Dorsolateralis Anterior Thalami Research Articles

Representation of time interval entrained by periodic stimuli in the visual thalamus of pigeons.

Animals use the temporal information from previously experienced periodic events to instruct their future behaviors. The retina and cortex are involved in such behavior, but it remains largely unknown how the thalamus, transferring visual information from the retina to the cortex, processes the periodic temporal patterns. Here we report that the luminance cells in the nucleus dorsolateralis anterior thalami (DLA) of pigeons exhibited oscillatory activities in a temporal pattern identical to the rhythmic luminance changes of repetitive light/dark (LD) stimuli with durations in the seconds-to-minutes range. Particularly, after LD stimulation, the DLA cells retained the entrained oscillatory activities with an interval closely matching the duration of the LD cycle. Furthermore, the post-stimulus oscillatory activities of the DLA cells were sustained without feedback inputs from the pallium (equivalent to the mammalian cortex). Our study suggests that the experience-dependent representation of time interval in the brain might not be confined to the pallial/cortical level, but may occur as early as at the thalamic level.

Neuropeptide Y mRNA and peptide in the night-migratory redheaded bunting brain

This study investigated the distribution of neuropeptide Y (NPY) in the brain of the night-migratory redheaded bunting (Emberiza bruniceps). We first cloned the 275-bp NPY gene in buntings, with ≥95% homology with known sequences from other birds. The deduced peptide sequence contained all conserved 36 amino acids chain of the mature NPY peptide, but lacked 6 amino acids that form the NPY signal peptide. Using digosigenin-labeled riboprobe prepared from the cloned sequence, the brain cells that synthesize NPY were identified by in-situ hybridization. The NPY peptide containing cell bodies and terminals (fibers) were localized by immunocytochemistry. NPY mRNA and peptide were widespread throughout the bunting brain. This included predominant pallial and sub-pallial areas (cortex piriformis, cortex prepiriformis, hyperpallium apicale, hippocampus, globus pallidus) and thalamic and hypothalamic nuclei (organum vasculosum laminae terminalis, nucleus (n.) dorsolateralis anterior thalami, n. rotundus, n. infundibularis) including the median eminence and hind brain (n. pretectalis, n. opticus basalis, n. reticularis pontis caudalis pars gigantocellularis). The important structures with only NPY-immunoreactive fibers included the olfactory bulb, medial and lateral septal areas, medial preoptic nucleus, medial suprachiasmatic nucleus, paraventricular nucleus, ventromedial hypothalamic nucleus, optic tectum, and ventro-lateral geniculate nucleus. These results demonstrate that NPY is possibly involved in the regulation of several physiological functions (e.g. daily timing feeding, and reproduction) in the migratory bunting.

Anatomical distribution of NPY-like immunoreactivity in the domestic chick brain (Gallus domesticus).

Neuropeptide Y-immunoreactive (NPY-ir) fibers and neurons in the brain of the domestic chick (Gallus domesticus) were described using an immunohistochemical technique. NPY-ir neurons were seen in the lobus parolfactorius; hyperstriatum, neostriatum, paleostriatum, and archistriatum; hippocampal and parahippocampal areas; dorsolateral corticoid area; piriform cortex; two thalamic areas contiguous to the n. rotundus; n. dorsolateralis anterior thalami, pars lateralis, and pars magnocellularis; n. periventricularis hypothalami; n. paraventricularis magnocellularis; regio lateralis hypothalami; n. infundibuli; inner zone of the median eminence; dorsal and lateral portions of the n. opticus basalis; n. raphes; and n. reticularis paramedianus. NPY-ir fibers were seen throughout the entire chick brain, but were more abundant in the hypothalamus where they formed networks and pathways. They were also observed in some circumventricular organs. The anatomical data of the present study regarding the distribution of NPY ir in the chick brain, together with the physiological findings of other studies, suggest that NPY plays a key role in the regulation of the neuroendocrine, vegetative, and sensory systems of birds by acting as a neuromodulator and/or neurotransmitter.

Distribution of pituitary adenylate cyclase‐activating polypeptide and pituitary adenylate cyclase‐activating polypeptide type I receptor mRNA in the chicken brain

To map in detail the brain areas in which pituitary adenylate cyclase-activating polypeptide (PACAP) may play a significant role in birds, the distribution of PACAP and PACAP type I receptor (PAC(1)-R) mRNA was examined throughout the entire chicken brain by using in situ hybridization histochemistry. Widespread distribution of both PACAP and its receptor mRNA was found. The telencephalic areas where the most intense signals for PACAP mRNA were found included the hyperstriatum accessorium, the hippocampus, and the archistriatum. In the diencephalon, a group of neurons that highly expressed PACAP mRNA was observed from the anterior medial hypothalamic nucleus to the inferior hypothalamic nucleus. Moderate expression was found in the paraventricular nucleus and the preoptic region. A second large group of neurons containing PACAP message was found within the nucleus dorsolateralis anterior thalami and extended caudally to the area around the nucleus ovoidalis and the nucleus paramedianus internus thalami. Furthermore, expression of PACAP message was observed within the bed nucleus of the pallial commissure, nucleus spiriformis medialis, optic tectum, cerebellar cortex, olfactory bulbs, and several nuclei within the brainstem (dorsal vagal and parabrachial complex, reticular formation). The highest expression of PAC(1)-R mRNA was found in the dorsal telencephalon, olfactory bulbs, lateral septum, optic tectum, cerebellum, and throughout the hypothalamus and thalamus. The presence of PACAP and PAC(1)-R mRNA in a variety of brain areas in birds suggests that PACAP mediates several physiologically important processes in addition to regulating the activity of the pituitary gland.

The Golgi architecture and some EM observations on the avian nucleus dorsolateralis anterior thalami: cell types, fibres and synapses

In Golgi preparations of the chicken diencephalon, various types of cells and fibres were studied in the nucleus dorsolateralis anterior thalami (DLA). Two groups of neurons were found: projection neurons with long axons and interneurons with locally branching axons. The projection neurons varied in the different areas of the DLA. In the medial part the neurons are large cells with long, moderately spiny dendrites, and in the dorsal part there are small cells with short, wavy and moderately spiny dendrites. These neurons differ completely from those found in the rostral and lateral parts, where the neurons have medium-sized cell bodies and curving, spiny dendrites, which branch tuft-like or with bifurcations. In the rostral and lateral parts of the DLA, thick afferent fibres were impregnated which developed their terminal branchings among the neurons. Owing to their terminal branching pattern and the shape of the terminals they are thought to be optic fibres. The terminal pattern of these fibres is similar to the optic terminals in the LGB of the mammalian brain. The interneurons are GABA positive, as attested by immunostaining in light microscopic and EM specimens. There are rather few of them. The HRP-filled projection neurons and the surrounding neuropil were investigated under EM: synaptic connections around the large terminals and/or around dendrites were identified, but this synaptic arrangement does not display the characteristics of a synaptic glomerulus.

The thalamo-hyperstriatal system is established by the time of hatching in chicks (Gallus gallus): a cholera toxin B subunit study.

Connections of the thalamo-hyperstriatal system of hatchling chicks were investigated using multiple injections of cholera toxin B subunit (CTb) in the wulst. In the diencephalon, cells with CTb-like immunoreactivity (CTb-LI) were seen bilaterally in n. dorsolateralis anterior thalami, pars lateralis dorsalis and ventralis, n. dorsolateralis anterior thalami, pars magnocellularis, and pars lateralis rostralis. Within this complex, more CTb-LI cells were observed in the ventral portions of the ipsilateral side, whereas more labeled cells were found in the dorsolateral portions of the contralateral side. Moreover, CTb-LI cells were seen bilaterally in n. superficialis magnocellularis. In the nonvisual thalamic structures, numerous CTb-LI cells were seen in n. dorsolateralis anterior thalami, pars medialis and n. dorsolateralis posterior thalami. In the ventral thalamus, intense CTb-LI fibers/terminals were present in the external half of the external laminae of n. geniculatus lateralis, pars ventralis. Moderate to minor concentrations of fibrous labeling were found in n. intercalatus thalami and n. ventrolateral thalami. Moreover, efferent projections of the wulst were evident in the most ventral half of the optic tectum and the pretectal areas. The latter included n. pretectalis medialis, n. spiriformis medialis, n. principalis precommissuralis, n. lentiformis mesencephali, pars magnocellularis, and n. superficialis synecephali. Also, CTb-LI fibers were seen in n. basal optic root. The present study provides strong evidence that neuronal connections of the thalamo-hyperstriatal system are well established by the time of hatching. Additionally, efferent projections from the wulst to the diencephalic, mesencephalic, and pretectal structures are evident.

An immunocytochemical analysis of the lateral geniculate complex in the pigeon (Columba livia)

The lateral geniculate complex (GL) of pigeons was investigated with respect to its immunohistochemical characteristics, retinal afferents, and the putative transmitters/modulators of its neurons. The distributions of serotonin-, choline acetyltransferase-, glutamic acid decarboxylase-, tyrosine hydroxylase-, neuropeptide Y- (NPY), substance P- (SP), neurotensin- (NT), cholecystokinin- (CCK), and leucine-enkephalin- (L-ENK) like immunoreactive perikarya and fibers were mapped. Retinal projections were studied following injections of Rhodamine-B-isothiocyanate into the vitreous. Transmitter-specific projections onto the visual Wulst and the optic tectum were studied by simultaneous double-labelling of retrograde tracer molecules and immunocytochemical labelling. The GL can be divided into three major subdivisions, the n. geniculatus lateralis, pars dorsalis (GLd; previously designated as the n. opticus principalis thalami, OPT), the n. marginalis tractus optici (nMOT), and the n. geniculatus lateralis, pars ventralis (GLv). All three subdivisions are retinorecipient. The GLd can be further subdivided into at least five components differing in their immunohistochemical characteristics: n. lateralis anterior (LA); n. dorsolateralis anterior thalami, pars lateralis (DLL), n. dorsolateralis anterior thalami, pars magnocellularis (DLAmc); n. lateralis dorsalis nuclei optici principalis thalami (LdOPT); and n. suprarotundus (SpRt). The LdOPT consists of an area of dense CCK-like and NT-like terminals of probable retinal origin. Three subnuclei (DLL, DLAmc, SpRt) were shown to project to the visual Wulst. Cholinergic and cholecystokinergic relay neurons participated in this projection. The nMOT occupies a position between the GLd and GLv and encircles the rostral pole of n. rotundus and the LA. It is characterized mainly by medium sized NPY-like perikarya which were shown to project onto the ipsilateral optic tectum. Bands of NPY-like fibers in the tectal layers 2, 4, and 7 could at least in part be due to this projection of the nMOT. Most of the antisera used revealed transmitter/modulator-specific fiber systems in the GLv which often showed a layer-specific distribution. Perikaryal labelling was only obtained with glutamic acid decarboxylase. On the basis of its chemoarchitectonics, topography, and connectional pattern, the GLd complex of pigeons is most directly equivalent to the mammalian GLd. However, although the different subdivisions of the avian GLd may represent functionally different channels within the thalamofugal pathway similar to the lamina-specific differentiation within the mammalian geniculostriate projection, direct comparison of subnuclei of birds and mammals is not justified at this time. The nMOT appears similar to the intergeniculate leaflet (IGL) and the avian GLv clearly corresponds in many features to the mammalian GLv.

Pretectal and tectal projections to the homologue of the dorsal lateral geniculate nucleus in the pigeon: an anterograde and retrograde tracing study with cholera toxin conjugated to horseradish peroxidase

The possibility of a projection from the pretectal nucleus, lentiformis mesencephali (LM), to the principal optic nuclei (OPT) of the dorsolateral thalamus was investigated using cholera toxin conjugated to horseradish peroxidase (CT-HRP). Injections of CT-HRP into LM produced massive anterograde labeling of the pars lateralis of the nucleus dorsolateralis anterior thalami (DLL), and sparse labeling of the pars magnocellularis (DLAmc). Injections of CT-HRP into OPT in turn produced massive retrograde labeling of both parvocellular and magnocellular divisions of LM. These results relate to possible neural mechanisms underlying optokinetic nystagmus. OPT injections also retrogradely labeled small neurons throughout the rostrocaudal extent of the tectum which were confined to superficial laminae.

Sex difference in the visual projections of young chicks: a quantitative study of the thalamofugal pathway

We investigated quantitatively the thalamo-hyperstriatal visual projections of chickens by injecting the fluorescent dye True blue (TB) in either side of the Wulst on day 2 post hatching. The ratios resulting from the comparison of the number of cells retrogradely labelled in the nuclei dorsolateralis anterior thalami (DLA) contralateral and ipsilateral to the site of injection (C/I ratios) revealed a structural asymmetry in the thalamofugal projections of male chicks ( n = 17) but not in those of females ( n = 12). In the males, TB injections in the right hyperstriatum resulted in higher C/I ratios (37 ± 14%) compared to injections in the left hyperstriatum (22 ± 7%). Thus, the left DLA (fed by the right eye) was found to give rise to a more developed visual projections compared to the right DLA (fed by the left eye). No such difference was found in female chicks (41 ± 12%, respectively): each DLA give rise to similarly developed visual projections. We also report evidence of higher densities of cell bodies labelled in the DLA of females compared to males. These results are discussed in the light of experiment demonstrating sex differences in functional asymmetry in chicks tested with the left or right eye occluded.

Synaptic organization of the nucleus dorsolateralis anterior thalami in the Japanese quail ( Coturnix coturnix japonica)

The nucleus dorsolateralis anterior thalami (DLA) of birds is the homologue of the mammalian dorsal lateral geniculate nucleus 6,16. The positions of terminals from the retina and visual Wulst upon identified relay neurons in the DLA were examined in Japanese quail with both light and electron microscopic techniques. Injection of horseradish peroxidase (HRP) into the visual Wulst showed that relay neurons projecting ipsilaterally or contralaterally were located in a rostrolateral subdivision (DLAlr) and in Zones A and B of a lateral subdivision (DLL) of the DLA. Removal of the contralateral eye resulted in dense terminal degeneration in the DLAlr and moderate terminal degeneration in Zones A and B. By contrast, lesions in the visual Wulst produced dense degenerating terminals in Zones A and B of the DLL. The somata and proximal dendrites of relay neurons or terminals from the retina in the DLA were identified electron microscopically following HRP injection into the visual Wulst or optic nerve, respectively. Terminals from the retina contained spherical vesicles, glycogen granules, and mitochondria with widely spaced cristae. Terminals from the retina made synaptic contact with proximal dendrites and somata of HRP-labeled relay neurons. Presynaptic dendrites formed symmetric synaptic contact with dendrites of relay neurons. Synaptic glomeruli were observed in the DLAlr that involved dendrites of relay neurons, terminals from the retina and presynaptic dendrites. Lesions of the visual Wulst resulted in degeneration of small terminals with spherical vesicles. These terminals were not involved in the synaptic glomeruli of the DLA, but made asymmetric contacts with spine of unidentified neurons and with terminals of presynaptic dendrites.

3H]-GABA selective retrograde labeling of neurons in the pigeon thalamo-Wulst pathway.

Evidence is presented which is consistent with a specific retrograde labeling of GABAergic neurons following [3H]-GABA application in their zone of termination. [3H]-GABA injection in the pigeon Wulst leads to perikaryal retrograde labeling in the ipsilateral thalamic visual relay, n. dorsolateralis anterior thalami, pars lateralis (DLLv). This result gives further support to the biochemical evidence of the existence, in the pigeon, of a GABAergic projection from DLLv to the ipsilateral visual Wulst.

Observations on the projections and intrinsic organization of the pigeon optic tectum: an autoradiographic study based on anterograde and retrograde, axonal and dendritic flow.

Three aspects of the labelling pattern seen after the injection of 13 different radioactive amino acids into the pigeon optic tectum have been described: The efferent projections of the optic tectum; the specific labelling of two pathways; and the dendritic organisation of tectal layer III neurons based on the retrograde and anterograde movement of label within these dendrites. Discrete injections of tritiated amino acid that involved all or only the superficial tectal layers suggested that layer III gave rise to the massive non-topographically organised and bilateral projections (fibers crossing within the decussato supraoptica ventrlis) upon the nuclei rotundus, subpraetectalis and interstitio-praetecto-subpraetectalis and to the ipsilaterally directed pathways terminating within the nuclei praetectalis, triangularis, subrotundus, dorsolateralis anterior thalami, posteroventralis and ventrolateralis thalami. Layer III neurons may also be the source of efferents to the posterior dorsolateral thalamus (the layer III pathway), the pontine grey and, bilaterally to the reticular formation and of the layer IV or tectal commisural pathway terminating within the contralateral tectal cortex. In contrast projections originating from layer II were generally topographically organised and terminated either within certain of the isthmic nuclei (n. isthmi pars parvocellularis, n. isthmo-opticus and n. semilunaris) or ran within layer I (layer I pathways) to end in the pretectum (griseum tectale) and ventral thalamus (n. ventrolateralis thalami, n. geniculatus, pars ventralis). A small projection from layer II upon the ipsilateral nucleus rotundus may also be present. Triated serine and tyrosine were found to be particularly effective in labeling perikarya as well as axons and terminals. The layer I pathway could be selectively labelled after tectal injections of 3H-GABA while the cell bodies of Ipc neurons were labelled in a retrograde fashion after tectal injections of 3H-glycine, serine or alanine. Intrinsic tectal labelling was found by correlation with Golgi material to reflect both anterograde and retrograde transport of label within dendrites of layer III cells. Anterograde movement of label indicated that the terminal portions of layer III cell dendrites ended in an orderly radial arrangement within sublayers IIb and IId, while the retrograde movement of label resulted in the labelin of layer III perikarya outside the injection field.