REVIEW ■ : Reorganization of Sensory Systems of Primates after Injury:
TL;DR: The orderly representations of sensory surfaces in the brains of adult mammals have the capacity to reor ganize after injuries that deprive these representations of some of their normal sources of activation.
Abstract: The orderly representations of sensory surfaces in the brains of adult mammals have the capacity to reor ganize after injuries that deprive these representations of some of their normal sources of activation. Such reorganizations can be produced by injury that occurs peripherally, such as nerve damage or amputation, or after injury to the CNS, such as spinal cord damage or cortical lesion. These changes likely are mediated by a number of different mechanisms, and can be extensive and involve the growth of new connections. Finally, some types of reorganizations may help mediate the recovery of lost functions, whereas others may lead to sensory abnormalities and perceptual errors. NEUROSCIENTIST 3:123-130, 1997
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TL;DR: This study evaluated 2 alternative approaches to treatment: one focusing on underlying cognitive processes and the second on errorless learning in everyday functional situations, both of which were based on the Defense and Veterans Brain Injury Center cognitive-didactic versus functional-experiential study methodology.
Abstract: This is a descriptive article outlining issues in the development and implementation of a multisite randomized rehabilitation trial for brain injury treatment. The goal of this article is to present practical and theoretical considerations in designing and conducting multicenter rehabilitation trials. Practical issues discussed include (a) treatment setting, (b) patient accessibility in determining the research question of interest, as well as inclusion and exclusion criteria, (c) research protocol development in the context of rehabilitation standard of care, and (d) protocol treatments in the context of realistic cost-benefits analysis. Rehabilitation theory is discussed as playing an important role designing the specifics of the protocol interventions. The Defense and Veterans Brain Injury Center Veterans Health Administration cognitive-didactic versus functional-experiential study methodology is used for illustrative purposes. This study evaluated 2 alternative approaches to treatment: one focusing on underlying cognitive processes and the second on errorless learning in everyday functional situations. Lessons learned over the course of completing the treatment trial are discussed.
35 citations
TL;DR: It is concluded that the lateral somatosensory thalamic complex is involved in the processing of neuropathic manifestations but cannot be considered as an obligatory or exclusive relay center for the neuropathic syndromes.
24 citations
TL;DR: There was no evidence reported that PRT is unsafe in people within the first 3 months after stroke, although there was a lack of reporting about adverse events, and the lack of demonstration of effect in improving muscle strength and activity suggests there is insufficient evidence to recommend the prescription of PRT for people withinThe first 3 weeks after stroke.
Abstract: BACKGROUND Progressive resistance training (PRT) can improve strength and function in people with chronic stroke, but less is known about whether this intervention is safe and beneficial during the first 3 months following stroke. OBJECTIVE To systematically review the evidence about the safety and effectiveness of PRT to improve activity in people within the first 3 months after stroke. METHODS After database searching and selection of studies a risk of bias assessment was conducted. Data for the primary outcome of safety was synthesised descriptively and meta-analyses for other outcomes were conducted using a random effects model. RESULTS The quality of the 5 included studies ranged from good to excellent (mean 24.2, range 20-28). For the trials investigating adverse events, none reported any significant increase in events after PRT. There was high level evidence that PRT had little or no effect on strength (SMD (standardized mean difference) 0.17, 95% CI -0.16 to 0.50, I(2) = 0%). There were no significant benefit for upper limb function (SMD 0.11, 95% CI -0.41 to 0.63, I(2) = 0%) and mobility (SMD 0.11, 95% CI -0.21 to 0.43, I(2) = 27%) after PRT compared with controls. CONCLUSIONS There was no evidence reported that PRT is unsafe in people within the first 3 months after stroke, although there was a lack of reporting about adverse events. The lack of demonstration of effect in improving muscle strength and activity suggests there is insufficient evidence to recommend the prescription of PRT for people within the first 3 months after stroke.
17 citations
TL;DR: Converging lines of evidence suggest that the cingulate cortex, which integrates and mediates sensory and motor response functions, contributes to affective coding throughout the pain experience.
Abstract: Publisher Summary This chapter reviews that different cortical areas participate in different aspects of pain sensation, perception, and pain-related behavior. Based on the weight of currently available evidence, it suggests that the activity in each of the cortical areas described contributes to different components of the pain experience: sensory discrimination, affective coding, and cognitive evaluation. Cortical participation is organized as temporally distributed bio-behavioral functions: (1) early identification, (2) recognition and immediate reaction, and (3) evaluation and sustained behavior. The chapter also reviews that all cortical areas discussed are active early in the course of the elaboration of pain, it is speculated that the clinical and behavioral impact of each cortical area varies at different times during the pain experience. Converging lines of evidence suggest that the cingulate cortex, which integrates and mediates sensory and motor response functions, contributes to affective coding throughout the pain experience.
17 citations
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TL;DR: A very strong direct relationship is reported between the amount of cortical reorganization and the magnitude of phantom limb pain (but not non-painful phantom phenomena) experienced after arm amputation, indicating that phantom-limb pain is related to, and may be a consequence of, plastic changes in primary somatosensory cortex.
Abstract: Although phantom-limb pain is a frequent consequence of the amputation of an extremity, little is known about its origin. On the basis of the demonstration of substantial plasticity of the somatosensory cortex after amputation or somatosensory deafferentation in adult monkeys, it has been suggested that cortical reorganization could account for some non-painful phantom-limb phenomena in amputees and that cortical reorganization has an adaptive (that is, pain-preventing) function. Theoretical and empirical work on chronic back pain has revealed a positive relationship between the amount of cortical alteration and the magnitude of pain, so we predicted that cortical reorganization and phantom-limb pain should be positively related. Using non-invasive neuromagnetic imaging techniques to determine cortical reorganization in humans, we report a very strong direct relationship (r = 0.93) between the amount of cortical reorganization and the magnitude of phantom limb pain (but not non-painful phantom phenomena) experienced after arm amputation. These data indicate that phantom-limb pain is related to, and may be a consequence of, plastic changes in primary somatosensory cortex.
1,692 citations
"REVIEW ■ : Reorganization of Sensor..." refers background or result in this paper
...This supposition is supported by evidence from non-invasive brain imaging studies in humans with forearm amputations that somatosensory cortex reorganizes, as in monkeys, with stump and face inputs reactivating hand cortex (23-25)....
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...Non-invasive imaging studies of somatosensory cortex in subjects with long-standing amputations of the forelimb reveal that hand cortex is responsive to inputs from the face and arm (23-25)....
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TL;DR: The cortical representations of the hand in area 3b in adult owl monkeys were defined with use of microelectrode mapping techniques 2–8 months after surgical amputation of digit 3, or of both digits 2 and 3.
Abstract: The cortical representations ofthe hand in area 3b in adult owl monkeys were defined with use of microelectrode mapping techniques 2-8 months after surgical amputation of digit 3, or of both digits 2 and 3. Digital nerves were tied to prevent their regeneration within the amputation stump. Suc cessive maps were derived in several monkeys to determine the nature of changes in map organization in the same individuals over time. In all monkeys studied, the representations of adjacent digits and pal mar surfaces expanded topographically to occupy most or all of the cortical territories formerly representing the amputated digit(s). With the expansion of the representations of these surrounding skin surfaces (1) there were severalfold increases in their magnification and (2) roughly corresponding decreases in receptive field areas. Thus, with increases in magnification, surrounding skin surfaces were represented in correspondingly finer grain, implying that the rule relating receptive field overlap to separation in distance across the cortex (see Sur et aI., '80) was dynamically maintained as receptive fields progressively decreased in size. These studies also revealed that: (1) the discontinuities between the representations of the digits underwent significant translocations (usually by hundreds of microns) after amputation, and sharp new discontinuous boundaries formed where usually separated, expanded digital representa tions (e.g., of digits 1 and 4) approached each other in the reorganizing map, implying that these map discontinuities are normally dynamically main tained. (2) Changes in receptive field sizes with expansion of representations of surrounding skin surfaces into the deprived cortical zone had a spatial distribution and time course similar to changes in sensory acuity on the stumps of human amputees. This suggests that experience-dependent map changes result in changes in sensory capabilities. (3) The major topographic changes were limited to a cortical zone 500-700 JIm on either side of the initial boundaries of the representation of the amputated digits. More dis tant regions did not appear to reorganize (i.e., were not occupied by inputs from surrounding skin surfaces) even many months after amputation. (4) The representations of some skin surfaces moved in entirety to locations within the former territories of representation of amputated digits in every
1,327 citations
"REVIEW ■ : Reorganization of Sensor..." refers background in this paper
...However, if several fingers were denervated, the representations of those fingers were not completely reactivated, and small zones of unresponsive cortex persisted (14)....
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TL;DR: The results show the need for a reevaluation of both the upper limit of cortical reorganization in adult primates and the mechanisms responsible for it.
Abstract: After limited sensory deafferentations in adult primates, somatosensory cortical maps reorganize over a distance of 1 to 2 millimeters mediolaterally, that is, in the dimension along which different body parts are represented. This amount of reorganization was considered to be an upper limit imposed by the size of the projection zones of individual thalamocortical axons, which typically also extend a mediolateral distance of 1 to 2 millimeters. However, after extensive long-term deafferentations in adult primates, changes in cortical maps were found to be an order of magnitude greater than those previously described. These results show the need for a reevaluation of both the upper limit of cortical reorganization in adult primates and the mechanisms responsible for it.
1,051 citations
Additional excerpts
...(20) C, caudal ; FA, forearm; M, medial....
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TL;DR: This rev iew addresses questions about the capacity of sensory and motor maps in the brains of adul t mammals to change as a resul t of alterations in the effectiveness of inputs, the availability of effectors, and direct damage.
Abstract: This rev iew addresses questions about t he capacity of sensory and motor maps in the brains of adul t mammals to change as a resul t of alterations in the effectiveness of inputs, the availability of effectors, and d irect damage. The issue of the mutabil ity of maps in adults is important because sensory and motor representations occupy much of the brains of mammals, regardless of the complexity and extent of neocortex (e.g. Kaas 1988, Wall 1988, Maunsell & Newsome 1987); behavioral recovery occurs after damage to central representations (e.g. Bor nschlegl & Asanuma 1987, Diirsteler et a11987, Eidelberg & Stein 1974); and such changes may relate to improvements in sensory and motor skills with experience (e.g. Gibson 1953). Tn addition, features of reorganization that are apparent in sensory and motor maps may characterize less easily studied areas of the brain. Specific questions addr essed in this review are as follows:
962 citations
TL;DR: This paper found that after the median nerve was transected and ligated in adult owl and squirrel monkeys, the cortical sectors representing it within skin surface representations in Areas 3b and 1 were completely occupied by 'new' and expanded representations of surrounding skin fields.
948 citations