| Background and purposeThe plasticity of human brain is the capacity of human to adapt to the environment.In the 1940 s,Donald hebb proposed a theoretical mechanism for synaptic plasticity.But much of the research on persistent changes in vertebrate neurons has been based on non-physiological experiments on brain cells,without human observation.Brain reorganization has been reported in the motor and sensory areas in human amputees.Alteration in brain structures of amputees can be observed by resting state fMRI,and then the theory of brain remodeling can be verified: the basic structure of nerve components exists,but the connection between nerve components changes.It can also explore relevant change sites as a monitoring indicator for further research.ALFF,fALFF,ReHo,DC and VMHC were used to study the changes in the brain after amputation for different scales,such as the spontaneous activity of neurons,the function of local neural network,and the neural activity in homologous brain regions.By studying the changes of corpus callosum through DTI technology,the changes of corpus callosum as the white matter structure connecting the two hemispheres of the brain after amputation were understood.Based on these,we hypothesis:(1)after amputation,the frequency of neural activity in corresponding brain regions will change;(2)after the amputation,the local consistency and degree center of brain area may be altered.(3)after amputation,the homotopic connection of both hemispheres of the brain will change;(4)specific corpus callosum subregion is involved in the brain reorganization process after lower limb amputation;(5)the white matter fiber bundles through these specific subregions will also be affected.Material and method1.Twelve adult patients with unilateral lower limb amputations and their corresponding normal controls were enrolled,and their resting state functional magnetic resonance images and high-resolution T1 structure images were taken.Using SPM8 software and DPABI software,ALFF and fALFF images of the two groups were calculated.The spontaneous activity patterns of brain regions were compared within the groups,and the differences between the amputee group and the normal control group were understood.2.Using the MRI data in the first part,ReHo and DC images of the two groups were calculated.The function of local neural network in the amputee group and the normal control group was compared between the two groups.3.Thirty-seven adult patients with unilateral lower limb amputations were recruited and compared with the normal population distribution.The amputation group was divided into left lower limb amputation group,right lower limb amputation group and normal control group.Static functional magnetic resonance images and high resolution T1 structure images were collected.Three sets of VMHC images are calculated using the software package.The changes of activity patterns in homologous brain areas were compared between the left lower limb amputation group and the normal control group,and the differences of spontaneous neural activity between the left lower limb amputation group and the normal control group were investigated.The mean VMHC changes in the left lower limb amputation group were calculated,and the VMHC values were correlated with the amputation time to understand whether the two were correlated.4.Thirty-seven adult patients with unilateral lower limb amputations were recruited and compared with normal population distribution to collect high-resolution T1 structural phase data and DTI data.Morphological indexes such as thickness and area of each subregion of the corpus callosum were measured on T1 structural phase data using the C8 toolkit.Process DTI data using FSL kit.Using diffusion tensor analysis toolkit(diffusion tensor analysis toolkit,FDT)computing generates each corpus callosum dispersion parameters of the images.FSL PDT tools were used to generate nerve fiber bundles connecting related regions,and the average DTI parameters(FA,AD,RD and MD)of each individual fiber bundle were extracted.The differences in multimodality measurements in each subregion between amputees and normal controls were compared.Finally,the relationship between clinical variables(amputation time and phantom limb pain levels)and imaging measurements in all patients was investigated using Spearman correlation analysis with age and gender modification.Results1.ALFF has more imaging interference in the cistern region,and fALFF can effectively reduce the impact of physiological noises of non-brain electrical activity in the cistern on ALFF results.Consistent with fALFF results,ALFF and fALFF results show increased activity in the posterior cingulate gyrus,precuneus,frontal lobe,parietal lobule and other areas.No significant differences in brain area were found after independent sample t test of ALFF and fALFF images in two groups of patients.2.ReHo and DC activity patterns were consistent with fALFF results,showing increased activity in areas such as posterior cingulate gyrus,precuneus,frontal lobe,and parietal lobule,and no significant differences in brain areas were found after independent sample t test of ReHo images and DC images in two groups of patients.3.There was no significant difference between the left lower limb amputation group and the right lower limb amputation group after independent sample t test.Between the left lower limb amputation group and the normal control group,there was a significant increase in the synchronous activities of bilateral lingual gyrus,precuneus,cuneus,calcarine,parietal_sup,occipital_sup,occipital_mid,occipital_inf.Results the comparison correction of permutation multiple through threshold-free cluster enhancement.The results of Pearson correlation between average VMHC value and amputation time in the lower limb amputation group showed no significant correlation,p=0.874.4.There were no statistically significant differences in morphological measurements of each subregion of the corpus callosum between the amputee group and the control group.DTI analysis of amputee patients showed that AD,RD and MD in the area of corpus callosum II had larger values than those in the healthy control group(P<0.05 after correction).Compared with the healthy control group,area II of the amputee group showed a decreased FA,but did not pass multiple comparison correction(p = 0.07 after correction).The results of fiber tracer imaging analysis showed that the average FA value of nerve fibers connecting both BA6 regions of amputees decreased significantly(p = 0.008),AD,RD and MD values increased significantly(p <0.001).After multiple comparison correction,there was no significant difference in the values of nerve fibers,FA,AD,RD and MD that connect the primary motor cortex and somatosensory cortex.Conclusion1.In amputees with prostheses,there was no comparison in the level of spontaneous neural activity.The neural activity function at the voxel level is consistent with that of normal people.2.The consistency of local neural activity and degree centrality of local neural network did not change in amputees using prosthesis.At this local neural network level,the function of amputees is the same as that of normal people,and is not damaged.3.Between the left lower limb amputation group and the normal control group,there was a significant increase in bilateral lingual gyrus,precuneus,cuneus,calcarine,parietal_sup,occipital_sup,occipital_mid,occipital_inf.Analysis of this may be due to the lack of feedback of somatosensory nerve in the brain after amputation.In the use of prostheses,more dependent visual information is modified,resulting in increased synchronous activity in related visual and visual integration areas.4.FA values were found to be less than those of the normal control group while AD,RD and MD were greater than those of the normal control group.The tracer imaging analysis also detected similar changes in nerve fibers passing through the subregion of corpus callosum II,which connects the premotor PMC and the auxiliary motor SMA.In comparison,the macroscopic morphological structure of the total area or average thickness was different.It was proposed that the abnormality of nerve fiber dispersion parameters in corpus callosum could be used as a sensitive indicator for follow-up when detecting the brain changes in patients after amputation. |
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