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PubMed1993

A possible visual pathway to the cat caudate nucleus involving the pulvinar.

Electrical stimulation of the thalamic nucleus pulvinar was found to influence unit activity in the feline caudate nucleus. Twenty-six (18.3%) units were encountered, in this subcortical region of the brain, that responded to activation of the pulvinar input in anesthetized cats and 41 (54%) in awake animals. In the two types of experiments, stimulation of the pulvinar induced mainly an initial excitatory reaction (81% and 78% of responsive cells, respectively). A latency analysis indicated that the majority of responses occurred at a long latency, while 9 (34.6%) cells in anesthetized cats and 5 (12%) in awake animals were excited at a short latency. The short latency is compatible with the involvement of a monosynaptic pathway between the pulvinar and the caudate nucleus. Units that responded to thalamic stimulation were found predominantly in the posterior regions of the caudate nucleus. These results confirm previous neuroanatomical findings of a direct projection from the pulvinar to the feline caudate nucleus. In awake animals, neurons activated by pulvinar stimulation were also tested, using visual stimuli of various orientations. Out of 41 units, 63% were classified as having "visual responses". Of these, 5 cells were found to respond selectively to a particular orientation of the visual stimulus. Three of these were excited at a short latency by pulvinar stimulation. The possible involvement of a direct pathway from the pulvinar to the caudate nucleus in the processing of visual information is discussed.

Animals↗
PubMed1987

Comparison of the effects of superior colliculus and pulvinar lesions on visual search and tachistoscopic pattern discrimination in monkeys.

In order to investigate whether pulvinar lesions produce behavioral impairments similar to those that follow superior colliculus lesions, monkeys were tested on a visual search task before and after receiving radiofrequency lesions of either the superior colliculus or pulvinar. The animals searched for a small target pattern within an array of varying numbers of irrelevant patterns. After receiving colliculus lesions, the animals showed marked post-operative increases in either search time, percent errors, or both. By contrast, pulvinar lesions had little or no effect on visual search performance. Similarly, in learning to search for a target they had not previously seen, animals with colliculus lesions were impaired relative to unoperated controls, whereas pulvinar-lesioned animals did not differ from controls. In an attempt to confirm the finding that pulvinar lesions impair tachistoscopic pattern discrimination, we determined exposure-duration thresholds of pulvinar- and colliculus-lesioned monkeys for performance of a pattern discrimination. The thresholds of the colliculus-lesioned monkeys were elevated 20-fold relative to controls. By contrast, thresholds of the pulvinar-lesioned monkeys were normal. We conclude that the pulvinar is not critical for the attentional processes in which the superior colliculus participates.

Animals↗
PubMedDate not supplied

Single neurons with both form/color differential responses and saccade-related responses in the nonretinotopic pulvinar of the behaving macaque monkey.

The nonretinotopic portion of the macaque pulvinar complex is interconnected with the occipitoparietal and occipitotemporal transcortical visual systems where information about the location and motion of a visual object or its form and color are modulated by eye movements and attention. We recorded from single cells in and about the border of the dorsal portion of the lateral pulvinar and the adjacent medial pulvinar of awake behaving Macaca mulatta in order to determine how the properties of these two functionally dichotomous cortical systems were represented. We found a class of pulvinar neurons that responded differentially to ten different patterns or broadband wavelengths (colors). Thirty-four percent of cells tested responded to the presentation of at least one of the pattern or color stimuli. These cells often discharged to several of the patterns or colors, but responded best to only one or two of them, and 86% were found to have statistically significant pattern and/or color preferences. Pattern/color preferential cells had an average latency of 79.1 +/- 46.0 ms (range 31-186 ms), responding well before most inferotemporal cortical cell responses. Visually guided and memory-guided saccade tasks showed that 58% of pattern/color preferential cells also had saccade-related properties, e.g. directional presaccadic and postsaccadic discharges, and inhibition of activity during the saccade. In the pulvinar, the mean presacadic response latency was earlier, and the mean postsaccadic response latency was later, than those reported for parietal cortex. We also discovered that the strength of response to patterns or colors changed depending upon the behavioral setting. In comparison to trials in which the monkey fixated dead ahead during passive presentations of pattern and color stimuli, 92% of the cells showed attenuated responses to the same passive presentation of patterns and colors during fixation when these trials were interleaved with trials which also required active saccades to pattern and color targets in the periphery. We conclude that properties which represent the functionally dichotomous object and spatial visual systems are found together in single pulvinar neurons and that the responses of these cells to pattern or color stimuli are influenced by the focus of spatial attention. The pulvinar is the first structure in the brain shown to have neurons which integrate both object and spatial properties and the response latencies indicate that this information is processed before that in cortex. These results are discussed in terms of role of the pulvinar in visual attention as well as its unique role in providing both object feature and spatial location information to the inferotemporal cortex.

Animals↗
PubMed1999

Do superior colliculus projection zones in the inferior pulvinar project to MT in primates?

In order to determine the relationship of superior colliculus inputs to thalamic neurons projecting to the middle temporal visual area (MT), injections of wheat germ agglutinin conjugated with horseradish peroxidase were placed in the superior colliculus of three owl monkeys, with injections of Fast Blue in the MT. The locations of labelled terminals and neurons in the posterior thalamus were related to four architectonically distinct nuclei of the inferior pulvinar (Stepniewska & Kaas, Vis. Neurosci. 14, pp.1043-1060, 1997). Fast Blue injections in the MT labelled neurons largely in the medial nucleus of the inferior pulvinar. A few labelled neurons were found in the adjoining central medial nucleus of the inferior pulvinar, as well as in the lateral pulvinar and the dorsal lateral geniculate nucleus. Superior colliculus inputs were most dense in the posterior and medial nuclei of the inferior pulvinar. There were sparser inputs to the central lateral nucleus of the inferior pulvinar, locations in the lateral and medial pulvinar, and the dorsal lateral geniculate nucleus. The results indicate that the medial nucleus of the inferior pulvinar, the major projection zone to the MT, does not receive a significant input from the superior colliculus.

Animals↗
PubMed2003

The visual pulvinar in tree shrews I. Multiple subdivisions revealed through acetylcholinesterase and Cat-301 chemoarchitecture.

Tree shrews are highly visual mammals closely related to primates. They have a large visual pulvinar complex, but its organization and relation to visual cortex is only partly known. We processed brain sections through the pulvinar with seven different procedures in an effort to reveal histologically distinct compartments. The results revealed three major subdivisions. A dorsal subdivision, Pd, stains darkly for acetylcholinesterase (AChE) and occupies the dorsoposterior one-third of the pulvinar complex. A ventral subdivision, Pv, stains darkly when processed with the Cat-301 antibody and occupies the ventroanterior fifth of the pulvinar complex along the brachium of the superior colliculus. Unexpectedly, part of Pv is ventral to the brachium. A large central subdivision, Pc, stains moderately dark for AChE and cytochrome oxidase (CO), and very light for Cat-301. Pc includes about half of the pulvinar complex, with parts on both sides of the brachium of the superior colliculus. These architectonic results demonstrate that the pulvinar complex of tree shrews is larger and has more subdivisions than previously described. The complex resembles the pulvinar of primates by having a portion ventral to the brachium and by having histochemically distinct nuclei; the number of nuclei is less than in primates, however.

Acetylcholinesterase↗
PubMed2003

Thalamocortical cells in the cat pulvinar nucleus transiently express nitric oxide synthase during development.

We examined the postnatal expression of the neuronal form of nitric oxide synthase (nNOS) within the pulvinar and lateral posterior (LP) nuclei of the cat thalamus using immunocytochemical techniques. During the first postnatal month, nNOS was expressed in many cells within the pulvinar nucleus and medial subdivision of the LP nucleus; fewer neurons in the lateral LP nucleus were stained by the nNOS antibody. We examined the pulvinar nucleus to determine what cell types express nNOS. A comparison of the soma sizes of nNOS-stained cells to the overall population of Nissl-stained cells and interneurons (stained with an antibody against glutamic acid decarboxylase) suggests that within the pulvinar nucleus, thalamocortical cells express nNOS during development. In addition, the nNOS antibody stained axon bundles that traverse the pulvinar nucleus to enter the optic radiations, suggesting that thalamocortical cell axons also contain nNOS during development. However, this staining pattern was dramatically reduced by postnatal day 42 and later ages; the size of the remaining nNOS-stained cells was closer to that of interneurons, a subset of which contain nNOS in the adult pulvinar nucleus. This contrasts with our previous findings that nNOS is specifically expressed within interneurons in the developing dorsal lateral geniculate nucleus (LGN) and serves as further confirmation that the pulvinar nucleus and LGN represent distinct categories of thalamic nuclei.

Animals↗
PubMed2005

Pattern-motion selectivity in the human pulvinar.

On the basis of anatomical and physiological data obtained on animal models, we recently proposed that neurons in the main visual extrageniculate nuclei complex, the pulvinar, are actively involved in higher-order visual processing. Pulvinar neurons have been shown to integrate the component signals of a plaid pattern into a coherent global percept (pattern-motion selectivity). Using positron emission tomography (PET), we have investigated the possibility that the human pulvinar is also involved in plaid-defined higher-order motion integration. Plaid patterns were presented to normal observers in two conditions (coherent vs. transparent) created by varying the relative spatial frequency of the two gratings comprising the plaid. Regions of interest analysis revealed a significant activation of the pulvinar in the coherent condition supporting the notion that the human pulvinar nucleus is involved in higher-order motion processing. Plaid pattern activation was also observed in the medial temporal gyrus (area MT/V5), a motion area with strong anatomical connections to the pulvinar. These data provide the first direct evidence that the human pulvinar is involved in complex motion integration, as previously shown in animal models, and further support the existence of cortico-thalamo-cortical computational networks involved in higher-order visual processing.

Adult↗
PubMedDate not supplied

Projections of the superior colliculus to subdivisions of the inferior pulvinar in New World and Old World monkeys.

Patterns of terminals labeled after WGA-HRP injections in the superior colliculus (SC) in squirrel monkeys and macaque monkeys, and after DiI application in marmosets, were related to the architecture of the pulvinar and dorsal lateral geniculate nucleus (LGN). In all studied species, the SC projects densely to two architectonic subdivisions of the inferior pulvinar, the posterior inferior pulvinar nucleus (PIp) and central medial inferior pulvinar nucleus (PIcM). These projection zones expressed substance P. Thus, sections processed for substance P reveal SC termination zones in the inferior pulvinar. The medial subdivision of the inferior pulvinar, PIm, which is known to project to visual area MT, does not receive a significant collicular input. Injections in MT of a squirrel monkey revealed no overlap between SC terminals and neurons projecting to area MT. Thus, PIm is not the significant relay station of visual input from the SC to MT. The SC also sends an input to the LGN, however, this projection is sparser than the input directed to pulvinar.

Animals↗
PubMed2004

Effects of inactivation of the lateral pulvinar on response properties of second visual area cells in Cebus monkeys.

1. In the present study, we investigated the influence of the pulvinar nucleus upon response properties of single cells in the second visual area (V2) of Cebus monkeys. The method used consisted of the inactivation of a portion of the lateral pulvinar by GABA injections while studying the response properties of cells in V2 at the same visuotopic location as that of the inactivation. 2. After GABA injection in the pulvinar, most cells in V2 (67%) showed changes in spontaneous and/or stimulus-driven activities. Contrary to the effect found with inactivation of the striate cortex, which promotes a reduction in the response of V2 neurons, we found that the main effect of pulvinar inactivation was an increment in stimulus-driven responses of V2 cells (39% of units studied). A reduction of responses was observed in 27% of units. 3. A change in orientation and/or direction selectivity was found in 91% of cells after inactivation of the pulvinar. Most commonly, the orientation selectivity of a neuron was decreased during pulvinar inactivation. 4. The inactivation results indicate that the pulvinar projections have a modulatory effect on the activity of V2 cells.

Animals↗
PubMedDate not supplied

Increased signal intensity in the pulvinar on T1-weighted images: a pathognomonic MR imaging sign of Fabry disease.

BACKGROUND AND PURPOSE: Fabry disease is a multisystem X-linked disorder characterized clinically by angiokeratoma, corneal and lenticular abnormalities, acroparesthesia, and renal and cardiac dysfunction and stroke. We sought to describe novel neuroimaging characteristics of Fabry disease. METHODS: Neuroradiologic records of 104 hemizygous patients with Fabry disease evaluated between 1994 and 2002 were reviewed. In total, 94 MR studies consisting of T1- and T2-weighted images were examined for the presence of hyperintensity on the T1-weighted images. Additional CT, gradient-echo (T2*-weighted), and fat-suppression MR studies were reviewed to characterize further the T1 abnormality in selected patients. In some patients, cerebral blood flow (CBF) was quantified by using arterial spin tagging (AST). RESULTS: Overall, 22 patients ( approximately 23%) demonstrated pulvinar hyperintensity on T1-weighted images; the frequency increased with age to over 30% by age 50 years. Susceptibility-weighted T2* studies demonstrated a low-signal-intensity abnormality in the pulvinar in the more severe cases, whereas CT demonstrated the pulvinar to be mineralized. CT attenuation corresponded with an increasing signal intensity on T1-weighted images. Posterior circulation CBF was found to be elevated on individual AST studies, especially in the thalamus. CONCLUSION: Hyperintensity in the pulvinar on T1-weighted images is a common finding in Fabry disease, likely reflecting the presence of calcification. Although other minreralizing abnormalities may result in calcification of deep gray nuclei, exclusive involvement of the pulvinar may be distinctively characteristic to Fabry disease. Increased CBF in the posterior circulation, particularly the thalamus, suggests that the dystrophic calcification is secondary to cerebral hyperperfusion and selective vulnerability of the pulvinar and adjacent thalamic nuclei. The finding of isolated pulvinar hyperintensity on T1-weighted images should suggest Fabry disease, particularly when seen in conjunction with other nonspecific neuroradiologic manifestations of the disease.

Adolescent↗
PubMed1998

Organization of the medial pulvinar nucleus in the macaque.

BACKGROUND: The medial pulvinar appears to subserve the integration of associative cortical information and projects to visuomotor-related cortex. In contrast to the other pulvinar subdivisions, the medial pulvinar is a polymodal structure. Therefore, we studied the structural organization of the medial pulvinar to determine how it differs from the surrounding unimodal nuclei. METHODS: Nissl-stained sections were examined to determine the boundaries of, and the distribution of neuronal sizes within, the medial pulvinar. In addition, Golgi-impregnated neurons were examined and drawn for analysis. Only rhesus monkey specimens were used, and the material had been prepared previously for other studies. RESULTS: Projection neurons have round to oval somata and moderate numbers of primary dendrites that extend for short distances before branching into many secondary branches. Two variations of projection neurons (P1 and P2) were distinguished on the basis of the diameters of their dendritic tree. Both varieties have short dendrites that radiate in all directions. They differ in that P2 cells have longer second tier dendrites than P1 cells. Three types of local circuit neurons, tufted, radiating and varicose, were distinguished on the basis of their dendritic morphology. Four types of afferent fibers were identified. Type 1 afferents form cone-shape terminal arbors. Type 2 afferents are similar to those reported for retinal or cortical terminals. Type 3 afferents are of medium thickness and of an unknown origin. Type 4 afferents are thin and have small varicosities consistent with previously described cortical afferents. Afferent fibers are predominantly oriented along the mediolateral axis of the nucleus. We observed putative contacts between some afferents and local circuit neurons and between local circuit neurons and projection neurons. CONCLUSIONS: Medial pulvinar neurons are generally smaller and rounder than those found in the adjacent pulvinar nuclei. These results provide additional evidence for structural distinctions between thalamic nuclei having different functions. However, the observed differences are subtle. In addition, the data in this report provide morphological evidence that cortical signals are likely to be integrated by means of the circuitry located within the nucleus.

Animals↗
PubMed1986

Histochemical and architectonic differentiation of zones of pretectal and collicular inputs to the pulvinar and dorsal lateral geniculate nuclei in the macaque.

The pattern of acetylcholinesterase (AChE) reactivity was studied in the pulvinar and dorsal lateral geniculate nucleus (DLG) of the adult macaque monkey. Discrete islands of AChE reactivity were found that correlated precisely in location with the pattern of projections from the superior colliculus and pretectum. Specifically, AChE overlies terminal fields of superior colliculus projections in the DLG, in four foci in the medial and lateral pulvinar, and in several foci in the inferior pulvinar. All of these tectal projection areas have very high AChE reactivity such that they are easily distinguished. In addition, the pretectum projects to a specific focus in the lateral pulvinar that also has a very dense AChE histochemical reaction. A number of these AChE foci could be further distinguished from other areas in the pulvinar by myeloarchitectonic characteristics. Some of the foci in the lateral and inferior pulvinars could also be distinguished by unique cytoarchitectonic features (as seen with both Nissl and Golgi stains). In an attempt to determine the possible origin of a cholinergic input to the pulvinar, horseradish peroxidase (HRP) injections and choline acetyltransferase immunohistochemistry were also done. The results of this experiment indicate that the AChE reactivity seen in the midbrain projection zones to the thalamus may be due to the precise overlap of terminal projections from the brainstem cholinergic cell groups, Ch5, Ch6, and Ch8. These results, taken together, imply that there are several anatomically and histochemically distinct zones related to extrageniculate pathways located within classically defined thalamic boundaries.

Acetylcholinesterase↗
PubMed1995

Neurochemical subdivisions of the inferior pulvinar in macaque monkeys.

The architecture of the pulvinar of rhesus monkeys was investigated by acetylcholinesterase (AChE) histochemistry, and by immunocytochemistry for calbindin-D28k and the SMI-32 antibody. The presence of four inferior subdivisions, comparable to those found in architectonic-connectional studies in squirrel monkeys (C.G. Cusick, J.L. Scripter, J.G. Darensbourg, and J.T. Weber, 1993, J. Comp. Neurol. 336:1-30), provided a basis for a proposed revised terminology for visual sectors of the macaque pulvinar. In the present study, the inferior pulvinar (PI) was identified as a neurochemically distinct region that included the traditional cytoarchitectonic nucleus PI and adjacent portions of the lateral and medial pulvinar nuclei, PL and PM. In calbindin-D28k stains, the lateral subdivision of the inferior pulvinar (PIL) had less intense neuropil staining than the adjacent central division, PIC. The PIL was characterized by large, intensely immunopositive neurons seldom found within PIC. PIL occupied the traditional PL and PI and exhibited a narrow shell zone, PIL-S, restricted to PL. The medial division of the inferior pulvinar (PIM) was in a location previously shown to be strongly connected with the middle temporal visual area (MT) in macaques. PIM was found in the medial one-half of the traditional PI and extended into adjacent portions of the traditional PM and PL. PIM was distinguished by less intense neuropil staining for calbindin and many cells stained with the SMI-32 antibody for neurofilament protein. In AChE stains, PIL was moderately dark, PIC appeared lighter, and PIM was characterized by small, intensely stained patches. The small posterior division (PIP) stained darkly for calbindin, lightly for AChE, and was unstained with the SMI-32 antibody. Thus, neurochemical, and perhaps connectional, subdivisions exist within PI, the region of the pulvinar that relays information to striate, "lower order" extrastriate, and inferotemporal visual cortex.

Acetylcholinesterase↗
PubMed1978

Functional organization in the cat's pulvinar complex.

The responses of 192 single units in the cat's pulvinar-complex, comprising the inferior, medial and lateral pulvinar nuclei, were studied in paralysed cats, lightly anaesthetized with N2O/O2 supplemented with pentobarbitone. About 60% of the cells were visually driven and their receptive fields classified as either diffuse, concentric, movement sensitive, direction sensitive or orientation sensitive. The response fields of such cells were commonly large. Response field maps for the movement and direction sensitive cells formed a heterogenous population with uniform on-off fields to more complex arrangements with on- or off-centres, often with only partial surrounds; other cells responded exclusively to moving stimuli. A dual representation of the visual field was found in the pulvinar-complex corresponding to the striate and tectal recipient zones described anatomically by others. The representation in the striate recipient zone comprised an oblique column running medio-laterally and rostro-caudally through the inferior pulvinar and lateral margin of the medial pulvinar. The peripheral visual field was represented laterally and the vertical meridian medially; the upper visual field was represented dorso-laterally in the medial pulvinar and the lower visual field caudo-ventrally within the inferior pulvinar. That this visuotopic organization corresponded to the striate recipient zone was established by tracing the retrograde transport of HRP. Medial to the striate zone evidence for a second visual field representation was found, apparently more randomly organized than the striate zone, corresponding to the presumed tectal recipient zone. These results support the assertion that cytoarchitectural boundaries do not necessarily delineate functional (visuotopically organized) regions. These observations suggest caution when comparing cytoarchitecturally defined regions between species; rather, 'functionally equivalent' regions should be compared.

Animals↗
PubMed1982

Localization and detection of visual stimuli in monkeys with pulvinar lesions.

Since the pulvinar receives a major ascending projection of the superior colliculus, pulvinar lesions might produce behavioral impairments resembling those that follow colliculus lesions. To test this possibility, we examined the effect of pulvinar lesions in monkeys on the localization and detection of brief light flashes, a task in which monkeys with colliculus lesions are severely impaired. Some of the pulvinar-lesioned monkeys showed localization impairments similar to those in monkeys with colliculus lesions. However, histological analyses of the lesions suggested that these deficits were related not to the pulvinar damage per se, but rather to interruption of corticotectal fibers that pass through the pulvinar. We conclude that the pulvinar is not critical for the ability to locate and detect brief visual stimuli.

Animals↗
PubMed1979

Pulvinar and lateral geniculate neuronal activity in the cat during operantly conditioned appetitive behavior.

Cats were trained to press a lever for 0.5--1.0 ml of milk reward both in the presence and absence of ambient light. 'Floating' microelectrodes were implanted in the pulvinar and lateral geniculate nuclei to allow chronic recording from single or multiple neurons over a period of 1--16 days. Thirty-one of 36 pulvinar neurons (86%) showed a consistent periodicity in the firing rate that was clearly related to certain phases of operant behavior. In the presence of ambient light, the firing rate was maximal shortly prior to or immediately after a rewarded bar press, particularly during the animal's initial contact with reward (the first lap). This burst of activity was followed by an abrupt and strong inhibition of firing which was, in most instances, associated with high voltage slow wave (6--9 c/sec) postreinforcement synchronization (PRS) of the electroencephalogram over the visual and association cortices as well as in the pulvinar. Postreinforcement inhibition of neuronal activity was also observed in the lateral geniculate. Neuronal firing in both nuclei dropped significantly below the respective mean rate observed for each nucleus during relaxed wakefulness. In the dark, however, the reward-induced inhibition was abolished in both nuclei. Moreover, some pulvinar neurons in the dark showed a conspicuous and significant increase in firing during the consummatory response (dark reversal pattern). These findings suggest that a transient but powerful inhibitory process triggered by positive reinforcement depends on visual input. Firing patterns of some pulvinar neurons were noted to be entrained not only by the rhythm of PRS oscillations (inhibitory phasing and postinhibitory discharges) but also by the much slower 3--4 c/sec rhythm of lapping and licking. Furthermore, the patterns of entrainment by initial lapping appear to be different from those observed during the later phase of the consummatory response, thus indicating that the pulvinar may receive information regarding the content of the delivery cup. No entrainment of neuronal activity was observed in the lateral geniculate. These findings reveal remarkable plasticity in the pulvinar neurons that is consistent with their role in polysensory integration.

Action Potentials↗
PubMed1989

The visual superior colliculus and pulvinar.

The data reviewed here suggest several relationships between the superior colliculus, pulvinar and saccadic eye movements. These will be summarized in a series of steps in the visual initiation of saccadic eye movements. Area Pdm of the pulvinar appears to be involved in visual spatial attention. As such it may participate in the earliest decisions to make an eye movement: the shift of attention. This function is suggested by the spatially selective enhancement seen in the activity of individual neurons and the effects of drug injections on attentional performance. The attentional function of area Pdm is probably accomplished in coordination with cortical area 7 and possibly other areas. The spatially non-selective enhancement found in PI and PL may precede or follow the enhancement in Pdm. The next oculomotor function may be played by the visual cells in the superficial layers of the colliculus. Here the enhancement effect appears to be related to target selection which is specifically used with saccadic eye movements. Lesions here lead to animals who are not easily distracted by peripheral events; they do not select saccade targets. Thus the visual regions of the superior colliculus and Pdm may provide separate initiatives to the saccadic system. Once the eye begins to move, there are many relations manifested in both brain areas. Many of the visual collicular cells and those in parts of the pulvinar are unresponsive to visual stimuli during eye movements. In the colliculus, this particular effect may function to minimize erroneous visual targets whereas in the pulvinar the process may be more important perceptually. Finally there is a population of cells in the pulvinar which discharge during and after saccadic eye movements. These cells may have a role in the termination of one attentional scan and the beginning of the next. The pathways through which these effects may be mediated are totally unclear. The visual signal from the superficial layers related to saccade initiation may impinge directly on the cells in the intermediate layers or may reach the oculomotor system through other pathways. The parts of the pulvinar which relate to visual spatial attention are interconnected with posterior parietal cortex and probably function in concert with that area. How those data get to the oculomotor system has yet to be determined. Since the pulvinar is extensively interconnected with the cortex, it is most likely through this route that eye movement information coming from the superior colliculus is brought to higher perceptual areas.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

Pulvinar and other subcortical connections of dorsolateral visual cortex in monkeys.

The present study used injections of neuroanatomical tracers to determine the subcortical connections of the caudal and rostral subdivisions of the dorsolateral area (DL) and the middle temporal crescent area (MT(C)) in owl monkeys (Aotus trivirgatus), squirrel monkeys (Saimiri sciureus), and macaque monkeys (Macaca fascicularis and M. radiata). Emphasis was on connections with the pulvinar. Patterns of corticopulvinar connections were related to subdivisions of the inferior pulvinar (PI) defined by histochemical or immunocytochemical architecture. Connections of DL/MT(C) were with the PI subdivisions, PICM, PICL, and PIp; the lateral pulvinar (PL); and, more sparsely, the lateral portion of the medial pulvinar (PM). In squirrel monkeys, there was a tendency for caudal DL to have stronger connections with PICL than PICM and for rostral DL/MT(C) to have stronger connections with PICM than PICL. In all three primates, DL/MT(C) had reciprocal connections with the pulvinar and claustrum; received afferents from the locus coeruleus, dorsal raphe, nucleus annularis, central superior nucleus, pontine reticular formation, lateral geniculate nucleus, paracentral nucleus, central medial nucleus, lateral hypothalamus, basal nucleus of the amygdala, and basal nucleus of Meynert/substantia innominata; and sent efferents to the pons, superior colliculus, reticular nucleus, caudate, and putamen. Projections from DL/MT(C) to the nucleus of the optic tract were also observed in squirrel and owl monkeys. Similarities in the subcortical connections of the dorsolateral region, especially those with the pulvinar, provide further support for the conclusion that the DL regions are homologous in the three primate groups.

Animals↗