LP-pulvinar Complex Research Articles

Structural and functional connectivity between the lateral posterior-pulvinar complex and primary visual cortex in the ferret.

The role of higher-order thalamic structures in sensory processing remains poorly understood. Here, we used the ferret (Mustela putorius furo) as a novel model species for the study of the lateral posterior (LP)-pulvinar complex and its structural and functional connectivity with area 17 [primary visual cortex (V1)]. We found reciprocal anatomical connections between the lateral part of the LP nucleus of the LP-pulvinar complex (LPl) and V1. In order to investigate the role of this feedback loop between LPl and V1 in shaping network activity, we determined the functional interactions between LPl and the supragranular, granular and infragranular layers of V1 by recording multiunit activity and local field potentials. Coherence was strongest between LPl and the supragranular V1, with the most distinct peaks in the delta and alpha frequency bands. Inter-area interaction measured by spike-phase coupling identified the delta frequency band being dominated by the infragranular V1 and multiple frequency bands that were most pronounced in the supragranular V1. This inter-area coupling was differentially modulated by full-field synthetic and naturalistic visual stimulation. We also found that visual responses in LPl were distinct from those in V1 in terms of their reliability. Together, our data support a model of multiple communication channels between LPl and the layers of V1 that are enabled by oscillations in different frequency bands. This demonstration of anatomical and functional connectivity between LPl and V1 in ferrets provides a roadmap for studying the interaction dynamics during behaviour, and a template for identifying the activity dynamics of other thalamo-cortical feedback loops.

Spatiotemporal profiles of receptive fields of neurons in the lateral posterior nucleus of the cat LP-pulvinar complex.

The pulvinar is the largest extrageniculate thalamic visual nucleus in mammals. It establishes reciprocal connections with virtually all visual cortexes and likely plays a role in transthalamic cortico-cortical communication. In cats, the lateral posterior nucleus (LP) of the LP-pulvinar complex can be subdivided in two subregions, the lateral (LPl) and medial (LPm) parts, which receive a predominant input from the striate cortex and the superior colliculus, respectively. Here, we revisit the receptive field structure of LPl and LPm cells in anesthetized cats by determining their first-order spatiotemporal profiles through reverse correlation analysis following sparse noise stimulation. Our data reveal the existence of previously unidentified receptive field profiles in the LP nucleus both in space and time domains. While some cells responded to only one stimulus polarity, the majority of neurons had receptive fields comprised of bright and dark responsive subfields. For these neurons, dark subfields' size was larger than that of bright subfields. A variety of receptive field spatial organization types were identified, ranging from totally overlapped to segregated bright and dark subfields. In the time domain, a large spectrum of activity overlap was found, from cells with temporally coinciding subfield activity to neurons with distinct, time-dissociated subfield peak activity windows. We also found LP neurons with space-time inseparable receptive fields and neurons with multiple activity periods. Finally, a substantial degree of homology was found between LPl and LPm first-order receptive field spatiotemporal profiles, suggesting a high integration of cortical and subcortical inputs within the LP-pulvinar complex.

Scaling of neuron number and volume of the pulvinar complex in new world primates: Comparisons with humans, other primates, and mammals

The lateral posterior nucleus and pulvinar (LP-pulvinar complex) are the principal thalamic nuclei associated with the elaborate development of the dorsal and ventral streams of the parietal cortex in primates. In humans, a novel site of origin for a subpopulation of pulvinar neurons has been observed, the ganglionic eminence of the telencephalon. This additional site of neuron origin has been proposed to contribute to the pulvinar's evolutionary expansion (Letinic and Rakic [2001] Nat Neurosci 4:930-936). Studies of neuron number in the LP-pulvinar complex in gibbon, chimpanzee, and gorilla compared to humans, however, did not show that the human LP-pulvinar was unexpectedly large (Armstrong [1981] Am J Phys Anthropol 55:369-383). Here we enlarge the allometric basis for comparison by determining neuron number in the LP-pulvinar complex of six New World primates (Cebus apella, Saimiri ustius, Saguinus midas niger, Alouatta caraya, Aotus azarae, and Callicebus moloch) as well as measuring LP-pulvinar volume in a further set of 24 species including additional primates, carnivores, and rodents. The volume of the LP-pulvinar complex scaled with positive allometry with respect to brain volume across all species examined. The scaling of the number of neurons in the LP-pulvinar complex was extremely similar in New World primates and anthropoid apes, with the human LP-pulvinar value close to the regression line. Comparison of the relative volumes of the LP-pulvinar in the larger sample confirmed this observation, and further demonstrated that both primates and carnivores showed a "grade shift" in its size compared to rodents, with the pulvinar comprising a greater proportion of total brain volume across the board. Diurnal, nocturnal, or crepuscular niche did not discriminate LP-pulvinar size across taxa.

Overlapping visual response latency distributions in visual cortices and LP-pulvinar complex of the cat

The visual system of the cat is considered to be organized in both a serial and parallel manner. Studies of visual onset latencies generally suggest that parallel processing occurs throughout the dorsal stream. These studies are at odds with the proposed hierarchies of visual areas based on termination patterns of cortico-cortical projections. In previous studies, a variety of stimuli have been used to compute latencies, and this is problematic as latencies are known to depend on stimulus parameters. This could explain the discrepancy between latency and neuroanatomical based studies. Therefore, the first aim of the present study was to determine whether latencies increased along the hierarchy of visual areas when the same stimuli are used. In addition, the effect of stimulus complexity was assessed. Visual onset latencies were calculated for area 17, PMLS, AMLS, and AEV neurons. Latencies were also computed from neurons in the lateral posterior (LP)-pulvinar complex given the importance of this extrageniculate complex in cortical intercommunication. Latency distributions from all regions overlapped substantially, and no significant difference was present, regardless of the type of stimulus used. The onset latencies in the LP-pulvinar complex were comparable to those seen in cortical areas. The data suggest that the initial processing of information in the visual system is parallel, despite the presence of a neuroanatomical hierarchy. Simultaneous response onsets among cortical areas and the LP-pulvinar suggest that the latter is more than a simple relay station for information headed to cortex. The data are consistent with proposals of the LP-pulvinar as a center for the integration and distribution of information from/to multiple cortical areas.

Retinal projections to the lateral posterior-pulvinar complex in intact and early visual cortex lesioned cats.

In intact cats, it is generally considered that the lateral posterior-pulvinar complex (LP-pulvinar) does not receive direct retinal terminals, with the exception of the retino-recipient zone known as the geniculate wing. There is, however, some evidence that early lesions of the visual cortex can occasionally induce the formation of novel retinal projections to the LP nucleus. Given the importance of knowing the connectivity pattern of the LP-pulvinar complex in intact and lesioned animals, we used the B fragment of cholera toxin, a sensitive anterograde tracer, to reinvestigate the retinal projections to the LP-pulvinar in normal cats and in cats with early unilateral lesions of the visual cortex (areas 17 and 18). Immunohistochemical localization of the toxin was performed to show the distribution and morphology of retinofugal terminals. A direct bilateral but predominantly contralateral retinal projection reached the caudal portion of LPl and LPm in the form of patches located mainly along its dorsomedial surface and many scattered terminals. The distribution of retinal projections to LP-pulvinar in intact and operated cats did not differ. Contrary to what had been previously reported, we found no evidence for lesion-induced sprouting of retinal axons in these higher-order thalamic nuclei. Retinal input to the LP-pulvinar might modulate visual responses driven by primary visual cortex or superior colliculus.

Global motion integration in the cat's lateral posterior-pulvinar complex.

Our laboratory previously showed that thalamic neurons in an extrageniculate nucleus, the lateral posterior-pulvinar complex (LP-pulvinar) could perform higher-order neuronal operations that had until then only been attributed to higher-level cortical areas. To further assess the role of the thalamus in the analysis of complex percepts, we have investigated whether neurons in the LP-pulvinar complex can signal the direction of motion of random-dot kinematograms wherein the individual elements of the pattern do not provide coherent motion cues. Our results indicate that a subset of LP-pulvinar cells can integrate the displacement of individual elements into a global motion percept and that their large receptive fields permit the integration of motion for elements separated by large spatial intervals. We also found that almost all of the global motion-sensitive neurons were not systematically pattern-motion-selective when tested with plaid patterns. The results indicate that LP-pulvinar cells can perform the higher-level spatio-temporal integration required to detect the global displacement of objects in a complex visual scene, further supporting the notion that extrageniculate thalamic cells are involved in higher-order motion processing. Furthermore, these results provide some evidence that there may be specialized mechanisms for processing different types of complex motion within the LP-pulvinar complex.

Contribution of area 17 to cell responses in the striate-recipient zone of the cat's lateral posterior-pulvinar complex.

The cat's lateral posterior-pulvinar complex (LP-pulvinar) contains three main representations of the visual field. The lateral part of the LP nucleus (LPl or striate-recipient zone) is the only region of these extrageniculate nuclei which receives afferents from the primary visual cortex. We investigated the contribution of area 17 to the response properties (orientation and spatial frequency tuning functions) of LPl neurons by cooling or lesioning the visual cortex. Responses of 40 LPl cells were studied before, during and after the reversible cooling of the striate cortex. When tested for orientation, a total of 10 units out of 28 was affected (36%). For most of these cells (eight of 10), cooling the visual cortex yielded a reduction of the cells' visual responses without altering their orientation-selectivity (there was no significant change in the orientation tuning width). For only two cells, inactivation led to an increase in the response amplitude. Also, blocking the visual cortex never modified the direction-selectivity of LPl cells. When tested for spatial frequency, 12 neurons out of 33 were affected (36%) by the experimental protocol. In most cases, we observed a reduction in the responses at each spatial frequency tested, with no change in tuning bandwidth. For only three LPl cells, the effects of inactivation of the visual cortex were restricted to specific spatial frequencies, altering the profile of the spatial frequency tuning function. In five cats, removing area 17 reduced the proportion of visual neurons in LPl and the spared visually evoked responses were noticeably depressed. Despite the reduction in responsiveness, a few LPl receptive fields within the cortical scotoma were still sensitive to the orientation and/or direction of a moving stimulus. This last observation suggests that some properties in LPl could be generated either by circuits intrinsic to the LPl or by afferents from extrastriate cortical areas. Overall, these results indicate that projections from the visual cortex to the striate-recipient zone of the LP-pulvinar complex are mainly excitatory. Despite the strong impact of the area 17 projections, our data suggest that the extrastriate cortex could also play a role in the establishment of response properties in the cat's LPl.

Chapter 19 Motion sensitivity and stimulus interactions in the striate-recipient zone of the cat's lateral posterior-pulvinar complex

The cat's lateral posterior-pulvinar complex (LP-pulvinar) establishes reciprocal connections with the anterior ectosylvian visual (AEV) and lateral suprasylvian (LS) cortices; two regions which are believed to be involved in motion analysis. We have investigated the motion sensitivity of neurons in the LP-pulvinar complex by: (1) studying the responses properties of cells in the striate-recipient zone of the LP nucleus (LPI) to the drift of a two-dimensional texture pattern (visual noise); and (2) determining the extent to which the latter stimulus can modify the spatial frequency tuning function of LPI cells. Experiments were carried out on anesthetized normal adult cats. Almost all LPI cells (55 out of 63, 87%) responded to the motion of visual noise. For most units (39 out of 55, 71%), responses varied as a function of the direction of motion (bandwidth of 49 degrees). One-third of the LPI units did not exhibit any preference for drift direction of noise. For practically all LPI cells, responses to noise varied as a function of drift velocity. Optimal velocities were distributed from 2 to 35 degrees/s with a mean value of 27.5 degrees/s (means bandwidth of 2.5 octaves). The influence of visual noise on the spatial frequency tuning function of 22 LPI cells was also studied. For half of LPI cells, responses at all spatial frequencies were reduced when the grating and the texture pattern were moving in opposite directions (anti phase condition). This masking effect of noise was rarely observed when both stimuli were drifted in the same direction (in phase condition). These results suggest that the LP-pulvinar complex may be part of extrageniculate pathways involved in the analysis of motion of visual targets and/or the analysis of the relative movement between an object and its surrounding environment.

The dorsal thalamus of jawed vertebrates: a comparative viewpoint.

In anamniotes, the dorsal thalamus comprises: (1) a caudal division, the collothalamus, which receives its predominant input from the midbrain roof and projects ipsilaterally to the telencephalon, predominantly to the striatum, and (2) a rostral division, the lemnothalamus, which predominantly receives a direct retinal (lemniscal) input and projects bilaterally to the telencephalon, predominantly to the pallium. In amniotes, collothalamic nuclei relay visual, auditory, and somatosensory-multisensory inputs from the midbrain roof to the ipsilateral telencephalon, terminating in both striatum and pallium. For example, the collothalamic visual nuclei consist of the LP-pulvinar complex in mammals and nucleus rotundus in diapsid reptiles, birds, and turtles. Among amniotes, the latter nuclei are homologous to each other as discrete nuclei, as are the collothalamic auditory and collothalamic somatosensory-multisensory nuclei. Lemnothalamic nuclei (and nuclear groups) in amniotes predominantly (and/or plesiomorphically) receive lemniscal inputs; some project to the telencephalon bilaterally, and most, in contrast to collothalamic nuclei, do not project to the striatum. In mammals, the lemnothalamic nuclei include most of those in the anterior, medial, intralaminar, and ventral nuclear groups and the dorsal lateral geniculate nucleus. In diapsid reptiles, they include the dorsomedial and dorsolateral anterior nuclei and the dorsal lateral optic nucleus; comparable nuclei are present in birds and turtles, with birds additionally having a discrete somatosensory lemniscal relay nucleus. These lemnothalamic nuclei in each amniote radiation are homologous as a field to the lemnothalamus (i.e., nucleus anterior) in anamniotes. Both divisions of the dorsal thalamus were elaborated to some degree in the common ancestral amniote stock. A further major elaboration of the lemnothalamus characterized the ancestral stock of mammals and may have been one of the key events in early mammalian evolution. Birds have independently, to a lesser degree, elaborated the lemnothalamus.

Visual receptive fields in the striate-recipient zone of the lateral posterior-pulvinar complex

The lateral posterior (LP)-pulvinar complex of the cat is known to contain multiple visual areas. In the present study, we examined the receptive field properties of single neurons isolated in the lateral division of this complex (the LPI). The LPI is designated the striate-recipient zone because it is the only region of the LP-pulvinar receiving cortical projections from areas 17 and 18. The recordings revealed that the striate-recipient zone of LP comprises 2 subareas, which we have termed LPI-1 and LPI-2. In the main segment (LPI-1), virtually all cells responded securely to visual stimuli. The vast majority of these neurons were binocular, with relatively small and well-defined receptive fields. More than half of the cells were found to be directionally selective, and almost this many were orientation specific. The orientation tuning of these cells was found to be quite precise, comparable to complex cells in area 17. In contrast, in the small dorsolateral segment of the striate-recipient zone (the LPI-2), a substantial proportion of cells could not be visually activated. Here, the visual cells had very large receptive fields, and relatively few were direction or orientation selective. The LPI-2 receives subcortical inputs from the superficial layers of the superior colliculus, the hypothalamus, and cerebellum, while the LPI-1 is innervated only by cortical axons. It is suggested that the subcortical connections of the LPI-2 account for the differences in the response properties of the 2 striate-recipient areas. The present results, in conjunction with our previous findings on the principal tectorecipient zone (Chalupa et al., 1983), permit 2 generalizations regarding the functional organization of the cat's LP-pulvinar complex. First, there are clear differences among the visual areas of the LP-pulvinar in the cellular processing of visual information. Second, these functional differences can be related to the principal sources of visual input to the various divisions of the LP-pulvinar.

Chapter 8: Receptive-field properties in the tecto- and striate-recipient zones of the cat's lateral posterior nucleus

The chapter addresses two basic questions during neurophysiological studies of the LP nucleus: First, are the visual receptive field properties of LPm cells different from those of neurons in the LPI; and second, if there are such differences, can these be related to the main sources of visual input to these two areas? The pulvinar-lateral posterior (LP) complex of the cat has been known for many years to be involved in visual function. Almost 30 years ago it was reported that visual evoked potentials could be recorded from the cat's pulvinar-LP complex With hindsight, it is now apparent that these early efforts to elucidate the functional organization of the pulvinar-LP complex were premature because they were carried out without the benefit of pertinent anatomical knowledge. Studies from the laboratory indicate that the LP-pulvinar complex contains multiple visual areas. The results of the experiments that are summarized in the chapter mentions the receptive field properties of two of the main visual zones in the LP nucleus.

Chapter 10: Synaptic organization of the lateralis medialis-suprageniculate nuclear (LM-Sg) complex in the cat

Publisher Summary The purpose of this chapter is to describe the afferent connections of the lateralis medialis-suprageniculate nuclear (LM-Sg) complex, and to point out the ultrastructural neural circuit of this complex. The anatomical patterns of connectivity and principles of organization of the LM-Sg complex have been recently established. Among the thalamic nuclei, the lateralis posterior-pulvinar the lateralis posterior-pulvinar (LP-pulvinar) complex is known to be a principal component of the “extrageniculate” thalamus. The most medial zone of the LP-pulvinar complex is the LM-Sg complex. There are certain differences in connective pattern between the LM-Sg complex and other subdivisions of the LP-pulVinar Complex. The deeper collicular layers sending axons to the LM- Sg complex contain neurons that respond to visual, somatic, and auditory, and/or multimodal stimuli. In addition, the chapter also examines the afferent connections of the LM-Sg complex using the wheat germ agglutinin - horseradish peroxidase (WGA-HRP) technique.

Anatomical organization of the visual system of the mink, Mustela vison.

The organization of the retinogeniculocortical visual system of the mink was studied by anterograde and retrograde tracer techniques, by physiological mapping, and by direct recordings from axonal terminals after injection of kainic acid. In the lateral geniculate nucleus, retinogeniculate afferents are segregated according to eye of origin between the two principal layers, A and A1. Within each of these layers there is a further parcellation according to functional type: on-center afferents terminate in the anterior leaflets of A and A1, and off-center afferents in the posterior leaflets. This separation is preserved in area 17: geniculocortical afferents terminate in ocular dominance patches in layer IV, and these patches coexist with an alternating, partially overlapping set of patches for on-center and off-center inputs that we have demonstrated previously (McConnell and LeVay: Proc. Natl. Acad. Sci. USA 81:1590-1593, '84). In both the lateral geniculate nucleus and in area 17, the contralateral eye predominates to a much greater extent than in the cat. Visual cortical areas corresponding to the cat's areas 17, 18, and 19 can be identified in the mink, but they are shifted posterolaterally in the hemisphere, and they show less emphasis on the representation of central retina. Mapping studies also revealed the existence of a fourth visual area in the splenial sulcus (area SV) adjacent to the representation of the far periphery in area 17. This area differs from the corresponding region in the cat in that it receives direct projections from the lateral geniculate nucleus and from areas 17 and 18. The lateral geniculate nucleus projects to each of the four cortical areas that were mapped. The bulk of the projection to area 17 is derived from the principal layers, A and A1, while most cells projecting to areas 18 and SV are found in the C-layer complex. The recurrent projection from area 17 to the lateral geniculate nucleus arises from pyramidal neurons in layer VI, and terminates through all layers of the lateral geniculate nucleus, but most densely in the interlaminar zones. Areas 18 and SV project predominantly to the C layers. Areas 17, 18, and SV are reciprocally connected with the claustrum and the LP-pulvinar complex, and project to the superior colliculus. All four visual cortical areas are mutually interconnected; these associational projections arise from both the supragranular and infragranular layers.

Enhancement of visual responses of area 7 neurons by electrical pre-conditioning stimulation of LP-pulvinar nuclei of the monkey.

The characteristics of visually evoked unit responses in area PG of the infraparietal lobule were studied in the awake trained Rhesus monkey. These responses are shown to be significantly modified by pairing the visual stimulus with pre-conditioning stimulation of targets in the LP Pulvinar complex. Pre-conditioning stimuli were either single pulses, or a 50 ms train of pulses at 100 Hz delivered through bipolar electrodes 20 ms prior to, simultaneously with, or 50 ms following the visual stimulus. In some cases, modifications of the visual responses appeared as more massive discharges; in others they became bursts of constant latencies, pattern and duration, that contained high frequency discharges. A pre-conditioning single stimulus delivered simultaneously to a few sites in the LP, medial and lateral pulvinar was more effective than stimulation at a single electrode site, and produced an enhancement that appeared like an additive effect of several inputs. In the enhanced condition, repetition of single pulse preconditioning stimulation resulted in a considerable build-up of the enhancement. A pre-conditioning train of stimuli delivered during enhancement resulted in a further increase in the constancy of response durations and patterns. These changes, lasting as long as five minutes, manifested hysteresis: when recovery was allowed without any pre-conditioning stimulation, the various response patterns appeared in a reverse order. It is proposed that this dependence of the responses on the neural state is based on a complex network of inputs to cells of area 7.

Electrophysiological and anatomical demonstration of an overlapping striate and tectal projection to the lateral posterior-pulvinar complex of the cat.

Extracellular unit activity was recorded in the lateral posterior (LP)-pulvinar complex. The responses of 254 neurons after electrical stimulation of the central-paracentral part of cortical area 17 and of 84 neurons after stimulation of both area 17 and the superior colliculus (SC) were investigated. Neurons in the LP-pulvinar complex responded to area 17-stimulation with excitatory-inhibitory effects; in some cases only with inhibition. Neurons affected by striate stimulation were found in the caudal region of the complex in a region that extended widely into the medial part of the lateralis posterior nucleus (LPm), the so-called tectorecipient part of the lateral posterior nucleus. Accordingly, 26 of the 84 neurons in which electrical stimulation of area 17 and of the SC was tested, were found to react to both types of stimulation. Cells responding only to SC-stimulation were found in the ventral region of the anterior LP-Pulvinar complex. Anatomical studies supported the finding that striate and tectal inputs overlap considerably in the LP-pulvinar complex. After depositing horseradish peroxidase (HRP) into various regions of the LP-pulvinar complex, retrogradely labeled cells were found in area 17 (layer V) as well as in the superficial layers of the SC. These results were confirmed by orthograde transport autoradiography after injection of labeled amino-acids into area 17. Our findings indicate that cortical and collicular inputs into the caudal part of the LP-pulvinar complex overlap considerably and that, in these overlapping regions, individual neurons may receive converging afferent excitation from both regions.

The integrative sensorimotor function of the LP-pulvinar complex.

An important number of studies have paid attention to the sensorial function of the LP-pulvinar complex and its probable polisensorial integrative role. In the present review, on the basis of some experimental results, we have tried to emphasize the importance of the LP-pulvinar complex in the motor function. In this sense, this thalamic complex appears as a probable sensorimotor integrative structure. Considering the behavior elicited by electrical as well as chemical stimulation of the LP-pulvinar complex, it would seem that this structure is related to the type of behavior that researches and examines the environment, mainly, by internal motivation. Furthermore, the possible role of the LP-pulvinar complex in the sleep and wakefulness mechanism and in the epileptic phenomena, is mentioned.

Differential responsiveness of cells in the visual zones of the cat's LP-pulvinar complex to visual stimuli.

Multiple visual field representations are contained within the feline LP-pulvinar complex; regions differentiated by their afferent and efferent connectivity patterns as the striate-, tecto- and retino-recipient zones. Cell responses from these visuotopic zones were investigated in immobilized cats under N2O/O2 supplemented with pentobarbitone or Althesin, using spot, bar and textured stimuli. Response fields recorded within the LP-pulvinar complex were classified as diffuse, concentric, movement-, direction- or orientation-sensitive. Concentric receptive fields were further classified as sustained (X), transient (Y) or tonic/phasic W-cells. Direction- and movement-sensitive cells predominated in the striate- and tecto-recipient zones, respectively. Motion of noise fields, or noise bars against an identical stationary noise background elicited vigorous responses from cells in the striate zone, many showing a preference for noise stimuli. In contrast, cells from the tectal zone and other divisions of the LP-pulvinar complex were insensitive to noise. The retino-recipient zone at the lateral margin of the pulvinar nucleus was characterized by cells with concentric receptive fields, the majority exhibiting properties similar to W-cells in the LGNd. The evidence supports the notion of functional subdivision within the LP-pulvinar complex corresponding to the visuotopically organized regions defined by their connectivity patterns. Consideration of the retino-recipient zone as an extension of the LGNd-MIN complex is discussed.

Parallel thalamic zones in the LP-pulvinar complex of the cat identified by their afferent and efferent connections

Parallel thalamic zones in the LP-pulvinar complex of the cat identified by their afferent and efferent connections

A surgical investigation of the clinical physiology of the LP-pulvinar complex in man

Cryogenic stereotactic lesions were placed in 55 pulvinar and 9 lateralis-posterior (LP) nuclei of 49 patients suffering from dystonia, athetosis, spasticity, torticollis, intractable pain, and other miscellaneous conditions. Ten of 19 cases (52.5%) of dystonia, 10 of 16 cases (62.5%) of athetosis and 7 of 10 cases (70%) of spasticity improved significantly following the cryogenic lesion. Thirteen patients with primary or secondary intractable pain were pain-free following surgery. No deleterious effects on motor, sensory, behavioral, or speech and language functions were noted. Electrophysiological studies during surgery not only helped in localisation of the pulvinar and LP nuclei but a wide distribution of evoked potentials from cortex was recorded following their stimulation. It appears that the pulvinar of man contributes to motor function. The LP-pulvinar complex is a poly-sensory data processor, contributing to a wide range of somato-sensory functions.