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At least 19 recordsLinked to original sources
PubMed1976

The cortical projections of the inferior pulvinar and adjacent lateral pulvinar in the rhesus monkey (Macaca mulatta): an autoradiographic study.

An autoradiographic technique was used to determine superior colliculus (SC) and pulvinar projections in the rhesus monkey. SC projects bilaterally to the inferior pulvinar (PI) while occipital cortex projects to PI and the lateral pulvinar (PL). PI has sustaining, topographical projections to layers IV, III and I of areas 18 and 19 (and VI and I of 17) which agrees with the central representation of the visual hemifield and suggests that there is more than one hemifield representation in prestriate cortex. PL adjacent to PI also projects to the same cortical areas and layers, while the portion of PL extending into the caudal pole of the pulvinar projects to layers IV, III and I of areas 20 and 21. Thus, occipital cortices are associated by cortico-thalamocortical connections and also receive direct lemniscal input via SC-PI and the dorsal lateral geniculate nucleus (DLG), while inferotemporal areas 20 and 21 receive only cortico-thalamocortical connections. It is concluded that Stoffels' principle of lamellation holds and, that one pulvinar subdivision projects to several cortical areas, that adjacent pulvinar subdivisions have overlapping projections to these cortical areas and their layers and that the pulvinar also projects to the same cortical area as DLG but to different layers. These connections are similar to those in lower mammals but not to those in the squirrel monkey and bushbaby.

Animals↗
PubMed1979

A comparison of the organization of the projections of the dorsal lateral geniculate nucleus, the inferior pulvinar and adjacent lateral pulvinar to primary visual cortex (area 17) in the macaque monkey.

Both anterograde and retrograde transport tracing methods were used to study the organization of the projections of the dorsal lateral geniculate (DLG), the inferior pulvinar and subdivisions of the lateral pulvinar to primary visual cortex (striate cortex or area 17). The DLG projects only to striate cortex. These projections are retinotopically organized, and do not extend to any cortical layers above layer IVA. In contrast the inferior pulvinar (PI) and the immediately adjacent portion of the lateral pulvinar (PL alpha 48) project to both striate and prestriate cortex. The projections from these two thalamic areas to the striate cortex are also retinotopically organized and exist in parallel with those from the DLG. In contrast to the DLG, the projections from PI and PL alpha terminate above layer IVA in striate cortex, i.e. layers I, II and III. In prestriate cortex the layers of termination include layers IV, III and I. The pulvinar terminations in layers II and III of area 17 occur in segregated patches as do the geniculate terminations in layers IVC and IVA. On the other hand the pulvinar terminations in layer I which overlie those in layers II and III of area 17 appeared to be continuous. Control studies show that the remainder of the lateral pulvinar overlying PL alpha does not project to striate cortex. It is concluded that there are 3 visuotopically organized inputs from the lateral thalamus to primary visual cortex and that each of these inputs have different layers of termination. The inputs from PI and DLG can convey direct retinal inputs while those from PI and PL alpha can also be involved in intrinsic cortico-thalamocortical connection with prestriate cortex. It remains, then that it cannot be tacitly assumed that the ascending inputs which influence the response properties of the primary cortical neurons arise solely from the dorsal lateral geniculate nucleus. It is also argued that these inputs to the supragranular layers may be excitatory as those from the DLG to the IVth layer.

Animals↗
PubMed1988

New view of the organization of the pulvinar nucleus in Tupaia as revealed by tectopulvinar and pulvinar-cortical projections.

The projections of the superficial layers of the superior colliculus to the pulvinar nucleus in Tupaia were reexamined by injecting WGA-HRP into the tectum. The main result was finding two different patterns of terminations in the pulvinar nucleus: a zone remote from the lateral geniculate nucleus, which occupies the dorsomedial and caudal poles of the pulvinar nucleus, was almost entirely filled with terminals in every case irrespective of the location of the injection site; and a second division of the pulvinar nucleus, adjacent to the lateral geniculate nucleus, contained irregular patches--much more densely populated--and the distribution of patches varied from case to case. We call the first projection "diffuse" and the patchy projection "specific." Next we injected several divisions of the extrastriate visual cortex to find the cortical target of each pathway. The diffuse path terminates in the ventral temporal area (Tv). The specific path terminates in the dorsal temporal area (Td) and area 18. We speculated about the significance of the two pathways: the specific path may be responsible for the preservation of vision after removal of the striate cortex; the diffuse path may have an important place in the evolution of the visual areas of the temporal and occipital lobe. We argued that the target of the diffuse path is in a position to relate limbic and visual impulses and relay the product of such integration to the other visual areas, striate as well as extrastriate cortex.

Animals↗
PubMed1976

Effect of pulvinar lesions on visual pattern discrimination in monkeys.

This study compares the performance (percent correct responses and reaction times) of three unoperated control monkeys with the postoperative performance of eight monkeys with pulvinar lesions, either inferior pulvinar or medial and lateral pulvinar, on a tachistoscopically presented visual pattern-discrimination task highly demanding of attention. To further emphasize and assess the attentional factor in visual pattern discrimination, all monkeys who attained criterion performance (90% correct response on three consecutive sessions of 100 trials each) were tested for the effects of visually distracting interference stimuli added to the original discriminative stimuli. In addition, retention of postoperatively learned discriminations was tested after a 6-wk interval withou training and compared with the performance of control monkeys. Four monkeys with only inferior pulvinar lesions and one monkey with inferior pulvinar plus medial and lateral pulvinar lesions were markedly impaired in the postoperative learning of a visual pattern discrimination. Three of these monkeys failed to acquire criterion perfromance in 9,000 or more training trials, while two learned to ceiterion level only after prolonged training (7,400 and 6,900 trials). In contrast, monkeys with medial and lateral pulvinar lesions showed no deficit in learning ability compared to unoperated control monkeys. Furthermore, the performance of the two monkeys with inferior pulvinar lesions, who attained the criterion level of learning only with difficulty, was further impaired by the addition of distracting interference stimuli, where the performance of monkeys with medial and lateral pulvinar lesions as well as the control monkeys was only temporarily disrupted by this procedure. None of the monkeys with pulvinar lesions, who were tested for retention of the postoperatively learned discrimination, showed appreciable deficits in comparison to control monkeys. All monkeys, including controls and those uith pulvinar lesions who were able to learn the visual pattern discrimination, showed a common pattern of reaction time (RT) change during the course of the learning; that is, RT was low during change-level performance, increased during learning, and decreased once criterion performance was achieved. Reaction times of monkeys with inferior pulvinar lesions tended to be longer than for controls or for those with medial and lateral pulvinar lesions. These results provide the first behavior evidence that the inferior pulvinar of monkeys is involved in visual pattern discrimination and add further support to the concept of a second visual system in which the inferior pulvinar plays a role. The attentional aspects of the visual pattern-discrimination task employed in this study and the additional effects obtained with distracting stimuli suggest that the impairments arising from inferior pulvinar lesions may be dependent in part on visual attentional factors.

Acoustic Stimulation↗
PubMed2003

The functional logic of cortico-pulvinar connections.

The pulvinar is an 'associative' thalamic nucleus, meaning that most of its input and output relationships are formed with the cerebral cortex. The function of this circuitry is little understood and its anatomy, though much investigated, is notably recondite. This is because pulvinar connection patterns disrespect the architectural subunits (anterior, medial, lateral and inferior pulvinar nuclei) that have been the traditional reference system. This article presents a simplified, global model of the organization of cortico-pulvinar connections so as to pursue their structure-function relationships. Connections between the cortex and pulvinar are topographically organized, and as a result the pulvinar contains a 'map' of the cortical sheet. However, the topography is very blurred. Hence the pulvinar connection zones of nearby cortical areas overlap, allowing indirect transcortical communication via the pulvinar. A general observation is that indirect cortico-pulvino-cortical circuits tend to mimic direct cortico-cortical pathways: this is termed 'the replication principle'. It is equally apt for certain pairs (or groups) of nearby cortical areas that happen not to connect with each other. The 'replication' of this non-connection is achieved by discontinuities and dislocations of the cortical topography within the pulvinar, such that the associated pair of connection zones do not overlap. Certain of these deformations can be used to divide the global cortical topography into specific sub-domains, which form the natural units of a connectional subdivision of the pulvinar. A substantial part of the pulvinar also expresses visual topography, reflecting visual maps in occipital cortex. There are just two well-ordered visual maps in the pulvinar, that both receive projections from area V1, and several other occipital areas; the resulting duplication of cortical topography means that each visual map also acts as a separate connection domain. In summary, the model identifies four topographically ordered connection domains, and reconciles the coexistence of visual and cortical maps in two of them. The replication principle operates at and below the level of domain structure. It is argued that cortico-pulvinar circuitry replicates the pattern of cortical circuitry but not its function, playing a more regulatory role instead. Thalamic neurons differ from cortical neurons in their inherent rhythmicity, and the pattern of cortico-thalamic connections must govern the formation of specific resonant circuits. The broad implication is that the pulvinar acts to coordinate cortical information processing by facilitating and sustaining the formation of synchronized trans-areal assemblies; a more pointed suggestion is that, owing to the considerable blurring of cortical topography in the pulvinar, rival cortical assemblies may be in competition to recruit thalamic elements in order to outlast each other in activity.

Brain Mapping↗
PubMed1993

Chemoarchitectonic subdivisions of the visual pulvinar in monkeys and their connectional relations with the middle temporal and rostral dorsolateral visual areas, MT and DLr.

The organization of the inferior pulvinar complex (PI) in squirrel monkeys was studied with histochemical localization of the calcium binding proteins calbindin-D28k and parvalbumin, and of cytochrome oxidase. With each of these markers, the inferior pulvinar complex can be subdivided into four distinct regions. Calbindin-D28k immunoreactivity is densely distributed in cells and neuropil within PI, except for a distinct centromedially located gap. This calbindin-poor zone, termed the medial division of the inferior pulvinar (PIM), corresponds precisely to a region that contains elevated cytochrome oxidase activity and parvalbumin immunostaining. The PIM extends slightly above and behind the classically defined limit of the inferior pulvinar, the corticotectal tract. Regions of inferior pulvinar with intense immunostaining for calbindin-D28k were the posterior division of the inferior pulvinar (PIP, medial to PIM) and the central division (PIC, lateral to PIM). A newly recognized lateral region, PIL, adjoins the lateral geniculate nucleus and stains more lightly for calbindin and parvalbumin immunoreactivity and for cytochrome oxidase. Staining patterns for calbindin, parvalbumin, and cytochrome oxidase in the pulvinar of rhesus monkeys closely resemble those shown in squirrel monkey inferior pulvinar, suggesting that a common organization exists in all primates. In order to examine cortical connection patterns of the histochemically defined compartments in the inferior pulvinar, injections of up to five neuroanatomical tracers (wheat germ agglutinin conjugated to horseradish peroxidase and fluorescent retrograde tracers) were placed in the same cerebral hemisphere. Single injection sites were in the middle temporal area (MT), and several separate injections were placed in a strip corresponding to the rostral subdivision of the dorsolateral area (DLr). Injections that involved only DLr and not MT labeled principally the PIC, and more sparsely PIP and PIL. DLr connections occupied a "shell" region dorsal to PIM that extended from PIC into the lateral and medial divisions of the pulvinar, PL and PM. Injection sites that included MT or were largely restricted to MT produced dense label in PIM and moderate label in PIC and PIL. The retinotopic organization within the inferior pulvinar was inferred from patterns of connections. Connections with cortex related most closely to central vision were found posteriorly in PIM and in adjacent portions of PIC as it wraps around the caudal pole of PIM. Cortex related to more peripheral locations in the lower visual field connected with more rostral PIM and PIC. Patterns of label within the portions of PL and PM that were immediately adjacent to PIM roughly paralleled those in PIM and PIC.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Connections between the pulvinar complex and cytochrome oxidase-defined compartments in visual area V2 of macaque monkey.

We examined the distribution of pulvinar afferents to visual area V2 of macaque monkey cerebral cortex in relation to the distribution of the metabolic enzyme cytochrome oxidase (CO). V2 contains three sets of stripelike subregions that are marked by differential staining for CO, and which have different corticocortical connections. The pulvinar provides the major subcortical input to V2, and this input is known to be patchy. We were interested to determine how the pattern of pulvinar afferents relates to the layout of the three stripelike compartments that characterize V2. We made large injections of WGA-HRP into the pulvinar (labelling both the inferior and lateral divisions) and mapped the resulting orthograde terminal and retrograde cell label within V2. We observed pulvinar terminal label mainly in lower layer 3 (at the layer 4 border), with light label in layer 1 as well; terminal label in layers 3-4 was distributed in discrete patches with faint bridges of light label between. Comparison with adjacent sections stained for CO or Cat-301 showed that pulvinar terminal zones aligned precisely with regions of increased CO staining, and targeted both "thick" (Cat-301+) and "thin" CO-rich stripes, avoiding the pale stripes (which aligned with the faint bridges of terminal label). Retrogradely labelled cells were found in layers 5A and 6, but the bulk of the feedback to pulvinar arose from layer 6 rather than layer 5 (unlike V1, where feedback to pulvinar arises primarily from layer 5B). These results show that the increased CO staining in certain subregions of V2 is closely correlated with the presence of thalamic terminals from the pulvinar. Although we cannot rule out the possibility that different sets of pulvinar neurons project to different CO compartments in V2, the presence of a prominent thalamic input shared by the "thick" and "thin" CO stripes (which receive different V1 afferents and make different feedforward projections to other visual cortical areas) could underlie the preferential intrinsic interconnections shown to exist between these V2 subregions and suggests another potential source of integration between the two cortical visual streams.

Animals↗
PubMed1993

Functional contributions of the primate pulvinar.

One of the major tasks facing the central nervous system is choosing which sensory events to use for perception and directed behavior. All organisms live in a rich sensory environment, and it is impossible to attend and respond to everything. Certain brain regions and systems must evaluate sensory signals and then determine which are salient. Based on recent data derived from diverse studies of the pulvinar of primates, it is the hypothesis of this paper that a major role of the pulvinar is to participate in the generation of visual salience, those processes which precede perception and action. This process of salience generation makes use of two broad mechanisms, the suppression of noise and the enhancement of significant signals. Outlined above are experiments which show that the visual activity which might be caused by eye movements is filtered from some pulvinar cells. Visual responses associated with certain directions of gaze are removed. Finally the ability to suppress the activity of distracting visual stimuli is dependent on the integrity of the pulvinar. Conversely, there are neurons within the pulvinar which respond best when animals actively select and thus engender certain stimuli with salience. Modulation of pulvinar functioning with transmitter-related drugs changes performance as if salience is being modulated. Humans and monkeys with destruction of the pulvinar behave as if they too cannot create or evaluate salience. Finally, when salience is demanded of humans by making their visual tasks more demanding, there is an increase in PET activity. The hypothesis here is that the pulvinar functions as an early center for the generation of visual salience. This is similar to the view of striate cortex as an early integration stage for the basic elements of visual processing (Hubel and Wiesel, 1968; Zeki, 1976; Allman et al., 1981). Vision does not take place within the complex microstructure of striate neurons, but all of the essential components are present there, and these are distributed to other cortical areas which construct specific aspects of visual perception. Similarly, regions of the pulvinar contain building blocks for visual/behavioral/oculomotor integration which they distribute to various cortical sites for shifts of attention and other types of response specification. When an organism must determine external visual salience, there are neurons within the pulvinar which signal this. Since the major efferents of these thalamic regions are the visual cortices (Benevento and Rezak, 1976; Lin and Kaas, 1979; Kennedy and Bullier, 1985), our present hypothesis is that these signals are used for the construction of visuomotor and visuo-perceptual states.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2001

Magnetic resonance imaging of the thalamic mediodorsal nucleus and pulvinar in schizophrenia and schizotypal personality disorder.

BACKGROUND: The importance of neuronal interactions in development, the cortical dependence of many thalamic nuclei, and the phenomenon of transsynaptic degeneration suggest possible abnormalities in thalamic nuclei with connections to other brain regions implicated in schizophrenia. Because frontal and temporal lobe volumes are diminished in schizophrenia, volume loss could characterize their primary thalamic relay nuclei (mediodorsal nucleus [MDN] and pulvinar). METHODS: Tracers delineated the thalamus, MDN, and pulvinar on contiguous 1.2-mm magnetic resonance images in 12 schizophrenic patients, 12 with schizotypal personality disorder (SPD), and 12 normal control subjects. The MDN and pulvinar were rendered visible by means of a Sobel intensity-gradient filter. RESULTS: Pixel overlap for delineation of all structures by independent tracers was at least 80%; intraclass correlations were r = 0.78 for MDN and r = 0.83 for pulvinar. Pulvinar volume was smaller in schizophrenic (1.22 +/- 0.24 cm(3)) and SPD (1.20 +/- 0.23 cm(3)) patients than controls (1.37 +/- 0.25 cm(3)). Differences for MDN were not statistically significant; however, when expressed as percentage of total brain volume, pulvinar and MDN together were reduced in SPD (0.14%) and schizophrenic (0.15%) patients vs controls (0.16%). Reductions were more prominent in the left hemisphere, with MDN reduced only in the schizophrenic group, and pulvinar in both patient groups. Total thalamic volume did not differ among the 3 groups. CONCLUSIONS: Measurement of MDN and pulvinar in magnetic resonance images is feasible and reproducible. Schizophrenic and SPD patients have volume reduction in the pulvinar, but only schizophrenic patients show reduction relative to brain volume in MDN.

Adult↗
PubMed2003

Diagnosing variant Creutzfeldt-Jakob disease with the pulvinar sign: MR imaging findings in 86 neuropathologically confirmed cases.

BACKGROUND AND PURPOSE: Variant Creutzfeldt-Jakob disease (vCJD) is a rare but important cause of dementia and death in young patients and is causally linked to bovine spongiform encephalopathy. Symmetrical hyperintensity in the pulvinar (posterior) nuclei of the thalamus (pulvinar sign) on brain MR images was described as a specific, noninvasive, diagnostic sign of vCJD in a previous small series. This purpose of this larger study was to evaluate this sign prospectively and further define the MR imaging characteristics of vCJD. METHODS: As part of the ongoing surveillance program in the United Kingdom, MR images of suspected cases of vCJD were collected during a 6-year period. All available images were assessed prospectively by one observer for the presence of the pulvinar sign. Images of neuropathologically confirmed cases were then assessed independently by two neuroradiologists for the degree of hyperintensity of the pulvinar on images of different MR sequences, and for the presence of abnormal hyperintensity in other areas of the brain. Discrepancies were reviewed jointly and a consensus opinion formed. RESULTS: Prospective analysis identified the pulvinar sign in 74 of 82 cases of vCJD. In the retrospective study, the pulvinar sign, as defined by hyperintensity of the pulvinar relative to the anterior putamen, was present on seven (9%) of 75 T1-weighted, 77 (71%) of 108 T2-weighted, 47 (81%) of 58 proton density-weighted, and 30 (100%) of 30 fluid-attenuated inversion-recovery (FLAIR) images. Diffusion-weighted images were available in two cases and were positive for the pulvinar sign in one. Other features were hyperintensity of the dorsomedial thalamic nuclei (93%), caudate head (40%), and periaqueductal gray matter (83%) on FLAIR images. CONCLUSION: In the appropriate clinical context, demonstration of the pulvinar sign on MR images is a highly accurate diagnostic sign for vCJD. FLAIR sequence is more sensitive than other sequences. Positive MR images may obviate more invasive diagnostic tests in most cases.

Brain↗
PubMed1976

Areal and laminar distribution of some pulvinar cortical efferents in rhesus monkey.

The areal and laminar distribution of the cortical efferents of the medial, lateral and inferior pulvinar nuclei (PM, PL and PI respectively) were determined in rhesus monkey using autoradiography and Horseradish Peroxidase (HRP). The autoradiographic data indicated that: areas 8a, 45 and 46 on the convexity and 11 and 12 on the orbital surface of the frontal lobe received projections from PM; areas 20, 21 and 22 in temporal lobe received projections from PM primarily with caudal-medial parts of PM projecting to more rostral-dorsal parts of temporal lobe and rostral-lateral parts of PM projecting to more caudal-ventral parts of temporal lobe but PL also sends some efferents to caudal temporal lobe; areas 5 and 7 in parietal lobe and 18 and 19 in occipital lobe received projections primarily from the region in pulvinar comprising PL and PI with the more ventral parts of this region porsal parts of this region projecting to the more dorsal-lateral and medial parts of parieto-occipital cortex and with PM comtributing slightly to these projections rostrally. The autoradiographic information on the pulvinar projections to frontal lobe and temporal pole was supplemented by data derived from cortical HRP injections. These indicated that although only PM of the pulvinar subnuclei projected to these regions, three other caudal thalamic structures, i.e., medial dorsal nucleus, nucleus limitans and suprageniculate nucleus also projected to these regions raising some questions about the identity of the densocellular part of the medial dorsal nucleus which has also been considered to be part of pulvinar. The laminar distribution of pulvinar cortical efferents was uniformly similar regardless of the pulvinar recipient area examined. Elevated numbers of silver grains were observed over all cortical layers, but the silver grains were densest over the deep parts of layer III. The thalamic reticular nucleus was the only diencephalic structure observed to receive projections from pulvinar and it did so from PM, PL and PI. The pulvinar's efferents are to homotypical rather than heterotypical cortex and its connections are most extensive with cortex rather than with subcortical structures.

Animals↗
PubMed1979

The morphology and distribution of striate cortex terminals in the inferior and lateral subdivisions of the Macaca monkey pulvinar.

The origin of the various types of axon terminals in Macaca pulvinar remains uncertain because of the contradictory results obtained in EM degeneration studies. We have used EM-autoradiography to determine the morphology of terminals in the inferior and lateral pulvinar which originate from neurons in visual cortex. After injections of H3 proline into area 17, both the small diameter (RS) and the large diameter (RL) terminals containing round vesicles and making asymmetric contacts are labeled in the two pulvinar subdivisions. Labeled and unlabeled terminals are intermixed within the pulvinar focus which suggests that the dendrites of the same pulvinar neuron receive overlapping inputs from several cortical areas. Because only 5% of the pulvinar terminals are RLs (Ogren and Hendrickson, '79), and this small number of RLs originates from at least two visual cortical areas plus the superior colliculus (Partlow et al., '77), superior colliculus input to inferior pulvinar is small compared to the combined RS and RL cortical input. Together the findings from this study and the preceding paper (Ogren and Henderickson, '79), show that while pulvinar is typical of other thalamic nuclei in the structure of its neurons and synapses, it differs in that the input from subcortical structures is minimal. It is suggested that inferior and lateral pulvinar function principally as integrators of visula cortical information.

Animals↗
PubMed1984

Anterograde degeneration in the superior colliculus following kainic acid and radiofrequency lesions of the macaque pulvinar.

Several studies have reported behavioral deficits following thermocoagulation of the primate pulvinar. However, these deficits may have resulted from damage to corticotectal fibers as they pass through the pulvinar. To evaluate this possibility and to determine whether kainic acid can be used to destroy pulvinar cells without damaging corticotectal fibers, we compared anterograde degeneration in the superior colliculus following kainic acid and radiofrequency lesions of the pulvinar. Kainic acid injections into the pulvinar produced total loss of neuronal perikarya within the inferior and lateral pulvinar. Four to 7 days following the kainic acid lesions, terminal and fiber degeneration within the superior colliculus was no greater than that produced by control injections of saline. By contrast, thermocoagulation lesions of the inferior and lateral pulvinar produced dense fiber and terminal degeneration throughout the superficial and intermediate layers of the superior colliculus. We conclude that whereas thermocoagulation of the pulvinar severely damages the corticotectal tract, kainic acid lesions spare these fibers of passage. Thus kainic acid lesions should provide an effective tool for studying the functional significance of the pulvinar.

Animals↗
PubMed1981

Efferent connections of the pulvinar nucleus in the cat.

Discrete unilateral electrolytic lesions were placed in the pulvinar nucleus of cats using the stereotaxic approach. The pathways of the degenerated fibres and their terminals were traced to the cerebral cortex and to subcortical nuclei by the method of Fink-Heimer (anterograde degeneration). The cortical projection sites of the pulvinar are the following: suprasylvian cortex, lateral cortex, ectosylvian cortex, cingulate gyrus, area postsubicularis and retrosplenial gyrus. However, the bulk of the cortical projections of the pulvinar nucleus were to mid- and posterior gyri of the suprasylvian cortex. In this study subcortical projections of the pulvinar have been seen to terminate in the superior colliculus, pretectal area, and the following thalamic nuclei: posterior, suprageniculate, dorsolateral, posterolateral, reticular, centromedian, centrolateral, parafascicular and dorsomedial. One of the purposes of this study was to explore possible anatomical connections of the pulvinar that might explain its presumed role in the pain mechanisms. The results of the present study, on subcortical connections of the pulvinar, provide a possible anatomical substrate for such a role where connections of the pulvinar to one or more of the thalamic nuclei implicated in pain mechanisms, the reticular, the intralaminar (centromedian, centrolateral and parafascicular) and the posterior could constitute the necessary anatomical pathway or pathways. Furthermore, the extensive projections of the pulvinar to several cortical regions including the cingulate gyrus could represent another means by which the pulvinar might influence cortical and limbic structures which are known to modify pain sensation.

Animals↗
PubMed2000

Neurochemical and connectional organization of the dorsal pulvinar complex in monkeys.

To investigate the organization of the dorsal pulvinar complex, patterns of neurochemical staining were correlated with cortico-pulvinar connections in macaques (Macaca mulatta). Three major neurochemical subdivisions of the dorsal pulvinar were identified by acetylcholinesterase (AChE) histochemistry, as well as immunostaining for calbindin-D(28K) and parvalbumin. The dorsal lateral pulvinar nucleus (PLd) was defined on histochemical criteria as a distinct AChE- and parvalbumin-dense, calbindin-poor wedge that was found to continue caudally along the dorsolateral edge of the pulvinar to within 1 mm of its caudal pole. The ventromedial border of neurochemical PLd with the rest of the dorsal pulvinar, termed the medial pulvinar (PM), was sharply defined. Overall, PM was lighter than PLd for AChE and parvalbumin and displayed lateral (PMl) and medial (PMm) histochemical divisions. PMm contained a central "oval" (PMm-c) that stained darker for AChE and parvalbumin than the surrounding region. The neurochemically defined PLd was labeled by tracer injections in the inferior parietal lobule (IPL) and dorsolateral prefrontal cortex but not the superior temporal gyrus (STG). Label within PMl was found after prefrontal and IPL and, to a lesser extent, after STG injections. The PMm was labeled after injections of the IPL and STG, but only sparsely following prefrontal injections. The histochemically distinct subregion or module of PMm, PMm-c, was labeled only by STG injections. Overlapping labeling was found in dorsal pulvinar divisions PMl and PLd following paired IPL/prefrontal, but not IPL/STG or these particular STG/prefrontal, injections. Thus, PLd may be a visuospatially related region whereas PM appears to contain several types of territories, some related to visual or auditory inputs, and others that receive directly converging input from posterior parietal and prefrontal cortex and may participate in a distributed cortical network concerned with visuospatial functions.

Acetylcholinesterase↗
PubMed2001

Characterization of pretectal-nuclear-complex afferents to the pulvinar in the cat.

We investigated anatomical and physiological properties of the projection from the pretectal nuclear complex (PNC) to the ipsilateral lateral posterior-pulvinar complex in the cat. After Phaseolus vulgaris leucoagglutinin injections into the PNC, the majority (70%) of anterogradely labeled terminals was localized in the pulvinar proper, the remaining 30% were scattered in the lateral and medial portions of the LP. No PNC neuron retrogradely labeled from the pulvinar was found to also express glutamic acid decarboxylase (GAD) mRNA, although a large number of neurons carrying the GAD label were found in close vicinity. In contrast, 69% of retrogradely labeled PNC cells also displayed glutamate-like immunoreactivity. Twenty-six out of 96 (27%) visually responsive pulvinar neurons were orthodromically activated by electrical stimulation of the ipsilateral PNC at latencies between 1 and 10 ms (median 1.9 ms). All orthodromically activated neurons responded well to the onset and offset of large visual stimuli and to sudden stimulus shifts. Whenever a saccadic eye movement was executed, these neurons were also activated, except during saccades in darkness. The comparison of saccade-evoked response with responses to visual stimuli that elicit similar retinal image shifts revealed that pretectorecipient pulvinar neurons also seem to receive a saccade-related non-visual input. All response properties correspond to those of a specific class of pulvinar neurons that have been termed "SV" neurons because they respond to visual stimulation as well as during saccades. They also closely resemble response properties of PNC neurons that project to the ipsilateral pulvinar. The results support the proposal that PNC cells not only directly activate their postsynaptic target neurons in the pulvinar, but that they also provide a visual input to these neurons that greatly contributes to their response characteristics.

Action Potentials↗
PubMed1975

The pulvinar nucleus of Galago senegalensis.

The present study was undertaken to analyze the connections of the pulvinar nucleus in a prosimian. The experiments, which rely on the Fink-Heimer ('67) method for staining degenerating axons and their terminals, fall into two parts: first, the tracing of ascending tectal projections to the caudal thalamus and second, the tracing of projections from this thalamic target to the cortex. Large lesions of the superior colliculus resulted in dense degeneration in the caudal half of the inferior subdivision of the pulvinar complex. This pathway could be identified when the lesion was restricted to the superficial layers of the superior colliculus, signifying that it is a visual pathway. In general, the projections of the deep and superficial layers of the superior colliculus were distinct and in this respect Galago resembles Tupaia. The inferior pulvinar nucleus in turn projects to area MT, a conspicuous subdivision of the temporal cortex. The superior division of the pulvinar, in contrast to the inferior division, is not a major target of ascending projections from the superior colliculus and projects to the areas of the occipital and temporal lobe intercalated between areas MT and 17. When these results are compared with similar studies in nonprimates, notably studies of Tupaia, a striking difference in organization emerges. In Tupaia, and in distantly related mammals such as the squirrel, the target of the tecto-pulvinar system includes area 18 adjacent to area 17. This feature is important since the two parallel projection systems seem to be related to each other in terms of the way in which the zero vertical meridian is spatially represented. However, in Galago the subdivision of the pulvinar receiving projections arising from the superior colliculus does not project to area 18. Area 18 is indeed the target of pulvinar projections, but these projections arise from that portion of the pulvinar which is not a recipient of ascending tectal projections. It is not easy to see how this primate organization, if indeed the Galago is representative of primates, evolved from the organization reflected in Tupais.

Animals↗