Thalamocortical connections of anterior and posterior parietal cortical areas in New World titi monkeys.

We examined the thalamocortical connections of electrophysiologically identified locations in the hand and forelimb representations in areas 3b, 1, and 5 in the New World titi monkeys (Callicebus moloch), and of area 7b/AIP. Labeled cells and terminals in the thalamus resulting from the injections were related to architectonic boundaries. As in previous studies in primates, the hand representation of area 3b has dense, restricted projections predominantly from the lateral division of the ventral posterior nucleus (VPl). Projections to area 1 were highly convergent from several thalamic nuclei including the ventral lateral nucleus (VL), anterior pulvinar (PA), VPl, and the superior division of the ventral posterior nucleus (VPs). In cortex immediately caudal to area 1, what we term area 5, thalamocortical connections were also highly convergent and predominantly from nuclei of the thalamus associated with motor, visual, or somatic processing such as VL, the medial pulvinar (PM), and PA, respectively; with moderate projections from VP, central lateral nucleus (CL), lateral posterior nucleus (LP), and VPs. Finally, thalamocortical connections of area 7b/AIP were from a range of nuclei including PA, PM, LP/LD, VL, CL, PL, and CM. The current data support two conclusions drawn from previous studies in titi monkeys and other primates. First, cortex caudal to area 1 in New World monkeys is more like area 5 than area 2. Second, the presence of thalamic input to area 5 from both motor nuclei and somatosensory nuclei of the thalamus, suggests that area 5 could be considered a highly specialized sensorimotor area.

Differences in mineral metabolism among nonhuman primates receiving diets with only vitamin D3 or only vitamin D2.

We tested for differences in aspects of mineral metabolism during the administration of diets with only vitamin D3 or only vitamin D2 in four nonhuman anthropoid primate species [two catarrhini, Macaca fascicularis (crab-eating macaque) and Macaca mulatta (rhesus macaque), and two platyrrhini, Saimiri sciureus (squirrel monkey) and Aotus vociferans (night monkey)]. All four species maintained approximately 2- to 3-fold higher serum 25-hydroxyvitamin D (25OHD) level while receiving vitamin D3 than while receiving similar amounts of vitamin D2. Serum 25OHD in M. mulatta receiving the standard primate dietary supplement of vitamin D3 was high enough (360 +/- 60 vs. 70 +/- 25 nM in vitamin D-supplemented humans; P less than 0.0001) to suggest that this widely used level of vitamin D3 supplementation is excessive for some M. mulatta. Serum 24,25-dihydroxyvitamin D [24,25-(OH)2D] in A. vociferans was uniquely high [P less than 0.01; species mean, 19 +/- 5, 95 +/- 12, and 27 +/- 5 nM in groups receiving diets with 1.5 IU vitamin D3/g, 6.6 IU vitamin D3/g, and 15 IU vitamin D2/g, respectively; mean 24,25-(OH)2D from the other three species pooled across three diets was 7 +/- 5 nM]. We confirmed relative resistance to 1,25-(OH)2D in S. sciureus, manifested by osteomalacia and moderately high serum 1,25-(OH)2D. Serum 1,25-(OH)2D in S. sciureus increased 4-fold (P less than 0.05) when the precursor in serum was changed from 250HD3 to 250HD2, suggesting that this species shows more severe resistance to 1,25-(OH)2D2 than to 1,25-(OH)2D3. In conclusion, we found many differences in vitamin D metabolism among four nonhuman anthropoid primate species. The striking feature in A. vociferans (high, 24,25-(OH)2D without high 25OHD in serum independent of whether diet contained only vitamin D3 or only vitamin D2) should allow determination of whether 24,25-(OH)2D functions as a unique agonist or an inactive metabolite in this species.

The squirrel monkey as an experimental model in the study of cerebral organization of emotional vocal utterances.

The different human nonverbal emotional vocal utterances (e.g., laughing, shrieking, moaning) and emotional intonation patterns (e.g., scolding, lamenting, caressing) can be shown to have their acoustic and emotional counterparts in the vocal repertoire of the squirrel monkey. This makes the latter an attractive model for investigations on the neural control of human emotional vocal utterances. Neurophysiological investigations in the squirrel monkey suggest that the cerebral control of emotional vocal utterances is organized hierarchically (Fig. 3). The lowest level - above that of the motor neurons - is represented by the reticular formation of the lateral pons and medulla; here, the motor coordination of laryngeal, respiratory and articulatory movements takes place. The next level is represented by the periaqueductal grey and laterally bordering tegmentum of the caudal midbrain. This area serves to couple specific motivational states to their corresponding vocal expressions. It is a necessary relay station for all vocalization-inducing stimuli. The periaqueductal area receives its input partly from limbic motivation-controlling regions (amygdala, hypothalamus, midline thalamus), partly from sensory pathways (collaterals of spinothalamic tract, fibers from superior and inferior colliculus), and partly from the anterior cingulate cortex. The latter represents the highest level within the system and seems to be responsible for the volitional control of emotional vocal utterances.

Circadian brain and body temperature rhythms in the squirrel monkey.

This study examines the hypothalamic temperature rhythm and its relationship with the colonic temperature rhythm of squirrel monkeys in 24-h light-dark cycles (LD 12:12) at four different ambient temperatures (Ta). The waveforms and phases of both temperature rhythms were similar in all TaS. The rhythm amplitudes were, however, reduced as Ta increased. The 24-h means also showed systematic decreases at higher TaS. The hypothalamic temperature was regulated over a narrower range than the colonic temperature and was higher than colonic temperature at all TaS except the warmest. Further, the mean nighttime temperatures were influenced more by Ta than were the mean daytime temperatures. In summary, the hypothalamic and colonic temperature rhythms are very similar in their circadian regulation. However, the mean temperature levels of these rhythms are controlled differentially. Thus these rhythms are the integrated response of both the circadian and thermoregulatory control systems.

Long collateral branches of substantia nigra pars reticulata axons to thalamus, superior colliculus and reticular formation in monkey and cat. Multiple retrograde neuronal labeling with fluorescent dyes.

In order to gain some impressions about the degree to which individual neurons of the pars reticulata of the substantia nigra send long collateral branches to more than one of its three major targets (thalamus, superior colliculus, reticular formation), two, or all three targets were injected with fluorescent dyes (Evan's blue, granular blue, nuclear yellow, propidium iodide) in six squirrel monkeys and four cats. The best results were obtained in the monkey brain with injections of Evan's blue in the thalamus, granular blue in the colliculus and nuclear yellow in the reticular formation. Whereas nigrothalamic and nigroreticular neurons are numerous and widely scattered throughout all parts of the pars reticulata, cells projecting only to the superior colliculus are fewer in number and restricted to a rostral-lateral zone. These results are consistent with earlier data obtained with the horseradish peroxidase method. Although double-labeled cells with projections to both the thalamus and reticular formation occur throughout the pars reticulata, such cells are somewhat more abundant at caudal levels of the nucleus. Cells containing dyes from both the superior colliculus and reticular formation are less common and restricted to the lateral part of the pars reticulata. A small number of cells near the rostral pole of the pars reticulata contain dye from both the tectal and thalamic injection. Typically, less than two dozen cells in any case can be confidently identified as containing all three dyes and these cells are located in the rostrolateral half of the pars reticulata. Fewer than 20% of the labeled nigral cells contain more than one dye. In the cat, thalamic injection of granular blue and tectal injection of nuclear yellow indicate that most nigrotectal cells are located in the middle of the mediolateral expanse of the pars reticulata in its rostral half. Nigrothalamic cells flank the nigrotectal group medially, laterally and caudally. Where these groups border one another, several cells contain both dyes indicating that they project to both the thalamus and colliculus. In both the cats and monkeys, a less extensive cell-labeling occurs in the contralateral nigra with a pattern similar to that in the ipsilateral substantia nigra. The results indicate that several neurons of the substantia nigra's pars reticulata send long collateral branches to two or even all three of the major targets. Many reticulata cells, however, appear to project either to the thalamus, or to the superior colliculus or to the reticular formation.

The pallidointralaminar and pallidonigral projections in primate as studied by retrograde double-labeling method.

The cellular origin and degree of collateralization of the pallidointralaminar and pallidonigral projections in squirrel monkey (Saimiri sciureus) were studied using Evans blue (EB) and a mixture of DAPI-Primuline (DP) as fluorescent retrograde tracers. In a first series of experiments EB was injected into the VA/VL thalamic nuclei whereas DP was delivered into the CM/Pf complex. After these injections numerous EB-labeled cells were scattered throughout the central 'motor' zone of the internal segment of the globus pallidus (GPi), compared to a smaller number of DP-positive neurons forming two small but distinct clusters in central GPi. The majority of the neurons within these two clusters were double-labeled. In addition, EB-labeled cells were disclosed in the lateral two-thirds of substantia nigra pars reticulata (SNr), whereas DP-positive neurons occurred in a wide variety of structures including the nucleus reticularis thalami, the SNr, the periaqueductal gray, the superior colliculus, the midbrain raphe nuclei, the pedunculopontine nucleus (TPP) area (bilaterally), and the locus coeruleus. In a second series of experiments, EB was injected into the CM/Pf complex whereas DP was delivered into the TPP area of the midbrain tegmentum. After these injections two small clusters of EB-labeled cells and a larger number of more uniformly distributed DP-positive cells occurred in the core of GPi. The cell clusters were similar in size and location to those observed after VA/VL-CM/Pf injection, but contained only a minority of double-labeled neurons. The distribution of non-pallidal cells projecting to CM/Pf complex was similar to that reported above, whereas retrogradely labeled cells resulting from TPP injection were disclosed in the paraventricular hypothalamic nucleus, the central amygdaloid nucleus, the preoptico-hypothalamic complex, the lateral habenula, the ventral tegmental area, and the SNr where some double-labeled cells were present. In a third series of experiments DP alone was injected into the entire substantia nigra (SN), involving both pars compacta and pars reticulata. The SN injection produced retrograde cell labeling in numerous structures such as the striatum, the rostral intralaminar nuclei, the subthalamic nucleus, the TPP area (bilaterally), the dorsal raphe nucleus and the locus coeruleus. At pallidal levels, a moderate number of DP-labeled cells occurred within the dorsal half of the external segment of the globus pallidus (GPe), whereas the GPi was virtually devoid of labeled neurons. The GPi appeared nevertheless surrounded ventromedially by numerous large-sized DP-positive cells belonging to the substantia innominata.(ABSTRACT TRUNCATED AT 400 WORDS)

The output organization of the substantia nigra in primate as revealed by a retrograde double labeling method.

The cellular origin and degree of collateralization of the efferent projections of the substantia nigra pars reticulata (SNr) in the squirrel monkey (Saimiri sciureus) were studied using the following combinations of fluorescent retrograde tracers: Evans blue and DAPI-Primuline, Fast blue and Nuclear yellow, True blue and Nuclear yellow. In a first series of experiments one tracer was injected in the ventral anterior (VA) and ventral lateral (VL) thalamic nuclei, and the complementary tracer was delivered in the peribrachial area of midbrain tegmentum. After thalamo-tegmental injections numerous nigrothalamic neurons occur in clusters, particularly in rostrolateral part of SNr, whereas the nigrotegmental neurons prevail in caudomedial segment of SNr. However, a significant overlap exists between these two populations. The nigrothalamic and nigrotegmental neurons are present in about equal number in SNr with as much as 60% of these neurons being double-labeled. In a second series of experiments injections were made concomitantly in VA/VL nuclei and in superior colliculus. After thalamo-collicular injections the nigrothalamic neurons are found in larger number than the nigrocollicular neurons which are mostly confined to the middle third of SNr. About 15-20% of all SNr positive neurons are double-labeled, although this proportion climbs to 30-40% in certain sections taken through the middle third of SNr. Finally, injections were made concomittantly in superior colliculus and in midbrain tegmentum. In contrast to the findings obtained after thalamo-tegmental and thalamo-collicular injections, only about 10% of SNr neurons appear to be double-labeled after colliculo-tegmental injections. All injections made in present study have produced retrograde cell labeling in contralateral SNr. However, by far the largest number of contralateral labeled neurons is found after superior colliculus injection. These findings reveal that the SNr neurons in primate, as those in rat and cat, display a high degree of axonal branching. As such, the output organization of SNr appears to differ markedly from that of the substantia nigra pars compacta, but is remarkably similar to that of the internal pallidum which is the other major output structure of the basal ganglia.

Circadian rhythm of body temperature persists after suprachiasmatic lesions in the squirrel monkey.

Squirrel monkeys (Saimiri sciureus) demonstrate prominent circadian (approx 24 h) rhythms in many behavioral and physiological variables including drinking and body temperature. Both of these rhythms can be entrained by a 24-h light-dark cycle (LD 12:12) but will free-run with an endogenous period in a constantly illuminated (LL:600 lx) environment free of time cues. After radio-frequency lesions were placed stereotaxically in the suprachiasmatic nuclei (SCN) of five monkeys, the circadian rhythm of drinking behavior was disrupted when the monkeys were maintained in LL. However, the circadian rhythm in core body temperature in these animals persisted in LL with a significant circadian spectral component following destruction of the SCN. The SCN thus appear to be of fundamental importance for regulating the circadian organization of drinking; however, an oscillator located elsewhere in the squirrel monkey is capable of generating the core body temperature rhythm.

Pulvinar neuron responses to spontaneous and trained eye movements and to light flashes in squirrel monkeys.

Single unit responses were recorded in the pulvinar nucleus of the squirrel monkey (Saimiri sciureus) while awake and alert, with the head fixed but free to make eye movements. Peri-saccadic time histograms revealed only post-saccadic responses to eye movements made spontaneously in the dark or in a uniformly illuminated field (Ganzfeld), or to trained eye movements made in response to a spot of light in the periphery. Of 120 pulvinar neurons that responded to eye movements in the light, approximately one-quarter was responsive to eye movements in the dark. In one group of monkeys about half of the eye movement-responsive cells in the light were responsive to light flash in the dark; in another group approximately half of the eye movement-responsive cells in the light were also responsive to trained eye movements. Of particular interest is the fact that pulvinar neurons responsive to eye movements were located within a restricted region oriented vertically and cutting across lateral and inferior pulvinar, rostrally, and lateral and medial pulvinar, caudally. The results have been interpreted as supporting the concept of convergence and integration of visual and oculomotor input in the pulvinar and also its potential role in the mediation of visual attention.