基于偶极子特征优化的情绪重评同步EEG-fMRI源定位研究

为研究情绪重评时的大脑皮层源活动,针对情绪重评实验范式下采集的15例健康人同步EEG-fMRI数据,首先提出一种新颖的基于偶极子特征优化的融合源定位方法:根据fMRI加权最小范数估计源定位结果,采用20 ms EEG滑动时间窗,提取每个时窗内的偶极子空间融合特征,将其作为动态融合先验进行加权最小范数估计溯源;随后将该结...     

Increased central immunoreactive beta-endorphin content in patients with Wernicke-Korsakoff syndrome and in alcoholics.

beta-endorphin, adrenocorticotrophin, and alpha-melanocyte stimulating hormone were measured by radioimmunoassay in three areas of human brain at necropsy in seven subjects with Wernicke-Korsakoff syndrome and in 52 controls. Thiamin concentration in six brain areas was also measured. Mamillary body beta-endorphin concentrations were significantly increased in those with the syndrome compared with controls, and those controls with high alcohol intake showed increased mamillary body beta-endorphin compared with controls with low alcohol intake. Brain thiamin concentration was similar in both groups, with the exception of the brainstem, where it was reduced in subjects with Wernicke-Korsakoff syndrome. Thalamic beta-endorphin in controls was inversely correlated with thiamin in frontal white matter, frontal cortex, parietal white matter and parietal cortex, while beta-endorphin in the hypothalamus of patients was inversely correlated with thiamin in frontal cortex, parietal white matter, thalamus and brainstem. These results suggest that there is a disturbance of the endorphinergic system in Wernicke-Korsakoff syndrome which may be related to alcohol intake.     

The EEG during Solution of Mathematical Logical Tasks

A model creating a dominant focus in the CNS arising on solution of specially constructed mathematical logical tasks was developed. The dominant state was accompanied by increases in coherence in the delta range. The low-frequency ranges (dealt, theta, alpha) showed increases in combinations of potentials in the frontal cortex. In the high-frequency ranges (beta1, beta2, gamma), coherence decreased in the frontal areas of the cortex, while increases were seen in the central, parietal, temporal, and occipital areas, with a predominance in the left hemisphere. Significant changes in the numbers of connections (increases) were seen in diagonal coherence values. Analysis of EEG spectral power showed that solution of tasks was associated with generalized increases in values in the delta range across the cortex. Theta activity increased in the frontal cortex and gamma activity increased in the occipital areas. Spectral power in the alpha range mainly decreased.     

The temporal pattern of motion in depth perception derived from ERPs in humans

Former studies have demonstrated the cortical regions being involved in visual motion processing. The strength of neuronal activation was found to depend on the direction of motion. In particular the detection of optic flow towards the observer seems of particular importance due to its obvious biological relevance. We used event related potentials (ERPs) to add data of the temporal dynamics of this neuronal processing. Using current density reconstruction, source maxima of differential activation in motion in depth versus planar motion in the time range from 50 to 400 ms after stimulus onset were localized, and the time courses of activation were elaborated. Source reconstruction revealed six regions contributing significant source activity related to the perception of motion in depth: occipital pole, bilateral fusiform gyrus, right lateral superior occipital cortex and bilateral superior parietal cortex. Our data provide evidence for an early involvement of visual occipital cortex in the perception of motion in depth stimuli, followed by activation within parietal cortex, presumably associated with attention information processing. Sub-dividing the effects of the direction of the stimuli in motion in depth perception, optic flow directed towards the observer-induced stronger activation, but this differential activation excluded the parietal cortex. Thus the temporal deconvolution of the electrophysiological data suggests that the differential processing of approaching stimuli is initiated at an early stage of visual perception within the visual association area.     

Steady-State Visual Evoked Potentials: Distributed Local Sources and Wave-Like Dynamics Are Sensitive to Flicker Frequency

Summary: Steady-state visual evoked potentials (SSVEPs) are used in cognitive and clinical studies of brain function because of excellent signal-to-noise ratios and relative immunity to artifacts. SSVEPs also provide a means to characterize preferred frequencies of neocortical dynamic processes. In this study, SSVEPs were recorded with 110 electrodes while subjects viewed random dot patterns flickered between 3 and 30 Hz. Peaks in SSVEP power were observed at delta (3 Hz), lower alpha (7 and 8 Hz), and upper alpha band (12 and 13 Hz) frequencies; the spatial distribution of SSVEP power is also strongly dependent on the input frequency suggesting cortical resonances. We characterized the cortical sources that generate SSVEPs at different input frequencies by applying surface Laplacians and spatial spectral analysis. Laplacian SSVEPs recorded are sensitive to small changes (1–2 Hz) in the input frequency at occipital and parietal electrodes indicating distinct local sources. At 10 Hz, local source activity occurs in multiple cortical regions; Laplacian SSVEPs are also observed in lateral frontal electrodes. Laplacian SSVEPs are negligible at many frontal electrodes that elicit strong potential SSVEPs at delta, lower alpha, and upper alpha bands. One-dimensional (anterior-posterior) spatial spectra indicate that distinct large-scale source distributions contribute SSVEP power in these frequency bands. In the upper alpha band, spatial spectra indicate the presence of long-wavelength (> 15 cm) traveling waves propagating from occipital to prefrontal electrodes. In the delta and lower alpha band, spatial spectra indicate that long-wavelength source distributions over posterior and anterior regions form standing-wave patterns. These results suggest that the SSVEP is generated by both (relatively stationary) localized sources and distributed sources that exhibit characteristics of wave phenomena. This research was supported by NIMH grant R01-68004.     

脑干功能失调产生高幅失律脑电的动态仿真研究

本研究以一类因脑干功能失调引起的癫痫的发病机制为切入点．基于脑干-丘脑-大脑皮层神经信息传导关系的生理平台，在Simulink平台上建立了相应的脑干-丘脑．大脑皮层的非线性动态模型。研究目的是在神经核团的层次上，研究由于脑干功能失调引起高幅失律脑电的机制。研究的重点是调节模型中大脑皮层-脑干之间的联系参数一增大兴奋性传导参数C1和减小抑制性传导参数C2，来仿真大脑皮层和脑干之间的信息传导障碍。模型的输出是丘脑核团突触后电位变化的总和，它与相应皮层处的脑电相对应。仿真结果是：当C1增大或C2减小时，与正常状况相比，模型输出的波幅增大，模型输出的相关维数下降，说明此时脑电的特性为高幅和失律。研究结果从信息学的角度支持了此类癫痫发病的脑干责任结构机制假说。     

Behavior-Reactive Neuron Populations in the Monkey Neostriatum

Comparative analysis of neuron activity in the monkey putamen during multistep behavior showed that putamen neurons are active during all the animal's behavioral actions. The difference between the number of active neurons at a given step of the behavior as compared with the preceding step was found to be significantly smaller than the number of neurons reorganizing their activity at this step. Reorganization of neuron activity in the putamen is regarded as a reflection of the efferent code controlling the behavior, while the extent of reorganization is regarded as a measure of the change in this code in association with the organization of a sequential behavioral action. Changes in the numbers of active neurons at different stage of behavior and reorganization of their activity occurred independently of each other. This may be associated with the two afferent systems of the striatum: that ascending from the brainstem and the corticofugal, which carries differential information to the neural network of the striatum from various parts of the cortex.     

EEG mapping in seasonal affective disorder

Given that the nature of hemispheric dysfunction is different in heterogeneous disorders, in the present investigation EEG power mapping was applied to establish neurophysiological profiles that might potentially discriminate patients with seasonal affective disorder (SAD) among other affective disorders. The baseline resting EEG activity was recorded from 31 depressed SAD patients and 30 controls. Power in the delta, theta-1, theta-2, alpha, beta-1 and beta-2 frequency bands was extracted by Fourier transformation. Patients were found to have a lower delta (in central, parietal, occipital, temporal, posterior-temporal areas), theta-1 (in central and parietal), theta-2 (in anterior-frontal, parietal, occipital) and alpha activity (in anterior-frontal, midfrontal, central, parietal and occipital areas) than controls. SAD subjects showed, compared to controls, an asymmetrical distribution of delta, theta-1, theta-2 and alpha activity in parietal and temporal regions due to an increase of EEG power over the right electrode sites, and beta activity in the lateral frontal region due to an increase of beta power over the right electrode site. It is assumed that differential hemispheric contributions of EEG spectra may discriminate between the varieties of depression or different depressive states.     

Zinc-rich afferents to the rat neocortex: projections to the visual cortex traced with intracerebral selenite injections

Infusion of sodium selenite to the occipital cortex of the rat was used for the specific tracing of zinc-rich pathways. Large numbers of labeled somata were found ipsilaterally in the visual, orbital and frontal cortices, and contralaterally in homotopic and heterotopic visual areas. Labeled neurons were also found ipsilaterally in the retrosplenial, parietal, sensory-motor, temporal and perirhinal cortex. In contrast to the cortico-cortical connections, ascending afferents to the visual cortex were not zinc-rich except for a few labeled neurons in the claustrum. Additional injections showed reciprocal zinc-rich connections between the visual cortex and the orbital and frontal cortices. The latter cortices also received ascending zinc-rich afferents from the claustrum. Selenite injections revealed the layered distribution and the morphology of these labeled neurons in the neocortex. Zinc-rich neurons were found in layers II–III, V and VI. However, none was found in layer IV. Zinc-rich somata appeared as pyramidal and inverted neurons. The contrasting chemical properties of cortical and subcortical visual afferents may account for the functional differences between these systems.     

Autoradiographic localization of delta opiate receptors in rat and human brain

In vitro quantitative receptor autoradiography was performed on frozen sections of rat and human brain to visualize delta opiate receptors using the specific ligand [3H][D-Pen2, D-Pen5]enkephalin. For comparison, rat brain sections were also labelled with [3H]D-Ala2, D-Leu5-enkephalin. Compounds which block mu and kappa binding were included to make the [3H]D-Ala2, D-Leu5-enkephalin binding more specific. The two ligands had similar, but not identical, distributions in rat forebrain sections. Sites labelled with [3H][D-Pen2,D-Pen5]enkephalin were distributed heterogeneously within the layers of the frontal and parietal cerebral cortex, with high densities in the superficial and deep cortical layers. The claustrum and striatum had the most delta sites, whereas the globus pallidus had no delta binding. The distribution of [3H]D-Ala2,D-Leu5-enkephalin binding sites was similar to that of [3H][D-Pen2,D-Pen5]enkephalin, except that there was less heterogeneity in the frontal cortex. In the human brain regions studied, the highest delta binding was in caudate, putamen, temporal cortex and amygdala. There was less heterogeneity in the binding of [D-Pen2,D-Pen5]enkephalin in the human cortex than in the rat. No delta binding was seen in the medial and lateral segments of the globus pallidus. In both species, a discrepancy between the high enkephalin content of the globus pallidus and the absence of delta binding was apparent.     

Confirmation of trisomy 22 by trypsin-giemsa staining.

A small-for-dates male infant with mental retardation, microcephaly, malformed ears, preauricular sinuses, epicanthal folds, micrognathia, congenital heart diseases, micropenis, and micropolygyria of the parietal and occipital lobes of the cerebral cortex was shown to have a 47,XY,+22 karyotype by trypsin-giemsa banding. Review of reported cases confirms that there may be distinctive trisomy 22 syndrome.     

Seeing faces activates three separate areas outside the occipital visual cortex in man

We have examined magnetic cortical responses of 15 healthy humans to 46 different pictures of faces. At least three areas outside the occipital visual cortex appeared to be involved in processing this input, 105-560 ms after the stimulus onset. The first active area was near the occipitotemporal junction, the second in the inferior parietal lobe, and the third in the middle temporal lobe. The source in the inferior parietal lobe was also activated by other simple and complex visual stimuli.     

Integrated Analysis of EEG and fMRI Using Sparsity of Spatial Maps

Integration of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) is an open problem, which has motivated many researches. The most important challenge in EEG-fMRI integration is the unknown relationship between these two modalities. In this paper, we extract the same features (spatial map of neural activity) from both modality. Therefore, the proposed integration method does not need any assumption about the relationship of EEG and fMRI. We present a source localization method from scalp EEG signal using jointly fMRI analysis results as prior spatial information and source separation for providing temporal courses of sources of interest. The performance of the proposed method is evaluated quantitatively along with multiple sparse priors method and sparse Bayesian learning with the fMRI results as prior information. Localization bias and source distribution index are used to measure the performance of different localization approaches with or without a variety of fMRI-EEG mismatches on simulated realistic data. The method is also applied to experimental data of face perception of 16 subjects. Simulation results show that the proposed method is significantly stable against the noise with low localization bias. Although the existence of an extra region in the fMRI data enlarges localization bias, the proposed method outperforms the other methods. Conversely, a missed region in the fMRI data does not affect the localization bias of the common sources in the EEG-fMRI data. Results on experimental data are congruent with previous studies and produce clusters in the fusiform and occipital face areas (FFA and OFA, respectively). Moreover, it shows high stability in source localization against variations in different subjects.     

MEG and EEG Sensitivity in a Case of Medial Occipital Epilepsy

Interictal or ictal events in partial epilepsies may project on scalp EEG contralaterally to the side of the epileptogenic lesion. Such paradoxical lateralization can be observed in case of para-sagittal generators, and is likely due to the spatial orientation of the generator, presenting an oblique projection towards the midline. We present here a case of medial occipital epilepsy investigated using EEG, MEG and stereoelectroencephalography (SEEG). MRI displayed a focal cortical dysplasia in the superior margin of the right calcarine fissure. SEEG demonstrated bilateral medial occipital interictal spikes, with an inversion of polarity at the level of the lesion and a contralateral propagation occurring in 10 ms. Interictal iterative EEG cartographies showed a large posterior field, with a maximum contralateral to the initial generator (EEG paradoxical lateralization). With the same number of channels, interictal iterative MEG cartographies were more precise and more complex than EEG ones, indicating an onset accurately lateralized. A few milliseconds later, MEG cartographies were quadripolar, thus indicating two homotopic active generators. These MEG and EEG cartographies have been reproduced using BESA dipole simulator. Relative merits of MEG and EEG are still debated. With 151 channels, MEG source localizations indicated the right medial occipital area, as demonstrated by SEEG. An investigation with a corresponding number of EEG channels was not performed. After a down sampling to 64 sensors, this precision was lost. MEG and EEG source localization results, both with 64 channels, were quite comparable, indicating both medial occipital areas. However, a careful analysis of MEG/EEG iterative cartographies, performed with the same number of channels in both modalities, demonstrated that, in this configuration, MEG sensitivity was superior to the EEG one, allowing separating two medial occipital sources, characterized in SEEG by a time delay of 10 ms.     

Homocysteine and electroencephalographic rhythms in Alzheimer disease: a multicentric study

High plasma concentration of homocysteine is an independent risk factor for Alzheimer’s disease (AD), due to microvascular impairment and consequent neural loss [Seshadri S, Beiser A, Selhub J, Jacques PF, Rosenberg IH, D’Agostino RB, Wilson PW, Wolf PA (2002) Plasma homocysteine as a risk factor for dementia and Alzheimer’s disease. N Engl J Med 346(7):476–483]. Is high plasma homocysteine level related to slow electroencephalographic (EEG) rhythms in awake resting AD subjects, as a reflection of known relationships between cortical neural loss and these rhythms? To test this hypothesis, we enrolled 34 mild AD patients and 34 subjects with mild cognitive impairment (MCI). Enrolled people were then subdivided into four sub-groups of 17 persons: MCI and AD subjects with low homocysteine level (MCI− and AD−, homocysteine level <11 μmol/l); MCI and AD subjects with high homocysteine level (MCI+ and AD+, homocysteine level ≥11 μmol/l). Resting eyes-closed EEG data were recorded. EEG rhythms of interest were delta (2–4 Hz), theta (4–8 Hz), alpha 1 (8–10.5 Hz), alpha 2 (10.5–13 Hz), beta 1 (13–20 Hz), and beta 2 (20–30 Hz). EEG cortical sources were estimated by low-resolution brain electromagnetic tomography (LORETA). Results showed that delta (frontal and temporal), theta (central, frontal, parietal, occipital, and temporal), alpha 1 (parietal, occipital, and temporal), and alpha 2 (parietal and occipital) sources were stronger in magnitude in AD+ than AD− group. Instead, no difference was found between MCI− and MCI+ groups. In conclusion, high plasma homocysteine level is related to unselective increment of cortical delta, theta, and alpha rhythms in mild AD, thus unveiling possible relationships among that level, microvascular concomitants of advanced neurodegenerative processes, and synchronization mechanisms generating EEG rhythms.     

Negative association between amyloid plaques and cerebral amyloid angiopathy in Alzheimer's disease

Cerebral amyloid angiopathy (CAA) is an important, though still relatively neglected, aspect of the pathology of Alzheimer's disease (AD), and both the source of amyloid beta protein (Abeta) in CAA, and its relationship to senile plaque (SP) Abeta, remain unclear. We have investigated the relationship between Abeta deposition in SP and CAA in four regions of brain from 69 patients with AD in order to gain insight into the pathogenetic mechanism(s) underlying these pathologies. CAA was present to some degree in all 69 patients, with the occipital cortex being affected more often and more severely than frontal, temporal and parietal cortices. By definition, SPs were present in all brain areas in all 69 patients, with greater uniformity of distribution than CAA, though the occipital cortex was less severely affected than the other brain regions. There was no significant (positive) correlation between CAA rating and that of SP for any one cortical region, but on combining data from all four regions there was a significant inverse correlation (P=0.037) between CAA and SP ratings. Such data suggest that the cellular sources and mechanisms leading to Abeta deposition as SP or CAA are likely to differ and may proceed independently of each other.     

大鼠大脑皮质微血管的一氧化氮合酶神经元及终末的正常分布研究

目的;研究正常大鼠大脑皮质额、顶、枕、颞叶的一氧化氮合酶（nitric oxide synthase,NOS）神经元及NOS阳性终末的分布,尤其注意它们与皮质微血管的关系。方法:采用NADPH-d组化方法。结果:NOS阳性神经元在皮质各层散在分布,数量较少,额、顶叶约半数的NOS神经元直接与皮质血管构成接触,枕、额叶中约三分之一的NOS神经元与皮质血管构成接触。而NOS阳性纤维多且密集成网状,额、顶叶的终末数量明显多于枕、颞叶,其中6％～7％的阳性终末分布至血管壁。结论:大脑皮质内的NOS神经元及NOS阳性终末参与皮质微循环的调节。     

Intracerebral sources of human auditory steady-state responses

The objective of this study was to localize the intracerebral generators for auditory steady-state responses. The stimulus was a continuous 1000-Hz tone presented to the right or left ear at 70 dB SPL. The tone was sinusoidally amplitude-modulated to a depth of 100% at 12, 39, or 88 Hz. Responses recorded from 47 electrodes on the head were transformed into the frequency domain. Brain electrical source analysis treated the real and imaginary components of the response in the frequency domain as independent samples. The latency of the source activity was estimated from the phase of the source waveform. The main source model contained a midline brainstem generator with two components (one vertical and lateral) and cortical sources in the left and right supratemporal plane, each containing tangential and radial components. At 88 Hz, the largest activity occurred in the brainstem and subsequent cortical activity was minor. At 39 Hz, the initial brainstem component remained and significant activity also occurred in the cortical sources, with the tangential activity being larger than the radial. The 12-Hz responses were small, but suggested combined activation of both brainstem and cortical sources. Estimated latencies decreased for all source waveforms as modulation frequency increased and were shorter for the brainstem compared to cortical sources. These results suggest that the whole auditory nervous system is activated by modulated tones, with the cortex being more sensitive to slower modulation frequencies.     

Different cortical activation patterns in blind and sighted humans during encoding and transformation of haptic images

In this study, we investigated whether the occipital cortex of blind humans is activated during haptic perception and/or transformation of a haptic image. Slow event-related brain potentials were monitored from 18 electrodes in 12 sighted and 15 congenitally blind participants while they were engaged in a haptic mental rotation task. In both groups, slow negative shifts appeared over (a) the frontal cortex at the beginning of each processing episode, (b) the left-central to parietal cortex during encoding and maintaining of a haptic image, and (c) the central to parietal cortex during image transformation. A pronounced slow negative potential over the occipital cortex emerged only in the blind individuals and was time-locked to the processing epochs. Its amplitude increased with the amount of processing load. The slow wave effects observed in the blind individuals could indicate that occipital areas participate in specific, nonvisual functions or they could reflect a coactivation of these areas whenever the activation level of task-specific processing modules located elsewhere in the cortex is raised by nonspecific thalamocortical input.     

超声刺激对大鼠多皮层ECoG的调控

目的:为了进一步揭示超声刺激的神经调控机制以及超声刺激引起的刺激效应范围,将超声刺激经颅施加到大鼠前额叶皮层部位,同步记录和分析前额叶、顶叶及枕叶皮层的皮层电位（Electrocorticogram, ECoG）的变化特征。方法:在大鼠麻醉状态下,利用脑立体定位仪将超声探头定位在大鼠前额叶部位的正上方,刺激时间为20 min。以功率谱密度（Power Spectral Density, PSD）、振幅及互相关系数值为指标,分析比较超声刺激前、刺激中、刺激后的ECoG总功率、平均幅值以及皮层间的互相关系数值。结果:（1）超声刺激会增加前额叶皮层ECoG的总PSD和平均幅值（P<0.05）,超声刺激停止后,在较短的时间内ECoG恢复到刺激前水平;（2）在顶叶及枕叶皮层,超声刺激对总ECoG及各频段信号的PSD、平均幅值无显著性影响。但在超声刺激过程中,枕叶ECoG的部分时间段的平均幅值相对于刺激前有显著性差异,即在超声刺激的后半段时间内,超声刺激产生刺激效应范围扩散到枕叶皮层。结论:超声刺激对刺激局部的ECoG具有调控作用,且这种调控具有及时性及快速恢复的特点。超声刺激对ECoG的调控效应范围总体上来说是局限性的,对远离刺激部位的其他脑皮层ECoG的影响尚无明确关系,其效应很可能是超声刺激局部引起的后续神经网络反应。 【关键词】超声刺激;ECoG;脑皮层;神经调控