus subparafasciculus, the interstitial nucleus of Cajal, the visual tegmental relay zone of the ventral tegmental area of Tsai, the mesencephalic, pontine, and medullary reticular formations, the nucleus of the posterior commissure, and a portion of the periaqueductal gray termed the supra-oculomotor periaqueductal gray; cerebellar and pontomedullary nuclei, including the superior, lateral, and medial vestibular nuclei, the deep cerebellar nuclei, and NRTP interneurons, and nuclei related to limbic functions including the lateral habenula, the mammillary nuclei, the hypothalamic nuclei, the preoptic nuclei, and the nucleus of diagonal band of Broca.
Fibers arising from the cerebellar nuclei were traced via the cerebellar commissure to the contralateral vestibular nuclear complex (particularly the n. Vestibular projections ascending mainly via the f lm terminated in the nuclei of the f lm, the nuclei of the posterior commissure, and particularly the extraocular motor nuclei.
of the posterior commissure, the superior colliculus, the n.
I-SRIF-containing neurons were also present in the nucleus of the posterior commissure, the nucleus of Edinger-Westphal, and the ventral division of the lateral geniculate nucleus.
Experiments in 5 monkeys revealed 3 major sources of input: (1) bilateral projections from the so-called frontal eye field (FEF), which is situated in the frontal cortex around the arcuate sulcus; (2) the intermediate and deep layers of mainly the contralateral superior colliculus; and (3) ipsilateral projections from brainstem structures such as the accessory oculomotor nuclei (nucleus interstitialis of Cajal, nucleus of Darkschewitsch, and nucleus of the posterior commissure), the mesencephalic reticular formation, the vestibular nuclei, the nucleus prepositus hypoglossi, and the cerebellar fastigial nucleus.
Experiments conducted after large HRP deposits invading almost all the collicular layers resulted in the labeling of visual centers (cortical areas 17, 18 and 18a, ventral lateral geniculate nucleus, nucleus of the posterior commissure, nucleus of the optic tract, anterior and olivary pretectal nuclei, parabigeminal nucleus); somatosensory centers (cortical area SmI, principal and spinal tract trigeminal nuclei) auditory centers (auditory cortex, inferior colliculus and nuclei of the lateral lemniscus) and various other centers (zona incerta, substantia nigra, cingulate and motor cortices, and some hypothalamic, thalamic, pontine reticular and deep cerebellar nuclei). Deposits limited to the deep SC layers resulted in the labeling of a smaller number of structures: visual centers (cortical area 18a, nucleus of the posterior commissure, parabigeminal nucleus); somatosensory centers (cortical area SmI, principal and spinal tract trigeminal nuclei); auditory centers (inferior colliculus, nuclei of the lateral lemniscus); and various other centers (zona incerta, substantia nigra, cingulate cortex, some hypothalamic nuclei, posterior thalamic nucleus, central gray, cuneiformis and subcuneiformis nuclei, pontine reticular nucleus pars oralis).
Systematic tracking with the stimulating electrode in and around the FFH revealed that effective sites of stimulation inducing negative field potentials in the IO subdivision of the oculomotor nucleus, identified as extracellular counterparts of the EPSPs in IO motoneurons, were also located in the interstitial nucleus of Cajal, nearby reticular formation and posterior commissure, besides within and near the medial part of the FFH.
The rostal mesencephalon at the level of the posterior commissure was studied by light microscopy in two patients with idiopathic Parkinson's disease, one patient with Alzheimer's disease, and one patient with senile dementia of Alzheimer's type.
Nucleus of the posterior commissure: fine, medium.
The retinal fibers terminate bilaterally in the following places: suprachiasmatic nucleus, dorsolateral optic nucleus, optic nucleus of the posterior commissure, cortical nucleus, ventral pretectal area, optic tectum, and the accessory optic terminal field.
However, counts of labeled cells in the lateral vestibular nucleus and nucleus of the posterior commissure showed that there is a steady rise in the number of labeled neurons as the animals increase in age..
Our results for neurons projecting to the spinal cord (spinal-projecting neurons) from the nucleus ambiuus, dorsal motor nucleus of the vagus, superior vestibular nucleus and nucleus f, nucleus Darshevch, nucleus Rolleri, nucleus prepositus hypoglossi, and nucleus of the posterior commissure have been reported before in other mammals but not in rats.
These cells project their axons into the contralateral tectum via the tectal commissure as well as into the ipsilateral tectum.
The stratum fibrosum marginale of the tectum was partially denervated by removing the torus longitudinalis and cutting the tectal commissure.
Most previous neuropathologic cases reported in human beings have consisted of much larger lesions with common involvement of the posterior commissure and pretectum.
In the pretectum, NBIC fibers terminate in the anterior and medial nuclei and the nucleus of the posterior commissure.
The neurological deficits following section of the midbrain commissures were studied in the cat. After a lesion of the commissures between the superior and inferior colliculi, with or without involvement of the posterior commissure, the animals showed a long lasting inattention for stimuli in the upper visual space, lack of exploratory head movements towards the neglected space, head ventroflexion and vertical paralysis of gaze. After a lesion of the commissure between the superior colliculi or of its rostral part only, the same symptomatology appeared, but it was short lasting. After a lesion of the posterior commissure, the head was kept dorsiflexed, the exploratory head movements towards the lower visual space were reduced and the stimuli presented in this space were often neglected.
The projection fibers reach the contralateral superior colliculus by crossing the collicular commissure.
Upgaze paralysis results from unilateral lesions in or near the posterior commissure. consequently these tracts, probably originating from the dorsolateral part of the riMLF, would decussate through the posterior commissure before they reach the oculomotor nuclei.
Aggregates of CRF-immunoreactive perikarya are found in the paraventricular, supraoptic, medial and periventricular preoptic, and premammillary nuclei of the hypothalamus, the bed nuclei of the stria terminalis and of the anterior commissure, the medial septal nucleus, the nucleus accumbens, the central amygdaloid nucleus, the olfactory bulb, the locus ceruleus, the parabrachial nucleus, the superior and inferior colliculus, and the medial vestibular nucleus.
In chick, the tectal and posterior commissures form a continuous band of axons lying in the dorsal aspect of the meso-diencephalon. It is likely that RZ corresponds to the posterior commissure while CZ corresponds to the tectal commissure..
A few contralateral optic fibers crossed again in the posterior commissure and terminated within ipsilateral visual pretectal structures.
Autoradiographic experiments showed that the incertofugal fiber systems reach ipsilaterally to the thalamus (lateral dorsal, central lateral, ventral lateral geniculate, parafascicular, subparafascicular and reuniens nuclei, and posterior nuclear complex), to the hypothalamus (dorsal, lateral and posterior hypothalamic areas), to the tectum (medial pretectal area, deep pretectal and pretectal nuclei, superior colliculus and periaqueductal gray) and to the midbrain tegmentum, pons and medulla oblongata (subcuneiform, cuneiform and red nuclei, nuclei of the posterior commissure and Darkschewitsch, interstitial nucleus of Cajal, pedunculopontine tegmental nucleus, oral and caudal pontine reticular nuclei, nucleus raphe magnus, gigantocellular reticular nucleus, pontine gray and inferior olivary complex).
The contralateral optic fibers project to the nucleus opticus dorsolateralis, nucleus of the posterior commissure, nucleus geniculatus lateralis, pretectal nuclear complex, nucleus corticalis, stratum fibrosum et griseum superficiale (SFGS), and a few optic fibers extend into the stratum griseum centrale.
It was evident that among the entire scope of its inputs, the FEF received a prominent afferent projection from the nucleus of the optic tract (NOT, nucleus limitans) and the suprageniculate nucleus, and projected to a medial subdivision of NOT, sublentiform nucleus, nucleus of the pretectal area, nucleus of the posterior commissure, and the rostral periaqueductal gray.
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.
The nucleus of the posterior commissure received cerebellar fibers chiefly from the DN, and additionally from the FN.
In the spinal grey matter, numerous labeled cells were regularly encountered in the marginal zone, the lateral part of the neck of the dorsal horn, and the dorsal grey commissure.
Only a few cells were labeled in the contralateral optic tectum, suggesting that few of the fibers of the intertectal commissure are actually commissural to the tectum.
Ipsilaterally, labelled cells were found in the lateral posterior thalamus, nucleus of the posterior commissure and deep mesencephalic reticular nucleus.
After injections of horseradish peroxidase into the central tegmental field of the midbrain reticular formation and centrum medianum of the thalamus in the cat, labelled neurons were found in the nucleus of solitary tract, cuneate and gracile nuclei, spinal nuclei of trigeminal nerve, external nucleus and brachium nucleus of inferior colliculus, nuclei of the lemniscus lateralis in the area pretectalis, nucleus of the posterior commissure and stratum intermediale of the superior colliculus and in reticular structures of medulla and pons.
Other optic fibers crossed the posterior commissure from the contralateral side of the brain and also innervated the ipsilateral tectum and thalamus. Optic fibers were also observed in the transverse commissure, tractus rotundus, horizontal commissure, tectobulbar tract, and fasciculus retroflexus.
Labeled pretectal neurons were found throughout all pretectal nuclei; the densest concentrations were in the medial pretectal nucleus, the anterior pretectal nucleus and the nucleus of the posterior commissure.
All labeled fibers bound for the contralateral side cross in the dorsal part of the midbrain tegmentum at the intercollicular levels via the so-called commissure of Probst.
Tectal afferents were demonstrated by retrograde HRP transport in the area dorsalis pars centralis of the telencephalon, torus longitudinalis, torus semicircularis, nucleus isthmi, nucleus profundus mesencephali, several pretectal nuclei, dorsomedial and dorsolateral thalamic nuclei, nucleus of the posterior commissure, mesencephalic and bulbar reticular nuclei and nucleus ruber.
Small microelectrophoretic injections of tritiated proline and leucine practically confined to the ZI were found to label a widespread, predominantly ipsilateral system of descending and ascending fibers distributed to reticular structures of the brain stem (mesencephalic reticular formation, nucleus tegmenti pedunculopontinus pars compacta, parabrachial area, nuclei reticularis pontis oralis, pontis caudalis, gigantocellularis and medullae oblongatae, pars ventralis), precerebellar nuclei (nucleus reticularis tegmenti pontis, pontine nuclei and inferior olivary complex), the middle and deep layers of the superior colliculus, the pretectum (anterior, posterior and medial pretectal nuclei), perioculomotor nuclei (interstitial nucleus of Cajal, nucleus of Darkschewitsch and nuclei of th posterior commissure), the parvocellular portion of the red nucleus, the central gray substance, the nucleus tegmenti dorsalis lateralis, the ventral horn of the cervical spinal cord, non-specific thalamic nuclei (parafascicular, centralis medius, paracentralis, centralis lateralis and ventromedial thalamic nuclei, nucleus reuniens), basal ganglia (entopeduncular nucleus and globus pallidus), hypothalamic structures (posterior hypothalamic nucleus, dorsal and lateral hypothalamic areas), and a subpallidal district of the substantia innominata.
HRP injections in the cerebellum labeled cells bodies in the area pretectalis, nucleus pretectalis, and the nucleus of the posterior commissure.
Cortical fibres from LS (in particular from PLLS; 15) reach the contralateral SC also via the commissure of SC.
In the mesencephalon, bilateral but more numerous ipsilateral labeled cells were found in the medial mesodiencephalic region including the nuclei of Cajal, Darkschewitsch and the posterior commissure.
The principal ascending bundle projects to the nucleus rotundus, three components of the ventral geniculate nucleus and the nucleus ventromedialis anterior ipsilaterally, before it crosses in the supraoptic commissure and terminates in the contralateral nucleus rotundus, ventral geniculate nucleus and a hitherto unnamed region dorsal to the nucleus of the posterior accessory optic tract.
In both species, efferents from the paleostriatal complex, a telencephalic region considered comparable to the mammalian basal ganglia on the basis of topographic, histochemical, and hodological criteria, were found to project to a prominent pretectal cell group called the dorsal nucleus of the posterior commissure (nDCP).
Pretectofugal fibers projecting to nuclei in this third category terminate ipsilaterally within the nucleus of Darkschewitsch, bilaterally within the nucleus of the posterior commissure and the interstitial nucleus of Cajal, and contralaterally within the somatic cell column of the oculomotor and trochlear nuclei.
Contralaterally, every subnucleus of IC except for PC projects via the commissure of IC to areas corresponding to the targets of the ipsilateral projections, such as the ventral and medial divisions of MGB and the parabrachial region and the interstitial nucleus of BIC, although these contraleral projections are in general much sparser than those ipsilateral.
In these animals, the projections were established through multiple aberrant pathways which included the oculomotor nerve, the trigeminal nerve and the posterior commissure.
It was demonstrated that the vestibular commissure plays the crucial role in mediating the mirror image optokinetic effects to Vn on the opposite side and assures the bidirectionality of the responses to binocular stimulation.
Cells labeled with the peroxidase reaction product were located in gyrus propreus, gyrus genualis, nucleus accumbens, bed nucleus of the stria terminalis, bed nucleus of the anterior commissure, nucleus of the diagonal band, substantia innominata, anterior amygdaloid area, ventromedial hypothalamic area, paraventricular nucleus, perifornical hypothalamic area, lateral hypothalamic area, dorsal hypothalamic area, field of Forel, midbrain reticular formation, superior colliculus, ventral central grey, lateral central gray, locus coeruleus, parabrachial nuclei, nucleus of the lateral lemniscus, oral pontine reticular nucleus, and the dorsal raphe.
The degeneration of the contralateral areas could be explained through a path of the anterior commissure..
(1) The NOTL-contralateral NOTL fibers, which connect bilateral NOTLs through a part of the posterior commissure.
HRP injections into the pretectal area, lateral geniculate body, suprachiasmatic nucleus and lateral hypothalamic area resulted in the labeling of neurons in the middle subgroup only when the supraoptic commissure and optic tract were injured by a pipette used in injections. Electrolytic lesions of the supraoptic commissure combined with collicular HRP injections resulted in no labeling of cells of the middle subgroup. From these findings, it could be concluded that neurons of the dorsal and ventral subgroups sent axons to the ipsilateral superior colliculus, and that fibers of neurons of the middle subgroup coursed through the supraoptic commissure to the contralateral superior colliculus..
Ascending contralateral projections exit rostrally and possibly laterally, enter the posterior and postoptic commissures and terminate in the contralateral AP, LGN, NP, NR, and rostral tectum. A medially directed projection enters the intertectal commissure, and some of these fibers may terminate sparsely in an area of the contralateral tectum homotopic to the lesion.
Visual structures: ventral lateral geniculate nucleus, parabigeminal nucleus, pretectal area (nucleus of the optic tract, posterior pretectal nucleus, nuclei of the posterior commissure).
No evidence was found for the existence of afferents from the paramedian pontine reticular formation, the nucleus Darkschewitsch, the nuclei of the posterior commissure, the lateral tegmentum and the dentate nucleus..
In addition to the 'pupilloconstrictor' response there is also another short-latency discharge in the short ciliary nerves following stimulation of the posterior commissure and the Edinger-Westphal nucleus.
The remaining fibers pass through the posterior commissure and terminate in the torus longitudinalis at the rostral end of the tract. Degenerating terminals were also seen in the torus longitudinalis when lesions were made in the optic tectum, tectal commissure, torus semicircularis, and in the area between the valvula and the corpus cerebelli.
The majority of the labeled cells were obtained from two injections performed at the level of the commissure of the superior colliculus (231 cells) whereas 5 injections performed at lower levels led to labeling of 49 cells.
After deep collicular injections numerous labeled cells were consistently found in the parabigeminal nucleus, the mesencephalic reticular formation, substantia nigra pars reticulata, the nucleus of posterior commissure, the pretectal area, zona incerta, and the ventral nucleus of the lateral geniculate body. In some cases, HRP-positive cells were seen in the nucleus of posterior commissure, the pretectal area, Forel's field, and nucleus reticularis thalami.
There is a cell migration between the ventral-most portions of the two ventromedial nuclei on days 9 through 11, and as a result a well-developed oculomotor commissure is established between these two subnuclei.
Six other cats underwent the same cortical ablations plus a transection of the commissure of the superior colliculus; postoperatively, they demonstrated good visually guided orienting behavior (i.e., the Sprague effect) but still could solve only the brightness task. These data indicate that, while a transection of the collicular commissure after visual decortication dramatically improves visual orienting, it does not obviously improve visual discrimination abilities..
Labeled axons also pass to the opposite, or contralateral colliculus via the tectal commissure.
The nucleus of the posterior commissure (NPC) and its subdivisions do not receive any of these inputs. The projections of the pretectum involve a number of structures within the thalamus and brain stem and there are differences in the projection targets of the pretectal region which receives direct visual input (i.e., SL and ON) and the region which does not (i.e., nucleus of the posterior commissure, NPC).
Goldfish with transections of the intertectal commissure learned but failed to transfer interocularly a simple visually cued avoidance task in a shuttle box, whereas posterior commissure lesions had no effect on this simple transfer task. However, fish with tectal commissure lesions could show normal interocular transfer of a shape discrimination, once discrimination pretraining with color cues had been carried out with each eye separately. Lesions of anterior commissure had no effect on either shape or color transfer, but fish with intended cuts of the postoptic commissures showed striking deficits of interocular transfer. As with comparable studies in the pigeon, it is concluded that postoptic, but not tectal, commissures are required for interocular transfer in the goldfish..
(1) Large occipito-temporal cortical lesions produce a stable field blindness, but the blindness is alleviated by a transection of the commissure of the superior colliculus (or a unilateral collicular ablation).
They are centrolateral (CL), paracentral (Pc), central medial (CeM) and centre median (CM), nuclei of the thalamus, zona incerta (ZI) and Forel's field H1 of the subthalamus, nucleus of the posterior commissure and anterior and posterior nuclei of the pretectum (Prt), stratum griseum intermedial and profundum of superior colliculus (CS), periaqueductal gray matter (GC) and pontine nuclei (NP).
They disseminate mainly in the colliculus superior, the pretectum, the nucleus of the posterior commissure, the preoculomotor complex and the intralaminar nuclei of the thalamus.
At the mesodiencephalic junction fibers enter the nucleus of the posterior commissure and pretectal nuclei, and others cross in the posterior commissure to distribute to these structures on the contralateral side. It rapidly diminishes in size as it attains more rostral levels where it is found in the bed nuclei of the stria terminalis and the anterior commissure. Neither division is conspicuous rostral to the anterior commissure.
They remain in this position until the level of the postoptic commissure where they decussate. The third bundle of tectofugal efferents leaves the tectum medially, at the level of the lesion, and enters the tectal commissure, through which it is distributed to the ipsilateral torus longitudinalis and contralateral optic tectum..
There were two dorsomedial projections: (1) a projection to the superior colliculus which terminated mainly in the medial third of the stratum opticum, and (2) a large projection via the superior thalamic radiation which terminated in the ipsilateral pretectal area; a continuation of this projection passed through the posterior commissure to attain the contralateral pretectal area. The three ventromedial projections involved: (1) a geniculopontine tract which coursed through the basis pedunculi and the lateral lemniscus to terminate in the dorsomedial and dorsolateral parts of the pons after giving terminals to the lateral terminal nucleus of the accessory optic tract, (2) a projection via Meynert's commissure to the suprachiasmatic nuclei of both sides of the brain stem as well as to the contralateral ventral lateral geniculate nucleus and lateral terminal nucleus of the accessory optic tract, and (3) a medial projection to the ipsilateral zona incerta.
No controlateral retinofugal fasicule crossing over in the posterior commissure as previously described in this species using the Nauta method (3) was observed.
Degenerated fibers of passage were identified in the tectal commissure, the posterior commissure, the ventral tegmental decussation and the supraoptic decussations.
After either bilateral occipitotemporal lesions (with a split of the tectal commissure) or bilateral area 17, 18, and 19 lesions, the cats could see with each eye only from the midline to 90 degrees ipsilateral.
Thus, removal of the contralateral tectum, or splitting of the collicular commissure, abolishes this inhibition and allows the return of function in the ipsilateral colliculus, and with it the recovery fronm hemianopia.
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