| Objective: There is a sensitive period(2-4 years after birth)that exists for optimal central auditory development due to heightened levels of neuroplasticity.During this period,the auditory stimulation can affect the development of white matter and cortical function to the greatest extent.Thus far,little is known about the brain development trajectory in sensorineural hearing loss(SNHL)patients within this sensitive period.Studying the effect of hearing loss on the brain structural and functional remodeling in this special time window is of great significance to the comprehensive understanding of brain development after deafness,and can provide further neuroimaging basis for the preoperative screening of cochlear implantation(CI).Multimodal magnetic resonance analysis is an important part of radiomics,which includes blood oxygen level-dependent functional magnetic resonance(f MRI)and diffusion tensor imaging(DTI).These techniques can be used to study the effects of diseases on brain function and structure in vivo.In recent years,multimodal magnetic resonance analysis has been widely used in studying the neuropathological mechanism of patients with hearing loss.It has been found that the structure or function of some brain regions can be used as neuroimaging markers to predict language function after CI.However,most of these studies focus on subjects with a relatively long course of hearing deprivation.These subjects are older than the critical stage of auditory cortex development plasticity,and their cortex development has beyond maximum plasticity.In this study,DTI and rs-FC analysis were used to analyze the development of white matter microstructures and the functional reorganization of the auditory cortex,and also the changes of intra-and inter-network functional connectivity based on the level of brain network during the sensitive period of developmental plasticity.The aim of this study is to explore the effects of auditory loss on the development of white matter structure and cortical function in this special time window.At the same time,DTI technique was used to investigate the changes of white matter microstructures in auditory conduction pathways of children with SNHL at different ages in order to improve the understanding of the effects of hearing loss at different developmental stages on white matter structure.Methods: In the first and second part of this study,46 children(mean age 17.59 months)with bilateral profound SNHL under three years old and 33 age-matched control infants(mean age 18.55 months)were enrolled.All the subjects were given chloral hydrate orally before scanning,and were scanned with Siemens Verio Tim 3.0T MR after sleeping.The collected data are processed as follows: 1.DTI data: The anisotropic fraction(FA)of white matter in the whole brain was compared by the tract–based spatial statistics(TBSS)analysis.2.Resting-state f MRI data: The resting-state functional connectivity method was used,and the left and right primary auditory cortex(A1)were used as seed regions for comparing the whole brain functional connectivity between groups.3.Using independent component analysis(ICA)method,six resting-state brain networks of interest were identified: auditory network,visual network,sensorimotor network,default mode network,frontal network and salience network.The differences of functional connections within and between networks were compared.In the third part of this study,16 children with SNHL less than 3 years old(mean age 18.66 months),16 children with SNHL older than 3 years old(mean age 53.67 months)and 16 infants in the each control group matched with sex and age of each SNHL group were included.All the subjects took chloral hydrate orally before scanning,and then performed conventional MRI and DTI scanning with Siemens Verio Tim 3.0T magnetic resonance after sleeping.For DTI data,we selected bilateral white matter below superior temporal gyrus,bilateral white matter below transverse temporal gyrus,bilateral auditory radiation and bilateral inferior colliculus as regions of interest to measure FA values,and compared them between SNHL group and control group at different ages.Results: 1.DTI data with TBSS analysis: Compared with the control group,SNHL group showed extensive white matter FA reduction,including bilateral superior longitudinal tract,inferior fronto-occipital tract,inferior longitudinal tract,right corticospinal tract,posterior thalamic radiation and left uncinate tract(p < 0.05,FWE correction).In contrast,the SNHL group did not show areas with increased FA values.2.Resting state functional connectivity analysis: intra-group comparison showed that left and right A1 seed regions in SNHL group and control group both showed extensive positive functional connectivity.These regions with significant connections to seed regions include bilateral superior temporal gyrus,middle temporal gyrus,insula,inferior frontal gyrus,angular gyrus and inferior parietal lobule(p < 0.05,FDR correction),which mainly covered auditory network,salience network and default mode network.Further more,there were differences in functional connectivity between the two groups with A1 seed regions.Compared with the control group,the functional connectivity of the right superior temporal gyrus and right insula was significantly enhanced(p < 0.05,FDR correction)when left A1 was the seed region.In addition,when the seed region was right A1,the functional connectivity of the right superior temporal gyrus and right insula increased significantly(p < 0.05,FDR correction).Compared with the control group,there was no area showed decreased functional connectivity in SNHL group.3.Independent component analysis of resting-state f MRI: Compared with the control group,the intra-network functional connectivity of the right inferior parietal lobule in default mode network decreased significantly in SNHL group(p < 0.05,FDR correction).The intra-network functional connectivity of the left insular lobe in auditory network,the left parahippocampus and the right anterior cingulate gyrus in the salience network increased significantly(p < 0.05,FDR correction).No significant changes in functional connectivity were found in the visual and sensorimotor networks.In addition,we found 7 significant connections between the brain networks of the control group,including four positive functional connections and three negative functional connections.In SNHL group,we found 12 significant connections between brain networks,including 5 positive functional connections and 7 negative functional connections.Further comparisons between the two groups showed that the functional connectivity between visual network and default mode network,auditory network and frontal network in SNHL group were significantly stronger than that in control group(p < 0.05,uncorrected).In the control group,there was no significant connection between the two networks,but there was a significant positive correlation in the SNHL group.4.DTI analysis of auditory conduction pathway in different age groups: there were significant differences in bilateral inferior superior temporal gyrus white matter,bilateral inferior transverse temporal gyrus white matter,bilateral auditory radiation and bilateral inferior colliculus FA values between below 3-year-old group and corresponding control group(p < 0.05).Compared with the control group,the FA value of white matter below the left temporal transverse gyrus had statistical difference(p < 0.05)in SNHL group older than 3-year-old.Conclusions: 1.In this study,we used multimodal magnetic resonance analysis to investigate the changes of white matter microstructures and auditory cortex functional connectivity in children with bilateral profound SNHL before 3 years old.It was found that the changes of white matter microstructures in SNHL children were mainly involved in auditory and linguistic pathways,which may reflect the delayed development of white matter in SNHL children.In addition,the functional connectivity between the primary auditory cortex and the brain areas related to auditory and linguistic networks was enhanced in SNHL group,which may reflect the functional compensation reorganization of the cerebral cortex after hearing loss.Our results provide new insights into the brain development trajectory of SNHL infants during early sensitive period.2.ICA technique was used to detect the characteristics of brain network development in children with bilateral profound SNHL within early sensitive period.It was found that compared with the control group,SNHL group showed decreased functional connectivity within default mode network,enhanced functional connectivity within auditory network and salience network.Further more,enhanced functional connectivity was found between visual-default mode network and auditory-frontal network,which suggested that the loss of intra-network functional connectivity and the compensatory reorganization of intra-network and inter-network functional connectivity coexist in SNHL infants within early sensitive period.It provides a new basis for understanding the brain development trajectory after hearing loss within early sensitive period at the level of brain network.3.DTI technique was used to quantitatively detect the changes of white matter microstructures in brain auditory conduction pathway.FA values of all ROIs in the auditory conduction pathway were decreased in SNHL group below 3 years old,while only FA value in the white matter beneath the left temporal transverse gyrus was decreased in the group age over 3 years old.These results suggested the delayed development of white matter myelination in the auditory pathway of children with SNHL.It might provide a new imaging basis for the view that early effective auditory stimulation is beneficial to maintaining or promoting the normal process of white matter myelination. |
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