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Study shows brain maintains internal:
New evidence of the IRM show that the cards of the hands and lips of the brain remain stable years after amputation, reshaping our understanding of neuroplasticity and guiding future strategies of prosthesis and rehabilitation.
Study: stable cortical cards before and after the amputation of the arm. Consequently, Image credit: seventy-five / shutterstock
In a recent study published in Nature neuroscienceA group of researchers has tested if the amputation of the adult arm triggers a large -scale cortical reorganization by following the representations of the hands. For example, lips with functional magnetic resonance imaging (IRM) before and up to 5 years after surgery.
Background
For decades, the students learned that after a lost hand, the face invades its territory in the brain. However, the amputees feel lively ghost fingers study shows brain maintains internal and can try to move them, suggest preserved cards. Moreover, Classical animal studies and early human imagery have supported an in -depth reorganization in the primary somatosensory cortex (S1). Furthermore, More recent human work indicates stability, with engaging ghost movements of manual models.
The authors also emphasize that ghost activity can be confirmed by residual muscle contractions of the members. For example, indicating real motor attempts rather than imagined actions. For example, The field lacks longitudinal data depending on the same people through surgery. Similarly,
Comparisons of affected. In addition, unassigned hemispheres and replication in the primary engine cortex (M1) are essential to reconcile models, and additional research is necessary to identify who reorganizes, when and why.
About the study
Three adults planned for unilateral arm amputation (P1. However, P2, P3) were studied twice before surgery and 3 months, 6 months and monitoring (1.5 years for study shows brain maintains internal P1; 5 years for P2). In addition, Sixteen valid witnesses (CTRL) were scanned at four sessions over 6 months. Consequently, A distinct group of 22 younger witnesses was also analyzed for P1.
A group of chronic amputees (n = 26) has provided a context. However, IRM was acquired on a 3 Tesla scanner. For example, The weighted magnetization in T1 has prepared a rapid acquisition gradient. Consequently, an echo plane imaging and a level of blood oxygenation (bold) echo, the flat imagery was collected (repetition time (TR) 1.5 s, echo time (TE) 35 ms, field of vision (FOV) 212 mm, Isotropic Voxels 2 mm).
During digitization. In addition, the participants carried out movements of each finger, lips and feet; After surgery, they attempted movements of the ghost hand and carried out scans of images control. Nevertheless, The analyzes focused on S1, the Brodmann 3B (BA3B) area, with replication in M1. study shows brain maintains internal Therefore, A general linear model (GLM) Beta weight of the estimated state.
Multivoxel analyzes have included the decoding of the Vector of Support (SVM) through sessions. Consequently, the similarity of representation (RSA) using Mahalanobis distances with crossed validation. Furthermore, Definitions of the region of interest (king). However, center of gravity (COG) and smoothing parameters (full width with a maximum of half (FWHM) 3 mm) followed the procedures.
4.5). Participants agreed that their image reproduced. Brain illustrations have been created in Biorender. »>
Study shows brain maintains internal
Study results
Through the sessions extending before. after surgery, the three cases of cases generated sensations of the ghost hand and could try to attempt ghost finger movements; The ghost movement has produced a stronger activity than imagining a movement and was accompanied study shows brain maintains internal by residual muscle contractions in the strain, confirming real engine control.
The activity of the hand and lips in the missing hand hemisphere was followed over time using paired tasks. COG displacements for the fingers of the hand. individual fell into the CTRL distribution valid at 6 months, and the Voxelwise finger models before amputation were strongly correlated with those of the final scan.
The decoders formed on the classified preamputation finger pairs of post-growth models above chance. and the RSA with distances from validated Mahalanobis has confirmed a significant consistency between sessions, including long-term follow-ups. Together, these multivoxel measures indicate the stability of the hand map in S1, with similar evidence in M1.
The study also tested a central prediction of remapping: increased activity of lips in the region of private S1. expansion of the limits of the lips map to the territory of the hand. None of the study shows brain maintains internal two diagrams emerged. Through the points of time. the univariate activity of the lips in the hand region remained in the CTRL range, the cog in the lips did not derive towards the hand and the limits of the lip card showed no expansion.
A participant (P2) has shown a temporary increase in the distance of representation of the lips. the couple at 6 months, who returned to the 5 -year -old beach. Compared to a chronic cohort of amputees (n = 26; approximately 23.5 years since the amputation). a cohort of secondary CTRL (n = 18), the ghost cogs of the participants and the lips of the participants fell into group distributions and the activity of the lips in the region of hand S1 corresponded to the chronic amputated model.
The authors note that some participants in the case showed slightly. but not significantly, a higher lip activity study shows brain maintains internal than chronic amputees.
Transitional differences have been detected but were idiosyncratic rather than systematic. At 6 months, P1 showed a temporary reduction in the average fingers compared to the CTRL which returned to the 1.5 -year -old beach; P3 has shown a similar transitional reduction in decoding to 6 months. P2 had already reduced classification accuracy before surgery due to an altered engine control. which complicates the interpretation of post -mputation changes.
The authors note that certain transitional reductions have not survived the statistical correction. can reflect the variability in sampling of the classifier between long intervals. In the unconnected hemisphere. the intact selectivity of the fingers by hand and the metrics of the lips showed a typical variability of session / session compared to the CTRL.
A separate analysis revealed that for the missing hand. only P3 showed a brief reduction in the average inter-deigits correlation at 3 months, study shows brain maintains internal which normalized 6 months.
Overall. longitudinal evidence demonstrates stable cortical cards by hand and lips through amputation, with only brief and specific reductions to participants near the early post-extension window.
Study shows brain maintains internal
Conclusions
In adults. the amputation of the arm has not triggered a large -scale remapping of S1 or M1. The representations of the hands. Additionally, the LIP cards have remained topographically stable, while the multivoxel structure could be decoded through surgery, with briefs hollow after amputation.
The results support a deeper conceptual change: S1 is not a passive relay of the peripheral input but maintains an internal. resilient body model which persists even after the sensory loss. This stability is clinically important because it supports training strategies that take advantage of intact hands representations for prosthetic control. targeted neurostimulation or sensory feedback. The longitudinal design, the small sample and the generalization of the study shows brain maintains internal adult cohort and the plasticity of children can differ.
Future work should test various etiologies. ages and rehabilitation routes to determine when cortical cards are reorganized and how interventions shape the results.
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