Articles de revues : « Somatotopic map »

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Schlerf, J. E., T. D. Verstynen, R. B. Ivry et R. M. C. Spencer. « Evidence of a Novel Somatopic Map in the Human Neocerebellum During Complex Actions ». Journal of Neurophysiology 103, n^o 6 (juin 2010) : 3330–36. http://dx.doi.org/10.1152/jn.01117.2009.

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The human neocerebellum has been hypothesized to contribute to many high-level cognitive processes including attention, language, and working memory. Support for these nonmotor hypotheses comes from evidence demonstrating structural and functional connectivity between the lateral cerebellum and cortical association areas as well as a lack of somatotopy in lobules VI and VII, a hallmark of motor representations in other areas of the cerebellum and cerebral cortex. We set out to test whether somatotopy exists in these lobules by using functional magnetic resonance imaging to measure cerebellar activity while participants produced simple or complex movements, using either fingers or toes. We observed a previously undiscovered somatotopic organization in neocerebellar lobules VI and VIIA that was most prominent when participants executed complex movements. In contrast, activation in the anterior lobe showed a similar somatotopic organization for both simple and complex movements. While the anterior somatotopic representation responded selectively during ipsilateral movements, the new cerebellar map responded during both ipsi- and contralateral movements. The presence of a bilateral, task-dependent somatotopic map in the neocerebellum emphasizes an important role for this region in the control of skilled actions.

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Grajski, Kamil A., et Michael M. Merzenich. « Hebb-Type Dynamics is Sufficient to Account for the Inverse Magnification Rule in Cortical Somatotopy ». Neural Computation 2, n^o 1 (mars 1990) : 71–84. http://dx.doi.org/10.1162/neco.1990.2.1.71.

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The inverse magnification rule in cortical somatotopy is the experimentally derived inverse relationship between cortical magnification (area of somatotopic map representing a unit area of skin surface) and receptive field size (area of restricted skin surface driving a cortical neuron). We show by computer simulation of a simple, multilayer model that Hebb-type synaptic modification subject to competitive constraints is sufficient to account for the inverse magnification rule.

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ETTLINGER, G. « Somatotopic map of the flying fox ». Nature 315, n^o 6017 (mai 1985) : 285. http://dx.doi.org/10.1038/315285a0.

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Meier, Jeffrey D., Tyson N. Aflalo, Sabine Kastner et Michael S. A. Graziano. « Complex Organization of Human Primary Motor Cortex : A High-Resolution fMRI Study ». Journal of Neurophysiology 100, n^o 4 (octobre 2008) : 1800–1812. http://dx.doi.org/10.1152/jn.90531.2008.

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A traditional view of the human motor cortex is that it contains an overlapping sequence of body part representations from the tongue in a ventral location to the foot in a dorsal location. In this study, high-resolution functional MRI (1.5 × 1.5 × 2 mm) was used to examine the somatotopic map in the lateral motor cortex of humans, to determine whether it followed the traditional somatotopic order or whether it contained any violations of that somatotopic order. The arm and hand representation had a complex organization in which the arm was relatively emphasized in two areas: one dorsal and the other ventral to a region that emphasized the fingers. This violation of a traditional somatotopic order suggests that the motor cortex is not merely a map of the body but is topographically shaped by other influences, perhaps including correlations in the use of body parts in the motor repertoire.

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BROWN, PAUL, RICHARD KOERBER et RONALD MILLECCHIA. « Assembly of the dorsal horn somatotopic map ». Somatosensory & ; Motor Research 14, n^o 2 (janvier 1997) : 93–106. http://dx.doi.org/10.1080/08990229771097.

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Killackey, Herbert P., Robert W. Rhoades et Carol A. Bennett-Clarke. « The formation of a cortical somatotopic map ». Trends in Neurosciences 18, n^o 9 (septembre 1995) : 402–7. http://dx.doi.org/10.1016/0166-2236(95)93937-s.

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MAZZA, M. B., M. DE PINHO et A. C. Roque. « Biologically Plausible Models of Topographic Map Formation in the Somatosensory and Auditory Cortices ». International Journal of Neural Systems 09, n^o 03 (juin 1999) : 265–71. http://dx.doi.org/10.1142/s0129065799000277.

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Computational models of the somatosensory and auditory systems have been constructed with the neurosimulator GENESIS. The somatosensory model consists of a cortical layer with 1024 pyramidal cells and 512 basket cells connected to a hand surface with 512 tactile receptors. The auditory model consists of a cortical layer with 2256 pyramidal cells and 1128 basket cells connected to a cochlea with 47 receptors. The models reproduce processes related to the formation and maintenance of somatotopic and tonotopic maps and exhibit several features observed in experiments with animals such as variability in the shapes and sizes of areas of cortical representation and, in the case of somatotopy, cortical magnification values in agreement with experimental findings and linear decay of receptive field overlap as a function of cortical distance between recording Bites in normal conditions.

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Knutsen, Per M., Celine Mateo et David Kleinfeld. « Precision mapping of the vibrissa representation within murine primary somatosensory cortex ». Philosophical Transactions of the Royal Society B : Biological Sciences 371, n^o 1705 (5 octobre 2016) : 20150351. http://dx.doi.org/10.1098/rstb.2015.0351.

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The ability to form an accurate map of sensory input to the brain is an essential aspect of interpreting functional brain signals. Here, we consider the somatotopic map of vibrissa-based touch in the primary somatosensory (vS1) cortex of mice. The vibrissae are represented by a Manhattan-like grid of columnar structures that are separated by inter-digitating septa. The development, dynamics and plasticity of this organization is widely used as a model system. Yet, the exact anatomical position of this organization within the vS1 cortex varies between individual mice. Targeting of a particular column in vivo therefore requires prior mapping of the activated cortical region, for instance by imaging the evoked intrinsic optical signal (eIOS) during vibrissa stimulation. Here, we describe a procedure for constructing a complete somatotopic map of the vibrissa representation in the vS1 cortex using eIOS. This enables precise targeting of individual cortical columns . We found, using C57BL/6 mice, that although the precise location of the columnar field varies between animals, the relative spatial arrangement of the columns is highly preserved. This finding enables us to construct a canonical somatotopic map of the vibrissae in the vS1 cortex. In particular, the position of any column, in absolute anatomical coordinates, can be established with near certainty when the functional representations in the vS1 cortex for as few as two vibrissae have been mapped with eIOS. This article is part of the themed issue ‘Interpreting BOLD: a dialogue between cognitive and cellular neuroscience’.

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Leblanc, Richard. « Charcot's motor brain map and 19th-century neurosurgery ». Journal of Neurosurgery 135, n^o 6 (décembre 2021) : 1843–48. http://dx.doi.org/10.3171/2020.10.jns202651.

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Neurosurgery is predicated on the knowledge of the structure-function relationship of the brain. When the topic is broached in its historiography, it begins with Fritch and Hitzig's report on the localization of motor function in the cortex of the dog and skips rapidly to Wilder Penfield's homunculus. In that gap are found the origins of modern neurosurgery in 3 papers published by Jean-Martin Charcot and Albert Pitres between 1877 and 1879 in which they describe the somatotopic organization of the human motor cortex and draw the first human brain map. Their findings, obtained through the clinicopathological method, gave relevance to David Ferrier's observations in animals. Their work was extensively cited, and their illustrations reproduced by Ferrier in his landmark lecture to the Royal College of Physicians in 1878. It was known to William Macewen, who used localization to guide him in resecting intracranial mass lesions, and to William Osler and John Hughlings Jackson, who were early advocates of intracranial surgery. This paper describes Charcot and Pitres' discovery of the cortical origin of human voluntary movement and its somatotopic organization, and their influence on 19th-century intracranial surgery. It fills a gap in the historiography of cerebral localization and neurosurgery.

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Wilson, P., D. E. Meyers et P. J. Snow. « The detailed somatotopic organization of the dorsal horn in the lumbosacral enlargement of the cat spinal cord ». Journal of Neurophysiology 55, n^o 3 (1 mars 1986) : 604–17. http://dx.doi.org/10.1152/jn.1986.55.3.604.

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The somatotopic organization of spinocervical tract cells and unidentified dorsal horn neurons that lie in the same depth range as the spinocervical tract cells has been examined in detail in the lumbosacral enlargement of cats anesthetized with alpha-chloralose. Only gentle hair movement or light touch of glabrous skin were used as stimuli. Within the region of the dorsal horn containing these neurons there is a precise somatotopic organization. However, there is considerable variation between animals in the relationship between the somatotopic map and the lumbosacral segmental boundaries. The somatotopic map described here is considered to be restricted to a 300- to 500-micron thick lamina. In the medial half to two-thirds of this lamina in the L6 and L7 segments the toes are represented in a rostrocaudal sequence from toe 2 to toe 5. Over the most medial 200-500 micron of this part of the dorsal horn are found cells that respond to stimulation of the glabrous skin of the toe pads and the central pad. The toe representation is surrounded by a strip of foot representation, which is in turn surrounded by a strip of leg representation. The most lateral part of the lamina curves ventrally in the L6 and L7 segments and contains a continuous rostrocaudal representation of the skin of the thigh. In this region are found both spinocervical tract cells and unidentified dorsal horn neurons with receptive fields on the thigh. The skin of the hindlimb is represented such that a line of discontinuity runs down the posteromedial thigh, leg, and foot. Skin lateral to this line is represented caudally, while skin medial to it is represented rostrally.

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Calford, M. B., M. L. Graydon, M. F. Huerta, J. H. Kaas et J. D. Pettigrew. « A variant of the mammalian somatotopic map in a bat ». Nature 313, n^o 6002 (février 1985) : 477–79. http://dx.doi.org/10.1038/313477a0.

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Chen, Xin, Jae Woong Wang, Adele Salin-Cantegrel, Rola Dali et Stefano Stifani. « Transcriptional regulation of mouse hypoglossal motor neuron somatotopic map formation ». Brain Structure and Function 221, n^o 8 (19 décembre 2015) : 4187–202. http://dx.doi.org/10.1007/s00429-015-1160-2.

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Brown, L. L. « Somatotopic organization in rat striatum : evidence for a combinational map. » Proceedings of the National Academy of Sciences 89, n^o 16 (15 août 1992) : 7403–7. http://dx.doi.org/10.1073/pnas.89.16.7403.

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Verstynen, Timothy, Kevin Jarbo, Sudhir Pathak et Walter Schneider. « In Vivo Mapping of Microstructural Somatotopies in the Human Corticospinal Pathways ». Journal of Neurophysiology 105, n^o 1 (janvier 2011) : 336–46. http://dx.doi.org/10.1152/jn.00698.2010.

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The human corticospinal pathway is organized in a body-centric (i.e., somatotopic) manner that begins in cortical cell bodies and is maintained in the axons as they project through the midbrain on their way to spinal motor neurons. The subcortical segment of this somatotopy has been described using histological methods on non-human primates but only coarsely validated from lesion studies in human patient populations. Using high definition fiber tracking (HDFT) techniques, we set out to provide the first in vivo quantitative description of the midbrain somatotopy of corticospinal fibers in humans. Multi-shell diffusion imaging and deterministic fiber tracking were used to map white matter bundles that originate in the neocortex, navigate complex fiber crossings, and project through the midbrain. These fiber bundles were segmented into premotor (dorsal premotor, ventral premotor, and supplementary motor area) and primary motor sections based on the cortical origin of each fiber streamline. With HDFT, we were able to reveal several unique corticospinal patterns, including the cortical origins of ventral premotor fibers and small (∼1–2 mm) shifts in the midbrain location of premotor versus primary motor cortex fibers. More importantly, within the relatively small diameter of the pyramidal tracts (∼5 mm), we were able to map and quantify the direction of the corticospinal somatotopy. These results show how an HDFT approach to white matter mapping provides the first in vivo, quantitative mapping of subcortical corticospinal topographies at resolutions previously only available with postmortem histological techniques.

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Parpia, Pasha. « Reappraisal of the Somatosensory Homunculus and Its Discontinuities ». Neural Computation 23, n^o 12 (décembre 2011) : 3001–15. http://dx.doi.org/10.1162/neco_a_00179.

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Neuroscience folklore has it that somatotopy in human primary somatosensory cortex (SI) has two significant discontinuities: the hands and face map onto adjacent regions in SI, as do the feet and genitalia. It has been proposed that these conjunctions in SI result from coincident sources of stimulation in the fetal position, where the hands frequently touch the face, and the feet the genitalia. Computer modeling using a Hebbian variant of the self-organizing Kohonen net is consistent with this proposal. However, recent work reveals that the genital representation in SI for cutaneous sensations (as opposed to tumescence) is continuous with that of the lower trunk and thigh. This result, in conjunction with reports of separate face innervation and its earlier onset of sensory function, compared to that of the rest of the body, allows a reappraisal of homuncular organization. It is proposed that the somatosensory homunculus comprises two distinct somatotopic regions: the face representation and that of the rest of the body. Principles of self-organization do not account satisfactorily for the overall homuncular map. These results may serve to alert computational modelers that intrinsic developmental factors can override simple rules of plasticity.

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Andermann, Mark L., et Christopher I. Moore. « A somatotopic map of vibrissa motion direction within a barrel column ». Nature Neuroscience 9, n^o 4 (19 mars 2006) : 543–51. http://dx.doi.org/10.1038/nn1671.

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Kitaura, Hiroki, Ryuichi Hishida et Katsuei Shibuki. « Transcranial imaging of somatotopic map plasticity after tail cut in mice ». Brain Research 1319 (mars 2010) : 54–59. http://dx.doi.org/10.1016/j.brainres.2010.01.020.

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Wang, Luyao, Zhilin Zhang, Tomohisa Okada, Chunlin Li, Duanduan Chen, Shintaro Funahashi, Jinglong Wu et Tianyi Yan. « Population Receptive Field Characteristics in the between- and Within-Digit Dimensions of the Undominant Hand in the Primary Somatosensory Cortex ». Cerebral Cortex 31, n^o 10 (10 mai 2021) : 4427–38. http://dx.doi.org/10.1093/cercor/bhab097.

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Abstract Somatotopy is an important guiding principle for sensory fiber organization in the primary somatosensory cortex (S1), which reflects tactile information processing and is associated with disease-related reorganization. However, it is difficult to measure the neuronal encoding scheme in S1 in vivo in normal participants. Here, we investigated the somatotopic map of the undominant hand using a Bayesian population receptive field (pRF) model. The model was established in hand space with between- and within-digit dimensions. In the between-digit dimension, orderly representation was found, which had low variability across participants. The pRF shape tended to be elliptical for digits with high spatial acuity, for which the long axis was along the within-digit dimension. In addition, the pRF width showed different change trends in the 2 dimensions across digits. These results provide new insights into the neural mechanisms in S1, allowing for in-depth investigation of somatosensory information processing and disease-related reorganization.

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Falci, Scott, Charlotte Indeck et Dave Barnkow. « Spinal cord injury below-level neuropathic pain relief with dorsal root entry zone microcoagulation performed caudal to level of complete spinal cord transection ». Journal of Neurosurgery : Spine 28, n^o 6 (juin 2018) : 612–20. http://dx.doi.org/10.3171/2017.9.spine17373.

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OBJECTIVESurgically created lesions of the spinal cord dorsal root entry zone (DREZ) to relieve central pain after spinal cord injury (SCI) have historically been performed at and cephalad to, but not below, the level of SCI. This study was initiated to investigate the validity of 3 proposed concepts regarding the DREZ in SCI central pain: 1) The spinal cord DREZ caudal to the level of SCI can be a primary generator of SCI below-level central pain. 2) Neuronal transmission from a DREZ that generates SCI below-level central pain to brain pain centers can be primarily through sympathetic nervous system (SNS) pathways. 3) Perceived SCI below-level central pain follows a unique somatotopic map of DREZ pain-generators.METHODSThree unique patients with both intractable SCI below-level central pain and complete spinal cord transection at the level of SCI were identified. All 3 patients had previously undergone surgical intervention to their spinal cords—only cephalad to the level of spinal cord transection—with either DREZ microcoagulation or cyst shunting, in failed attempts to relieve their SCI below-level central pain. Subsequent to these surgeries, DREZ lesioning of the spinal cord solely caudal to the level of complete spinal cord transection was performed using electrical intramedullary guidance. The follow-up period ranged from 1 1/2 to 11 years.RESULTSAll 3 patients in this study had complete or near-complete relief of all below-level neuropathic pain. The analyzed electrical data confirmed and enhanced a previously proposed somatotopic map of SCI below-level DREZ pain generators.CONCLUSIONSThe results of this study support the following hypotheses. 1) The spinal cord DREZ caudal to the level of SCI can be a primary generator of SCI below-level central pain. 2) Neuronal transmission from a DREZ that generates SCI below-level central pain to brain pain centers can be primarily through SNS pathways. 3) Perceived SCI below-level central pain follows a unique somatotopic map of DREZ pain generators.

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Millecchia, R. J., L. M. Pubols, R. V. Sonty, J. L. Culberson, W. E. Gladfelter et P. B. Brown. « Influence of map scale on primary afferent terminal field geometry in cat dorsal horn ». Journal of Neurophysiology 66, n^o 3 (1 septembre 1991) : 696–704. http://dx.doi.org/10.1152/jn.1991.66.3.696.

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1. Thirty-one physiologically identified primary afferent fibers were labeled intracellularly with horseradish peroxidase (HRP). 2. A computer analysis was used to determine whether the distribution of cutaneous mechanoreceptive afferent terminals varies as a function of location within the dorsal horn somatotopic map. 3. An analysis of the geometry of the projections of these afferents has shown that 1) terminal arbors have a greater mediolateral width within the region of the foot representation than lateral to it, 2) terminal arbors have larger length-to-width ratios outside the foot representation than within it, and 3) the orientation of terminal arbors near the boundary of the foot representation reflects the angle of the boundary. Previous attribution of mediolateral width variations to primary afferent type are probably in error, although there appear to be genuine variations of longitudinal extent as a function of primary afferent type. 4. Nonuniform terminal distributions represent the first of a three-component process underlying assembly of the monosynaptic portions of cell receptive fields (RFs) and the somatotopic map. The other two components consist of the elaboration of cell dendritic trees and the establishment of selective connections. 5. The variation of primary afferent terminal distributions with map location is not an absolute requirement for development of the map; for example, the RFs of postsynaptic cells could be assembled with the use of a uniform terminal distribution for all afferents, everywhere in the map, as long as cell dendrites penetrate the appropriate portions of the presynaptic neuropil and receive connections only from afferent axons contributing to their RFs.(ABSTRACT TRUNCATED AT 250 WORDS)

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Killackey, Herbert P. « Static and Dynamic Aspects of Cortical Somatotopy : A Critical Evaluation ». Journal of Cognitive Neuroscience 1, n^o 1 (janvier 1989) : 3–11. http://dx.doi.org/10.1162/jocn.1989.1.1.3.

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The demonstration that functional somatotopic maps within the adult neocortex undergo some degree of reorganization following peripheral injury has aroused considerable interest. The evidence for such reorganization in the rat and monkey is reviewed and it is concluded that in both species there is good evidence for limited functional map reorganization in the adult neocortex following peripheral injury. The significance of such functional map reorganization, particularly in terms of whether or not cortical maps are continuously modifiable throughout life, is discussed. It is concluded that the current evidence for map reorganization is best interpreted in terms of the unmasking of preexisting neuronal circuits rather than as evidence of dynamic cortical selection processes.

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Maldjian, Joseph A., Allan Gottschalk, Rita S. Patel, John A. Detre et David C. Alsop. « The Sensory Somatotopic Map of the Human Hand Demonstrated at 4 Tesla ». NeuroImage 10, n^o 1 (juillet 1999) : 55–62. http://dx.doi.org/10.1006/nimg.1999.0448.

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Antón-Bolaños, Noelia, Alejandro Sempere-Ferràndez, Teresa Guillamón-Vivancos, Francisco J. Martini, Leticia Pérez-Saiz, Henrik Gezelius, Anton Filipchuk, Miguel Valdeolmillos et Guillermina López-Bendito. « Prenatal activity from thalamic neurons governs the emergence of functional cortical maps in mice ». Science 364, n^o 6444 (2 mai 2019) : 987–90. http://dx.doi.org/10.1126/science.aav7617.

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The mammalian brain’s somatosensory cortex is a topographic map of the body’s sensory experience. In mice, cortical barrels reflect whisker input. We asked whether these cortical structures require sensory input to develop or are driven by intrinsic activity. Thalamocortical columns, connecting the thalamus to the cortex, emerge before sensory input and concur with calcium waves in the embryonic thalamus. We show that the columnar organization of the thalamocortical somatotopic map exists in the mouse embryo before sensory input, thus linking spontaneous embryonic thalamic activity to somatosensory map formation. Without thalamic calcium waves, cortical circuits become hyperexcitable, columnar and barrel organization does not emerge, and the somatosensory map lacks anatomical and functional structure. Thus, a self-organized protomap in the embryonic thalamus drives the functional assembly of murine thalamocortical sensory circuits.

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Zhang, Jun. « Dynamics and Formation of Self-Organizing Maps ». Neural Computation 3, n^o 1 (février 1991) : 54–66. http://dx.doi.org/10.1162/neco.1991.3.1.54.

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Amari (1983, 1989) proposed a mathematical formulation on the self-organization of synaptic efficacies and neural response fields under the influence of external stimuli. The dynamics as well as the equilibrium properties of the cortical map were obtained analytically for neurons with binary input-output transfer functions. Here we extend this approach to neurons with arbitrary sigmoidal transfer function. Under the assumption that both the intracortical connection and the stimulus-driven thalamic activity are well localized, we are able to derive expressions for the cortical magnification factor, the point-spread resolution, and the bandwidth resolution of the map. As a highlight, we show analytically that the receptive field size of a cortical neuron in the map is inversely proportional to the cortical magnification factor at that map location, the experimentally well-established rule of inverse magnification in retinotopic and somatotopic maps.

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Hudson, Heather M., Michael C. Park, Abderraouf Belhaj-Saïf et Paul D. Cheney. « Representation of individual forelimb muscles in primary motor cortex ». Journal of Neurophysiology 118, n^o 1 (1 juillet 2017) : 47–63. http://dx.doi.org/10.1152/jn.01070.2015.

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Stimulus-triggered averaging (StTA) of forelimb muscle electromyographic (EMG) activity was used to investigate individual forelimb muscle representation within the primary motor cortex (M1) of rhesus macaques with the objective of determining the extent of intra-areal somatotopic organization. Two monkeys were trained to perform a reach-to-grasp task requiring multijoint coordination of the forelimb. EMG activity was simultaneously recorded from 24 forelimb muscles including 5 shoulder, 7 elbow, 5 wrist, 5 digit, and 2 intrinsic hand muscles. Microstimulation (15 µA at 15 Hz) was delivered throughout the movement task and individual stimuli were used as triggers for generating StTAs of EMG activity. StTAs were used to map the cortical representations of individual forelimb muscles. As reported previously (Park et al. 2001), cortical maps revealed a central core of distal muscle (wrist, digit, and intrinsic hand) representation surrounded by a horseshoe-shaped proximal (shoulder and elbow) muscle representation. In the present study, we found that shoulder and elbow flexor muscles were predominantly represented in the lateral branch of the horseshoe whereas extensors were predominantly represented in the medial branch. Distal muscles were represented within the core distal forelimb representation and showed extensive overlap. For the first time, we also show maps of inhibitory output from motor cortex, which follow many of the same organizational features as the maps of excitatory output. NEW & NOTEWORTHY While the orderly representation of major body parts along the precentral gyrus has been known for decades, questions have been raised about the possible existence of additional more detailed aspects of somatotopy. In this study, we have investigated this question with respect to muscles of the arm and show consistent features of within-arm (intra-areal) somatotopic organization. For the first time we also show maps of how inhibitory output from motor cortex is organized.

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Jones, E. G., P. R. Manger et T. M. Woods. « Maintenance of a somatotopic cortical map in the face of diminishing thalamocortical inputs ». Proceedings of the National Academy of Sciences 94, n^o 20 (30 septembre 1997) : 11003–7. http://dx.doi.org/10.1073/pnas.94.20.11003.

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Sato, Akira, Sumito Koshida et Hiroyuki Takeda. « Single-cell analysis of somatotopic map formation in the zebrafish lateral line system ». Developmental Dynamics 239, n^o 7 (19 mai 2010) : 2058–65. http://dx.doi.org/10.1002/dvdy.22324.

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Schlaggar, Bradley L., et Dennis D. M. O'Leary. « Early development of the somatotopic map and barrel patterning in rat somatosensory cortex ». Journal of Comparative Neurology 346, n^o 1 (1 août 1994) : 80–96. http://dx.doi.org/10.1002/cne.903460106.

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Romanelli, Pantaleo, Gary Heit, Bruce C. Hill, Alli Kraus, Trevor Hastie et Helen M. Brontë-Stewart. « Microelectrode recording revealing a somatotopic body map in the subthalamic nucleus in humans with Parkinson disease ». Journal of Neurosurgery 100, n^o 4 (avril 2004) : 611–18. http://dx.doi.org/10.3171/jns.2004.100.4.0611.

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Object. The subthalamic nucleus (STN) is a key structure for motor control through the basal ganglia. The aim of this study was to show that the STN in patients with Parkinson disease (PD) has a somatotopic organization similar to that in nonhuman primates. Methods. A functional map of the STN was obtained using electrophysiological microrecording during placement of deep brain stimulation (DBS) electrodes in patients with PD. Magnetic resonance imaging was combined with ventriculography and intraoperative x-ray film to assess the position of the electrodes and the STN units, which were activated by limb movements to map the sensorimotor region of the STN. Each activated cell was located relative to the anterior commissure—posterior commissure line. Three-dimensional coordinates of the cells were analyzed statistically to determine whether those cells activated by movements of the arm and leg were segregated spatially. Three hundred seventy-nine microelectrode tracks were created during placement of 71 DBS electrodes in 44 consecutive patients. Somatosensory driving was found in 288 tracks. The authors identified and localized 1213 movement-related cells and recorded responses from 29 orofacial cells, 480 arm-related cells, 558 leg-related cells, and 146 cells responsive to both arm and leg movements. Leg-related cells were localized in medial (p < 0.0001) and ventral (p < 0.0004) positions and tended to be situated anteriorly (p = 0.063) relative to arm-related cells. Conclusions. Evidence of somatotopic organization in the STN in patients with PD supports the current theory of highly segregated loops integrating cortex—basal ganglia connections. These loops are preserved in chronic degenerative diseases such as PD, but may subserve a distorted body map. This finding also supports the relevance of microelectrode mapping in the optimal placement of DBS electrodes along the subthalamic homunculus.

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Hollmann, Vanessa, Volker Hofmann et Jacob Engelmann. « Somatotopic map of the active electrosensory sense in the midbrain of the mormyridGnathonemus petersii ». Journal of Comparative Neurology 524, n^o 12 (2 février 2016) : 2479–91. http://dx.doi.org/10.1002/cne.23963.

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Song, Hanlim, Wonbin Jung, Eulgi Lee, Ji-Young Park, Min Sun Kim, Min-Cheol Lee et Hyoung-Ihl Kim. « Capsular stroke modeling based on somatotopic mapping of motor fibers ». Journal of Cerebral Blood Flow & ; Metabolism 37, n^o 8 (1 janvier 2016) : 2928–37. http://dx.doi.org/10.1177/0271678x16679421.

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Recently, several capsular stroke models have been reported with different targets of destruction. This study was performed to establish an accurate internal capsule (IC) target for capsular stroke modeling in rats. We injected adeno-associated virus serotype 5 (AAV)-CaMKII-EYFP into forelimb motor cortex and AAV-CaMKII-mCherry into hindlimb motor cortex (n = 9) to anterogradely trace the pyramidal fibers and map their somatotopic distribution in the IC. On the basis of the neural tracing results, we created photothrombotic infarct lesions in rat forelimb and hindlimb motor fiber (FMF and HMF) areas of the IC (n = 29) and assessed motor behavior using a forelimb-use asymmetry test, a foot-fault test, and a single-pellet reaching test. We found that the FMFs and HMFs were primarily distributed in the inferior portion of the posterior limb of the IC, with the FMFs located largely ventral to the HMFs but with an area of partial overlap. Photothrombotic lesions in the FMF area resulted in persistent motor deficits. In contrast, lesions in the HMF area did not result in persistent motor deficits. These results indicate that identification of the somatotopic distribution of pyramidal fibers is critical for accurate targeting in animal capsular stroke models: only infarcts in the FMF area resulted in long-lasting motor deficits.

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Chen, Li Min, Robert M. Friedman, Benjamin M. Ramsden, Robert H. LaMotte et Anna Wang Roe. « Fine-Scale Organization of SI (Area 3b) in the Squirrel Monkey Revealed With Intrinsic Optical Imaging ». Journal of Neurophysiology 86, n^o 6 (1 décembre 2001) : 3011–29. http://dx.doi.org/10.1152/jn.2001.86.6.3011.

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Optical imaging of intrinsic cortical activity was used to study the somatotopic map and the representation of pressure, flutter, and vibration in area 3b of the squirrel monkey ( Saimiri sciureus) cortex under pentothal or isoflurane anesthesia. The representation of the fingerpads in primary somatosensory cortex was investigated by stimulating the glabrous skin of distal fingerpads (D1–D5) with Teflon probes (3-mm diam) attached through an armature to force feedback-controlled torque motors. Under pentothal anesthesia, intrinsic signal maps in area 3b obtained in response to stimulation (trapezoidal indentation) of individual fingerpads showed focal activations. These activations (ranging from 0.5 to 1.0 mm) were discrete and exhibited minimal overlap between adjacent fingerpad representations. Consistent with previously published maps, a somatotopic representation of the fingerpads was observed with an orderly medial to lateral progression from the D5 to D1 fingerpads. Under isoflurane anesthesia, general topography was still maintained, but the representation of fingerpads on adjacent fingers had higher degrees of overlap than with pentothal anesthesia. Multi- and single-unit recordings in the activation zones confirmed the somatotopic maps. To examine preferential inputs from slowly adapting type I (SA) and rapidly adapting type I (RA) and type II (PC) mechanoreceptors, we applied stimuli consisting of sinusoidal indentations that produce sensations of pressure (1 Hz), flutter (30 Hz), and vibration (200 Hz). Under pentothal anesthesia, activation patterns to these different stimuli were focal and coincided on the cortex. Under isoflurane, activation zones from pressure, flutter, and vibratory stimuli differed in size and shape and often contained multiple foci, although overall topography was maintained. Subtraction and vector maps revealed cortical areas (approximate 250-μm diam) that were preferentially activated by the sensations of pressure, flutter, and vibration. Multi- and single-unit recordings aided in the interpretation of the imaging maps. In conclusion, the cortical signals observed with intrinsic signal optical imaging delineated a somatotopic organization of area 3b and revealed different topographical cortical activation patterns for pressure, flutter, and vibratory stimuli. These patterns were dependent on anesthesia type. Possible relationships of these anesthesia effects to somatosensory cortical plasticity are discussed.

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Fassett, Hunter, Claudia Turco, Jenin El-Sayes et Aimee Nelson. « Alterations in Motor Cortical Representation of Muscles Following Incomplete Spinal Cord Injury in Humans ». Brain Sciences 8, n^o 12 (16 décembre 2018) : 225. http://dx.doi.org/10.3390/brainsci8120225.

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(1) Background: The primary motor cortex (M1) experiences reorganization following spinal cord injury (SCI). However, there is a paucity of research comparing bilateral M1 organization in SCI and questions remain to be answered. We explored the presence of somatotopy within the M1 representation of arm muscles, and determined whether anatomical shifts in these representations occur, and investigated the symmetry in organization between the two hemispheres.; (2) Methods: Transcranial magnetic stimulation (TMS) was used to map the representation of the biceps, flexor carpi radialis and abductor pollicis brevis (APB) bilaterally in nine individuals with chronic incomplete cervical spinal cord injury and nine aged- and handed-matched uninjured controls. TMS was delivered over a 6 × 5 point grid that encompassed M1 using an intensity specific to the resting motor threshold for each muscle tested.; (3) Results: Results indicate that, compared to controls, muscle representations in SCI are shifted medially but preserve a general somatotopic arrangement, and that territory dedicated to the APB muscle is greater.; (4) Conclusions: These findings demonstrate differences in the organization of M1 between able-bodied controls and those with incomplete cervical SCI. This altered organization may have future implications in understanding the functional deficits observed in SCI and rehabilitation techniques aimed at restoring function.

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Choi, Mi-Hyun, Sung-Phil Kim, Hyung-Sik Kim et Soon-Cheol Chung. « Inter- and Intradigit Somatotopic Map of High-Frequency Vibration Stimulations in Human Primary Somatosensory Cortex ». Medicine 95, n^o 20 (mai 2016) : e3714. http://dx.doi.org/10.1097/md.0000000000003714.

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Meredith, M. Alex, H. Ruth Clemo et Barry E. Stein. « Somatotopic component of the multisensory map in the deep laminae of the cat superior colliculus ». Journal of Comparative Neurology 312, n^o 3 (15 octobre 1991) : 353–70. http://dx.doi.org/10.1002/cne.903120304.

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Crockett, David P., Steven Maslany, Suzan L. Harris et M. David Egger. « Enhanced cytochrome-oxidase staining of the cuneate nucleus in the rat reveals a modifiable somatotopic map ». Brain Research 612, n^o 1-2 (mai 1993) : 41–55. http://dx.doi.org/10.1016/0006-8993(93)91642-6.

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Saadon-Grosman, Noam, Zohar Tal, Eyal Itshayek, Amir Amedi et Shahar Arzy. « Discontinuity of cortical gradients reflects sensory impairment ». Proceedings of the National Academy of Sciences 112, n^o 52 (11 décembre 2015) : 16024–29. http://dx.doi.org/10.1073/pnas.1506214112.

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Topographic maps and their continuity constitute a fundamental principle of brain organization. In the somatosensory system, whole-body sensory impairment may be reflected either in cortical signal reduction or disorganization of the somatotopic map, such as disturbed continuity. Here we investigated the role of continuity in pathological states. We studied whole-body cortical representations in response to continuous sensory stimulation under functional MRI (fMRI) in two unique patient populations—patients with cervical sensory Brown-Séquard syndrome (injury to one side of the spinal cord) and patients before and after surgical repair of cervical disk protrusion—enabling us to compare whole-body representations in the same study subjects. We quantified the spatial gradient of cortical activation and evaluated the divergence from a continuous pattern. Gradient continuity was found to be disturbed at the primary somatosensory cortex (S1) and the supplementary motor area (SMA), in both patient populations: contralateral to the disturbed body side in the Brown-Séquard group and before repair in the surgical group, which was further improved after intervention. Results corresponding to the nondisturbed body side and after surgical repair were comparable with control subjects. No difference was found in the fMRI signal power between the different conditions in the two groups, as well as with respect to control subjects. These results suggest that decreased sensation in our patients is related to gradient discontinuity rather than signal reduction. Gradient continuity may be crucial for somatotopic and other topographical organization, and its disruption may characterize pathological processing.

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Lu, Xiaofeng, Shigehiro Miyachi, Yumi Ito, Atsushi Nambu et Masahiko Takada. « Topographic distribution of output neurons in cerebellar nuclei and cortex to somatotopic map of primary motor cortex ». European Journal of Neuroscience 25, n^o 8 (16 avril 2007) : 2374–82. http://dx.doi.org/10.1111/j.1460-9568.2007.05482.x.

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Moritz, Chet T., Timothy H. Lucas, Steve I. Perlmutter et Eberhard E. Fetz. « Forelimb Movements and Muscle Responses Evoked by Microstimulation of Cervical Spinal Cord in Sedated Monkeys ». Journal of Neurophysiology 97, n^o 1 (janvier 2007) : 110–20. http://dx.doi.org/10.1152/jn.00414.2006.

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Documenting the forelimb responses evoked by stimulating sites in primate cervical spinal cord is significant for understanding spinal circuitry and for potential neuroprosthetic applications involving hand and arm. We examined the forelimb movements and electromyographic (EMG) muscle responses evoked by intraspinal microstimulation in three M. nemestrina monkeys sedated with ketamine. Trains of three stimulus pulses (10–80 μA) at 300 Hz were delivered at sites in regularly spaced tracks from C6 to T1. Hand and/or arm movements were evoked at 76% of the 745 sites stimulated. Specifically, movements were evoked in digits (76% of effective sites), wrist (15% of sites), elbow (26%), and shoulder (17%). To document the muscle activity evoked by a stimulus current just capable of eliciting consistent joint rotation, stimulus-triggered averages of rectified EMG were calculated at each site where a movement was observed. Typically, many muscles were coactivated at threshold currents needed to evoke movements. Out of the 13–15 muscles recorded per animal, only one muscle was active at 14% of the effective sites and two to six muscles were coactivated at 47% of sites. Thus intraspinal stimulation at threshold currents adequate for evoking movement typically coactivated multiple muscles, including antagonists. Histologic reconstruction of stimulation sites indicated that responses were elicited from the dorsal and ventral horn and from fiber tracts in the white matter, with little somatotopic organization for movement or muscle activation. The absence of a clear somatotopic map of output sites is probably a result of the stimulation of complex mixtures of fibers and cells.

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Leergaard, Trygve B., Kjersti A. Lyngstad, John H. Thompson, Sofie Taeymans, Bart P. Vos, Erik De Schutter, James M. Bower et Jan G. Bjaalie. « Rat somatosensory cerebropontocerebellar pathways : Spatial relationships of the somatotopic map of the primary somatosensory cortex are preserved in a three-dimensional clustered pontine map ». Journal of Comparative Neurology 422, n^o 2 (26 juin 2000) : 246–66. http://dx.doi.org/10.1002/(sici)1096-9861(20000626)422:2<246 ::aid-cne7>3.0.co;2-r.

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Gabbiani, F., et W. Metzner. « Encoding and processing of sensory information in neuronal spike trains ». Journal of Experimental Biology 202, n^o 10 (15 mai 1999) : 1267–79. http://dx.doi.org/10.1242/jeb.202.10.1267.

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Recently, a statistical signal-processing technique has allowed the information carried by single spike trains of sensory neurons on time-varying stimuli to be characterized quantitatively in a variety of preparations. In weakly electric fish, its application to first-order sensory neurons encoding electric field amplitude (P-receptor afferents) showed that they convey accurate information on temporal modulations in a behaviorally relevant frequency range (<80 Hz). At the next stage of the electrosensory pathway (the electrosensory lateral line lobe, ELL), the information sampled by first-order neurons is used to extract upstrokes and downstrokes in the amplitude modulation waveform. By using signal-detection techniques, we determined that these temporal features are explicitly represented by short spike bursts of second-order neurons (ELL pyramidal cells). Our results suggest that the biophysical mechanism underlying this computation is of dendritic origin. We also investigated the accuracy with which upstrokes and downstrokes are encoded across two of the three somatotopic body maps of the ELL (centromedial and lateral). Pyramidal cells of the centromedial map, in particular I-cells, encode up- and downstrokes more reliably than those of the lateral map. This result correlates well with the significance of these temporal features for a particular behavior (the jamming avoidance response) as assessed by lesion experiments of the centromedial map.

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Wall, JT, MF Huerta et JH Kaas. « Changes in the cortical map of the hand following postnatal median nerve injury in monkeys : modification of somatotopic aggregates ». Journal of Neuroscience 12, n^o 9 (1 septembre 1992) : 3445–55. http://dx.doi.org/10.1523/jneurosci.12-09-03445.1992.

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Montoya, Pedro, Karin Ritter, Ellena Huse, Wolfgang Larbig, Christoph Braun, Stephanie Töpfner, Werner Lutzenberger, Wolfgang Grodd, Herta Flor et Niels Birbaumer. « The cortical somatotopic map and phantom phenomena in subjects with congenital limb atrophy and traumatic amputees with phantom limb pain ». European Journal of Neuroscience 10, n^o 3 (mars 1998) : 1095–102. http://dx.doi.org/10.1046/j.1460-9568.1998.00122.x.

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Honey, CM, Z. Ivanishvili, CR Honey et MK Heran. « C.06 Somatotopic organization of the human spinothalamic tract : CT-guided mapping in awake patients undergoing cordotomy ». Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 45, s2 (juin 2018) : S15. http://dx.doi.org/10.1017/cjn.2018.101.

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Background: After correlating in vivo macrostimulation-induced pain or temperature sensation during percutaneous cervical cordotomy with simultaneous CT imaging of the electrode tip location, we present a modern description of the somatotopy of the human cervical spinothalamic tract Methods: Twenty patients with medically refractory, unilateral, nociceptive pain due to malignancy received contralateral cervical percutaneous cordotomy. In a post-hoc analysis of the data, each individual’s cervical spinal cord was measured from the CT image using PACS software. The location of the electrode tip during each stimulation-induced response was then superimposed on a diagram of their cord Results: The lower limb responses were found more superficial and posterior to those of the upper limb. Interestingly, the region for upper limb responses surrounded that for lower limb primarily anteriorly and medially (deep) but also posteriorly Conclusions: This work simultaneously combined awake physiologic localization of fibers within the human -spinothalamic tract (STT) with neuroimaging documenting their precise anatomical localization within the spinal cord. The resultant map of the STT demonstrates, for the first time, that fibers from the lower limb are located superficially and posteriorly within the anterolateral spinal cord with the fibers from the upper limb surrounding them primarily deep and anteriorly but also posteriorly

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Staiger, Jochen F., et Carl C. H. Petersen. « Neuronal Circuits in Barrel Cortex for Whisker Sensory Perception ». Physiological Reviews 101, n^o 1 (1 janvier 2021) : 353–415. http://dx.doi.org/10.1152/physrev.00019.2019.

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The array of whiskers on the snout provides rodents with tactile sensory information relating to the size, shape and texture of objects in their immediate environment. Rodents can use their whiskers to detect stimuli, distinguish textures, locate objects and navigate. Important aspects of whisker sensation are thought to result from neuronal computations in the whisker somatosensory cortex (wS1). Each whisker is individually represented in the somatotopic map of wS1 by an anatomical unit named a ‘barrel’ (hence also called barrel cortex). This allows precise investigation of sensory processing in the context of a well-defined map. Here, we first review the signaling pathways from the whiskers to wS1, and then discuss current understanding of the various types of excitatory and inhibitory neurons present within wS1. Different classes of cells can be defined according to anatomical, electrophysiological and molecular features. The synaptic connectivity of neurons within local wS1 microcircuits, as well as their long-range interactions and the impact of neuromodulators, are beginning to be understood. Recent technological progress has allowed cell-type-specific connectivity to be related to cell-type-specific activity during whisker-related behaviors. An important goal for future research is to obtain a causal and mechanistic understanding of how selected aspects of tactile sensory information are processed by specific types of neurons in the synaptically connected neuronal networks of wS1 and signaled to downstream brain areas, thus contributing to sensory-guided decision-making.

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Andersson, Elisabeth, Ann L. Persson et Christer PO Carlsson. « Are Auricular Maps Reliable for Chronic Musculoskeletal Pain Disorders ? : A Double-Blind Evaluation ». Acupuncture in Medicine 25, n^o 3 (septembre 2007) : 72–79. http://dx.doi.org/10.1136/aim.25.3.72.

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Aim To examine the proposed somatotopic relation between the regions in which patients report musculoskeletal pain and tender points located on the external ears according to a map based on commonly used auricular acupuncture maps. Methods Twenty-five patients (16 women) from a chronic pain clinic were included. Patients were asked, before examination of the external ears, if they had past or present musculoskeletal pain in any of 11 body regions. An ear map, collapsed into 11 zones representing the musculoskeletal system, was used. The ear examiner was blinded to the patients’ pain conditions, medical history and ongoing treatment. Patients communicated with the examiner only to express if tenderness was present in the external ear on palpation using a spring-loaded pressure stylus commonly used for auricular acupuncture. The degree of tenderness was registered on a 5-point scale and dichotomised (no tenderness or tenderness). Agreements between the patients’ painful body regions and tenderness in the external ear zones were presented as percentage, kappa values, sensitivity and specificity. Results The 25 patients reported 116 past or present musculoskeletal pain regions and had 110 tender ear zones. No statistically significant agreements were found between the painful body regions and the corresponding tender ear zones. Conclusions Our results did not show agreements between patients’ reported musculoskeletal pain regions and tender zones in the external ears assessed according to commonly used maps in auricular acupuncture using a pressure stylus. However, very tender points occur on the external ear in a population with chronic musculoskeletal pain.

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Kao, T., J. S. Shumsky, E. B. Knudsen, M. Murray et K. A. Moxon. « Functional role of exercise-induced cortical organization of sensorimotor cortex after spinal transection ». Journal of Neurophysiology 106, n^o 5 (novembre 2011) : 2662–74. http://dx.doi.org/10.1152/jn.01017.2010.

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Spinal cord transection silences neuronal activity in the deafferented cortex to cutaneous stimulation of the body and untreated animals show no improvement in functional outcome (weight-supported stepping) with time after lesion. However, adult rats spinalized since neonates that receive exercise therapy exhibit greater functional recovery and exhibit more cortical reorganization. This suggests that the change in the somatotopic organization of the cortex may be functionally relevant. To address this issue, we chronically implanted arrays of microwire electrodes into the infragranular layers of the hindlimb somatosensory cortex of adult rats neonatally transected at T8/T9 that received exercise training (spinalized rats) and of normal adult rats. Multiple, single neuron activity was recorded during passive sensory stimulation, when the animals were anesthetized, and during active sensorimotor stimulation during treadmill-induced locomotion when the animal was awake and free to move. Our results demonstrate that cortical neurons recorded from the spinalized rats that received exercise 1) had higher spontaneous firing rates, 2) were more likely to respond to both sensory and sensorimotor stimulations of the forelimbs, and also 3) responded with more spikes per stimulus than those recorded from normal rats, suggesting expansion of the forelimb map into the hindlimb map. During treadmill locomotion the activity of neurons recorded from neonatally spinalized rats was greater during weight-supported steps on the treadmill compared with the neuronal activity during nonweight supported steps. We hypothesize that this increased activity is related to the ability of the animal to take weight supported steps and that, therefore, these changes in cortical organization after spinal cord injury are relevant for functional recovery.

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Sanchez-Panchuelo, R. M., S. Francis, R. Bowtell et D. Schluppeck. « Mapping Human Somatosensory Cortex in Individual Subjects With 7T Functional MRI ». Journal of Neurophysiology 103, n^o 5 (mai 2010) : 2544–56. http://dx.doi.org/10.1152/jn.01017.2009.

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Functional magnetic resonance imaging (fMRI) is now routinely used to map the topographic organization of human visual cortex. Mapping the detailed topography of somatosensory cortex, however, has proven to be more difficult. Here we used the increased blood-oxygen-level-dependent contrast-to-noise ratio at ultra-high field (7 Tesla) to measure the topographic representation of the digits in human somatosensory cortex at 1 mm isotropic resolution in individual subjects. A “traveling wave” paradigm was used to locate regions of cortex responding to periodic tactile stimulation of each distal phalangeal digit. Tactile stimulation was applied sequentially to each digit of the left hand from thumb to little finger (and in the reverse order). In all subjects, we found an orderly map of the digits on the posterior bank of the central sulcus (postcentral gyrus). Additionally, we measured event-related responses to brief stimuli for comparison with the topographic mapping data and related the fMRI responses to anatomical images obtained with an inversion-recovery sequence. Our results have important implications for the study of human somatosensory cortex and underscore the practical utility of ultra-high field functional imaging with 1 mm isotropic resolution for neuroscience experiments. First, topographic mapping of somatosensory cortex can be achieved in 20 min, allowing time for further experiments in the same session. Second, the maps are of sufficiently high resolution to resolve the representations of all five digits and third, the measurements are robust and can be made in an individual subject. These combined advantages will allow somatotopic fMRI to be used to measure the representation of digits in patients undergoing rehabilitation or plastic changes after peripheral nerve damage as well as tracking changes in normal subjects undergoing perceptual learning.

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Xerri, C., et Y. Zennou-Azogui. « Influence of the postlesion environment and chronic piracetam treatment on the organization of the somatotopic map in the rat primary somatosensory cortex after focal cortical injury ». Neuroscience 118, n^o 1 (avril 2003) : 161–77. http://dx.doi.org/10.1016/s0306-4522(02)00911-9.

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Karol, Eduardo A., Adriana Pérez, Gerardo Cueto et Bettina Karol. « Reducing unnecessary morbidity from percutaneous thermocoagulation in the treatment of trigeminal neuralgia—Part C : a starting point for a somatotopic map of the human gasserian ganglion ». Neurological Research 27, n^o 8 (décembre 2005) : 835–42. http://dx.doi.org/10.1179/016164105x63593.

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