Nucleus Rotundus

(2) Neurogenesis in the nucleus rotundus (Rot) and in the dorsal lateral geniculate nucleus (GLd) occurred from S11-12 to S15.  

So for example the right nucleus rotundus is less modulated by right forebrain influences than the left nucleus rotundus by the left ones.  

The nucleus rotundus of the turtles Emys orbicularis and Testudo horsfieldi was analysed by axonal tracing methods and post-embedding GABA immunocytochemistry. Occasional GABA-ir-labelled axon terminals were observed; these may arise from the rare GABAergic neurons in the central tectal layer, or from neurons in the ventral pretectal nucleus, which projects both to the optic tectum and nucleus rotundus. The existence in reptiles of reciprocal connections between the nucleus rotundus and the optic tectum as a phylogenetically ancient feedback system is discussed..  

First, visually evoked extracellular responses recorded in the dorsal anterior subdivision of the thalamic nucleus rotundus (RtDa), receiving the ascending tectal output, are closely synchronized to this feedback signal.  

Using histochemical determination of activity of the mitochondrial oxidative enzyme cytochrome oxidase (CO) in brain structures, metabolic activity both in turtles and in lizards has been shown to be higher in centers of the tectofugal channel (the tectal stratum griseum centrale, SGC; nucleus pretectalis ventralis, Ptv; thalamic nucleus rotundus, Rot; telencephalic visual area of the anterior dorsal ventricular ridge, Advr) than in the thalamofugal channel centers (the thalamic nucleus geniculatus lateralis pars dorsalis, GLd; cortex dorsolateralis, Cxdl; and pallial thickening, Path) of the visual system.  

Furthermore, the SGC-I neurons project with an interdigitating topography to the nucleus rotundus, where the direction of motion is computed.  

The tectofugal pathway in birds goes from the optic tectum to the telencephalic entopallium via the thalamic nucleus rotundus (nRt).  

Here we show by single unit recording that there exist three classes of looming-sensitive neurons in the pigeon tectal layer 13, which sends looming information to the nucleus rotundus or to the tectopontine system.  

The sauropsidian nucleus rotundus and its mammalian homologue(s) occupy a central position in this pathway. In general, rotundic connections in reptiles and birds are quite similar, especially with regards to pretectal and tectal afferences; as a novel finding, we describe varicose fibers arising from nucleus rotundus that reached the developing chick striatum. Overall, telencephalic projections from the posterior/intralaminar complex of the mammalian thalamus can be compared with the telencephalic projections of the reptilian nucleus rotundus. With the exception of the isocortical connections, the mouse suprageniculate nucleus shares a number of afferent and efferent connections with the sauropsidian nucleus rotundus.  

We showed that the Enta, which is located within the dorsal peduncle of the lateral forebrain bundle (Pedd), has roughly topographically organized reciprocal connections with the dorsal thalamic visual nuclei, the nucleus rotundus (Rot) and dorsal lateral geniculate nucleus (GLd).  

Similarly, in the diencephalon and midbrain, prominent LAMP labeling was observed in such limbic areas as the dorsomedial thalamus, the hypothalamus, the ventral tegmental area, and the central midbrain gray, as well as in a few nonlimbic areas such as nucleus rotundus, the shell of the nucleus pretectalis, the superficial tectum, and the parvocellular isthmic nucleus.  

This was studied in the lateralized visual system of pigeons by recording from single units of the left and right diencephalic nucleus rotundus of the tectofugal pathway while visually stimulating the ipsilateral and/or contralateral eye.  

Part of the tectofugal pathway, the ectostriatum receives a large ascending thalamic input from the nucleus rotundus, the homolog of the mammalian pulvinar complex.  

Experiment II analyzed the morphology of the nucleus rotundus and optic tectum in long-term detelencephalated and control birds, using a Klüver-Barrera staining and image analyzer system. Morphometric analysis revealed a decreased number of neurons and increased vascularity, associated with increases in the perimeter (p < 0.001) in the nucleus rotundus.  

Several of the diencephalic target nuclei of the tectothalamic projection, such as the principal pretectal nucleus, subpretectal nucleus, and nucleus rotundus, contain distinct subregions or populations of neurons expressing OL-protocadherin.  

The presence of these glomerular-like synapses in layer 3 proves that the optic terminals in layer 3 also take part in the transmission of optic impulses to the nucleus rotundus..  

The perientopallium, on the other hand, can be defined by relatively sparse projections from nucleus rotundus, a calretinin-positive plexus of nerve fibers, and weak cytochrome oxidase activity and parvalbumin immunoreactivity.  

Organization of the fibre connections in the chick nucleus rotundus (Rt) was investigated by an axonal tracing method using wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP).  

The nucleus rotundus (ROT) is a major relay station in the tectofugal pathway of the avian visual system.  

The nucleus rotundus is the largest nucleus of the avian thalamus. The nucleus rotundus is generally believed to contain internal divisions processing information on color, form, motion, and looming of visual objects. Results show that each cadherin is expressed by one coherent part of the nucleus rotundus that is connected to other brain structures by fiber tracts expressing the same subtype of cadherin. Overall, the expression of the four cadherins encompasses almost the entire nucleus rotundus.  

A key component of this pathway is the projection from the optic tectum onto the nucleus rotundus and the nucleus subpretectalis.  

Using electrophysiological recordings, we investigated the influence of these two nuclei and nucleus rotundus on the processing of binocular visual information by treating the nuclei with picrotoxin or electrolytic lesions. Treatment of nucleus rotundus with picrotoxin increases contralaterally and bilaterally, but not ipsilaterally evoked responses.  

In the telencephalon and diencephalon a few S100-positive neurons were observed in basal ganglia, nucleus paraventricularis hypothalami, nucleus rotundus and nucleus geniculatus lateralis, pars ventralis.  

The present study examined the efficiency of fluorescent carbocyanine dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylinodocarbocyanine perchlorate and cholera toxin B subunit in tracing the crossed tectal projection to the nucleus rotundus of the thalamus (tectorotundal pathways) of paraformaldehyde-fixed and living chick embryos. The tracers were injected into the optic tectum under three experimental conditions (carbocyanine postfix, carbocyanine in vivo, and cholera toxin B subunit in vivo) and the anterograde transport of the nucleus rotundus was monitored and compared.In the carbocyanine postfix method, small crystals of carbocyanine dye were inserted into the tectum of paraformaldehyde-fixed embryos. Results showed that tectal neurons did not begin to innervate the ipsilateral nucleus rotundus until embryonic day 9 and the contralateral nucleus rotundus until embryonic day 17. By embryonic day 8, the labeled axons terminated in the ipsilateral nucleus rotundus and the crossed tectorotundal projection was first detected by embryonic day 10. After a 6- to 10-h survival period, heavily labeled axons were found to innervate bilaterally the nucleus rotundus by embryonic day 8.  

The ascending tectal projection arises exclusively from cells located in layer 13 of the optic tectum and is directed bilaterally toward the thalamic nucleus rotundus.  

In order to reveal a detailed organization of Ec, we decided to systematically analyze the afferent connections of Ec by injecting small amounts of sensitive tracers (biotinylated dextran amine and cholera toxin subunit B) selectively into different regions of Ec and the thalamic center of the tectofugal pathway (the nucleus rotundus, Rt).  

In two species of turtle (Emys orbicularis and Testudo horsfieldi), retrograde and anterograde tracer techniques were used to study projections from the optic tectum to the nucleus rotundus (Rot) and to the dorsal lateral geniculate nucleus (GLd).  

The present work is an analysis of the afferent projections to the thalamic nucleus rotundus in a lizard, both at the light- and electron-microscopic level, using biotinylated dextran amine (BDA) as a neuroanatomical tracer. This study has confirmed previously reported afferent projections to nucleus rotundus in reptiles and has also identified a number of new cellular aggregates projecting to this dorsal thalamic nucleus. 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. Tectal axons entering nucleus rotundus were fine and varicose and formed exclusively asymmetric synaptic contacts, mainly on small dendritic profiles. After comparing our results with those in other reptiles, birds and mammals, we propose that the sauropsidian nucleus rotundus forms part of a visual tectofugal pathway that conveys mesencephalic visual information to the striatum and dorsal ventricular ridge, and is similar to the mammalian colliculo-posterior/intralaminar-striatoamygdaloid pathway, the function of which may be to participate in visually guided behaviour..  

The projection is heavier on the suprapeduncular nucleus, which in turn projects on nucleus rotundus in the dorsal thalamus. nucleus rotundus is the origin of a prominent projection to the lateral striatum among other forebrain areas.  

In these layers, the dendritic branches of layer 13 neurons that project to the nucleus rotundus have previously been shown to receive retinal fibre input.  

These recrossing projections connect the contralateral tectum opticum with the ipsilateral nucleus rotundus, which in turn projects to the ectostriatum. This study shows that contralateral and ipsilateral information converges on single neurons within the nucleus rotundus, the ectostriatal region and the lateral neostriatum. The number of neurons responding to ipsilateral stimuli increases from nucleus rotundus to the lateral neostriatum. The strength of ipsilateral responses is rather weak within the nucleus rotundus and ectostriatum, but shows a sharp increase in the lateral neostriatum. For most neurons of nucleus rotundus and ectostriatum, an additional ipsilateral stimulus did not significantly affect the response to a contralateral one.  

Several brainstem regions, including nucleus rotundus, the medial spiriform nucleus (SpM), the principle nucleus of the trigeminal nerve, nucleus laminaris and scattered cell groups throughout the isthmus and pontine reticular formation stain intensely for iron.  

In birds, the thalamic nucleus rotundus relays visual information from the midbrain optic tectum to the forebrain ectostriatum. Using brain slices, the present study investigates the firing patterns and morphological features of 41 neurons in various divisions of the pigeon nucleus rotundus.  

Most notable are cells in the pigeon's nucleus rotundus: these respond selectively to looming stimuli, some firing at a specific time before the stimulus collides with the bird.  

At least three identified cell types in the stratum griseum centrale (SGC) of the chick optic tectum mediate separate pathways from the retina to different subdivisions of the thalamic nucleus rotundus. This difference is likely to have functional significance for the differential processing of visual information in the separate pathways from the retina to different subdivisions of the thalamic nucleus rotundus..  

Many NPY perikarya were noted to surround the nucleus rotundus and to be present in the supraoptic nucleus.  

The present study demonstrates this isthmic component to be characterized by a unique connectivity and immunohistochemical pattern: 1) SLu receives tectal afferents and projects back onto the outer retinorecipient tectal layers; 2) it projects bilaterally onto the nucleus rotundus and thus modulates the ascending tectofugal system; 3) in addition, previous studies have demonstrated SLu projections onto the lateral spiriform nucleus (SpL), which mediates basal ganglia output onto the tectum.  

In the brain, PPSS I mRNA was expressed in the optic tectum (OT) and in many hypothalamic nuclei, including the nucleus rotundus (NR), nucleus anterioris hypothalami (NAH), nucleus anterior tuberis (NAT), nucleus lateral tuberis (NLT), as well as in the pituitary (adenohypophysis).  

A direct projection of the nucleus of the basal optic root (nBOR) onto the nucleus rotundus (Rt) in the pigeon would link the accessory optic system to the ascending tectofugal pathway and could thus combine self- and object-motion processes.  

NPY mRNA was widely distributed in the broiler brain, and highly expressed in the hippocampus, nucleus commissurae pallii, infundibular hypothalamic nucleus, nucleus pretectalis pars ventralis and neurons around the nucleus rotundus.  

The present paper reports for the first time in birds the modulatory effects of the nucleus of the basal optic root (nBOR) on visual neurons in the nucleus rotundus in particular and those of the accessory optic system on the tectofugal pathway in general. Response latency measurements implied that there might be at least two pathways from the nBOR to the nucleus rotundus, one being a direct excitatory pathway and the other an indirect inhibitory pathway possibly mediated by the subpretectal nucleus and the interstitio-pretecto-subpretectal nucleus, which have been thought to send inhibitory afferents to the nucleus rotundus.  

The projection of the nucleus rotundus upon the ectostriatum is equivalent to that of the pulvinar nucleus upon the extrastriate cortex in mammals. In this system, the optic tectum relays retinal input to the nucleus rotundus, which then ascends to the ectostriatum of the telencephalon. We used multiple injections of cholera toxin B subunit (CTb) in the ectostriatum of chick embryos to retrogradely trace projections to the nucleus rotundus. We found CTb-labeled neurons in the nucleus rotundus at embryonic day 7.5-8. By embryonic day 8-8.5, increased numbers of CTb-labeled neurons were seen in the nucleus rotundus. It was noted that the time of this initial connection between the nucleus rotundus and the ectostriatum is nearly synchronous with that of the retinotectal and tectorotundal pathways, respectively (Crossland et al., 1975; Thanos & Bonhoeffer, 1987; Wu et al., 2000).  

These aggregates represent the anlagen of specific diencephalic brain nuclei, e.g., the lateroanterior nucleus, the ventral geniculate nucleus, the nucleus rotundus, the perirotundic area, the principal precommissural nucleus, and the lateral spiriform nucleus.  

Visual information processing within the ascending tectofugal pathway to the forebrain undergoes essential rearrangements between the mesencephalic tectum opticum and the diencephalic nucleus rotundus of birds. The outer tectal layers constitute a two-dimensional map of the visual surrounding, whereas nucleus rotundus is characterized by functional domains in which different visual features such as movement, color, or luminance are processed in parallel. Five different cell populations were distinguished that could be differentiated according to their dendritic ramifications within different retinorecipient laminae and their axons projecting to different subcomponents of the nucleus rotundus.  

Two ascending gamma-aminobutyric acid (GABA)ergic pathways to thalamic visual centers were revealed: a weak projection from the retinorecipient nucleus lentiformis mesencephali to the ipsilateral nucleus geniculatus lateralis pars dorsalis and a considerably stronger projection from the nonretinorecipient nucleus pretectalis ventralis to the nucleus rotundus. The interstitial nucleus of the tectothalamic tract is also involved in reciprocal projections of the pretectum and nucleus rotundus.  

To elucidate the organization and evolution of the tectorotundotelencephalic pathways in birds and reptiles, we reinvestigated at both light and electron microscopic levels the efferent projections of nucleus rotundus in a lizard, using the sensitive tracer biotinylated dextran amine. Our results indicate that nucleus rotundus projects to targets in the basal ganglia (lateral parts of striatum and olfactory tubercle and possibly the globus pallidus), the anterior dorsal ventricular ridge (ADVR), and the amygdaloid complex (the central and possibly lateral amygdaloid nuclei). The connections and pathways involving nucleus rotundus suggest that this nucleus conveys visual information which may play a role in visuomotor, emotional, and visceral functions..  

A similar dendritic morphology and projection pattern can be found in cells of the avian optic tectum that project upon the nucleus rotundus, a thalamic nucleus homologous to the mammalian caudal/inferior pulvinar.  

Testosterone-treated males (both captive and free-living) had a smaller telencephalon and nucleus rotundus, but not a smaller HF or ectostriatum, than controls.  

These aggregates represent the anlagen of specific diencephalic brain nuclei, e.g., the lateroanterior nucleus, the ventral geniculate nucleus, the nucleus rotundus, the perirotundic area, the principal precommissural nucleus, and the lateral spiriform nucleus.  

Based on findings in other reptiles, it seems likely that the SDH-rich zone in rostrolateral DVR represents the zone of termination of nucleus rotundus visual input to the DVR, whereas the zone in ventromedial DVR represents the zone of termination of nucleus reuniens auditory input.  

The organisation of the tectofugal visual projections to the rotundal nuclei was more symmetrical (males only examined) although there was a trend towards a greater number of projections from the left optic tectum to its ipsilateral nucleus rotundus than from the right optic tectum to its ipsilateral nucleus rotundus.  

In the tectorotundal system, neurons of the stratum griseum centrale (SGC) of the optic tectum send their axons bilaterally to the nucleus rotundus (Rt).  

Minor visual centres also became re-innervated but, in addition, regenerating axons formed persistent projections into the opposite optic nerve and to non-retino-recipient regions such as the nucleus rotundus, hypothalamus, and olfactory nerve, as well as the posterior and tectal commissures.  

Using control animals and pigeons which were monocularly deprived for 10 days after hatching, the present study could show that the cellular soma sizes of the nucleus rotundus within the tectofugal visual pathway are modified by light experience depending on the timepoint and direction of lateralized stimulation.  

Rhodamine B Isothiocyanate (RITC), Fluorogold (FG) and True blue (TB) were injected into either the visual Wulst (thalamofugal pathway) or the nucleus rotundus (Rt; tectofugal pathway) and the retrogradely labelled neurones in the nucleus geniculatus lateralis pars dorsalis (GLd) or the optic tectum, respectively, were counted.  

nucleus rotundus is a prominent nucleus in the dorsal thalamus of nonmammalian amniotes.  

The DVR received projections from the nucleus rotundus and the dorsal cortex exclusively from the perirotundal complex (including lateral geniculate nucleus).  

We show that the ventral tectum opticum (TO) has significantly more projections onto the nucleus rotundus (Rt) than dorsal tectal areas.  

The nucleus rotundus is a large thalamic nucleus in birds and plays a critical role in many visual discrimination tasks. In order to test the hypothesis that there are functionally distinct subdivisions in the nucleus rotundus, effects of selective lesions of the nucleus were studied in pigeons.  

Three types of looming-selective neurons have been found in the nucleus rotundus of pigeons, each computing a different optical variable related to image expansion of objects approaching on a direct collision course with the bird.  

The nucleus rotundus receives GABA-like immunoreactive fibres from the nuclei subpretectalis and postero-ventralis thalami. Also, a contralateral influence is present in the nucleus rotundus that may interact in the cooperation of the eyes.  

We now report that due to an asymmetry of commissural projections in the pigeon the left nucleus rotundus of the ascending tectofugal visual system predominantly represents inputs from both eyes while the right nucleus rotundus mainly represents the contralateral left eye.  

Variation in courtship success was found to be related to variation in two areas of the avian brain: the song control nucleus, area X, and the thalamic visual area, nucleus rotundus. Volume of nucleus rotundus was positively correlated with song potency, vocalizing to females and courtship persistence.  

This connection could be responsible for direct optic transmission via ganglion cells to the nucleus rotundus.  

The vtt is composed of fibers from ganglion and multipolar cells of the layer 7 that project bilaterally to the nucleus of the vtt, the ventrolateral thalamic nucleus, the medial posterior thalamic nucleus (MP), the nucleus rotundus (Rot), the IGL, and the cell plate of the GLD.  

Neuronal responses of 114 cells to electrical stimulation of the optic tectum were extracellularly recorded from the contralateral nucleus rotundus (nRt) in pigeons (Columba livia), and the effects of two glutamatergic antagonists CNQX and CPP, as well as those of GABA, were examined on rotundal cells.  

387:449-465) examined a portion of the tectofugal pathway, the projection from the optic tectum to the nucleus rotundus thalami, in pigeons.  

interstitio-pretecto-subpretectalis (SP/IPS), to the nucleus rotundus (Rt) in chicks was studied by using retrograde tracing techniques.  

Previous lesion studies of color-reversal learning in pigeons show that an impairment results when (1) the tectofugal visual pathway is damaged at either the thalamic level (nucleus rotundus) or the telencephalic level (ectostriatum), or (2) the thalamofugal visual pathway is damaged at the telencephalic level (the visual Wulst).  

However, incubation temperature and gonadal sex are both important in determining the metabolic capacity in the anterior hypothalamus, external amygdala, dorsal lateral nucleus of the hypothalamus, dorsal lateral nucleus of the thalamus, dorsal ventricular ridge, habenula, lateral hypothalamus, nucleus rotundus, nucleus sphericus, periventricular nucleus of the hypothalamus, preoptic area, periventricular nucleus of the preoptic area, septum, striatum, torus semicircularis, and ventromedial nucleus of the hypothalamus.  

The volumes of neither the magnocellular nucleus of the anterior neostriatum nor the nucleus rotundus, a control region, differed seasonally.  

The morphology of nucleus rotundus, a visual thalamic nucleus, was investigated in one species of reptiles. The topographical location of nucleus rotundus and its relationship to surrounding thalamic nuclear groups are described. nucleus rotundus in Caiman can be subdivided into three areas: (1) an outer shell; (2) an inner core; and (3) a cell poor zone located between the shell and core. Both qualitative and quantitative data suggest that relay cells located in the core of nucleus rotundus are not a homogeneous population of neurons but comprise several subtypes..  

IMEL binding in the tectofugal nucleus rotundus, however, was consistently highest under short day conditions.  

AVT gene expressing neurons were distributed within the hypothalamus (in the medial and ventral aspects of the rostral preoptic area, in the lateral forebrain bundle, close to the ependyma of the third ventricle and in several periventricular hypothalamic nuclei) and in some extrahypothalamic regions (around the nucleus rotundus, close to the nucleus commissurae pallii and in a region probably corresponding to the nucleus strial terminalis).  

The avian nucleus rotundus, a nucleus that appears to be homologous to the inferior/ caudal pulvinar of mammals, is the major target of an ascending retino-tecto-thalamic pathway.  

No effects were found from lesions in anterior preoptic or pretectal areas and only slight attenuation of red preferences by lesions in nucleus rotundus, opticus principalis thalami and geniculatus lateralis pars ventralis.  

Meanwhile, GABA may be an inhibitory transmitter in the pigeon nucleus rotundus..  

Finally, BBS/GRP-like IR material was detected in the nucleus habenularis, the nucleus rotundus, several thalamic nuclei, and the optic tectum of the dorso-posterior diencephalon.  

For example, the collothalamic visual nuclei consist of the LP-pulvinar complex in mammals and nucleus rotundus in diapsid reptiles, birds, and turtles.  

Anterograde degeneration was also noted in nuclei and tracts related to the visual tectofugal system-the brachium of the superior colliculus, nucleus rotundus, pretectal nuclei, and the ectostriatum.  

Localization of specific central 2-[ 125I]iodomelatonin binding in the rainbow trout showed high levels of binding associated with neuronal areas involved in the processing of visual signals, particularly the optic tectum and nucleus rotundus..  

An unexpected consequence of ONX was that 2-[ 125I]- iodomelatonin binding was decreased in certain secondary (nucleus rotundus, isthmi nuclei) and tertiary level (ectostriatum) nuclei along the prominent tectofugal visual pathway.  

The dorsolateral thalamic VINs were found lateral and dorsal to the lateral forebrain bundle, lateral to the nucleus periventricularis magnocellullaris, and around the nucleus rotundus..  

The projection from the chick optic tectum to the nucleus rotundus was investigated by iontophoresis of the anterograde tracer Phaseolus vulgaris lectin (PHA-L) into the optic tectum and by Golgi impregnation. PHA-L labelled fibres were observed within the ipsilateral nucleus rotundus and to course through the supraoptic decussation to the contralateral nucleus rotundus. Before reaching the nucleus rotundus, PHA-L labelled fibres gave off short terminal branches in the caudoventral thalamic nucleus. Within the ipsilateral nucleus rotundus, the labelled fibres formed an extensive fibre net with a dense core and a less dense periphery. PHA-L labelled fibres in the contralateral nucleus rotundus exhibited a qualitatively similar but sparser distribution. There appeared to be a topographic representation of the optic tectum within the nucleus rotundus. Electron microscopy revealed that PHA-L labelled tectal fibres established asymmetric synapses with principal neurons in the nucleus rotundus..  

Radioactive labeling was observed in areas which receive primary, secondary, and tertiary visual input: the superficial layers of the optic tectum, lateral geniculate nucleus, nucleus rotundus, dorsal ventricular ridge, and striatum.  

The locus of this forebrain somesthetic region was then compared with the location of the DVR projection areas of auditory (nucleus reuniens) and visual (nucleus rotundus) thalamic nuclei.  

A gonadal modulatory role was not always evident in all brain areas as revealed by long-day photic cycles producing diminished (p < 0.01) binding levels in the anterior neostriatum and the nucleus rotundus of both castrated and gonadally intact animals, although elevated values were also found in the substantia grisea centralis (p < 0.05) of the same animals.  

Having injected Phaseolus Vulgaris Lectin (PhA-L) iontophoretically to subpretectal (SP) and postero-ventralis (PV) thalamic nuclei, labelled fibers and terminals appeared in nucleus rotundus (Rt).  

Four major tectal outputs were studied: 1) the ipsilateral ascending projection to nucleus rotundus of thalamus; 2) the ipsilateral ascending projection to the dorsal and ventral lateral geniculate nuclei of the thalamus; 3) the crossed descending projection to paramedian regions of the pons and medulla; and 4) the ipsilateral descending projection to cell groups of the ventrolateral pons and medulla. The projection to nucleus rotundus was found to arise exclusively from multipolar neurons of the stratum griseum centrale, while the projection to the geniculate nuclei was found to arise from radial cells with long ascending dendrites in the stratum griseum periventriculare.  

Instead, we found that damage to nucleus rotundus (the thalamic component of the tectofugal pathway) resulted in deficits that were far in excess of those that had been obtained after IHA and HD lesions.  

In situ hybridization reveals that the gamma 4-subunit mRNA is abundant in several brain regions, including the ectostriatum, nucleus rotundus and hyperstriatum ventrale, which are involved in visual processing and learning..  

The fluorescent retrograde tracers Rhodamine B Isothiocyanate (RITC) and Fast Blue (FB) were injected either into the thalamic nucleus rotundus or into the complexus neck muscle in pigeons.  

High receptor density was detected in the major targets of direct retinal input (optic tectum, nucleus of the optic basal rout, ventrolateral geniculate nucleus), as well as areas representing terminals in the visual pathways (nucleus rotundus, ectostriatum, thalamo-hyperstriatal pathway).  

The responses of single cells to luminance, color and computer-generated spots, bars, kinematograms, and motion-in-depth stimuli were studied in the nucleus rotundus of pigeons. These results indicate that visual information processing of color, ambient illumination, and motion in depth are segregated into different subdivisions at the level of nucleus rotundus in the avian brain..  

Relatively high densities of [ 3H] muscimol binding sites were also observed in the torus semicircularis of the mesencephalon and in the thalamic nucleus rotundus and posterolateral nucleus, plus the mitral cell layer of the olfactory bulb, the amygdala pars lateralis and the striatum of the telencephalon.  

After having iontophoretically injected Phaseolus vulgaris Lectin into nucleus rotundus, labelled terminals were examined in ectostriatum centrale by EM.  

Phaseolus vulgaris leucoagglutinin extracellular injection was performed in nucleus rotundus thalami and the course of labelled fibers and their termination were examined in chicken.  

This impaired performance on color discrimination was not, however, as severe as that of a bird with lesions in the nucleus rotundus.  

Interconnections between the visual thalamus and the pretectum were investigated in one species of reptiles, Caiman crocodilus, by injections of horseradish peroxidase into nucleus rotundus. Nucleus pretectalis was identified as a major target of rotundal efferents as well as a significant input to nucleus rotundus.  

Structures that contained high numbers of alpha 7-like immunoreactive (LI) somata included the intergeniculate leaflet, nucleus intercalatus thalami, nucleus ovoidalis, organum paraventricularis, nucleus rotundus, isthmic nuclei, nucleus trochlearis, oculomotor complex, nucleus interstitio-pretecto-subpretectalis, stratum griseum centrale of the optic tectum, and nucleus semilunaris.  

We describe a subpopulation of neurons in the nucleus rotundus of the pigeon brain that respond selectively to objects moving on a collision course towards the bird..  

The EM preparates displayed in the nucleus rotundus also symmetrical type of synapses with flattened vesicles, known this type as inhibitory synapsis.  

The structural arrangement of nucleus rotundus was studied by Golgi method.  

The analysis of EM structure of nucleus rotundus completes the results got by Golgi study.  

Eight brain regions were chosen for binding characterization and pharmacological analysis: optic tectum, Edinger-Westphal nucleus, oculomotor nucleus, nucleus rotundus, ventral supraoptic decussation, ventrolateral geniculate nucleus, neostriatum, and ectostriatum.  

archistriatal, neostriatal and hyperstriatal regions, hippocampus, piriform cortex); b) medium-sized cell bodies located around the nucleus rotundus, ventrolateral, and lateral anterior thalamic nuclei; c) small clustered cells within the periventricular and medial preoptic nuclei.  

The relation between the 'sensory' versus 'mnemonic' deficits from damage to nucleus rotundus in the trained hemisphere are discussed..  

The discrimination threshold at 510 and 640 nm has been measured before and after the bilateral lesion with kaïnic acid of two main thalamic structures: the nucleus rotundus (Rt) and the nucleus geniculatus lateralis ventralis (GLv).  

Very high levels of labelling of delta binding sites were, however, found in the nucleus rotundus.  

The retrogradely labeled neurons were distributed mainly in the immediate vicinity of the lateral, dorsal, and ventral aspects of the nucleus rotundus.  

The activity of these enzymes was studied by a one-point assay in 5 nuclei of the song system (X, MAN, HVc, RA, ICo), 2 nuclei of the visual system (ectostriatum, nucleus rotundus) and in limbic and hypothalamic areas.  

We have found that the enlargement of the epileptic brain is not uniform: it is most marked in the telencephalon, and is present to a lesser degree in the cerebellum, but neither the optic tectum nor the diencephalic nucleus rotundus shows a significant increase in size.  

Histochemical mapping of AChE activity in the chick diencephalon shows differential staining of several subregions within the nucleus rotundus.  

The characterization of neuron populations by their immunoreactivity against parvalbumin- and calbindin (28-kDa)-antisera has been used to study the postnatal development of the visual diencephalic nucleus rotundus and the mesencephalic nucleus isthmi complex in zebra finches. In nucleus rotundus, parvalbumin-immunoreactivity was restricted to the neuropil during the first 10 days and appears additionally in somata around day 12 where it remains until adulthood. Thus, the adult nucleus rotundus shows an almost complementary distribution of calbindin- and parvalbumin-immunoreactive structures: the numerous, heavily parvalbumin-positive somata, which are surrounded by dense immunoreactive neuropil are in sharp contrast to the complete absence of calbindin-immunoreactive somata. A comparison between the two calcium-binding proteins and GABA-immunoreactivity in adult brains revealed different relationships in the two nuclei: while in nucleus rotundus GABA-staining pattern neither resembles that of parvalbumin nor of calbindin, in the nucleus isthmi complex all three staining patterns coincide..  

Lesion in the nucleus rotundus before monocular discrimination retarded acquisition of the original monocular learning but did not cause deficits in interocular transfer, whereas the rotundal lesion after the monocular discrimination learning resulted in deficits in interocular transfer.  

Previous experiments with 2-deoxyglucose (2-DG) suggested the existence of a critical period for the effects of monocular deprivation in the nucleus rotundus of zebra finches. The present study concerns the time course of this sensitive period for the morphological effects of monocular deprivation in two areas of the tectofugal visual pathway of zebra finches, the nucleus rotundus of the thalamus and the telencephalic ectostriatum. The measurements of the volume of the nucleus rotundus parallel the cell size measurements, with the exception that the second increase in sensitivity occurs with deprivation onset at day 50 instead of day 40.  

tectum opticum, nucleus rotundus of thalamus and ectostriatum of telencephalon--of 13-day chick embryos. Being phylogenetically more ancient structures, tectum opticum and nucleus rotundus reveal differentiation earlier than ectostriatum which is phylogenetically younger..  

In nonmammalian forms, the major target of ascending tectal visual signals is nucleus rotundus, a thalamic nucleus that projects in turn to the subpallial telencephalon. nucleus rotundus was found to project to a sector of the ipsilateral anterior dorsal ventricular ridge (ADVR) of the telencephalon.  

Intermediate densities were found in the forebrain, particularly the paleostriatum primitivum, the nucleus rotundus and the cerebellum.  

The excitatory projection probably leads from the eye to the contralateral tectum opticum, then recrosses back to the nucleus rotundus of the ipsilateral side where it reaches the ectostriatum. In unilaterally enucleated birds, the ipsilateral response is enhanced in the ectostriatum and can be detected in the nucleus rotundus, too.  

nucleus rotundus and nucleus dorsolateralis posterior (DLP) are the thalamic components of two parallel pathways within the tectofugal division of the pigeon visual system.  

NPY-like containing perikarya were localized within the hippocampus, bed nucleus of the stria terminalis and surrounding the nucleus rotundus and nucleus of the basal optic root.  

Ultrastructural effects of monocular deprivation starting at hatching have been studied in the neuropil of nucleus rotundus, the thalamic visual relay station of the tectofugal pathway in birds. Alterations obtained by monocular deprivation were: The synaptic density increases by 35% in the nucleus rotundus of both sides of the brain above normal values in juvenile birds.  

140:35-52, '70) have described an ascending tectofugal visual pathway from the optic tectum to the ectostriatum by way of the nucleus rotundus of the thalamus. Single-unit recording demonstrated that cells in DLPc respond to whole-field illumination at the same latency as cells in the nucleus rotundus, indicating that the tecto-DLPc-neostriatal pathway transmits visual information to the telencephalon.  

The development and maturation of synapses in the nucleus rotundus of the zebra finch were examined at 1, 5, 10, 20, and 100 days posthatching.  

The number of retrogradely labeled and unlabeled neurons in two sensory thalamic nuclei, nucleus rotundus (vision) and nucleus reuniens pars centralis (audition) were counted.  

The postnatal development of two visual areas (nucleus rotundus and ectostriatum) and two song control areas (hyperstriatum ventrale pars caudale, HVc, and nucleus robustus archistriatalis, RA) of the zebra finch brain was followed from birth to adulthood. The nucleus rotundus, the diencephalic station of the tectofugal pathway, exhibits the fastest development: rotundal neurons reach their maximum size at 20 days of age; the volume of this structure reaches adult size at the same time.  

Tectorotundal axons reach the diencephalon via the tectothalamic tract and give rise to fine terminal collaterals in the nucleus of the tectothalamic tract ipsilaterally and in nucleus rotundus bilaterally. Single axons form sheetlike terminal fields that span the rostrocaudal extent of nucleus rotundus.  

We evaluated in zebra finches the effects of monocular deprivation on morphological and physiological features of the nucleus rotundus, the thalamic relay station of the tectofugal pathway.  

After their training was completed, a unilateral electrolytic lesion was made either in the nucleus rotundus or in the nucleus opticus principalis thalami (OPT).  

During conditioning single neurons in the nucleus rotundus and ectostriatum, the thalamic and telencephalic relays of the tectofugal pathway, showed enhancement of their phasic light-evoked responses.  

Many large HRP-labeled cells were recognized in the nucleus rotundus (Rt).  

This is an electron microscopic study of one of these, the dorsal area, which receives its thalamic input from the tectorecipient nucleus rotundus.  

Additional afferents to nLM originate from the ipsilateral tectum, the nucleus rotundus, the mesencephalic pretectal gray, the contralateral nLM, and the nucleus of the basal optic root.  

The present work describes the results of a quantitative study of the nucleus rotundus of C. The overall neuronal density of the nucleus and the density of light and dark cells which forms the neuronal population of the nucleus rotundus were also determined; the light cells were the most represented.  

The rostrolateral area receives a thalamic projection from nucleus rotundus, which receives visual information.  

When performance was stable, bilateral electrolytic lesions were placed in: nucleus rotundus (RT), nucleus opticus principalis thalami (the OPT complex); and RT plus the OPT complex. Lesions confined to the OPT complex did not impair resolution threshold while lesions confined to the nucleus rotundus produced permanent threshold elevations.  

Because the labeled types of neurons have been characterized as the main visual receptive neurons of the optic tectum, and because the nucleus prethalamicus of teleosts projects to the telencephalon, this nucleus can now be considered homologous to the nucleus rotundus of reptiles and birds and to the nucleus lateralis posterior-pulvinar complex of mammals, that is, it provides a relay for retinotectal visual input to the telencephalon.  

Histological structure and neuronal geometry of the nucleus prethalamicus of holocentrid teleosts, which is homologous to the nucleus rotundus of reptiles and birds and to the nucleus lateralis posterior-pulvinar complex of mammals, were studied by means of the Bodian, Nissl, toluidine blue, and Golgi methods.  

nucleus rotundus, a tectorecipient thalamic nucleus in reptiles and birds, is described for the first time in a snake.  

Intensity difference thresholds were assessed behaviorally in 7 painted turtles (Chrysemys picta) before and after lesions of nucleus rotundus thalami or control lesions. Three subjects with control lesions and two subjects with slight bilateral damage to nucleus rotundus showed no permanent elevation of threshold postoperatively. In contrast, two subjects with severe damage to nucleus rotundus showed threshold elevations postoperatively and did not recover with further training. The impairment shown by these subjects with damage to nucleus rotundus appeared to be only on the more difficult problems; they performed as they had preoperatively on easy discriminations..  

Two of the ventral thalamic populations have been frequently placed in the dorsal thalamus and called the nucleus rotundus and the lateral geniculate nucleus.  

Responses to photic stimulation were recorded from the visual wulst, the stratum opticum and the nucleus rotundus.  

Observations of neurons in the Golgi-Cox stained diencephalon in chickens revealed that the nucleus rotundus, corpus geniculatum laterale ventrale, nucleus entopeduncularis inferior and nucleus ovoidalis have well-defined boundaries whereas the other cell groups have ill-defined boundaries. Large, round cell bodies of the nucleus rotundus have very fine dendrites running straight in all directions.  

nucleus rotundus receives an input from the tectum mesencephali, the pretectal area, and from the mesencephalic reticular formation.  

nucleus rotundus in a large, tectorecipient nucleus in the dorsal thalamus of the pond turtles Pseudemys scripta and Chrysemys picta. Astrocytes, oligodendrocytes, and neurons can be identified in both 1-micrometer sections stained with toluidine blue and electron micrographs of nucleus rotundus. There is no indication of interaction between neurons in nucleus rotundus, either via axonal collaterals or presynaptic dendrites.  

nucleus rotundus is the primary thalamic recipient of projections from the optic tectum in pond turtles. Three types of analyses are used in this paper to characterize the organization of the projection of the optic tectum to nucleus rotundus. These preparations show that shafts of axons in the tectothalamic tract give rise to thinner, primary collaterals that enter nucleus rotundus from its caudolateral aspect and form sparsely branching arbors within the nucleus. Although the total size of such arbors is unknown, the evidence suggests that each arbor is large in relation to the size of nucleus rotundus. Thus, injection sites restricted to central tectum label axons throughout nucleus rotundus. Second, subtotal lesions of the tectum produce degeneration throughout nucleus rotundus in silver degeneration preparations. It seems unlikely that nucleus rotundus can be involved in neuronal transactions that preserve detailed spatial information, but it may be involved in processing information on other visual parameters such as stimulus velocity or color..  

In one group of pigeons, the lesions were confined to nucleus rotundus (Rt).  

The relative importance of acetylcholine, dopamine, endogenous opiates, gamma-aminobutyric acid (GABA), glutamate, glycine, noradrenaline, and serotonin as transmitters in the pigeon visual system was estimated by measuring the activity of choline acetyltransferase (ChAT), glutamic acid decarboxylase (GAD), and aromatic amino acid decarboxylase (AAD) as well as the binding of dihydroalprenolol, etorphine, kainic acid, muscimol, serotonin, spiroperidol, strychnine, and quinuclidinyl benzilate (QNB) in the tectum opticum, nucleus rotundus, ectostriatum, dorsolateral thalamus, and hyperstriatum (Wulst).  

The abrupt reorganization of the fibers occurs as the tracts split around the nucleus rotundus to form the brachia of the optic tracts. The fibers are then arranged with temporal fibers nearest the nucleus rotundus and nasal fibers on the opposite edges of the brachia.  

The dorsal diencephalic cell groups are found in the following locations: (1) lateral and dorsal to the lateral forebrain bundle (DD1); (2) in the area ventral to the dorsomedial anterior thalamic nucleus and dorsolateral to PVM (DD2); and (3) at the dorsolateral border of nucleus rotundus (DD3).  

An extensive set of efferents is present to the torus longitudinalis, nucleus rotundus, corpus cerebelli and the various levels of the reticular formation.  

Following iontophoretic peroxidase injections in several parts of the tectum anterograde transport of the enzyme revealed tectal projections to the lateral geniculate nucleus, dorsal tegmentum, pretectal nuclei, nucleus rotundus, torus longitudinalis, torus semicircularis, nucleus isthmi, contralateral tectum and to the mesencephalic and bulbar reticular formations.  

Restricted projections to ADVR originate in nucleus rotundus, nucleus reuniens and nucleus caudalis. nucleus rotundus projects to zone 4 of dorsal area, nucleus caudalis projects to zones 2-4 of dorsal division of medial area, and nucleus reuniens projects to zones 2-4 of both the ventral division of medial area and the ventral area.  

This study describes some properties of the map of nucleus rotundus onto dorsal area of anterior dorsal ventricular ridge (ADVR) in emydid turtles by correlating results of anterograde and retrograde tracing experiments with observations from Golgi- and myelin-stained brains. This paper indicates that the rotundal pathway is organized such that longitudinally aligned groups of neurons in nucleus rotundus project to longitudinal regions in zone 4 of dorsal area.  

At this time numerous abnormal targets were labeled, including nucleus rotundus, nucleus isthmi, cerebellum, pituitary gland and ipsilateral optic tectum.  

An increase in acid phosphatase activity was found in the optic tectum, nucleus rotundus, nucleus geniculatus lateralis and area pretectalis between 2 and 15 days postoperatively.  

Kainic acid had a local necrotizing effect; for example, it destroys neurons in the PC, nucleus rotundus, nucleus spiriformis lateralis, nucleus ruber and neurons of the cerebellar cortex.  

The present findings show that the ventrolateral optic nucleus exhibits homological features of the dorsal lateral geniculate nucleus in other vertebrate groups, whereas the lateral geniculate nucleus of the nurse shark is much more comparable to the nucleus rotundus of teleosts and birds and would be more appropriately so named.  

nucleus rotundus was not detected.  

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.  

It is shown that the organization of particularly the thalamus is characterized by the presence of specific projection areas of each of the two trigeminal systems: a) the ability of infrared preception is reflected particularly in the presence of an unique thalamic nucleus: the nucleus pararotundus and probably also in the enlargement of nucleus rotundus; and b) distinct subnuclei in the thalamic ventral nuclear complex are related to the various nuclei of the common sensory trigeminal system.  

In the region of nucleus rotundus and some other thalamo-pretectal structures, focal potentials and single unit reactions to both types of stimulation were registered.  

Labeled axons from striatal injections pass caudally in the lateral forebrain bundle to enter (via dorsal peduncle) nuclei dorsomedialis, medialis posterior, entopeduncularis anterior, and a zone surrounding nucleus rotundus.  

Neurons in nucleus rotundus have a unimodal soma size distribution and a common dendritic branching pattern. Three cytoarchitectural regions can be differentiated in nucleus rotundus: a shell, a cell-poor region and a core.  

Ascending ipsilateral projections to pretectal-diencephalic areas exit the tectum rostrally and laterally and terminate in the area pretectalis (AP), lateral geniculate (LGN), nucleus pretectalis (NP), and nucleus rotundus (NR).  

After injection of horseradish peroxidase into the frontal organ of Rana temporaria, labeled perikarya were found in the medial part of the amygdala, the preoptic area, the nucleus rotundus, the pretectal area, and the lateral parts of the midbrain central griseum..  

The amphisbaenids share with the Typhlopidae the absence of the lateral and pretectal geniculate bodies, and share with the squamate reptiles, differing from the typhlopids, the remaining structures of the dorsal thalamus, characterized by the well-developed nucleus rotundus.  

The striatum receives projections by way of the dorsal peduncle of the lateral forebrain bundle from four dorsal thalamic nuclei: nucleus rotundus, nucleus reuniens, the posterior part of the dorsal lateral geniculate nucleus and nucleus dorsomedialis.  

These results show that the higher telencephalic visual area (the so-called Wulst) can modulate tectal activity, and so control the output of this region, by an example, to thalamic nucleus rotundus, second station of the tectofugal visual pathway.  

Retinal information is also channeled indirectly through the tectum to nucleus rotundus. nucleus rotundus is either absent or poorly differentiated and there is a strong convergence of the direct and indirect visual pathways at DLGN..  

Synaptic organization of the nucleus rotundus was studied with the electron microscope in three teleost species belonging to the same order.  

A small projection from layer II upon the ipsilateral nucleus rotundus may also be present.  

In birds, superficial laminae of the optic tectum receive a massive retinal input; the tectum in turn projects upon the nucleus rotundus thalami, which then sends its efferents to the ectostriatal core of the telencephalon. To examine the detailed organization of this principal ascending visual pathway, small injections of the marker horseradish peroxidase (HRP) were placed in various sites throughout the ectostriatum (E) or nucleus rotundus (Rt) in pigeons. Cells which lie at various depths in the stratum griseum centrale (SGC) of the tectum project upon distinct subdivisions of nucleus rotundus.  

At thalamic level, HRP-positive neurons were located around nucleus rotundus, i.e., mainly within nuclei dorsomedialis anterior, dorsolateralis anterior and less abundantly in nuclei ventralis and reuniens. In such a case, a very large number of HRP-positive cells were disclosed within all thalamic nuclei surrounding nucleus rotundus, ipsilaterally. In addition, numerous labeled neurons were also found in nucleus rotundus itself and within nucleus reuniens.  

In the hypothalamus and the nucleus rotundus of the diencephalon and in the nucleus reticularis superior of the mesencephalon, sinusoidal waves appeared during stimulation at 8-13/sec.  

The remaining contingent eventually splits into the so-called strio-lobar bundle (SLB) and the lateral forebrain (LFB), but, previous to splitting, it contributes most of the telencephalic projection to the optic tectum in Eugerres, and gives abundant terminals to the ipsilateral nucleus rotundus or prethalamicus in both Eugerres and Holocentrus.  

Three groups of fibers emerge from the lesioned region (a) a medial group, which runs towards the midline and terminates in the ipsilateral torus longitudinalis and the contralateral tectum; (b) an ascending group, which enters the dorsocaudal region of the diencephalon and terminates in pretectal cell groups, in the dorsomedial optic thalamic nucleus, and in the nucleus rotundus or prethalamicus; and (c) a descending group, which funnels down into the midbrain tegmentum. A recurrent fascicle leaves the mainstream and ascends to terminate in scattered diencephalic cell groups, in the nucleus geniculatus posterior pars ventralis, and in the nucleus rotundus or prethalamicus.  

- Without afferent optic pathways there is no significnat change in cellular components of nucleus lateralis anterior, nucleus geniculatus lateralis ventralis, nucleus griseus tectalis, nucleus rotundus and nucleus pretectalis principalis.  

nucleus rotundus receives a major input from the optic tectum in crocodiles, Caiman crocodilus. Telencephalic projections of nucleus rotundus were studied in Caiman by means by the Fink-Heimer procedure after anodal, stereotaxic lesions. Efferent axons of nucleus rotundus assemble on the ventromedial aspect of this nucleus and swing ventrolaterally to enter the dorsal peduncle of the lateral forebrain bundle.  

That is, the optic tectum gives rise to ipsilateral ascending projections to pretectal nuclei, to nucleus rotundus and to nucleus geniculatus lateralis pars ventralis of the diencephalon and, in addition, to a contralateral ascending pathway which courses via the supraoptic decussation to the contralateral diencephalon. A lesion which involved both the retinal-recipient layers and stratum griseum centrale resulted in degeneration in only one additional structure, nucleus rotundus.  

The nucleus rotundus of 21 species of teleosts was studied by a modified Bodian and the Golgi method to clarify the histological organization, with special reference to the cell lamination and the glomerular formation.  

A number of cases of intended destruction of the ventral geniculate also had extensive damage of the overlying nucleus rotundus. In several of these cases of combined destruction of nucleus rotundus and ventral geniculate, the previously reported discrimination deficits following nucleus rotundus lesions did not appear. In those cases in which the nucleus rotundus deficit was observed, the lesions were found to include the nucleus subpretectalis, which, like nucleus rotundus, receives tectofugal fibers via the brachium of the superior colliculus.  

Areas which were stimulated repeatedly at 100 muA and were always negative for sperm release included: the telencephalon with the exception of the preoptic region, the optic tectum, the cerebellum, the inferior lobe of the hypothalamus, the nucleus rotundus and the dorsal medulla.  

Extracellular studies have been made on the background activity and reactions to visual stimuli in neurons of nucleus rotundus and nucleus suprapeduncularis of the thalamus in the tortoise E.  

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