Part Of Caudate Nucleus Research Articles

Projections from striate and extrastriate visual cortices of the cat to the reticular thalamic nucleus

We have studied the pattern of connectivity of the visual cortical areas 17, 18, 19, 20a, 21a, posteromedial lateral (PMLS), and the posterolateral lateral (PLLS) suprasylvian areas with the reticular thalamic nucleus (RTN) of the cat ventral thalamus. Three cortical areas per hemisphere were injected iontophoretically with either 4% wheat germ agglutinin-horseradish peroxidase, 4% dextran-fluororuby, or 4% dextran-biotin. The visual field representations of the injection sites were determined by reference to previously published visuotopic maps of the cortex. The locations of labelled fibres, presumed terminals and cell bodies were determined with the aid of a camera lucida attachment and computer aided stereometry. In the ventral thalamus, the primary visual cortices (areas 17 and 18) project in a topographic manner to both the perigeniculate nucleus (PGN) and the RTN. By contrast, the "higher" visual cortical areas (areas 19, 21a, 20a, PMLS, and PLLS) project only to the RTN. Our experiments demonstrate the existence of a single, albeit coarse, visuotopic map within the RTN but do not support the notion of separate subregions within the RTN that can be related specifically to a particular visual cortical area. The putative single visuotopic map in the RTN appears to be organised in such a way that the vertical meridians are represented along the rostrocaudal axis of the RTN, whereas the horizontal meridians are mapped within the dorsoventral axis of the nucleus. The upper visual field is represented within regions of the RTN adjacent to the caudal part of the dorsal lateral geniculate nucleus (LGNd), whereas the lower visual field is represented in the parts of the RTN rostral to the LGNd. The map also shows a ventrodorsal shift along the rostrocaudal axis of the RTN such that in the rostral RTN the representation of vertical meridian is placed more ventrally than that in the caudal part of the nucleus.

Projections from striate and extrastriate visual cortices of the cat to the reticular thalamic nucleus

We have studied the pattern of connectivity of the visual cortical areas 17, 18, 19, 20a, 21a, posteromedial lateral (PMLS), and the posterolateral lateral (PLLS) suprasylvian areas with the reticular thalamic nucleus (RTN) of the cat ventral thalamus. Three cortical areas per hemisphere were injected iontophoretically with either 4% wheat germ agglutinin-horseradish peroxidase, 4% dextran-fluororuby, or 4% dextran-biotin. The visual field representations of the injection sites were determined by reference to previously published visuotopic maps of the cortex. The locations of labelled fibres, presumed terminals and cell bodies were determined with the aid of a camera lucida attachment and computer aided stereometry. In the ventral thalamus, the primary visual cortices (areas 17 and 18) project in a topographic manner to both the perigeniculate nucleus (PGN) and the RTN. By contrast, the “higher” visual cortical areas (areas 19, 21a, 20a, PMLS, and PLLS) project only to the RTN. Our experiments demonstrate the existence of a single, albeit coarse, visuotopic map within the RTN but do not support the notion of separate subregions within the RTN that can be related specifically to a particular visual cortical area. The putative single visuotopic map in the RTN appears to be organised in such a way that the vertical meridians are represented along the rostrocaudal axis of the RTN, whereas the horizontal meridians are mapped within the dorsoventral axis of the nucleus. The upper visual field is represented within regions of the RTN adjacent to the caudal part of the dorsal lateral geniculate nucleus (LGNd), whereas the lower visual field is represented in the parts of the RTN rostral to the LGNd. The map also shows a ventrodorsal shift along the rostrocaudal axis of the RTN such that in the rostral RTN the representation of vertical meridian is placed more ventrally than that in the caudal part of the nucleus. J. Comp. Neurol. 410:467–488, 1999. © 1999 Wiley-Liss, Inc.

The projections from the parafascicular thalamic nucleus to the subthalamic nucleus and the striatum arise from separate neuronal populations: A comparison with the corticostriatal and corticosubthalamic efferents in a retrograde fluorescent double-labelling study

The parafascicular thalamic nucleus projects to the subthalamic nucleus and the striatum. Double-retrograde fluorescent tracing was used to determine whether these projections arise from the same neurons via axon collaterals. True Blue was injected into the subthalamic nucleus and Nuclear Yellow was injected into the striatum of each rat and the parafascicular thalamic nucleus was examined under the fluorescence light-microscope. Individual parafascicular neurons were not double-labelled with the tracers. The True Blue- and Nuclear Yellow-labelled neurons wee located in different parts of the parafascicular nucleus ipsilateral to the injections. In the rostral part of the parafascicular nucleus, True Blue-labelled neurons were located ventral to the fasciculus retroflexus, and in the caudal part of the nucleus. True Blue-labelled neurons were located close to the medial and lateral borders of fasciculus retroflexus. Nuclear Yellow-labelled neurons were found mainly to encircle the fasciculus retroflexus in the rostral part of the parafascicular nucleus and in the dorsolateral sector of the caudal part of the parafascicular nucleus. Double-labelled neurons were, however, found in the cortex. The proportion of neurons projecting to both the subthalamic nucleus and the striatum accounted for 38% of the total number of corticosubthalamic neurons in the prefrontal cortex, 15.5% in the cingulate cortex and 9% in the sensorimotor cortex. The present finding of an individualization between the parafascicular efferents to the subthalamic nucleus and the striatum emphasize the importance of this projection and provides further evidence of the associative functions attributable to the subthalamic nucleus.

Rostrocaudal differences in morphology and neurotransmitter content of cells in the subretrofacial vasomotor nucleus

The rostral ventrolateral medulla (RVLM) contains sympathoexcitatory neurons that exert a powerful control over the sympathetic outflow to the cardiovascular system. In the cat there is a concentration of such neurons (but not neurons subserving other functions) within a narrow longitudinal column in the RVLM termed the subretrofacial (SRF) nucleus. Furthermore, it has been suggested that there are subgroups of cells, located at different rostrocaudal levels of the SRF nucleus, that preferentially or exclusively control different vascular beds (e.g. in the kidney and hindlimb). The aim of this study was to map quantitatively the rostrocaudal distribution within the nucleus of different cell types, defined according to morphological and/or chemical criteria, and to correlate this with the regional vasomotor effects (in hindlimb and kidney) evoked by stimulation of SRF cells at the corresponding rostrocaudal levels. SRF cells were highly heterogeneous with respect to both their morphology and chemical properties. They varied greatly in size (equivalent diameter ranging from 10–40 μm) as well as in shape and orientation. An immunohistochemical examination using the avidin-biotin procedure revealed that many SRF cells (estimated 57% of all SRF cells) were immunoreactive for tyrosine hydroxylase (TH, a marker of catecholamine cells). In addition, there were SRF cells immunoreactive for neuropeptide Y (NPY, 11% of total), enkephalin (ENK, 16% of total), and serotonin (5HT, 10% of total), but not for substance P, galanin or somatostatin. Different cell types, defined according to their morphology and/or chemical properties, were unevenly distributed throughout the nucleus. In the most caudal part of the SRF nucleus, virtually all cells were TH-positive, and the large majority (estimated 80%) were NPY-positive, suggesting that many cells at this level contained both TH and NPY. In contrast, in the most rostral part of the SRF nucleus, only 30% of cells were TH-positive, and no NPY-positive cells were observed. Both 5HT- and ENK-positive cells were found throughout the rostrocaudal extent of the nucleus, but predominantly within its rostral part. Furthermore, TH-positive cells in the rostral SRF nucleus were on average significantly larger (mean equivalent diameter 18–43% greater) than TH/NPY-positive cells in the caudal part of the nucleus, but smaller than 5HT- or ENK-positive cells at the same level. Overall, rostral cells (regardless of their chemical type) were larger than caudal cells within the SRF nucleus (mean equivalent diameter 13–28% greater). Talking into account both morphological and chemical properties, a minimum of four distinct cell subgroups in the SRF nucleus could be defined: caudal TH/NPY-positive cells, rostral TH-positive (but NPY-negative) cells, 5HT-positive cells (possibly also containing ENK), and cells that were not immunoreactive for any of these compounds. Large (> 100%) increases in blood pressure and iliac vascular resistance were elicited by microinjection of picomolar amounts of sodium glutamate into sites throughout the entire rostrocaudal extent of the SRF nucleus. In contrast, large or moderate (> 50%) increases in renal sympathetic nerve activity were evoked only from sites within the most rostral part of the nucleus. Correlation of the functional and immunohistochemical data indicates that NPY/TH-positive cells in the caudal SRF nucleus contribute to the regulation of the hindlimb but not the renal vascular bed. Secondly, they suggest that both catecholamine

Connections of the corpus cerebelli in the thornback guitarfish, Platyrhinoidis triseriata (Elasmobranchii): A study with WGA‐HRP and extracellular granule cell recording

The neuronal connections of the cerebellar corpus in the guitarfish Platyrhinoidis triseriata were investigated by WGA-HRP injections and extracellular recording of sensory evoked electrical activity. Injections of WGA-HRP into the corpus resulted in retrograde labeling of the following cell groups bilaterally: pretectal and accessory optic nuclei, interstitial nucleus of Cajal, nucleus ruber, oculomotor and possibly trochlear nucleus, central (periaqueductal) gray, nucleus H, reticular formation of the midbrain, cerebellar nucleus, caudal part of nucleus F, tentatively locus coeruleus and subcoeruleus field, octaval and trigeminal nuclei, intermediate octavolateralis nucleus, medial inferior reticular formation, lateral reticular nucleus, and spinal cord. Unilaterally labeled cells were seen in the contralateral inferior olive, which was found to project in sagittal zones onto the molecular layer of the corpus. Terminal fields of efferent Purkinje cell axons were labeled over the ipsilateral cerebellar nucleus exclusively. Purkinje cells in different parts of the corpus project topographically onto subdivisions of the nucleus. Mapping of evoked electrical multiple unit activity recorded from the granule cell layer of the corpus shows separate visual and tactile areas, mostly confined to the anterior and posterior lobes, respectively. Granule cells within the tactile area also responded to lateral line stimuli and, at two distinct medial locations in the caudal and rostral parts of the posterior lobe, to weak electric field stimulation in the bath. The body surface is somatotopically represented in the tactile area, but discontinuities in the map might indicate that the somatotopy is "fractured".

Striato-pallidal influence on food intake, body weight and locomotor activity

The food and water intake, body weight, and locomotor activity (wheel runs) were studied before and after stereotaxic electrolytic lesions at different planes of caudate nuclei of adult male and female albino rats. Lesions of lateral preoptic area, medial forebrain bundle and marginal regions of globi pallidi led to aphagia and adipsia lasting for 8–38 days. Locomotor activity, however, remained normal and there was no motor deficit. There was significant increase in wheel running (100%–450%), after tiny lesions in the anterior part of caudate nucleus (A 8·6) whereas marked drop (50–90%) in daily wheel running was observed with posterior lesions at A 7·6. Increase in body weight (30–35%) and food and water intake (15–20%) without any change in locomotor activity resulted after tiny symmetrical lesions involving caudate nucleus just above the globus pallidus (A 7·4). Lesions involving nucleus accumbens, medial preoptic area and ventromedio-marginal part of caudate nucleus, however led to 10–25% decrease in body weight in spite of 30–35% increase in food intake. The results suggest a differential striato-pallidal regulation of food and water intake, body weight and activity.