音乐刺激激活人脑情感系统的fMRI研究

目的：利用fMRI技术，对音乐欣赏相关脑功能区进行定位，并初步探讨音乐情感反应和音乐治疗的可能神经机制。方法：采用组块设计模式，对30名非音乐专业志愿者进行被动聆听音阶、轻音乐和恐怖音乐（各3段）实验。应用SPM99软件对实验结果进行组分析，获得平均激活图。结果：轻音乐和恐怖音乐可激活大脑与情感加工相关的脑区．前者主要包括双侧前额皮层外侧部（左侧为著）、左侧眶额皮层、扣带回前部、左侧岛叶前部、右侧丘脑和左侧豆状核；后者主要包括双侧前额皮层外侧部（右侧为著）、双侧眶额皮层、双侧额内回和扣带回前部和双侧杏仁复合体，结论：音乐可有效激活人脑与情感加工相关脑区；大脑对喜悦和恐惧情感具有不同（或部分交叉）的神经加工网络．其中．轻音乐引起的正性情感加工可能是音乐治疗的部分神经基础。     

Effective Connectivity of Cortical Sensorimotor Networks During Finger Movement Tasks: A Simultaneous fNIRS,fMRI, EEG Study

Recently, interest has been growing to understand the underlying dynamic directional relationship between simultaneously activated regions of the brain during motor task performance. Such directionality analysis (or effective connectivity analysis), based on non-invasive electrophysiological (electroencephalography—EEG) and hemodynamic (functional near infrared spectroscopy—fNIRS; and functional magnetic resonance imaging—fMRI) neuroimaging modalities can provide an estimate of the motor task-related information flow from one brain region to another. Since EEG, fNIRS and fMRI modalities achieve different spatial and temporal resolutions of motor-task related activation in the brain, the aim of this study was to determine the effective connectivity of cortico-cortical sensorimotor networks during finger movement tasks measured by each neuroimaging modality. Nine healthy subjects performed right hand finger movement tasks of different complexity (simple finger tapping-FT, simple finger sequence-SFS, and complex finger sequence-CFS). We focused our observations on three cortical regions of interest (ROIs), namely the contralateral sensorimotor cortex (SMC), the contralateral premotor cortex (PMC) and the contralateral dorsolateral prefrontal cortex (DLPFC). We estimated the effective connectivity between these ROIs using conditional Granger causality (GC) analysis determined from the time series signals measured by fMRI (blood oxygenation level-dependent-BOLD), fNIRS (oxygenated-O₂Hb and deoxygenated-HHb hemoglobin), and EEG (scalp and source level analysis) neuroimaging modalities. The effective connectivity analysis showed significant bi-directional information flow between the SMC, PMC, and DLPFC as determined by the EEG (scalp and source), fMRI (BOLD) and fNIRS (O₂Hb and HHb) modalities for all three motor tasks. However the source level EEG GC values were significantly greater than the other modalities. In addition, only the source level EEG showed a significantly greater forward than backward information flow between the ROIs. This simultaneous fMRI, fNIRS and EEG study has shown through independent GC analysis of the respective time series that a bi-directional effective connectivity occurs within a cortico-cortical sensorimotor network (SMC, PMC and DLPFC) during finger movement tasks.     

Estimate of Causality Between Independent Cortical Spatial Patterns During Movement Volition in Spinal Cord Injured Patients

Static hemodynamic or neuroelectric images of brain regions activated during particular tasks do not convey the information of how these regions communicate to each other. Cortical connectivity estimation aims at describing these interactions as connectivity patterns which hold the direction and strength of the information flow between cortical areas. In this study, we attempted to estimate the causality between distributed cortical systems during a movement volition task in preparation for execution of simple movements by a group of normal healthy subjects and by a group of Spinal Cord Injured (SCI) patients. To estimate the causality between the spatial distributed patterns of cortical activity in the frequency domain, we applied a series of processing steps on the recorded EEG data. From the high-resolution EEG recordings we estimated the cortical waveforms for the regions of interest (ROIs), each representing a selected sensor group population. The solutions of the linear inverse problem returned a series of cortical waveforms for each ROI considered and for each trial analyzed. For each subject, the cortical waveforms were then subjected to Independent Component Analysis (ICA) pre-processing. The independent components obtained by the application of the ThinICA algorithm were further processed by a Partial Directed Coherence algorithm, in order to extract the causality between spatial cortical patterns of the estimated data. The source-target cortical dependencies found in the group of normal subjects were relatively similar in all frequency bands analyzed. For the normal subjects we observed a common source pattern in an ensemble of cortical areas including the right parietal and right lip primary motor areas and bilaterally the primary foot and posterior SMA areas. The target of this cortical network, in the Granger-sense of causality, was shown to be a smaller network composed mostly by the primary foot motor areas and the posterior SMA bilaterally. In the case of the SCI population, both the source and the target cortical patterns had larger sizes than in the normal population. The source cortical areas included always the primary foot and lip motor areas, often bilaterally. In addition, the right parietal area and the bilateral premotor area 6 were also involved. Again, the patterns remained substantially stable across the different frequency bands analyzed. The target cortical patterns observed in the SCI population had larger extensions when compared to the normal ones, since in most cases they involved the bilateral activation of the primary foot movement areas as well as the SMA, the primary lip areas and the parietal cortical areas.     

A simultaneous ERP/fMRI investigation of the P300 aging effect

One of the most reliable psychophysiological markers of aging is a linear decrease in the amplitude of the P300 potential, accompanied by a more frontal topographical orientation, but the precise neural origins of these differences have yet to be explored. We acquired simultaneous electroencephalogram (EEG)/functional magnetic resonance imaging (fMRI) recordings from 14 older and 15 younger adults who performed a 3-stimulus visual oddball task designed to elicit P3a and P3b components. As in previous reports, older adults had significantly reduced P3a/P3b amplitudes over parietal electrodes but larger amplitudes over frontal scalp with no between-group differences in accuracy or reaction time. Electroencephalogram/functional magnetic resonance imaging fusion revealed that the P3a age effects were driven by increased activation of left inferior frontal and cingulate cortex and decreased activation of inferior parietal cortex in the older group. P3b differences were driven by increased activation of left temporal regions, right hippocampus, and right dorsolateral prefrontal cortex in the older group. Our results support the proposal that the age-related P300 anterior shift arises from an increased reliance on prefrontal structures to support target and distractor processing.     

Differential effects of age on subcomponents of response inhibition

Inhibitory deficits contribute to cognitive decline in the aging brain. Separating subcomponents of response inhibition may help to resolve contradictions in the existing literature. A total of 49 healthy participants underwent functional magnetic resonance imaging (fMRI) while performing a Go/no-go-, a Simon-, and a Stop-signal task. Regression analyses were conducted to identify correlations of age and activation patterns. Imaging results revealed a differential effect of age on subcomponents of response inhibition. In a simple Go/no-go task (no spatial discrimination), aging was associated with increased activation of the core inhibitory network and parietal areas. In the Simon task, which required spatial discrimination, increased activation in additional inhibitory control regions was present. However, in the Stop-signal task, the most demanding of the three tasks, aging was associated with decreased activation. This suggests that older adults increasingly recruit the inhibitory network and, with increasing load, additional inhibitory regions. However, if inhibitory load exceeds compensatory capacity, performance declines in concert with decreasing activation. Thus, the present findings may refine current theories of cognitive aging.     

握力刺激强度与运动皮层激活相关性的fMRI研究

目的研究握力刺激强度与运动皮层激活程度的相关性。方法16例正常右利手受试者根据视觉刺激提示右手进行固定频率的三种不同握力运动,同时进行BOLD fMRI扫描,用spm5计算得到不同握力的脑激活区并比较差异。结果在三种不同握力运动中,对侧主运动区、对侧躯体感觉区、对侧辅助运动区(SMA)和对侧运动前区(PMC)明显激活;同侧激活区较小或者未见激活区;同侧小脑激活区较对侧明显激活。随着握力强度的增高,M1和S1激活强度、范围都提高;小脑激活程度有所降低。结论正常人手握力运动时脑皮质运动网络被激活,握力刺激强度与M1、S1的激活程度呈正相关。     

Virtual Pain Stimulation of Allodynia Patients Activates Cortical Representation of Pain and Emotions: A Functional MRI Study

Summary: The present study investigated neural correlates of affect processing in allodynia patients (n=8) and healthy controls (n=12) with the aid of virtual tactile stimulation. Whole brain functional magnetic resonance imaging was performed for allodynia patients and healthy volunteers while they were shown a video demonstrating light stimulation of the palm and another stimulation aimed at producing anticipation of palm stimulation. Contrasting with controls, patients displayed activation of the cortical areas related to pain and emotions: prefrontal cortex (Brodmann's area BA 10) and anterior cingulate cortex (BA 24). These findings may indicate involvement of an emotional component of pain perception in all odynia patients. We thank Dr. Olga Zinchuk and Ms. Beth Smith for scientific advice, and Kazuo Morio and Toshikazu Sasaki for technical assistance. This work was partially supported by the Japanese Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (B), 14370467, 2002–2004 and Young Scientists (B), 15790793, 2003–2005.     

Spatial Correspondence Between Functional MRI (fMRI) Activations and Cortical Current Density Maps of Event-Related Potentials (ERP): A Study with Four Tasks

We investigated the spatial correspondence between functional MRI (fMRI) activations and cortical current density maps of event-related potentials (ERPs) reconstructed without fMRI priors. The presence of a significant spatial correspondence is a prerequisite for direct integration of the two modalities, enabling to combine the high spatial resolution of fMRI with the high temporal resolution of ERPs. Four separate tasks were employed: visual stimulation with a pattern-reversal chequerboard, recognition of images of nameable objects, recognition of written words, and auditory stimulation with a piano note. ERPs were acquired with 19 recording channels, and source localisation was performed using a realistic head model, a standard cortical mesh and the multiple sparse priors method. Spatial correspondence was evaluated at group level over 10 subjects, by means of a voxel-by-voxel test and a test on the distribution of local maxima. Although not complete, it was significant for the visual stimulation task, image and word recognition tasks (P < 0.001 for both types of test), but not for the auditory stimulation task. These findings indicate that partial but significant spatial correspondence between the two modalities can be found even with a small number of channels, for three of the four tasks employed. Absence of correspondence for the auditory stimulation task was caused by the unfavourable situation of the activated cortex being perpendicular to the overlying scalp, whose consequences were exacerbated by the small number of channels. The present study corroborates existing literature in this field, and may be of particular relevance to those interested in combining fMRI with ERPs acquired with the standard 10-20 system.     

A Comparative Study of the Behavioral Patterns of RLA/Verh and RHA/Verh Rats in the Exploration Box

Roman high- and low-avoidance (RHA/Verh and RLA/Verh) rats differ in their emotionality profiles. As emotional processes are considered to play an important role in exploratory behavior, differences between the Roman sublines in responding to a novel environment can be anticipated. The present study provides a quantitative (based on the frequency of particular responses) and qualitative (based on the frequency of behavioral sequences) comparison of exploratory behavior of RHA/Verh and RLA/Verh rats. Rats of both sexes were tested individually for 30 min in an exploration box containing a few objects. Observation periods were divided, based on earlier studies, into three consecutive blocks of 5, 10, and 15 min, respectively. Analysis of quantitative data showed differences in sniffing (RHA/Verh scoring higher) and in immobility (RLA/Verh scoring higher), both persisting throughout all measurement periods. Males of both sublines were generally more active and exploratory than their respective females. The analysis of sequential data revealed that during the first 5 min RHA/Verh rats showed a less diverse but more exploratory repertoire and that during the first 15 min males of both sublines showed more behavioral sequences than females. This study indicates that the Roman rat sublines should provide a useful model to study the mechanisms of exploratory behavior.     

Sex steroids to maintain cognitive function in women after the menopause: A meta-analyses of treatment trials

It is still debated whether estrogen treatment after the menopause could result in improved cognitive function in women. This debate is based on many animal and cell culture data showing that estrogens can positively affect the aging brain. Observational data also show a halved risk of dementia in women who took estrogens around the age of menopause. However, large treatment trials have shown negative effects of long-term treatment with estrogens in older women. The present meta-analyses included 36 randomised treatment trials and tested various hypotheses which have been developed to attempt to explain discrepant data. Results indicated that, contrary to expectations, age of women and duration of time elapsed when treatment was initiated since menopause (‘window of opportunity’ hypothesis) did not significantly affect treatment outcome, nor did it matter whether women were symptomatic or not. It was not clear whether bilateral oophorectomy affected the outcome, as this effect was based on only a few studies from the same group and some observational studies show negative effects on cognition in surgical menopausal women treated with hormones for more than 10 years. Duration of treatment overall significantly affected outcome. More negative effects were seen in longer studies, where positive effects were mainly seen in short term studies (<4 months). Treatment with combined estrogens and progestagens also negatively affected the outcome. Whether women with symptoms should be treated for a couple of months or using other (intermittent) modes of treatment and whether this could have long-term positive consequences remains to be investigated.