精神分裂症幻听患者初级听觉皮质的脑磁图研究

目的 探讨在不同频率纯音刺激下男性精神分裂症幻听患者初级听觉皮质的脑磁图(MEG)定位.方法 对均为右利手的10例男性精神分裂症幻听患者(研究组)和11名男性健康受试者(对照组),分别给予频率为0.5,2,4,8 kHz的纯音刺激,强度90 dB,持续200ms,刺激声间隔1 s.用脑磁图设备记录刺激后产生的听觉诱发磁场,并将MEG资料叠加到核磁共振成像以获得磁源性影像.结果 (1)对照组初级听觉皮质均定位于双侧颞横回;与对照组比较,研究组右侧初级听觉皮质位置更靠近颞横回外部,左侧明显偏向颞上回后外下部(P<0.05).(2)在分别给予2 kHz和4kHz纯音刺激时,研究组大脑双侧M100潜伏期[2 kHz:左(97±16)ms,右(97±10)ms,4 kHz:左(93±13)ms,右(99±14)ms]均短于对照组[2 kHz:左(121±15)ms,右(113±6)ms,4 kHz:左(113±13)ms,右(114±6)ms](均P<0.01),而波幅[2 kHz:左(89±10)fT,右(118±37)fT,4 kHz:左(81±9)fT,右(108±14)fT]高于对照组[2 kHz:左(73±12)fT,右(79±13)fT,4 kHz:左(69±14)fT,右(81±20)fT](均P<0.05～0.01).结论 男性精神分裂症幻听患者的初级听觉皮质位置与正常人不同,其M100波幅高,潜伏期短,这些功能及解剖结构的异常可能是精神分裂症幻听产生的病理生理机制之一.     

精神分裂症患者正反序工作记忆的脑磁图研究

目的:通过脑磁图影像学方法研究精神分裂症患者工作记忆受损情况.方法:分别对12例精神分裂症患者和10名正常人正反序记忆时同时采集脑磁图信号,与磁共振解剖像叠加形成磁源性成像,进行脑区活动分析.结果:正序记忆时患者右额上回激活较正常人明显增多(P<0.05),简单记忆任务时,就动员了较多的脑部资源,随着任务难度增大,额叶...     

卒中后吞咽障碍患者脑磁图下吞咽皮质环路预探索研究

目的 探讨卒中后吞咽障碍患者皮质吞咽中枢在脑磁图中的激活情况,为吞咽皮质中枢的功能探
讨提供资料。
方法 采用151通道Omega2000全头型生物磁仪（CTF.co,Canada）对6例卒中后吞咽障碍的患者进行
脑磁信号的采集。以等电流偶极（equivalent current dipole,ECD）记录肌电信号开始前－2500 ms内激
活脑区的部位及时间顺序。以每隔20 s、25 s、30 s、35 s时间不等的方式向受试者口腔注射室温纯净
水0.5～1 ml共10次。所有检查者均行头颅磁共振成像（magnetic resonance imaging,MRI）检查,并与脑
磁图的磁场变化结果融合,形成磁源性成像（magnetic source imaging,MSI）。
结果 5例患者得到磁源性影像。所激活的脑区包括岛叶、初级运动感觉皮质、扣带、丘脑等。部分
脑区呈现反复激活,脑内吞咽皮质激活存在3个相对较为固定的环路。中央前后回、岛叶、丘脑、扣带
回持续稳定激活,其初次激活发生在一定时间段内。后扣带较前扣带回及岛叶激活较晚。
结论 吞咽皮质在处理吞咽信息中可能存在一定的环路。后扣带回激活较晚可能是由于卒中后吞咽
皮质功能活动受损的表现。     

脑磁图语言区定位技术在癫痫外科的应用价值

脑磁图(Magnetoencephalography,MEG)语言区定位技术在基础研究和临床上都得到了广泛应用。MEG能够对完成各种语言任务的正常人进行语言区定位,其结果与经典语言中枢基本一致;部分癫痫患者由于病灶累及语言区,导致语言区的重建或移位,MEG能够准确评估语言区的改变;MEG与传统的语言区定侧技术如术前Wada实验和术中植入电极后电刺激相比,结果具有高度的一致性;由于MEG对颞叶语言区敏感,而fMRI对额叶语言区敏感,两种方法结合使用能够更准确的定侧优势半球;MEG语言区定位技术在癫痫外科领域获得了较为广泛的应用和充分的肯定。     

脑磁图静息态脑网络定位与皮质脑电图的对照研究

目的：探讨脑磁图（ MEG）静息态脑网络定位与皮质脑电图（ ECoG）的一致性。方法选取难治性癫痫患者16例,术前均运用脑磁图静息态网络定位,同时运用传统的脑磁图Dipole法和SAM法皮质脑电图定位,与皮质脑电图的结果对照,分别比较两种技术的吻合度。结果16例患者均有明显的棘波放电, Dipole定位局限10例,散发6例,SAM值升高单病灶11例,多病灶5例。16例患者均显示静息态脑网络异常,敏感度100％（16／16）。 Dipole定位ECoG的定位符合率为62．5％（10／16）,SAM与ECoG的定位符合率为68．7％（11／16）,MEG脑网络功能异常与ECoG 的定侧符合率为100％,定位符合率为81．2％（13／16）。结论脑磁图静息态网络定位可以敏感地定位癫痫放电区,可以为癫痫手术规划提供帮助。     

脑磁图定位皮质运动区与术中皮质电刺激运动诱发电位的对照研究

目的评价脑磁图（MEG）术前定位初级运动皮质（M1）的准确性。方法选取顺序入院的中央区胶质瘤26例,术前均运用MEG定位皮质运动区,与MRI导航影像融合,在神经导航下定位MEG激活区。术中对MEG成功定位的病例行直接皮质电刺激（DCES）,比较两种技术的吻合度。结果因病人不能配合,MEG定位失败2例,余24例均定位成功,每例激活区1～5个。DCES成功监测24例,所有选择的DCES靶点共41个,阳性靶点24个,1个/例。以所有的41个靶点分析,MEG定位M1区与DCES定位的吻合率为58.5%;而以第1组病灶侧M1区和第2组病灶侧中央区的MEG激活区中27个靶点分析,两者吻合率为88.9%;仅以第1组M1区的MEG激活区中17个靶点分析,两者吻合率为100%。结论 MEG可以灵敏而可靠地定位M1区,可用于中央区胶质瘤病人术前手术规划。     

Effects of phonological contrast on auditory word discrimination in children with and without reading disability: a magnetoencephalography (MEG) study

Poor readers perform worse than their normal reading peers on a variety of speech perception tasks, which may be linked to their phonological processing abilities. The purpose of the study was to compare the brain activation patterns of normal and impaired readers on speech perception to better understand the phonological basis in reading disability. Whole-head magnetoencephalography (MEG) was recorded as good and poor readers, 7–13 years of age, performed an auditory word discrimination task. We used an auditory oddball paradigm in which the ‘deviant’ stimuli (/bat/, /kat/, /rat/) differed in the degree of phonological contrast (one versus three features) from a repeated standard word (/pat/). Both good and poor readers responded more slowly to deviants that were phonologically similar compared to deviants that were phonologically dissimilar to the standard word. Source analysis of the MEG data using minimum norm estimation (MNE) showed that compared to good readers, poor readers had reduced left-hemisphere activation to the most demanding phonological condition reflecting their difficulties with phonological processing. Furthermore, unlike good readers, poor readers did not show differences in activation as a function of the degree of phonological contrast. These results are consistent with a phonological account of reading disability.     

The bereitschaftspotential paradigm in investigating voluntary movement organization in humans using magnetoencephalography (MEG)

In 1965, Kornhuber and Deecke [1]first described the bereitschaftspotential (BP), a paradigm for investigating the organization of voluntary movement in humans, using electroencephalography (EEG). This paradigm has since been used in many studies for investigating motor control in healthy humans and patients. Over the last years, the advantages of magnetoencephalography (MEG) have been applied to the BP paradigm by a number of researchers. The main advantage of magnetoencephalography over electroencephalography is that MEG has a higher localization accuracy. This is due to the fact that the different structures of the head (brain, liquor cerebrospinalis, skull and scalp) influence the magnetic fields less than the volume current flow that causes the EEG. Additionally, the MEG is reference free, so that the localization of sources with a given precision is easier for MEG than it is for EEG. The present protocol shows in detail how the bereitschaftspotential paradigm can be applied using MEG. Some additional paradigms for investigating motor plasticity, somatosensory gating, Parkinson disease, and the efference copy theory are suggested as well.     

Left superior temporal blood flow increases in schizophrenic and schizophreniform patients with auditory hallucination: A longitudinal case study using123I-IMP SPECT

Summary Serial assessments of regional cerebral blood flow were performed using¹²³I-IMP SPECT in two schizophrenic and three schizophreniform patients with persistent auditory hallucination. The initial SPECT study in the period with prominent auditory hallucination revealed an increased accumulation of¹²³I-IMP in the left superior temporal area which corresponded to the auditory association cortex. In the follow-up SPECT study performed after clinical improvement, the distribution of¹²³I-IMP had normalized. One of the case with schizophrenia showed a similar increased uptake of¹²³I-IMP in the left superior temporal area in the third SPECT scan performed when a psychotic relapse with auditory hallucination occurred. MRI scans in two of the five patients demonstrated reduced volume of the temporal lobes. These findings suggest that the auditory hallucinations in schizophrenia may be involved in functional hyperactivity in the left superior temporal cortex which might be based partly on structural abnormalities in the temporal lobes.     

Modulation of the auditory cortex during speech: an MEG study

Several behavioral and brain imaging studies have demonstrated a significant interaction between speech perception and speech production. In this study, auditory cortical responses to speech were examined during self-production and feedback alteration. Magnetic field recordings were obtained from both hemispheres in subjects who spoke while hearing controlled acoustic versions of their speech feedback via earphones. These responses were compared to recordings made while subjects listened to a tape playback of their production. The amplitude of tape playback was adjusted to match the amplitude of self-produced speech. Recordings of evoked responses to both self-produced and tape-recorded speech were obtained free of movement-related artifacts. Responses to self-produced speech were weaker than were responses to tape-recorded speech. Responses to tones were also weaker during speech production, when compared with responses to tones recorded in the presence of speech from tape playback. However, responses evoked by gated noise stimuli did not differ for recordings made during self-produced speech versus recordings made during tape-recorded speech playback. These data suggest that during speech production, the auditory cortex (1) attenuates its sensitivity and (2) modulates its activity as a function of the expected acoustic feedback.     

MEG language lateralization in partial epilepsy using dSPM of auditory event-related fields

ObjectiveMethods employed to determine hemispheric language dominance using magnetoencephalography (MEG) have differed significantly across studies in the choice of language-task, the nature of the physiological response studied, recording hardware, and source modeling methods. Our goal was to determine whether an analysis based on distributed source modeling can replicate the results of prior studies that have used dipole-modeling of event-related fields (ERFs) generated by an auditory word-recognition task to determine language dominance in patients with epilepsy.MethodsWe analyzed data from 45 adult patients with drug-resistant partial epilepsy who performed an auditory word-recognition task during MEG recording and also completed a language fMRI study as part of their evaluation for epilepsy surgery. Source imaging of auditory ERFs was performed using dynamic statistical parametric mapping (dSPM). Language laterality indices (LIs) were calculated for four regions of interest (ROIs) by counting above-threshold activations within a 300–600 ms time window after stimulus onset. Language laterality (LL) classifications based on these LIs were compared to the results from fMRI.ResultsThe most lateralized MEG responses to language stimuli were observed in a parietal region that included the angular and supramarginal gyri (AngSmg). In this region, using a half-maximal threshold, source activations were left dominant in 32 (71%) patients, right dominant in 8 (18%), and symmetric in 5 patients (11%). The best agreement between MEG and fMRI on the ternary classification of regional language dominance into left, right, or symmetric groups was also found at the AngSmg ROI (69%). This was followed by the whole-hemisphere and temporal ROIs (both 62%). The frontal ROI showed the least agreement with fMRI (51%). Gross discordances between MEG and FMRI findings were disproportionately of the type where MEG favored atypical right-hemispheric language in a patient with right-hemispheric seizure origin (p < 0.05 at three of the four ROIs).SignificanceIn a parietal region that includes the angular and supramarginal gyri, language laterality estimates based on dSPM of ERFs during auditory word-recognition shows a degree of MEG-fMRI concordance that is comparable to previously published estimates for MEG-Wada concordance using dipole counting methods and the same task. Our data also suggest that MEG language laterality estimates based on this task may be influenced by the laterality of epileptic networks in some patients. This has not been reported previously and deserves further study.     

The signal detection ability of patients with auditory hallucination: Analysis using the continuous performance test

Signal detection theory is appropriate for analyzing the problem of whether auditory hallucination arises from a sensory or judgmental disorder. In the present study the sensory discrimination ability and decision bias of psychiatric patients with auditory hallucination was investigated by using the visual continuous performance test. Based on signal detection theory the d' (d prime) and the lnbeta value (the natural logarithm of the beta value) were calculated. The d' is indicator of discriminating ability, whereas the lnbeta value is an indicator of decision bias. The psychiatric inpatients with the diagnosis of schizophrenia mainly were divided into 11 patients with auditory hallucinations (AH(+)) and 11 patients without hallucinations (AH(-)). As compared with the AH(-) group, the AH(+) group showed the same d' value and a significantly lower lnbeta value. As compared with the normal control group, the AH(+) group showed a significantly lower d' value and a nearly normal lnbeta value. These results suggest that auditory hallucination is characterized by a cognitive deficit of unreasonably maintaining a relatively risk-taking decision bias in spite of decreased discriminating ability, which opposes the interpretation of Bentall and Slade (1985). The AH(+) group was divided into subgroups with bizarre delusions (BD(+)) and without bizarre delusions (BD(-)). The BD(+) group showed a stronger tendency toward a lower d' value and normal lnbeta value, which the AH(+) group had.     

Desynchronization in the right auditory cortex during musical hallucinations: A MEG study

Desynchronization in the right auditory cortices, including the transverse gyrus of Heschl, planum temporale and supramarginal cortex, occurred during musical hallucinations in a 78‐year‐old woman with hearing impairment and depression. This phenomenon was assessed using a novel, spatially filtered magnetoencephalography (MEG) analysis, termed synthetic aperture magnetometry (SAM). In general, the affected areas are consistent with neuroimaging studies of normal musical perception and imagery, suggesting that musical hallucinations involve abnormal spontaneous activity in the neural substrate dedicated to musical perception and imagery in which false imagery occurs.     

Distinct contrast response functions in striate and extra-striate regions of visual cortex revealed with magnetoencephalography (MEG).

OBJECTIVE: To spatially and temporally characterise the cortical contrast response function to pattern onset stimuli in humans. METHODS: Magnetoencephalography (MEG) was used to investigate the human cortical contrast response function to pattern onset stimuli with high temporal and spatial resolution. A beamformer source reconstruction approach was used to spatially localise and identify the time courses of activity at various visual cortical loci. RESULTS: Consistent with the findings of previous studies, MEG beamformer analysis revealed two simultaneous generators of the pattern onset evoked response. These generators arose from anatomically discrete locations in striate and extra-striate visual cortex. Furthermore, these loci demonstrated notably distinct contrast response functions, with striate cortex increasing approximately linearly with contrast, whilst extra-striate visual cortex followed a saturating function. CONCLUSIONS: The generators that underlie the pattern onset visual evoked response arise from two distinct regions in striate and extra-striate visual cortex. SIGNIFICANCE: The spatially, temporally and functionally distinct mechanisms of contrast processing within the visual cortex may account for the disparate results observed across earlier studies and assist in elucidating causal mechanisms of aberrant contrast processing in neurological disorders.