| Objective: This study is a cross between clinical neurosurgery and cognitive neuroscience.It focused on the electrophysiological characters of resting-state electroencephalogram(EEG)from the patients,who underwent neurosurgical operation due to visual or auditory dysfunction.The study analysed: 1.the change in resting-state EEG from the patients who shortly have the space-occupying lesion pressing on optic chiasm removed,the change in visual function and the relationship between the change in EEG and the change in vision;2.the characters of resting-state EEG from the patients with visual loss due to space-occupying lesion pressing on optic chiasm,and the relationship between the EEG and visual function;3.the characters of resting-state EEG from the patients with unilateral acoustic neuroma and the relationship between the EEG and auditory function.The target of the study was at the electrophysiological mechanism in visual and auditory system,especially the function of alpha band,instead of any specific neurosurgical issue.Methods:The whole study consisted of three parts.Part A: nine patients were recruited.They suffered from space-occupying lesion in sellar region,which pressed the optic chiasm and lead to partial vision loss;they underwent neurosurgical procedure by endonasal trans-sphenoidal approach and had the lesion removed.After operation,they gradually got visual recovery.Visual acuity,visual field and resting-state EEG were tested for the patients before operation and shortly(3-7 days)after operation.Part B: seventeen patients were recruited.They suffered from space-occupying lesion in sellar region,which pressed the optic chiasm and lead to partial vision loss.Visual acuity,visual field and resting-state EEG were tested for the patients before operation;and resting-state EEG were collected from their matched healthy controls.Part C: five patients were recruited.They suffered from unilateral acoustic neuroma,which lead to tinnitus and hearing loss.Audiometric threshold and resting-state EEG were tested for the patients before operation;and resting-state EEG were collected from their matched healthy controls.Behavioral parameters included: visual acuity,which tested two eyes separately;“Mean deviation”,“Pattern standard deviation”,“Visual field index” and “Total deviation” were collected from visual field,which tested the central 30 degree visual field of the two eyes separately;audiometric thresholds,which were tested manually at 250 Hz,500 Hz,1k Hz,2k Hz,4k Hz and 8k Hz.Electrophysiological parameters were calculated from resting-state EEG.Resting-state EEG here referred to a scalp EEG recording from a seated,awake,eyes-closed,motionless subject in quiet and dimmed environment.Each raw resting-state EEG recording in this study lasted for 15 minutes.To analyze the resting-state EEG recordings,regions-of-interest(ROIs)were defined as occipital region,parietal region,frontal region and temporal region;EEG frequency bands were defined as classic bands,which included delta(1-3 Hz),theta(3-7 Hz),alpha 1(7-11 Hz),alpha 2(11-14 Hz),beta(14-30 Hz),gamma(30-40 Hz),alpha(7-14 Hz),and were additionally defined basing on individual peak alpha frequency(IPAF)as individual alpha frequency bands,which included individual alpha 1,individual alpha2 and individual alpha.After pre-processing,the data analysis of resting-state EEG consisted of spectral power analysis,functional connectivity analysis and network analysis.Spectral power of resting-state EEG was calculated by the Matlab function pwelch,according to each of the 10 frequency bands(7 classic bands+3 individual alpha bands)within each of the 4 ROIs.Coherence,an electrophysiological parameter to represent functional connectivity,was firstly calculated at each frequency between each pair out of the 30 EEG channels by the Matlab function mscohere;and was secondly averaged over frequency bands.In order to carry out network analysis,Brain Connectivity Toolbox was applied to calculate brain‘s functional “small-world”properties: strength,clustering coefficient(CC),and characteristic path length(CPL).As for statistic analysis,SPSS 23 was applied.With t-test,spectral power,coherence and network properties of resting-state EEG were compared between pre-and post-operation of the patients with optic chiasm pressed,separately(Part A).With t-test,spectral power,coherence and network properties of resting-state EEG were compared between the patients and their matched healthy controls,separately(Part B and Part C).With t-test,spectral power and coherence of resting-state EEG were compared between lesion-side hemisphere and contra-lesion-side hemisphere of the patients with acoustic neuroma,separately(Part C).Pearson Correlations were calculated between the change of behavioral parameters and the change of electrophysiological parameters of the patients with optic chiasm pressed,where the change lied in with or without the space-occupying lesion in sellar region(Part A).Pearson Correlations were calculated between the behavioral parameters and the electrophysiological parameters of the patients with optic chiasm pressed and of the patients with acoustic neuroma,separately(Part B and Part C).Results:Part A:1.The patients with visual dysfunction due to space-occupying lesion in sellar region got remarkable visual improvement after neurosurgical procedure by endonasal trans-sphenoidal approach.2.The spectral power of the post-operative resting-state EEG were significantly higher than that of the pre-operative resting-state EEG in occipital lobes(within theta,alpha 1 and alpha 2),in parietal lobes(within delta,theta,alpha 1 and alpha 2),in frontal lobes(within delta,theta,alpha 1 and alpha 2)and in temporal lobes(within theta and alpha 1),separately and correspondingly.The spectral power of individual alpha bands were higher in post-operative resting-state EEG than that in pre-operative EEG in parietal lobes and in frontal lobes at the level of p<0.01,while in occipital lobes and in temporal lobes at the level of p<0.05.3.The post-operative coherence between frontal lobes were significantly higher than the corresponding pre-operative coherence(within delta,theta,alpha 1 and alpha 2);and the post-operative coherence between frontal lobes and occipital lobes were significantly higher than the corresponding pre-operative coherence(within alpha 1and alpha 2).4.As a whole,the coherence between each pair of channels turned higher in post-operative resting-state EEG than in pre-operative EEG in theta and in alpha,while it turned lower in post-operative resting-state EEG than in pre-operative EEG in delta and in gamma.As a whole,the extent of the change in coherence in alpha band was most of all bands.5.From both pre-and post-operative resting-state EEG,the top 60 functional connectivity,which links had the strongest coherence,displayed both at midline or around midline regions and the peripheral regions of brain.The differences of the top60 functional connectivity distribution between pre and post-operative resting-state EEG showed an obvious pattern: comparing to pre-operative state,functional connectivity with relatively high coherence showed up in theta and alpha bands,linking occipital lobes with midline regions of brain shortly after operation.The top60 links,which improved coherence most shortly after operation,also distributed at midline or around midline regions of brain,connecting occipital lobes with parietal lobes and frontal lobes in delta,theta and alpha bands.6.Comparing to pre-operative state,post-operative functional network had a shorter CPL in alpha but a longer CPL in gamma.7.After operation,the more the patients improved their visual acuity,the more the spectral power improved in parietal lobes(in delta,theta and gamma),the more CC decreased in beta;the more the patients improved in visual field,the less the coherence between occipital lobes and frontal lobes in theta increased,or it even decreased.Part B:1.Comparing the patients with visual dysfunction due to space-occupying lesion in sellar region to their matched healthy controls,no statistically significant difference was found in the spectral power in the ROIs either within classic frequency bands or within individual alpha bands.2.The coherence between occipital lobes and frontal lobes within theta and beta bands in the patients‘ resting-state EEG were significantly lower than those in the matched controls‘,separately.3.Comparing to their matched healthy controls,the patients‘ functional network had a longer CPL in beta.4.The better the patients‘ visual fields were,the higher the coherence between parietal lobes in alpha 1 and in alpha were.Part C:1.The spectral power of the resting-state EEG from the patients with unilateral acoustic neuroma were significantly lower than that of the resting-state EEG from the matched controls in frontal lobes(within alpha 1,individual alpha 2 and individual alpha).2.The coherence between frontal lobes within theta band in the patients‘ resting-state EEG was significantly lower than that in the matched controls‘,while the coherence between temporal lobes within beta band in the patients‘ resting-state EEG was significantly higher than that in the matched controls‘.3.Comparing to their matched healthy controls,the patients‘ functional network had a shorter CPL in beta.4.The acoustic neuroma patients‘ resting-state EEG showed lower spectral power in frontal lobe in individual alpha 1 and in temporal lobe in individual alpha 2 in the lesion-side hemisphere than those in the contra-lesion-side hemisphere,separately.5.The acoustic neuroma patients‘ resting-state EEG showed a stronger coherence between parietal lobe and occipital lobe in alpha 2 in the lesion-side hemisphere than that correspondingly in the contra-lesion-side hemisphere.Conclusion: 1.Alpha band plays an important role in visual recovery shortly after the space-occupying lesion removed.2.Both the extent of visual function recovery shortly after operation and the extent of visual dysfunction with long-term space-occupying lesion‘s pressure correlated with the electrophysiological markers in parietal lobes.3.Unilateral acoustic neuroma changed the functional connectivity between parietal lobe and occipital lobe.Alpha band might play a key role in setting up functional links with occipital lobes,in order to integrate information. |
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