The projection pattern of the suprageniculate nucleus to the caudate nucleus in cats

Anatomical and Functional Comparison of the Caudate Tail in Primates and the Tail of the Striatum in Rodents: Implications for Sensory Information Processing and Habitual Behavior

The tail of the striatum (TS) is located at the caudal end in the striatum. Recent studies have advanced our knowledge of the anatomy and function of the TS but also raised questions about the differences between rodent and primate TS. In this review, we compare the anatomy and function of the TS in rodent and primate brains. The primate TS is expanded more caudally during brain development in comparison with the rodent TS. Additionally, five sensory inputs from the cortex and thalamus converge in the rodent TS, but this convergence is not observed in the primate TS. The primate TS, including the caudate tail and putamen tail, primarily receives inputs from the visual areas, implying a specialized function in processing visual inputs for action generation. This anatomical difference leads to further discussion of cellular circuit models to comprehend how the primate brain processes a wider range of complex visual stimuli to produce habitual behavior as compared with the rodent brain. Examining these differences and considering possible neural models may provide better understanding of the anatomy and function of the primate TS.

Relay and higher-order thalamic nuclei show an intertwined functional association with cortical-networks

Almost all functional processing in the cortex strongly depends on thalamic interactions. However, in terms of functional interactions with the cerebral cortex, the human thalamus nuclei still partly constitute a terra incognita. Hence, for a deeper understanding of thalamic-cortical cooperation, it is essential to know how the different thalamic nuclei are associated with cortical networks. The present work examines network-specific connectivity and task-related topical mapping of cortical areas with the thalamus. The study finds that the relay and higher-order thalamic nuclei show an intertwined functional association with different cortical networks. In addition, the study indicates that relay-specific thalamic nuclei are not only involved with relay-specific behavior but also in higher-order functions. The study enriches our understanding of interactions between large-scale cortical networks and the thalamus, which may interest a broader audience in neuroscience and clinical research.

Intralaminar and tectal projections to the subthalamus in the rat

Projections from the posterior intralaminar thalamic nuclei and the superior colliculus (SC) to the subthalamic nucleus (STN) and the zona incerta (ZI) have been described in the primate and rodent. The aims of this study was to investigate several questions on these projections, using modern neurotracing techniques in rats, to advance our understanding of the role of STN and ZI. We examined whether projection patterns to the subthlamus can be used to identify homologues of the primate centromedian (CM) and the parafascicular nucleus (Pf) in the rodent, the topography of the projection including what percent of intralaminar neurons participate in the projections, and electron microscopic examination of intralaminar synaptic boutons in STN. The aim on the SC‐subthalamic projection was to examine whether STN is the main target of the projection. This study revealed: (i) the areas similar to primate CM and Pf could be recognized in the rat; (ii) the Pf‐like area sends a very heavy topographically organized projection to STN but very sparse projection to ZI, which suggested that Pf might control basal ganglia function through STN; (iii) the projection from the CM‐like area to the subthalamus was very sparse; (iv) Pf boutons and randomly sampled asymmetrical synapses had similar distributions on the dendrites of STN neurons; and (v) the lateral part of the deep layers of SC sends a very heavy projection to ZI and moderate to sparse projection to limited parts of STN, suggesting that SC is involved in a limited control of basal ganglia function.

Co-oscillation and synchronization between the posterior thalamus and the caudate nucleus during visual stimulation

Recent results suggest significant cross-correlation between the spike trains of the suprageniculate nucleus (SG) of the posterior thalamus and the caudate nucleus (CN) during visual stimulation. In the present study visually evoked local field potentials (LFPs) were recorded simultaneously in the CN and the SG in order to investigate the coupling between these structures at a population level. The effect of static and dynamic visual stimulation was analyzed in 55 SG-CN LFP pairs in the frequency range 5-57Hz. Statistical analysis revealed significant correlation of the relative powers of each investigated frequency band (5-8Hz, 8-12Hz, 12-35Hz and 35-57Hz) during both static and dynamic visual stimulation. The temporal evolution of cross-correlation showed that in the majority of the cases the SG was activated first, and in approximately one third of the cases, the CN was activated earlier. These observations suggest a bidirectional information flow. The most interesting finding of this study is that different frequency bands exhibited significant cross-correlation in a stimulation paradigm-dependent manner. That is, static stimulation usually increased the cross-correlation of the higher frequency components (12-57Hz) of the LFP, while dynamic stimulation induced changes in the lowest frequency band (5-8Hz). This suggests a parallel processing of dynamic and static visual information in the SG and the CN. To our knowledge we are the first to provide evidence on the co-oscillation and synchronization of the CN and the SG at a population level upon visual stimulation, which suggests a significant cooperation between these structures in visual information processing.

Visual stimulation synchronizes or desynchronizes the activity of neuron pairs between the caudate nucleus and the posterior thalamus

Recent morphological and physiological studies have suggested a strong relationship between the suprageniculate nucleus (Sg) of the posterior thalamus and the input structure of the basal ganglia, the caudate nucleus (CN) of the feline brain. Accordingly, to clarify if there is a real functional relationship between Sg and CN during visual information processing, we investigated the temporal relations of simultaneously recorded neuronal spike trains of these two structures, looking for any significant cross-correlation between the spiking of the simultaneously recorded neurons. For the purposes of statistical analysis, we used the shuffle and jittering resampling methods. Of the recorded 288 Sg-CN neuron pairs, 26 (9.2%) showed significantly correlated spontaneous activity. Nineteen pairs (6.7%) showed correlated activity during stationary visual stimulation, while 21 (7.4%) pairs during stimulus movement. There was no overlap between the neuron pairs that showed cross-correlated spontaneous activity and the pairs that synchronized their activity during visual stimulation. Thus visual stimulation seems to have been able to synchronize, and also, by other neuron pairs, desynchronize the activity of CN and Sg. In about half of the cases, the activation of Sg preceded the activation of CN by a few milliseconds, while in the other half, CN was activated earlier. Our results provide the first piece of evidence for the existence of a functional cooperation between Sg and CN. We argue that either a monosynaptic bidirectional direct connection should exist between these structures, or a common input comprising of parallel pathways synchronizing them.

Striatal projections from the lateral and posterior thalamic complexes. An anterograde tracer study in the cat

Striatal projections from the lateral intermediate (LI) and posterior (Po) thalamic complexes were studied with the anterograde tracers wheat germ agglutinin-horseradish peroxidase and Phaseolus vulgaris leucoagglutinin. Projections to the lateral part of the head and body of the caudate nucleus (CN) and to the putamen (Pu) were found to arise from the ventral parts of the caudal subdivision of the LI besides the well established sources in the intralaminar and ventral thalamic nuclei. No projections to the CN and only a few to the Pu were found to arise from the medial division of the Po. The presence of terminal and intercalated varicosities in the thalamostriatal fibers suggests that they form both terminal and en passant synapses. Thalamostriatal fibers from these thalamic sectors were unevenly distributed within the CN, with patches of either low-density innervation or with no projections at all interspersed within irregular, more densely innervated areas. The former coincided with the acetylcholinesterase-poor striosomes and the latter areas of dense projection with the extrastriosomal matrix.

A single-cell study of the axonal projections arising from the posterior intralaminar thalamic nuclei in the rat

Thalamostriatal projections arising from the posterior intralaminar nuclei (P1; the parafascicular nucleus and the adjacent caudalmost part of the posterior thalamic group) were studied in rats by tracing the axons of small pools of neurons labelled anterogradely with biocytin. Thirteen P1 cells were also stained by juxta cellular application of the tracer. Relay cells of P1 nuclei have a morphology that differs radically from the classical descriptions of the bushy cells which represent the main neuronal type of the sensory thalamic relay nuclei. P1 cells have ovoid or polygonal somata of approximately 20-25 microm, from which emerge four or five thick, long and poorly branched dendrites bearing spines and filamentous appendages; their dendritic domains extend for up to 1.5 mm. Before leaving the nucleus 20% of axons give off collaterals that ramify locally. All axons course through the thalamic reticular nucleus, where they also distribute collaterals, and arborize massively in the striatum and sparsely in the cerebral cortex. At the striatal level four or five collaterals leave the main axon and terminate in patches scattered dorsoventrally within a rostrocaudally oriented slab. As revealed by calbindin D-28k immunohistochemistry, only the matrix compartment receives terminations from P1 axons. The cortical branch form small terminal puffs centred upon layer VI of the motor cortex. Before entering the striatum some axons of the parafascicular nucleus give rise to descending collaterals that arborize in the entopeduncular nucleus, in the subthalamic nucleus and in the vicinity of the red nucleus. Other axons arising from the caudal part of the posterior group send descending branches only to the entopeduncular nucleus. These findings show that P1 cells belong to a distinct category of thalamic relay neurons which, beside their massive projection to the striatum, also distribute collaterals to other components of the basal ganglia. Moreover, these results provide the first direct evidence that virtually all P1 cells project to both striatum and cerebral cortex. Finally, it is proposed on the basis of morphological, histochemical and hodological criteria that the caudal part of the posterior thalamic group in the rat is homologous to the suprageniculate-limitans nuclei of cats and primates.

The role of the basal ganglia in nociception and pain

The involvement of the basal ganglia in motor functions has been well studied. Recent neurophysiological, clinical and behavioral experiments indicate that the basal ganglia also process non-noxious and noxious somatosensory information. However, the functional significance of somatosensory information processing within the basal ganglia is not well understood. This review explores the role of the striatum, globus pallidus and substantia nigra in nociceptive sensorimotor integration and suggests several roles of these basal ganglia structures in nociception and pain. Electrophysiological experiments have detailed the non-nociceptive and nociceptive response properties of basal ganglia neurons. Most studies agree that some neurons within the basal ganglia encode stimulus intensity. However, these neurons do not appear to encode stimulus location since the receptive fields of these cells are large. Many basal ganglia neurons responsive to somatosensory stimulation are activated exclusively or differentially by noxious stimulation. Indirect techniques used to measure neuronal activity (i.e., positron emission tomography and 2-deoxyglucose methods) also indicate that the basal ganglia are activated differentially by noxious stimulation. Neuroanatomical experiments suggest several pathways by which nociceptive information may reach the basal ganglia. Neuroanatomical studies have also indicated that the basal ganglia are rich in many different neuroactive chemicals that may be involved in the modulation of nociceptive information. Microinjection of opiates, dopamine and gamma-aminobutyric acid (GABA) into the basal ganglia have varied effects on pain behavior. Administration of these neurochemicals into the basal ganglia affects supraspinal pain behaviors more consistently than spinal reflexive behaviors. The reduction of pain behavior following electrical stimulation of the substantia nigra and caudate nucleus provides additional evidence for a role of the basal ganglia in pain modulation. Some patients with basal ganglia disease (e.g., Parkinson's disease, Huntington's disease) have alterations in pain sensation in addition to motor abnormalities. Frequently, these patients have intermittent pain that is difficult to localize. Collectively, these data suggest that the basal ganglia may be involved in the (1) sensory-discriminative dimension of pain, (2) affective dimension of pain, (3) cognitive dimension of pain, (4) modulation of nociceptive information and (5) sensory gating of nociceptive information to higher motor areas. Further experiments that correlate neuronal discharge activity with stimulus intensity and escape behavior in operantly conditioned animals are necessary to fully understand how the basal ganglia are involved in nociceptive sensorimotor integration.

Detection of somatic DNA recombination in the transgenic mouse brain

A DNA construct containing the bacterial beta-galactosidase gene (lacZ) was used to study somatic DNA recombination in the transgenic mouse brain. Recombination-positive areas of the adult brain were stained blue with X-gal, a substrate of beta-galactosidase. Blue-colored cells appeared soon after birth, and continued to emerge in postnatal tissue. Staining was prominent in sensory as opposed to motor regions of the brain, and was present in more than 70 discrete areas of the nervous system. The possibility of DNA rearrangement is discussed with respect to the development of the central nervous system.

Compartmental organization of the thalamostriatal connection in the cat

The compartmental organization of the thalamostriatal connection in the cat was studied by labelling thalamic fibers in anterograde axonal transport experiments and comparing their striatal distributions with the arrangement of striosomes and matrix tissue identified by histochemical staining methods. When analyzed according to their principal compartmental targets in dorsal striatum, the thalamic deposits indicated the existence of medial and lateral divisions within the thalamostriatal projection. Nuclei of the medial division, which includes parts of the thalamic midline, projected primarily to striosomes. The lateral division, which embraces the anterior and posterior intralaminar groups, the rostral ventral tier nuclei, and parts of the posterior lateral nuclear complex, predominantly innervated matrix tissue. In the dorsal division of the nucleus accumbens, the medial system preferentially terminated in zones that stain heavily in butyrylcholinesterase and substance P preparations, but fibers from both the medial and the lateral systems largely avoided the histochemically marked compartments such as the border islands of the nucleus accumbens that are seen elsewhere in the ventral striatum. Medial division: Thalamic deposits involving the paraventricular and rhomboid nuclei of the thalamic midline elicited labelling of striosomes and, invariably, ventral extrastriosomal matrix, the nucleus accumbens, and the amygdala. This projection was topographically organized: rostral thalamic deposits elicited labelling in the medial caudate nucleus and the medial nucleus accumbens. More caudal injections produced more lateral labelling. Lateral division: The lateral division is composed of at least three projection systems distinguished by their patterns of matrix innervation. Deposits involving the anterior intralaminar nuclei and the striatally projecting cells located lateral to the stria medullaris (anterior intralaminar complex) produced an even, diffuse labelling of the matrix tissue and weak labelling of the striosomes. Injections placed in the ventroanterior, ventrolateral, and ventromedial nuclei (rostral ventral complex) elicited fibrous labelling of matrix tissue that often showed nonstriosomal inhomogeneities. Deposits involving the centromedian and parafascicular nuclei (posterior intralaminar complex) produced a highly variable pattern of matrix labelling that included both homogeneous and decidedly patchy innervations of the extrastriosomal matrix. Each of these lateral thalamostriatal systems showed a similar spatial organization, whereby dorsoventral and mediolateral thalamic axes were roughly preserved in the projection to striatum.

Organization of the thalamostriatal projections in the rat, with special emphasis on the ventral striatum

The organization of the thalamic projections to the ventral striatum in the rat was studied by placing injections of the retrograde tracer cholera toxin subunit B in the ventral striatum and small deposits of the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) in individual midline and intralaminar thalamic nuclei. In order to provide a complete map of the midline and intralaminar thalamostriatal projections, PHA-L injections were also made in those parts of the intralaminar nuclei that project to the dorsal striatum. The relationship of thalamic afferent fibres with the compartmental organization of the ventral striatum was assessed by combining PHA-L tracing and enkephalin immunohistochemistry. The various midline and intralaminar thalamic nuclei project to longitudinally oriented striatal sectors. The paraventricular thalamic nucleus sends most of its fibres to medial parts of the nucleus accumbens and the olfactory tubercle, whereas smaller contingents of fibres terminate in the lateral part of the nucleus accumbens and the most ventral, medial, and caudal parts of the caudate-putamen complex. The projections of the parataenial nucleus are directed towards central and ventral parts of the nucleus accumbens and intermediate mediolateral parts of the olfactory tubercle. The intermediodorsal nucleus projects to lateral parts of the nucleus accumbens and the olfactory tubercle and to ventral parts of the caudate-putamen. The projection of the rhomboid nucleus is restricted to the rostrolateral extreme of the striatum. A diffuse projection to the ventral striatum arises from neurons ventral and caudal to the nucleus reuniens rather than from cells inside the nucleus. Fibres from the central medial nucleus terminate centrally and dorsolaterally in the rostral part of the nucleus accumbens and medially in the caudate-putamen. Successively more lateral positions in the caudate-putamen are occupied by fibres from the paracentral and central lateral nuclei, respectively. The lateral part of the parafascicular nucleus projects to the most lateral part of the caudate-putamen, whereas projections from the medial part of this nucleus terminate in the medial part of the caudate-putamen and in the dorsolateral part of the nucleus accumbens. Furthermore, a rostral to caudal gradient in a midline or intralaminar nucleus corresponds to a dorsal to ventral and rostral to caudal gradient in the striatum. In the ventral striatum, thalamic afferent fibres in the "shell" region of the nucleus accumbens avoid areas of high cell density and weak enkephalin immunoreactivity.(ABSTRACT TRUNCATED AT 400 WORDS)

Retinotopic organization within the lateral posterior complex of the cat

Electrophysiological mapping methods were employed to systematically study the retinotopic organization within the cat's lateral posterior complex (LP). Visual responses were recorded in all the major subdivisions of the LP as well as in several adjoining cell groups. Specifically, separate representations of the visual field were identified for pulvinar, zones LP1-c, LP1-r, LPi, and LPm. Partial representations of the visual field were also evident in the geniculate wing, subdivisions of the lateral posterior shell, the inferior division of the posterior nuclear group, the suprageniculate nucleus, and the central lateral nucleus. Sufficient mapping observations were made to define the internal organization of major visual representations. Additionally, there was a very close correspondence between the mapping observations when they were compared with the cytoarchitectural criteria for recognizing functional cell groups (Updyke: J. Comp. Neurol. 219:143-181, '83).