bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology of the cells within the inferior temporal gyrus that project to the prefrontal cortex in the macaque monkey
Authors: de Lima Ana D. , Voigt Thomas , Morrison John H. 
Published: January 2005

AbstractThe primate neocortex possesses an extraordinary degree of regional specialization. Virtually all cortical functions are dependent upon a complex system of reciprocal connections between related cortical regions that allow for distributed information processing. Although some aspects of the organization of these corticocortical projections are understood, little is known about the morphology and afferents to the cells of origin of long corticocortical projections in primates. We combined intracellular injection of Lucifer Yellow (LY) in fixed tissue with in vivo retrograde transport of fast blue to study the dendritic morphology of neurons within the inferior temporal gyrus (ITG) and the superior temporal sulcus (STS) that furnish corticocortical projections to the prefrontal cortex. The fast blue retrogradely labeled cells formed two clearly defined bands within the inferior temporal cortex: a supragranular band that corresponded to layer III, and an infragranular band that corresponded to layers V and VI. After Lucifer Yellow intracellular filling, these retrogradely labeled cells projecting to the prefrontal cortex were found to be morphologically very heterogeneous. Although all filled cells had spiny dendrites, they presented a wide range of cell body sizes and dendritic tree morphologies. In layer III, the majority of cells were typical pyramids of various sizes. In layers V–VI, numerous typical pyramidal cells were present. In addition, significant numbers of modified pyramidal forms were found, including vertical and horizontal fusiform cells, asymmetrical pyramids and multipolar cells. The entire dendritic arbor of individual subtypes in layers III, V, and VI was restricted to a few cortical layers, but as a group these cells had dendrites spanning the whole cortical depth. We suggest that corticocortically projecting cells are distinct from subcortically projecting cells and consist of a defined set of morphological and functional subgroups, each of which is driven by a distinct set of afferents and likely possesses different response properties.
Ibotenic acid lesions of the lateral substantia nigra restore visual orientation behavior in the hemianopic cat
Authors: Wallace Steven F. , Rosenquist Alan C. , Sprague James M. 
Published: January 2005

AbstractTransaction of non‐tectotectal fibers in the caudal one‐half of the commissure of the superior colliculus restores visual orienting to a cat previously rendered hemianopic by a large unilateral visual cortical lesion. Other observations related to this recovery phenomenon (i.e., the Sprague effect) have suggested that the caudal commissural fibers whose destruction produces the recovery (1) are contralateral afferents to the superior colliculus on the side of the cortical lesion, and (2) profoundly influence visuo‐motor processing in this superior colliculus. We performed anatomical and behavioral experiments to determine which of the more than 40 contralateral collicular afferents are directly involved in the Sprague effect.To guide subsequent behavioral studies, we performed a pilot anatomical experiment in which we injected WGA‐HRP unilaterally into one superior colliculus at identical retinotopic loci in each of a pair of cats. One cat was normal (control), and the other (experimental) had previously received a caudal transection of the collicular commissure. Quantitative comparison of the retrograde labeling in collicular afferents revealed that a number of mesencephalic regions contain neurons that project to the colliculus via the caudal collicular commissure. Additional collicular injections of WGA‐HRP demonstrated the exact location and distribution of collicular afferent neurons within these nuclei.In the behavioral experiments, we attempted to replicate the Sprague effect by destroying the neurons giving rise to the axons in the caudal collicular commissure. Ibotenic acid lesions of these neurons were performed in cats that were hemianopic following the removal of the contralateral visual cortex. Small lesions of a “critical zone” in the rostro‐lateral substantia nigra pars reticulata and possibly the overlying ventral zona incerta consistently produced a visual recovery whereas lesions, of the other collicular afferents did not. Paradoxically, large nigral lesions that also included the critical zone did not result in a recovery. A conceptual framework for these findings involving striato‐nigro‐tecto‐preoculomotor interactions is presented.
Nontopographic projection of olfactory sensory neurons in the crayfish brain
Authors: Mellon DeForest , Munger Steven D. 
Published: January 2005

AbstractWe have used tritiated leucine to trace the input projection pattern of olfactory sensory neurons in crayfishes. The olfactory neurons are associated with cuticular sensilla on the external antennular filaments. Each sensillum, or aesthetasc, harbors the distal dendritic segments of about 175 bipolar sensory neurons, the cell bodies for which are grouped in a subcuticular ensemble or ganglion. About 150–175 individual ganglia may be found on each antennule in an adult crayfish. When an aesthetasc is exposed to tritated leucine, the tracer is taken up by the associated olfactory sensory neurons and is transported along the axons to their central terminations within the glomeruli of the ipsilateral olfactory lobe. We tested the possibility that the sensory neurons from specific aesthetascs project to specific glomeruli. By restricting access of the leucine to small groups of aesthetascs, we exposed less than 2% of the olfactory sensory neurons to the tracer. Nonetheless, all glomeruli were labeled following such treatment. We conclude that the sensory neurons are generally distributed to the olfactory glomeruli. If each neuron terminates in a single glomerulus, these data support a divergent pattern of sensory projection from individual ganglia to all regions of the olfactory lobe.
Collaterals of primate spinothalamic tract neurons to the periaqueductal gray
Authors: Zhang Dongxian , Carlton Susan M. , Sorkin Linda S. , Willis William D. 
Published: January 2005

AbstractCollateral projections are an important feature of the organization of ascending projections from the spinal cord to the brain. Primate spinothalamic tract (STT) neurons with collaterals to the periaqueductal gray (PAG) were studied by means of a fluorescent double‐labeling method. Granular Blue and rhodamine‐labeled latex microspheres were placed in the ventral posterior lateral (VPL) nucleus of the thalamus and the periaqueductal gray, respectively. Single and double labeled neurons were studied in the upper cervical cord, cervical enlargement, thoracic cord, lumbar enlargement, and sacral segments.The laminar distribution of double labeled neurons was similar to that of spinomesencephalic tract (SMT) neurons. Most double labeled (STT‐SMT) neurons were located in contralateral laminae I, V, VII, and X. Relatively more lamina I STT‐SMT neurons were found in the cervical enlargement and more lamina V STT‐SMT neurons in the lumbar enlargement. The density of STT‐SMT neurons in the upper cervical segments and cervical enlargement was almost equal. The density of STT‐SMT neurons in the lumbar enlargement was 40% of that in the cervical enlargement. The thoracic and sacral segments had the lowest density of STT‐SMT neurons, about 10% of that in the cervical enlargement. STT‐SMT neurons constituted 14.7% of SMT neurons and 6% of STT neurons in the cervical enlargement and 15.3% of SMT neurons and 2.9% of STT neurons in the lumbar enlargement.The branch points of eight STT‐SMT axons were studied electrophysiologically. The average percentage of conduction time spent in the parent axon was more than 85% for an antidromic action potential from the VPL nucleus and 91% from the PAG. Branch points of STT‐SMT axons were calculated to be 9–13 mm caudal to the PAG, in the pons or rostral medulla.
Cholecystokinin and neurotensin mRNAs are differentially expressed in subnuclei of the ventral tegmental area
Authors: Jayaraman A. , Nishimori T. , Dobner P. , Uhl G. R. 
Published: January 2005

AbstractImmunohistochemical studies of ventral tegmental area (VTA) neurons indicate that individual cells can contain dopamine as well as the neuropeptide neurotransmitters cholecystokinin (CCK) and neurotensin (NT). We have defined the distribution of the cells expressing the mRNAs encoding these two dopamine cotransmitter peptides in each of the subnuclei of the ventral tegmental area, and quantitated the extent of expression of each gene by using in situ hybridization methods.These studies reveal significant differences in the patterns of expression of each of these two genes within various subdivisions of the VTA. The rostral linear nucleus contained numerous CCK positive cells, some of which appeared to express preproCCK‐mRNA at a very high level, but this nucleus contained relatively few NT‐expressing cells. The parabrachialis pigmentosus contained numerous NT and CCK positive cells. The paranigralis and interfascicularis nuclei displayed positive CCK cells but with expression at only modest levels. NT cells were very few in these nuclei. The caudal linear nuclei contained the highest number of NT‐expressing neurons and these cells expressed very high levels of NT mRNA.The selective distribution of these peptide genes within the VTA subnuclei may have specific consequences. Studies of the connectivity of neurons in the VTA show that the different subnuclei of this region project to several functionally and architectonically different regions of the cerebral cortex and subcortically to nuclei related to the limbic system. Results from our study show very prominent expression of CCK mRNAs in those subnuclei that project heavily to the prefrontal, other cortical areas, and the amygdaloid complex. The NT gene is expressed prominently in those subnuclei of VTA that project heavily to the entorhinal cortex and amygdaloid complex.These results provide support for a differential role for the NT‐expressing neurons than that of CCK‐expressing neurons of VTA in “reward” mechanisms and in drug‐seeking and motivational behavior. These observations could be applied to create working hypotheses and experimental paradigms to test the differential functional activity of the subdivisions of VTA and their potential roles in the pathogenesis and treatment of drug‐seeking behavior and other neuropsychiatric disorders.
Horseradish peroxidase labeling of the efferent and afferent pathways of the avian tangential vestibular nucleus
Authors: Cox Robert G. , Peusner Kenna D. 
Published: January 2005

AbstractThe efferent and afferent pathways of the chick tangential nucleus were studied by using horseradish peroxidase (HRP: Sigma type VI) to label nerve cell bodies and fibers. Depositions of HRP into the tangential nucleus, as well as into the second cervical level of the spinal cord, show that the axons of tangential neurons on leaving the nucleus form an anteriorly coursing tract that passes through the ventrolateral vestibular nucleus without branching and then to the contralateral medial longitudinal fasciculus (MLF). Within the MLF, the tangential axons course posteriorly, forming collaterals that innervate the abducens nucleus, and then proceed to the cervical spinal cord. This pathway was demonstrated for the axons of the two main neurons, the principal and elongate cells, in 1‐day, 1‐week, and 7‐week‐old animals. In addition, we propose the existence of an unidentified, ipsilateral pathway to the spinal cord for the tangential axons, since HRP injections into one side of the spinal cord resulted in the bilateral labeling of tangential neurons. No labeled cells were found in the tangential nucleus following HRP depositions into the uvula, flocculus, pontine reticular formation, nucleus piriformis, nucleus jumeaux, vestibulocerebellar nucleus, retrotangential nucleus, or the dorsomedial part of the medial vestibular nucleus.The tangential nucleus receives afferents from the colossal vestibular fibers (spoon endings), small collaterals of fine vestibular ampullary fibers, flocculus, and high cervical levels of the spinal cord. From our small sample, it appears that the spinal cord fibers form most of the afferent terminals in the tangential nucleus in 1‐day, 1‐week, and 7‐week‐old animals.
Descending pathways to the spinal cord, III: Sites of origin of the corticospinal tract
Authors: Nudo R. J. , Masterton R. B. 
Published: January 2005

AbstractThe somata of corticospinal neurons were labeled with horseradish peroxidase that had been applied to a hemisection of the spinal cord at the C1‐C2 junction in 22 species of mammals. After tetramethylbenzidine processing, with and without counterstaining with cresyl violet or neutral red, the labeled cells in systematic sets of sections throughout the cerebral cortex were plotted and counted. Several morphological features of the corticospinal cells were examined including their cell type, number, density, concentration, laminar distribution, and their distribution across the cortical surface.The results show that the labeled corticospinal neurons were invariably layer V pyramidal cells. However, in many mammals they were found to be stacked one above the other within layer V, sometimes many neurons deep. Despite the concentration of corticospinal neurons within layer V, many unlabeled neurons were also present within the layer throughout the extent of the labeled region.The results also indicate that at least two spatially distinct regions of neocortex originate corticospinal fibers in each of the animals in the sample. In addition to these two regions, a third segregated region is present in the cortex of primates and an apparently different third region is present in the cortex of Glires ((Rodentia and Lagomorpha)). The third region of corticospinal cortex in primates is located on the lateral surface of the cortex in prosimians and New World monkeys and is buried in the caudal bank of the inferior arcuate sulcus in Old World monkeys.The results also show a predominantly contralateral corticospinal tract in all but 4 of the 22 mammals in the sample. Although these 4 mammals are each members of the order Insectivora, a less modified member of the same order possessed the predominantly contralateral projection of most mammals, hence denying the notion that a predominantly ipsilateral tract is a characteristic of Insectivora.
Descending pathways to the spinal cord, IV: Some factors related to the amount of cortex devoted to the corticospinal tract
Authors: Nudo R. J. , Masterton R. B. 
Published: January 2005

AbstractIn the companion paper to this one ((Nudo and Masterton: J. Comp. Neurol. 296:559–583. '90)), we have presented data indicating that in each of 22 mammals, there are either 2 or 3 separate regions of neocortex contributing corticospinal fibers. In this paper, we describe the variation in the absolute size of these cortical regions, the total amount of neocortex contributing corticospinal fibers ((CST cortex)), and the total amount of neocortex ((total cortex)) in each of the animals. We then use strict statistical tests to examine the relationships between these measures and several other quantitative measures or descriptions of the animals' size, ancestral heritage, motor prowess, and ecological adaptation.The results show that the absolute amout of CST cortex is more closely related to the total amount of neocortex than to any other quantitative measure available. The further variation—that is, the variation in the amount of CST cortex relative to total neocortex—appears to have been random over the inferred ancestral lineages of most animals in the sample, but seems to have been almost absent along the anthropoid lineage. Because this constancy in the relative amount of CST cortex over a very long period of anthropoid ancestry is apparently unusual if not unique among mammals, it may contain a clue to the special role of the corticospinal tract among primates.Finally, the distribution of the CST among the 3 cortical regions in primates was found to be more closely related to their particular mode of ecological adaptation than to their particular combination of digital dexterity and hand‐eye coordination.
Burst generating and regular spiking layer 5 pyramidal neurons of rat neocortex have different morphological features
Authors: Chagnac‐Amitai Yael , Luhmann Heiko J. , Prince David A. 
Published: January 2005

AbstractIntracellular recordings were obtained from pyramidal neurons in layer 5 of rat somatosensory and visual cortical slices maintained in vitro. When directly depolarized, one subclass of pyramidal neurons had the capacity to generate intrinsic burst discharges and another generated regular trains of single spikes. Burst responses were triggered in an all‐or‐none manner from depolarizing afterpotentials in most bursting neurons. Regular spiking cells responded to electrical stimulation of ascending afferents with a typical EPSP‐IPSP sequence, whereas IPSPs were hard to detect in bursting cells. Orthodromic activation of the latter evoked a prominent voltage‐dependent depolarization that could trigger a burst response. Intracellularly labelled bursting and regular spiking cells were located in layer 5b, but had distinctly different morphologies. Bursting neurons had a large pyramidal soma, a gradually emerging apical dendrite, and an extensile apical and basal dendritic tree. Their axonal collateral arborization was predominantly limited to layers 5/6. In contrast, regular spiking cells had a more rounded soma with abruptly emerging apical dendrite, a smaller dendritic arborization, and 2 to 8 ascending axonal collaterals that arborized widely in the supragranular layers. Both bursting and regular spiking cells had main axons that entered the subcortical white matter.These data show that some subgroups of pyramidal neurons within the deeper parts of layer 5 of rat cortex are morphologically and physiologically distinct and have different intracortical connections. Bursting cells presumably function to amplify and synchronize cortical outputs, whereas regular spiking output neurons provide excitatory feedback to neurons at all cortical levels and receive a more effective orthodromic inhibitory input. These data support the hypothesis that differences in gross neuronal structure, perhaps even the subtle differences that distinguish subclasses of neurons in a given lamina, are predictive of underlying differences in the type and distribution of ion channels in the nerve cell membrane and connections of cells within the cortical circuit.
Cutaneus trunci muscle reflex of the guinea pig
Authors: Blight Andrew R. , McGinnis Michael E. , Borgens Richard B. 
Published: January 2005

AbstractThe cutaneus trunci muscle reflex in guinea pigs was studied with a combination of video analysis, electromyography, lesioning, and light microscopy. The muscle forms a bilateral, subdermal sheet over much of the trunk. Local contractions of the dorsal part of the muscle are produced in response to brief tactile or electrical stimulation of the skin and consist of a twitch centered 1–2 cm rostral of the stimulus site. The reflex receptive field covers most of the thoracic and lumbar dorsal surface. The sensory information is carried via segmental dorsal cutaneous nerves. Receptive fields of adjacent nerves overlap and form rectangular areas perpendicular to the midline, at thoracic levels. Motor innervation projects through the lateral thoracic nerves of the brachial plexus. The motoneurons are located near the cervical thoracic junction ((C7‐T1)). Lesions of the lower thoracic cord indicate that ascending sensory information is carried to the motor nuclei via the ventral half of the lateral funiculus. This pathway conveys information primarily from ipsilateral skin. There is a weaker input from contralateral skin, crossing at segmental levels. Electromyographic responses to brief electrical stimulation of lower thoracic skin occur usually as 10–12 msec bursts at latencies of 10–20 msec, and do not readily habituate or fatigue at stimulus frequencies below 10 Hz. The reflex persists under light pentobarbital anesthesia. This combination of characteristics makes the reflex useful for a variety of physiological and pathophysiological studies.
Cholinergic manipulation alters stimulus‐evoked metabolic activity in cat somatosensory cortex
Authors: Juliano Sharon L. , Ma Wu , Bear Mark F. , Eslin Don 
Published: January 2005

AbstractThe role of acetylcholine (ACh) in cerebral cortical activity has recently been reevaluated. It now seems clear that this neurotransmitter increases the magnitude of cortical responses. Although substantial information has been gathered regarding the role of ACh in sensory information processing, little is known about the participation of ACh in the organization of maps in the cerebral cortex. To address this issue, we used 2 methods to manipulate the supply of ACh in the somatosensory cortex of cats: (1) unilateral neurotoxic lesions of the basal forebrain and (2) unilateral topical applications of the cholinergic antagonist, atropine. For each experimental condition, the animal received an injection of 2‐deoxyglucose (2DG) while identical somatic stimuli were delivered to the right and left forepaws. In the somatosensory cortex, the 2DG uptake most often occurred in the form of patches that extended from layer II to IV. When the patches were reconstructed into 2‐dimensional maps of activity throughout the somatosensory cortex, they formed strips that ran in the rostrocaudal direction. The reconstructed maps revealed that the 2DG patterns in ACh‐depleted and the normal cortex were similar in their overall topographic distribution. Depletion or antagonism of ACh, however, caused the stimulus‐evoked metabolic label to be reduced in dimension and density. Measurements of background activity levels were obtained by using (1) cytochrome oxidase histochemistry or (2) metabolic activity values in regions of somatosensory cortex that were not specifically stimulated. This analysis indicated that background values in the ACh‐depleted hemispheres were not different from those in the normal hemispheres. The absence of ACh therefore appears to reduce the cortical response to stimulation, while background activity values do not change. These observations indicate that ACh plays a significant role in the processing of sensory information and the organization of somatosensory cortical maps.