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Search Results: 1 - 10 of 1315 matches for " Vania Apkarian "
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Spared nerve injury rats exhibit thermal hyperalgesia on an automated operant dynamic thermal escape Task
Marwan Baliki, Oscar Calvo, Dante R Chialvo, A Vania Apkarian
Molecular Pain , 2005, DOI: 10.1186/1744-8069-1-18
Abstract: The discovery of animal models that exhibit different elements of clinical pain syndromes, coupled with advances in tools for quantification of pain behavior, have greatly advanced understanding of mechanisms involved in acute and chronic pain. Pain in animals can only be determined by evaluating behavioral cues. Animal studies measure two types of pain behavior: simple withdrawal reflexes and complex voluntary and intentional behaviors [1]. Various methods have been used in assessing reflexive pain behaviors such as tail flick, limb withdrawal, or orofacial reflexes in response to acute painful stimuli. However, reflex behavior as a measure of pain perception has long been debated among pain researchers. Chapman [1] argued that they could be merely a measure of reflex activity instead of true pain sensation since reflexes can be exerted in spinalized or anesthetized animals. For example, the tail flick and paw withdrawal responses can be elicited in spinal animals [2] and therefore represent spinal reflexes; while vocalization [3] and paw licking on the hotplate test can be elicited in decerebrate animals [3-6] and therefore represent spinal-bulbospinal reflexes. Other investigators also suggest that changes in reflex activity might be due to alterations in motor as well as sensory processing [7,8]. Considerably less effort has been dedicated to measure supraspinal nocifensive behaviors that require integrated behavior, which may be more dependent on cortical activity.The most commonly used stimulus modalities are electrical, mechanical and thermal. The adequacy and shortcomings of each of these modalities has also been widely debated. Electrical stimulation has been criticized since skin receptors are bypassed and synchronous afferent patterns are generated [9]. Although stimulus location and current density can be well controlled with electrical stimulation, it usually requires restraining the animal thus leading to high levels of anxiety and stress that are know
Brain Morphological Signatures for Chronic Pain
Marwan N. Baliki, Thomas J. Schnitzer, William R. Bauer, A. Vania Apkarian
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0026010
Abstract: Chronic pain can be understood not only as an altered functional state, but also as a consequence of neuronal plasticity. Here we use in vivo structural MRI to compare global, local, and architectural changes in gray matter properties in patients suffering from chronic back pain (CBP), complex regional pain syndrome (CRPS) and knee osteoarthritis (OA), relative to healthy controls. We find that different chronic pain types exhibit unique anatomical ‘brain signatures’. Only the CBP group showed altered whole-brain gray matter volume, while regional gray matter density was distinct for each group. Voxel-wise comparison of gray matter density showed that the impact on the extent of chronicity of pain was localized to a common set of regions across all conditions. When gray matter density was examined for large regions approximating Brodmann areas, it exhibited unique large-scale distributed networks for each group. We derived a barcode, summarized by a single index of within-subject co-variation of gray matter density, which enabled classification of individual brains to their conditions with high accuracy. This index also enabled calculating time constants and asymptotic amplitudes for an exponential increase in brain re-organization with pain chronicity, and showed that brain reorganization with pain chronicity was 6 times slower and twice as large in CBP in comparison to CRPS. The results show an exuberance of brain anatomical reorganization peculiar to each condition and as such reflecting the unique maladaptive physiology of different types of chronic pain.
Reproducibility of Structural, Resting-State BOLD and DTI Data between Identical Scanners
Lejian Huang, Xue Wang, Marwan N. Baliki, Lei Wang, A. Vania Apkarian, Todd B. Parrish
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0047684
Abstract: Increasingly, clinical trials based on brain imaging are adopting multiple sites/centers to increase their subject pool and to expedite the studies, and more longitudinal studies are using multiple imaging methods to assess structural and functional changes. Careful investigation of the test-retest reliability and image quality of inter- or intra- scanner neuroimaging measurements are critical in the design, statistical analysis and interpretation of results. We propose a framework and specific metrics to quantify the reproducibility and image quality for neuroimaging studies (structural, BOLD and Diffusion Tensor Imaging) collected across identical scanners and following a major hardware repair (gradient coil replacement). We achieved consistent measures for the proposed metrics: structural (mean volume in specific regions and stretch factor), functional (temporal Signal-to-Noise ratio), diffusion (mean Fractional Anisotropy and Mean Diffusivity in multiple regions). The proposed frame work of imaging metrics should be used to perform daily quality assurance testing and incorporated into multi-center studies.
Lidocaine patch (5%) is no more potent than placebo in treating chronic back pain when tested in a randomised double blind placebo controlled brain imaging study
Javeria A Hashmi, Marwan Baliki, Mona L Chanda, Lejian Huang, Elle Parks, Thomas Schnitzer, Vania Apkarian
Molecular Pain , 2012, DOI: 10.1186/1744-8069-8-29
Abstract: There was no significant difference between the treatment groups in either pain intensity, sensory and affective qualities of pain or in pain related brain activation at any time point. However, 50% patients in both the Lidocaine and placebo arms reported a greater than 50% decrease in pain suggesting a marked placebo effect. When tested against an untreated CBP group at similar time points, the patch treated subjects showed significantly greater decrease in pain compared to the untreated group (n?=?15).These findings suggest that although the 5% Lidocaine is not better than placebo in its effectiveness for treating pain, the patch itself induces a potent placebo effect in a significant proportion of CBP patients.
A preliminary fMRI study of analgesic treatment in chronic back pain and knee osteoarthritis
Marwan N Baliki, Paul Y Geha, Rami Jabakhanji, Norm Harden, Thomas J Schnitzer, A Vania Apkarian
Molecular Pain , 2008, DOI: 10.1186/1744-8069-4-47
Abstract: Mechanisms underlying CBP and OA pain states are undoubtedly different, and for the most part remain uncharacterized. Peripherally, CBP is mostly a consequence of musculoskeletal and neural damage [1], though accumulating evidence also implicates central, particularly supraspinal, processes in the signs and symptoms of the condition [2-5]. OA pain, in contrast, has generally been characterized as a chronic inflammatory response [6], although other mechanisms, such as the upregulation of Na channels [7] and increased local production of NO (contributing to cartilage degradation and inflammation) [8] have recently been identified. While there is little evidence specifically concerning central processes in OA pain, animal model studies [9,10] and human sensory testing [11] indicate reduced pain thresholds at sites removed from the OA joint that resolve in humans after joint replacement, implying that central sensitization [12] may contribute to OA pain.A recent study characterizing pain properties on a questionnaire shows that OA and CBP (without radiculopathy) patients have similar subjective symptoms but differ from patients with signs of neuropathic pain [13]. Moreover, recent open-labeled clinical trials show the efficacy of 5% lidocaine patch (Lidoderm) therapy on pain in both CBP [14-16] and OA patients [17,18]. Lidocaine patch treatment is approved therapy for post-herpetic neuralgia (PHN) [19], and in two recent studies we described its effects on brain activity in PHN patients regarding spontaneous pain [20] and tactile allodynia pain [21], showing that spontaneous pain and related brain activity decrease with treatment, while stimulus evoked tactile allodynia and its related activity remain unaffected. Here we study brain activity for spontaneous pain in CBP and knee joint stimulation evoked pain in OA patients, comparing the effects of lidocaine therapy within and between the conditions. As CBP is manifested primarily as a continuous, spontaneous pain condit
Scale-free brain functional networks
Victor M. Eguiluz,Dante R. Chialvo,Guillermo A. Cecchi,Marwan Baliki,A. Vania Apkarian
Quantitative Biology , 2003, DOI: 10.1103/PhysRevLett.94.018102
Abstract: Functional magnetic resonance imaging (fMRI) is used to extract {\em functional networks} connecting correlated human brain sites. Analysis of the resulting networks in different tasks shows that: (a) the distribution of functional connections, and the probability of finding a link vs. distance are both scale-free, (b) the characteristic path length is small and comparable with those of equivalent random networks, and (c) the clustering coefficient is orders of magnitude larger than those of equivalent random networks. All these properties, typical of scale-free small world networks, reflect important functional information about brain states.
Predictive Dynamics of Human Pain Perception
Guillermo A. Cecchi ,Lejian Huang,Javeria Ali Hashmi,Marwan Baliki,María V. Centeno,Irina Rish,A. Vania Apkarian
PLOS Computational Biology , 2012, DOI: 10.1371/journal.pcbi.1002719
Abstract: While the static magnitude of thermal pain perception has been shown to follow a power-law function of the temperature, its dynamical features have been largely overlooked. Due to the slow temporal experience of pain, multiple studies now show that the time evolution of its magnitude can be captured with continuous online ratings. Here we use such ratings to model quantitatively the temporal dynamics of thermal pain perception. We show that a differential equation captures the details of the temporal evolution in pain ratings in individual subjects for different stimulus pattern complexities, and also demonstrates strong predictive power to infer pain ratings, including readouts based only on brain functional images.
Inflammatory and neuropathic pain animals exhibit distinct responses to innocuous thermal and motoric challenges
Rami Jabakhanji, Jennifer M Foss, Hugo H Berra, Maria V Centeno, A Vania Apkarian, Dante R Chialvo
Molecular Pain , 2006, DOI: 10.1186/1744-8069-2-1
Abstract: Assessing the level of pain in animals is a key element in pain research. Current pain assessment techniques are mainly limited to estimating animal responses elicited by stimuli to the, presumably, affected area using either: 1) thermal (paw immersion test, hot plate test, radiant heat test, acetone test), 2) tactile (Von Frey filaments), and/or 3) mechanical (paw pressure) stimuli. These responses are invariably reflexive in nature, and are informative only about the thresholds of the sensory variables being probed, thermal, tactile, or mechanical. These thresholds are obviously important in the assessment of painful states, but are not the complete perceptual pain experience from a whole organism perspective. Assessing pain perception using reflexes is also problematic, because responses are present even in anesthetized, spinalized, and de-cerebrate animals, all questionable conditions, for more extensive discussion of these issues see [1,2]. Finally, an important methodological concern is the variability of most current techniques, which involves a significant level of animal-experimenter interaction, making differences in the test execution and in the manipulation of animals between experimenters confounding factors [3].A long list of human brain imaging studies has repeatedly shown the involvement of the cortex in human pain perception [4]. Consistent and guided by these results multiple groups have begun charting the contribution of the cortex to pain behavior in the rat, and demonstrated modulation of spinal cord nociceptive neurons with cortical manipulations [5-9]. Consequently, more objective methods are desirable to assess global pain behavior in unrestrained, awake, behaving animals, which incorporate the contribution of the cortex in pain conditions. Recently, we reported a new automated method to assess learned responses to acute thermal pain in rats [1]. As expected, the measured responses collected with this method, differed significantly between he
El banco central como síndico
Samuel Arturo Apkarian
Invenio , 2003,
Abstract: Este trabajo parte del estudio de un fallo jurisprudencial, cuestionando la incompatibilidad del desempe o de la sindicatura del Banco Central de la República Argentina en las quiebras deentidades financieras, atribuida por la ley 24.318, dada la inconveniencia que surgía en algunos casos,debido a la colisión de las calidades de síndico y acreedor por parte del mencionado organismo. Seanaliza también el alcance dado al concepto de síndico ad hoc , concluyendo con un especial énfasis en la importancia de la función de la sindicatura dentro del proceso concursal.
Some Applications of the Difference Analysis for Stochastic Systems
A. Yu. Shahverdian,A. V. Apkarian
Physics , 2002,
Abstract: The work relates to a new way for analysis of one-dimensional stochastic systems, based on consideration of its higher order difference structure. From this point of view, the deterministic and random processes are analyzed. A new numerical characteristic for one-dimensional stochastic systems is introduced. The applications to single neuron models and neural networks are given.
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