Bayesian fMRI data analysis with sparse spatial basis function priors

In previous work we have described a spatially regularised General Linear Model (GLM) for the analysis of brain functional Magnetic Resonance Imaging (fMRI) data where Posterior Probability Maps (PPMs) are used to characterise regionally specific effects. The spatial regularisation is defined over regression coefficients via a Laplacian kernel matrix and embodies prior knowledge that evoked responses are spatially contiguous and locally homogeneous. In this paper we propose to finesse this Bayesian framework by specifying spatial priors using Sparse Spatial Basis Functions (SSBFs). These are defined via a hierarchical probabilistic model which, when inverted, automatically selects an appropriate subset of basis functions. The method includes non-linear wavelet shrinkage as a special case. As compared to Laplacian spatial priors, SSBFs allow for spatial variations in signal smoothness, are more computationally efficient and are robust to heteroscedastic noise. Results are shown on synthetic data and on data from an event-related fMRI experiment.     

丘脑性失语患者的认知功能训练

背景由于丘脑与认知功能有关,如何对丘脑性失语进行语言康复训练,是很多康复工作者关心的热点问题之一.目的探讨认知功能训练对丘脑失语患者的治疗作用.设计病例分析.单位河南省新乡市中心医院神经内科.对象选取1999-06/2002-08在新乡市中心医院神经内科住院的均经头颅CT、MRI证实为丘脑卒中的患者30例,这些患者均伴有失语及认知功能障碍,均为高中毕业,其中男16例,女14例;脑出血13例,脑梗死17例,随机分为治疗组和对照组,每组15例.方法所选病例均进行神经内科常规药物治疗,包括抗炎、限液、脱水、支持等治疗.两组均接受语言训练,包括听理解训练、口语表达训练、阅读训练、书写训练(一对一方式,1次/d,30 min/次),治疗组患者在此基础上接受认知神经心理法训练(一对一方式,1次/d,45 min/次),共治疗2个月.治疗前后语言能力的评估选用北京医科大学附属第一医院神经内科的标准化汉语失语检查法中有代表性的7个项目(信息量、流利性、复述、是非题、听辨认、口头指令、选词填空)进行评估.采用简易精神状态量表评估认知功能.主要观察指标两组患者治疗前后信息量、流利性、是非题、复述、听辨认、口头指令、选词填空、简易精神状态量表得分.结果30例患者全部进入结果分析.治疗组与对照组治疗前在语言及认知功能评分方面差异无显著性意义(P＞0.05).治疗后治疗组语言功能及认知功能恢复程度均较对照组差异有显著性意义(P＜0.05).其中复述、听理解能力评分明显高于对照组[(72.6±24.5),(41.2±16.1)分;(63.7±17.8),(35.8±14.9)分,P＜0.01].结论丘脑性失语患者进行语言训练的同时进行认知训练可提高语言恢复能力,在进行语言训练时,应将认知训练纳入失语患者常规治疗中.     

丘脑性失语患者的认知功能训练

背景：由于丘脑与认知功能有关,如何对丘脑性失语进行语言康复训练,是很多康复工作者关心的热点问题之一.目的：探讨认知功能训练对丘脑失语患者的治疗作用.设计：病例分析.单位：河南省新乡市中心医院神经内科.对象：选取1999-06/2002-08在新乡市中心医院神经内科住院的均经头颅CT、MRI证实为丘脑卒中的患者30例,这些患者均伴有失语及认知功能障碍,均为高中毕业,其中男16例,女14例;脑出血13例,脑梗死17例,随机分为治疗组和对照组,每组15例.方法：所选病例均进行神经内科常规药物治疗,包括抗炎、限液、脱水、支持等治疗.两组均接受语言训练,包括听理解训练、口语表达训练、阅读训练、书写训练（一对一方式,1次/d,30 min/次）,治疗组患者在此基础上接受认知神经心理法训练（一对一方式,1次/d,45 min/次）,共治疗2个月.治疗前后语言能力的评估选用北京医科大学附属第一医院神经内科的标准化汉语失语检查法中有代表性的7个项目（信息量、流利性、复述、是非题、听辨认、口头指令、选词填空）进行评估.采用简易精神状态量表评估认知功能.主要观察指标：两组患者治疗前后信息量、流利性、是非题、复述、听辨认、口头指令、选词填空、简易精神状态量表得分.结果：30例患者全部进入结果分析.治疗组与对照组治疗前在语言及认知功能评分方面差异无显著性意义（P＞0.05）.治疗后治疗组语言功能及认知功能恢复程度均较对照组差异有显著性意义（P＜0.05）.其中复述、听理解能力评分明显高于对照组[（72.6&;#177;24.5）,（41.2&;#177;16.1）分;（63.7&;#177;17.8）,（35.8&;#177;14.9）分,P＜0.01].结论：丘脑性失语患者进行语言训练的同时进行认知训练可提高语言恢复能力,在进行语言训练时,应将认知训练纳入失语患者常规治疗中.     

Experiences of participation in goal setting for people with stroke-induced aphasia in Norway. A qualitative study

Purpose: The body of research into client participation in aphasia rehabilitation is increasing, but the evidence on how it is implemented into clinical practice is still scarce. Particularly, the importance of including the “insider's perspective” has been demanded. The aim of this study was to explore how people with aphasia experienced client participation during the process of goal setting and clinical decision making in language rehabilitation.

Methods: Fifteen people with stroke-induced aphasia participated in semi-structured in-depth interviews. A qualitative analysis using Systematic Text Condensation was undertaken.

Results: Analysis revealed four main themes: (1) pleased with services, (2) vagueness in language rehabilitation, (3) personal goals exist, and (4) desired level of participation.

Conclusion: Even though people with stroke-induced aphasia overall are pleased with the language rehabilitation, there is a need for greater emphasis on making the framework of language rehabilitation less vague. Therapists should also spend more time on collaboration with people with stroke-induced aphasia and use available methods to support communication and collaboration. The findings underscore the need for further exploration of the potential outcomes of implementing client participation in goal setting and clinical decision making for persons with stroke-induced aphasia.

• Implications for rehabilitation

• All persons with stroke induced aphasia should be asked about their goals for rehabilitation not only once, but during the whole continuum of their rehabilitation journey.

• Rehabilitation professionals should place greater emphasis on client participation by asking people with stroke induced aphasia how they prefer to participate at different stages of rehabilitation.

• To ensure active participation for those who wants it, existing tools and techniques which promoted collaborative goal setting should be better incorporated.

     

A general statistical analysis for fMRI data.

We propose a method for the statistical analysis of fMRI data that seeks a compromise between efficiency, generality, validity, simplicity, and execution speed. The main differences between this analysis and previous ones are: a simple bias reduction and regularization for voxel-wise autoregressive model parameters; the combination of effects and their estimated standard deviations across different runs/sessions/subjects via a hierarchical random effects analysis using the EM algorithm; overcoming the problem of a small number of runs/session/subjects using a regularized variance ratio to increase the degrees of freedom.     

Nonadditive two-way ANOVA for event-related fMRI data analysis

A significant recent development in functional magnetic resonance imaging (fMRI) is the introduction of event-related fMRI, also known as time-resolved fMRI. Because the exact shape of the MR response in an event-related fMRI experiment is often not known, traditional methods developed for block design experiments, such as t test and correlation analysis, are not well-suited for extracting activated pixels from the event-related data. In this work, a statistical technique based on nonadditive two-way analysis of variance is developed for use in event-related studies. Theoretical and experimental work were carried out for establishing a statistical threshold to determine pixel activation. Experimental studies were performed to demonstrate the utility of this approach.     

Correlator beware: correlation has limited selectivity for fMRI data analysis

Groups of time-courses created from fMRI data by the frequently used correlation analysis are often highly heterogeneous. This heterogeneity is due to the limited selectivity of correlation when trying to match brain time-courses to an externally imposed activation paradigm. Thus, this process unnecessarily generates many type I errors (false positives). Furthermore, as a consequence of the heterogeneity, time-courses identified and grouped by correlation may in fact describe different activations. After demonstrating this inadequacy, we give one particular approach to partition such a heterogeneous group into internally more homogeneous subgroups, using Kendall's coefficient of concordance W, and show its applicability and application to both simulated and in vivo data. Such group partition and "purification" will help subsequent inferential methods to deal more efficiently with false positives.     

Using voxel-specific hemodynamic response function in EEG-fMRI data analysis

Most existing analytical techniques for EEG-fMRI data need specific assumptions about the hemodynamic response function (HRF). These assumptions may not be appropriate when the HRF varies from subject to subject or from region to region. In this article, we introduce a deconvolution method for EEG-fMRI activation detection, which can be implemented with voxel-specific HRFs. A comparison of performance is made between three fixed HRFs and the deconvolution method under the framework of the general linear model. The main results are as follows: (1) the volume of detected regions from the deconvolved HRFs is larger. (2) In some subjects, the deconvolution technique can find areas of activation that have not been detected with the three fixed HRFs at our threshold of significance. (3) Deconvolution obtained higher adjusted coefficients of multiple determination compared to those obtained with the three fixed HRFs. The results suggest that the fixed HRF methods may not be the most appropriate for the analysis of epileptic activity with EEG-fMRI, and the deconvolution method may be a better choice.     

Detection and detrending in fMRI data analysis

This article addresses the impact that colored noise, temporal filtering, and temporal detrending have on the fMRI analysis situation. Specifically, it is shown why the detection of event-related designs benefit more from pre-whitening than blocked designs in a colored noise structure. Both theoretical and empirical results are provided. Furthermore, a novel exploratory method for producing drift models that efficiently capture trends and drifts in the fMRI data is introduced. A comparison to currently employed detrending approaches is presented. It is shown that the novel exploratory model is able to remove a major part of the slowly varying drifts that are abundant in fMRI data. The value of such a model lies in its ability to remove drift components that otherwise would have contributed to a colored noise structure in the voxel time series.     

缺血性脑卒中所致假性延髓麻痹患者短期预后的相关影响因素

目的:回顾性分析缺血性脑卒中所致假性延髓麻痹短期预后的相关影响因素,筛选出预测指标,以指导早期干预措施和治疗方案。方法:选择2004-05/2005-04在哈尔滨医科大学附属第二医院神经科住院的急性缺血性脑卒中患者中发生假性延髓麻痹的患者126例,均自愿参加观察。选择患者的性别、年龄、既往史(高血压史、糖尿病史、冠状动脉粥样硬化性心脏病史、脑卒中次数、吸烟史、饮酒史)、入院时检查(血压、血糖、胆固醇、三酰甘油、纤维蛋白原)、假性延髓麻痹类型、偏瘫程度、合并感染、合并电解质紊乱、头CT或MRI病灶数18个因素进行单因素分析;应用Logistic模型分析影响疾病短期预后的相关因素和预测因素。入院后正规治疗20d,第21天评价短期预后。显效为假性延髓麻痹症状基本消失,能顺利进食流质食物;好转为能顺利进食固体食物,但进食流质食物仍有呛咳。短期预后好为显效和好转的患者,短期预后差为无变化、恶化和死亡的患者。结果:患者126例全部进入结果分析,无脱落。①单因素分析结果:短期预后好组患者84例,短期预后差组患者42例,单因素分析结果显示两组患者有7个因素差异具有显著性意义(P<0.05),包括年龄、脑卒中次数、假性延髓麻痹类型、偏瘫程度、合并感染、合并电解质紊乱、CT或MRI病灶数。②Logistic模型分析结果:合并感染、完全性假性延髓麻痹、年龄大、CT或MRI病灶数多、合并电解质紊乱是短期预后差的具有预测意义的影响因素。结论:患者的年龄、假性延髓麻痹类型、合并感染、合并电解质紊乱、CT或MRI病灶数在一定程度上能够预测缺血性脑卒中所致假性延髓麻痹短期预后的发展趋势。对有此趋势的患者应早期干预、充分救治。     

缺血性脑卒中所致假性延髓麻痹患者短期预后的相关影响因素

目的：回顾性分析缺血性脑卒中所致假性延髓麻痹短期预后的相关影响因素，筛选出预测指标，以指导早期干预措施和治疗方案。方法：选择2004-05／2005—04在哈尔滨医科大学附属第二医院神经科住院的急性缺血性脑卒中患者中发生假性延髓麻痹的患者126例。均自愿参加观察。选择患者的性别、年龄、既往史（高血压史、糖尿病史、冠状动脉粥样硬化性心脏病史、脑卒中次数、吸烟史、饮酒史）、入院时检查（血压、血糖、胆固醇、三酰甘油、纤维蛋白原）、假性延髓麻痹类型、偏瘫程度、合并感染、合并电解质紊乱、头CT或MRI病灶数18个因素进行单因素分析；应用Logistic模型分析影响疾病短期预后的相关因素和预测因素。入院后正规治疗20d，第21天评价短期预后。显效为假性延髓麻痹症状基本消失，能顺利进食流质食物；好转为能顺利进食固体食物，但进食流质食物仍有呛咳。短期预后好为显效和好转的患者，短期预后差为无变化、恶化和死亡的患者。结果：患者126例全部进入结果分析，无脱落。①单因素分析结果：短期预后好组患者84例，短期预后差组患者42例，单因素分析结果显示两组患者有7个因素差异具有显著性意义（P〈0．05），包括年龄、脑卒中次数、假性延髓麻痹类型、偏瘫程度，合并感染、合并电解质紊乱、CT或MRI病灶数。②Logistic模型分析结果：合并感染、完全性假性延髓麻痹、年龄大、CT或MRI病灶数多、合并电解质紊乱是短期预后差的具有预测意义的影响因素。结论：患者的年龄、假性延髓麻痹类型，合并感染、合并电解质紊乱、CT或MRI病灶数在一定程度上能够预测缺血性脑卒中所致假性延髓麻痹短期预后的发展趋势。对有此趋势的患者应早期干预、充分救治。     

脑卒中失语病人言语功能恢复的分析与对策

目的分析首次发病失语症病人近期结局的影响因素,为制定有效的康复治疗和功能训练方案提高理论依据。方法采用回顾性问卷法对32例脑卒中失语病人进行评价,所得资料进行单因素分析和多元逐步回归分析。结果发现失语症的预后与发病的严重程度、病灶范围大小、年龄、失语症的种类及康复治疗开始的时间、方法等因素有关。结论针对病人失语症的特点进行康复治疗和功能训练且尽早介入对提高脑卒中失语病人的言语功能恢复率有重要意义。     

Structure-seeking multilinear methods for the analysis of fMRI data

In comprehensive fMRI studies of brain function, the data structures often contain higher-order ways such as trial, task condition, subject, and group in addition to the intrinsic dimensions of time and space. While multivariate bilinear methods such as principal component analysis (PCA) have been used successfully for extracting information about spatial and temporal features in data from a single fMRI run, the need to unfold higher-order data sets into bilinear arrays has led to decompositions that are nonunique and to the loss of multiway linkages and interactions present in the data. These additional dimensions or ways can be retained in multilinear models to produce structures that are unique and which admit interpretations that are neurophysiologically meaningful. Multiway analysis of fMRI data from multiple runs of a bilateral finger-tapping paradigm was performed using the parallel factor (PARAFAC) model. A trilinear model was fitted to a data cube of dimensions voxels by time by run. Similarly, a quadrilinear model was fitted to a higher-way structure of dimensions voxels by time by trial by run. The spatial and temporal response components were extracted and validated by comparison to results from traditional SVD/PCA analyses based on scenarios of unfolding into lower-order bilinear structures.     

Structural analysis of fMRI data: a surface-based framework for multi-subject studies

We present a method for fMRI data group analysis that makes the link between two distinct frameworks: surface-based techniques, which process data in the domain defined by the surface of the cortex, and structural techniques, which use object-based representations of the data as opposed to voxel-based ones. This work is a natural surface-based extension of the volume-based structural approach presented in a previous paper. A multi-scale surface-based representation of individual activation maps is first computed for each subject. Then the inter-subject matching and the activation detection decision are performed jointly by optimization of a Markovian model. Finally, a significance measure is computed in a non-parametric way for the results, in order to assess their relevance and control the risk of type I error. The method is applied on simulated and real data and the results are compared to those produced by standard analyses. The surface-based structural analysis is shown to be particularly robust to inter-subject spatial variability and to produce relevant results with good specificity and sensitivity. We also demonstrate the advantages of the surface-based approach by comparing with the results of a 3D structural analysis.     

Reliability of fMRI for studies of language in post-stroke aphasia subjects

Quantifying change in brain activation patterns associated with post-stroke recovery and reorganization of language function over time requires accurate understanding of inter-scan and inter-subject variability. Here we report inter-scan variability measures for fMRI activation patterns associated with verb generation (VG) and semantic decision/tone decision (SDTD) tasks in 4 healthy controls and 4 aphasic left middle cerebral artery (LMCA) stroke subjects. A series of 10 fMRI scans was completed on a 4T Varian scanner for each task for each subject, except for one stroke subject who completed 5 and 6 scans for SDTD and VG, thus yielding 35 and 36 total stroke subject scans for SDTD and VG, respectively. Group composite and intraclass correlation coefficient (ICC) maps were computed across all subjects and trials for each task. The patterns of reliable activation for the VG and SDTD tasks correspond well to those regions typically activated by these tasks in healthy and aphasic subjects. ICCs for activation were consistently high (R(0.05) approximately 0.8) for individual tasks among both control and aphasic subjects. These voxel-wise measures of reliability highlight regions of low inter-scan variability within language circuitry for control and post-recovery stroke subjects. ICCs computed from the combination of the SDTD/VG data were markedly reduced for both control and aphasic subjects as compared with the ICCs for the individual tasks. These quantitative measures of inter-scan variability support the proposed use of these fMRI paradigms for longitudinal mapping of neural reorganization of language processing following left hemispheric insult.     

反应扩充疗法联合低频重复经颅磁刺激对脑卒中非流畅性失语的临床疗效

目的:探讨反应扩充疗法(response elaboration training,RET)联合低频重复经颅磁刺激(rTMS)对脑卒中后非流畅性失语症患者的语言疗效。方法:纳入2018年9月至2019年11月本院收治的60例脑卒中非流畅性失语症患者,按随机数字表法分为常规组(仅采用传统语言训练),r TMS组(传统语言训练+低频rTMS治疗),RET+rTMS组(传统语言训练+RET+低频r TMS治疗),每组各20例。所有患者治疗前和治疗4周后均进行西方失语症成套测验(WAB)与汉语标准失语症检查法(CRRCAE)动作说明、画面说明2个亚项,以及实用性语言交流能力检查(CADL)评估,并进行组间比较。结果:治疗后,RET+rTMS组患者WAB自发言语、听理解、命名、复述、AQ得分均明显高于常规组(P0.05),RET+rTMS组自发言语、命名及AQ得分高于rTMS组(P0.05);治疗后,RET+rTMS组患者CRRCAE动作说明和画面说明得分均明显高于常规组和rTMS组(P0.05),rTMS组患者动作说明得分高于治疗前(P0.05),常规组以上两项得分与治疗前差异无显著性意义(P0.05);治疗后,rTMS组与RET+rTMS组患者CADL得分均高于常规组(P0.05),RET+rTMS组CADL得分高于rTMS组(P0.05)。结论:反应扩充疗法联合低频重复经颅磁刺激能显著改善非流畅性失语症患者的语言表达能力。     

Using non-negative matrix factorization for single-trial analysis of fMRI data

The analysis of single trials of an fMRI experiment is difficult because the BOLD response has a poor signal to noise ratio and is sometimes even inconsistent across trials. We propose to use non-negative matrix factorization (NMF) as a new technique for analyzing single trials. NMF yields a matrix decomposition that is useful in this context because it elicits the intrinsic structure of the single-trial data. The results of the NMF analysis are then processed further using clustering techniques. In addition to analyzing single trials in one brain region, the method is also suitable for investigating interdependencies between trials across brain regions. The method even allows to analyze the effect that a trial has on a subsequent trial in a different region at a significant temporal offset. This distinguishes the present method from other methods that require interdependencies between brain regions to occur nearly simultaneously. The method was applied to fMRI data and found to be a viable technique that may be superior to other matrix decomposition methods for this particular problem domain.     

卒中后失语症患者失语症类型及严重程度影响因素的回顾性分析

目的：通过回顾性研究,分析卒中后失语症患者的相关临床资料包括病灶部位、性质、性别、年龄及学历与失语症类型及其严重程度的关系。方法：收集2019年1月1日~2021年12月31日在我院康复医学科住院的首次卒中后失语症（PSA）患者的性别、年龄、学历、卒中类型、病程等临床资料、影像学资料、西方失语成套测验（WAB）评定结果。分析失语症类型、WAB评分与临床资料相关性。结果：PSA患者最常见损伤部位为左侧皮层损伤（31例,33.3%）,其次为左侧基底节区损伤（28例,30.1%）。WAB严重程度与损伤部位相关,皮层+皮层下同时存在损伤的患者其WAB失语商、自发言语、听理解、命名得分更低（P＜0.05）;进一步比较发现,皮层+皮层下同时存在损伤比单单皮层损伤的患者其失语商、自发言语、听理解、命名评分更低（P＜0.05）,皮层+皮层下同时损伤患者的失语商和全部WAB单项评分（自发言语、听理解、复述、命名）明显低于仅皮层下损伤患者（P＜0.05）,也比其他部位损伤的患者有更差的失语商、听理解、命名得分（P＜0.05）。缺血性卒中组完全性失语占比较出血性卒中组明显增高（P＜0.05）,缺血性卒中组患者失语商明显低于出血性卒中组患者（P＜0.05）,单项分数中,自发言语、听理解、复述方面,缺血性卒中组明显低于出血性卒中组（P＜0.05）,而2组间命名的单项得分差异无统计学意义。年龄、性别和学历不影响失语症类型、WAB得分。结论：PSA最常见于左侧皮层、基底节损伤,PSA类型、严重程度受病灶部位和卒中性质影响而不是年龄、性别和学历,皮层+皮层下同时存在损伤病灶更易导致严重失语症状。     

fMRI temporal clustering analysis in patients with frequent interictal epileptiform discharges: comparison with EEG-driven analysis

Temporal clustering analysis (TCA) is an exploratory data-driven technique that has been proposed for the analysis of resting fMRI to localise epileptiform activity without need for simultaneous EEG. Conventionally, fMRI of epileptic activity has been limited to those patients with subtle clinical events or frequent interictal epileptiform EEG discharges, requiring simultaneous EEG recording, from which a linear model is derived to make valid statistical inferences from the fMRI data. We sought to evaluate TCA by comparing the results with those of EEG correlated fMRI in eight selected cases. Cases were selected with clear epileptogenic localisation or lateralisation on the basis of concordant EEG and structural MRI findings, in addition to concordant activations seen on EEG-derived fMRI analyses. In three, areas of activation were seen with TCA but none corresponding to the electro-clinical localisation or activations obtained with EEG driven analysis. Temporal clusters were closely coincident with times of maximal head motion. We feel this is a serious confound to this approach and recommend that interpretation of TCA that does not address motion and physiological noise be treated with caution. New techniques to localise epileptogenic activity with fMRI alone require validation with an appropriate independent measure. In the investigation of interictal epileptiform activity, this is best done with simultaneous EEG recording.