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1.
Objective: The functional relationship between calculated alpha band spectral power and inter-/intra-hemispheric coherence during a three-level working memory task of patients with mild cognitive impairment (MCI) was investigated. Methods: Subjects included 35 MCI patients according to the DSM-IV criteria (mean age: 62.3, SD: 6.5) and 34 healthy controls (mean age: 57.4, SD: 4.0) were selected from the community at large. All subjects performed a simple calculation and recall task with three levels of working memory load while electroencephalograph (EEG) signal was recorded. The spectral EEG power was computed over alpha1 (8.0～10.0 Hz) and alpha2 (10.5～13.0 Hz) frequency bands and was compared between rest stage and working memory processing stage by two-way ANOVA. Post hoc testing analyzed the differences between each two levels of working memory load during task processing. The inter-hemisphere EEG coherence of frontal (F3-F4), central (C3-C4), parietal (P3-P4), temporal (T5-T6) as well as occipital (O1-O2) was compared between MCI patients and normal controls. The EEG signals from F3-C3, F4-C4, C3-P3, C4-P4, P3-O1, P4-O2, T5-C3, T6-C4, T5-P3 and T6-P4 electrode pairs resulted from the intra-hemispheric action for alpha1 and alpha2 frequency bands. Result: There was significantly higher EEG power from MCI patients than from normal controls both at rest and during working memory processing. Significant differences existed between rest condition and three-level working memory tasks (P<0.001). The inter-and intra-hemispheric coherence during working memory tasks showed a "drop to rise" tendency compared to that at rest condition. There was significantly higher coherence in MCI patients than in the controls. When task difficulties increased, the cortical connectivity of intra-hemispheric diminished while the inter-hemispheric connectivity dominantly maintained the cognitive processing in MCI patients. Conclusion: The results of the present study indicate that the alpha frequency band may be the characteristic band in distinguishing MCI patients from normal controls during working memory tasks. MCI patients exhibit greater inter-hemispheric connectivity than intra-hemispheric connectivity when memory demands increase. MCI patients mobilize a compensatory mechanism to maintain the processing effectiveness while the processing efficiency is reduced.  相似文献   

2.
To investigate the features of electroencephalography (EEG) power and coherence at rest and during a working memory task of patients with mild cognitive impairment (MCI). Thirty-five patients (17 males, 18 females; 52～71 years old) and 34 sex- and age-matched controls (17 males, 17 females; 51～63 years old) were recruited in the present study. Mini-Mental State Examination (MMSE) of 35 patients with MCI and 34 normal controls revealed that the scores of MCI patients did not differ significantly from those of normal controls (P＞0.05). Then, EEGs at rest and during working memory task with three levels of working memory load were recorded. The EEG power was computed over 10 channels: right and left frontal (F3, F4), central (C3,C4), parietal (P3, P4), temporal (TS, T6) and occipital (O1, O2); inter-hemispheric coherences were computed from five electrode pairs of F3-F4, C3-C4, P3-P4, T5-T6 and O1-O2 for delta (1.0～3.5 Hz), theta (4.0～7.5 Hz), alpha-1 (8.0～10.0 Hz), alpha-2 (10.5～13.0 Hz), beta-1 (13.5～18.0 Hz) and beta-2 (18.5～30.0 Hz) frequency bands. All values of the EEG power of MCI patients were found to be higher than those of normal controls at rest and during working memory tasks. Furthermore, the values of EEG power in the theta, alpha-1, alpha-2 and beta-1 bands of patients with MCI were significantly high (P＜0.05) in comparison with those of normal controls. Correlation analysis indicated a significant negative correlation between the EEG powers and MMSE scores. In addition, during working memory tasks, the EEG coherences in all bands were significantly higher in the MCI group in comparison with those in the control group (P＜0.05). However, there was no significant difference in EEG coherences between two groups at rest. These findings comprise evidence that MCI patients have higher EEG power at rest, and higher EEG power and coherence during working conditions. It suggests that MCI may be associated with compensatory processes at rest and during working memory tasks. Moreover, failure of normal cortical connections may be exist in MCI patients.  相似文献   

3.
To investigate inter- and intra-hemispheric electroencephalography (EEG) coherence at rest and during photic stimulation of patients with Alzheimer‘s disease (AD). Thirty-five patients (12 males, 23 females; 52-64 y) and 33 sex- and age-matched controls (12 males, 21 females; 56-65 y) were recruited in the present study. EEG signals from C3-C4, P3-P4, TS-T6 and O1-O2 electrode pairs resulted from the inter-hemispheric action, and EEG signals from C3-P3, C4-P4, P3-O1, P4-O2, C3-O1, C4-O2, TS-O1 and T6-O2 electrode pairs resulted from the intra-hemispheric action. The influence of inter- and intra-hemispheric coherence on EEG activity with eyes closed was examined, using fast Fourier transformation from the 16 sampled channels. The frequencies of photic stimulation were fixed at 5, l0 and 15 Hz, respectively. The general decrease of AD patients in inter- and intra-hemispheric EEG coherence was more significant than that of the normal controls at the resting EEG, with most striking decrease observed in the alpha-1 (8.0-9.0 Hz) and alpha-2 (9.5-12.5 Hz) bands. During photic stimulation, inter- and intra-hemispheric EEG coherences of the AD patients having lower values in the alpha (9.5-10.5 Hz) band than those of the control group. It suggests that under stimulated and non-stimulated conditions, AD patients had impaired inter- and intra-hemispheric functional connections, indicating failure of brain activation in alpha-related frequency.  相似文献   

4.
眼跳任务常用于研究额叶纹状体环路的机能,使用延迟眼跳任务可有效分离抑制空间工作记忆,深入探究注意缺陷多动障碍(ADHD)儿童的执行功能损伤.48名儿童(ADHD-I型11人,ADHD-C型19人,对照组18人)完成2种实验任务:正向眼跳和延迟眼跳.结果发现:(1)ADHD儿童存在抑制功能损伤,延迟眼跳中对照组错误率的成绩优势非常显著,延迟时间的加长使ADHD组的错误率显著提高,但不影响对照组错误率.(2)ADHD儿童存在一定的空间工作记忆损伤,延迟眼跳中ADHD组有较差的精确性,且延迟时间越长组间差异越显著.(3)ADHD儿童有较长的反应时和较慢的眼跳速度.  相似文献   

5.
时空信息和工作记忆广度对情境模型更新的影响   总被引：1，自引：0，他引：1  
目的:时空信息和工作记忆广度对语篇理解中情境模型更新的影响。方法:采用2×2×3混合实验设计,以探测词的反应时为指标,以故事短文为实验材料,采用词汇再认的方法进行实验。结果:时间表征的主效应显著,F(2,86)=17.298,P<0.001;角色行为和探测物体之间的一致性的主效应显著,F(1,43)=8.614,P<0.01;工作记忆广度的主效应接近显著,F(1,43)=4.045,P=0.051。结论:时间信息以隐含的形式给出时,时空信息影响情境模型的更新,空间的转换对情境模型的更新起主要作用。工作记忆广度影响情境模型空间维度的加工,高工作记忆广度读者比低工作记忆广度读者更容易产生情境模型的更新。  相似文献   

6.
余华梁 《闽江学院学报》2013,34(2):42-44,127
利用瞬态自旋光栅方法,在室温下实验研究了本征GaAs量子阱中电子自旋扩散的动力学过程.测得了不同周期的瞬态自旋光栅的衰减率,根据普遍认同的公式:Γ=q2Ds+l/τs,计算得到电子自旋扩散系数Ds=104 cm2/s,以及电子自旋弛豫时间τs=46 ps.测得的电子自旋扩散系数与文献报道的N型GaAs量子阱的实验测量结果相吻合,说明样品导电类型对电子自旋扩散系数没有显著影响.而电子自旋弛豫时间τs=46 ps与由饱和吸收方法测得的结果:τs=103 ps有明显区别.进一步分析了自旋光栅调制度随时间的衰减规律,对自旋极化衰减率公式:Γ=q2Ds+l/τs进行了修正.  相似文献   

7.
Forty‐seven boys identified by their third grade teachers as conduct problems were administered the ITPA and subdivided into three groups on the basis of race and social class: (1) the working class Negro group (N = 21); (2) the working class White group (N = 14); and (3) the middle class White group (N = 12). The total sample (N = 47) performed significantly below the standardization population on Auditory Reception, Visual Memory, Verbal Expression and Grammatic Closure and significantly above on Sound Blending. The working class Negro group did significantly poorer on the ITPA than the other two groups which did not differ significantly from each other. All three subgroups performed significantly below the standardization population on visual sequential memory. This latter result may indicate a non‐verbal learning disability which interferes with learning appropriate social behavior.

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8.
本文从理论上研究了二苯醚的电子结构,结果表明,二苯醚的苯氧基在空间的位置对二苯醚的原子电荷分布和体系能量影响较大,从而影响二苯醚的亲电取代反应.二苯醚的O—Ph键旋转,形成不同构象之间的最大与最小体系能量值之差[ΔE=5.258 03a.u.(3 299.466 4 kcal.mol-1)]很大,O23-C1单键不可自由旋转.当C1-O23-C7与苯环垂直时,体系能量[E(90)=E(270)=-534.885 08a.u]最低,为最稳定的优势构象.二苯醚中苯氧基表现为吸电基,它的作用使邻、间位碳原子的负电荷比苯环碳原子少,使对位碳原子的负电荷比苯环碳原子多,对位反应的途径最有利,苯氧基主要表现为对位定位基.  相似文献   

9.
三种百合科植物的染色体组型分析   总被引：2，自引：0，他引：2  
对生长在陕西秦岭南坡的三种百合科植物：七叶一枝花（ParispolyphyllaSm．）、野百合（LiliumbrowniiF．E．BrownexMiellez）、川百合（LiliumdavidiiDuchartre）进行了染色体组型分析．其结果是：七叶一枝花的核型公式为K（2n）=10=6m＋4m[SAT]，核型分级为1A型．野百合的核型公式为K（2n）=24=10m＋14st，核型分级为3B型．川百合的核型公式为K（2n）=24=8m＋6sm＋10st，核型分级为3B型．同时，在两种百合的染色体核型分析中都发现有一至两条B染色体存在．  相似文献   

10.
In order to investigate the characteristics of sensorimotor cortex during motor execution(ME), voluntary, stimulated and imaginary finger flexions were performed by ten volunteer subjects. Electroencephalogram(EEG) data were recorded according to the modified 10-20 International EEG System. The patterns were compared by the analysis of the motion-evoked EEG signals focusing on the contralateral(C3) and ipsilateral(C4) channels for hemispheric differences. The EEG energy distributions at alpha(8—13 Hz), beta(14—30 Hz) and gamma(30—50 Hz) bands were computed by wavelet transform(WT) and compared by the analysis of variance(ANOVA). The timefrequency(TF) analysis indicated that there existed a contralateral dominance of alpha post-movement event-related synchronization(ERS) pattern during the voluntary task, and that the energy of alpha band increased in the ipsilateral area during the stimulated(median nerve of wrist) task. Besides, the contralateral alpha and beta event-related desynchronization(ERD) patterns were observed in both stimulated and imaginary tasks. Another significant difference was found in the mean power values of gamma band(p0.01)between the imaginary and other tasks. The results show that significant hemispheric differences such as alpha and beta band EEG energy distributions and TF changing phenomena(ERS/ERD) were found between C3 and C4 areas during all of the three patterns. The largest energy distribution was always at the alpha band for each task.  相似文献   

11.
The Development of Memory and Processing Capacity   总被引：1，自引：0，他引：1  
The assumption of some developmental theories that short-term memory is the workspace of higher cognitive processes, and consequently that span measures processing capacity, is claimed to be inconsistent with the working memory literature. 4 experiments, using children aged 5 to 12 years, contrast this theory with a model in which short-term memory and the processing space component of working memory are at least partly distinct. Experiments 1 and 2 varied processing load, holding duration constant. The processing load manipulation had little effect on recall of a short-term memory preload. Experiments 3 and 4 failed to support the prediction that the greater processing efficiency of older children would be associated with slower loss of information from short-term memory. Although counting and rehearsal rates increased with age, and correlated with span, they did not predict the rate of loss of memory preload due to intervening counting. The data suggest that effects obtained with short-term memory span do not provide clear indications of overall working memory development, because short-term memory span and the processing space component of working memory entail distinct systems.  相似文献   

12.
Using strict and lenient mathematics achievement cutoff scores to define a learning disability, respective groups of children who are math disabled (MLD, n=15) and low achieving (LA, n=44) were identified. These groups and a group of typically achieving (TA, n=46) children were administered a battery of mathematical cognition, working memory, and speed of processing measures (M=6 years). The children with MLD showed deficits across all math cognition tasks, many of which were partially or fully mediated by working memory or speed of processing. Compared with the TA group, the LA children were less fluent in processing numerical information and knew fewer addition facts. Implications for defining MLD and identifying underlying cognitive deficits are discussed.  相似文献   

13.
This study investigates the interplay of working memory, cognitive style, and behaviour. Year 8 (aged 13 years) students (n = 205) at a UK urban secondary school were tested to ascertain predictors of General Certificate of School Education (GCSE) achievement. Assessment included Riding's cognitive style dimensions, working memory capacity, and a profile of school behaviour. A stepwise multiple regression analysis indicated that behaviour, working memory, verbal–imagery style by working memory, wholist–analytic style by working memory, and verbal–imagery style by wholist–analytic style predicted GCSE outcome, accounting for 58% of the variance. Generally, poor GCSE grade points were predicted by low behaviour scores, and by low working memory capacity in analytics and verbalisers. The results are discussed in terms of possible interventions that may improve student GCSE performance.  相似文献   

14.
This study examined temporal resolution of auditory perception (TRAP) in relation to speech perception and phonological working memory in one experiment and in relation to measures of rapid naming, understanding of grammatical contrasts, and phonological awareness in a second experiment. In the TRAP test, 6- to 9-year-old children discriminated four pairs of two sine tones, 878 Hz and 1350 Hz, presented in blocks with stepwise decreasing interstimulus intervals from 256 ms to 8 ms. In Experiment 1, weak but significant correlations between TRAP and speech perception and phonological working memory were found, as well as a significantly lower TRAP performance by girls. Experiment 2 indicated a significant relation between TRAP and the phonological awareness task. The results give qualified support to the notion of a weak relationship between TRAP and speech perception and language skills among typical children. However, the gender differences in TRAP performance, the limited variance explained by the regression models, and the finding that only one of the language parameters correlated with TRAP do not support the notion of a causal relationship between language skills and TRAP. The possibility that TRAP is connected to general neurological maturation rather than specifically to language abilities is discussed.  相似文献   

15.
Working memory refers to a mental workspace, involved in controlling, regulating, and actively maintaining relevant information to accomplish complex cognitive tasks (e.g. mathematical processing). Despite the potential relevance of a relation between working memory and math for understanding developmental and individual differences in mathematical skills, the nature of this relationship is not well-understood. This paper reviews four approaches that address the relation of working memory and math: 1) dual task studies establishing the role of working memory during on-line math performance; 2) individual difference studies examining working memory in children with math difficulties; 3) studies of working memory as a predictor of mathematical outcomes; and 4) longitudinal studies of working memory and math. The goal of this review is to evaluate current information on the nature of the relationship between working memory and math provided by these four approaches, and to present some of the outstanding questions for future research.  相似文献   

16.
Understanding the impact of political violence on child maladjustment is a matter of international concern. Recent research has advanced a social ecological explanation for relations between political violence and child adjustment. However, conclusions are qualified by the lack of longitudinal tests. Toward examining pathways longitudinally, mothers and their adolescents (M = 12.33, SD = 1.78, at Time 1) from 2-parent families in Catholic and Protestant working class neighborhoods in Belfast, Northern Ireland, completed measures assessing multiple levels of a social ecological model. Utilizing autoregressive controls, a 3-wave longitudinal model test (T1, n = 299; T2, n = 248; T3, n = 197) supported a specific pathway linking sectarian community violence, family conflict, children's insecurity about family relationships, and adjustment problems.  相似文献   

17.
在冰盐浴条件下,对硝基苯胺重氮盐与丙二酸二乙酯反应,合成了标题化合物C_(13)H_(15)N_3O_7。经IR、~1HNMR、元素分析和X-射线单晶测定,确认了其结构。化合物属单斜晶系,C2/c空间群,晶胞参数:α=14.331(11)■,b=6.847(5)■,c=32.63(3)■,β=98.149(14)°,V=3169(4)■~3,Z=8,D_c=1.364Mg/m~3,μ=0.112 mm~(-1),F (000)=1360,R=0.0783,wR=0.2461。  相似文献   

18.
引导和构建结构决定性质的教学思想,理解结构与化学反应性能的关系.通过氨基取代直链型脂肪族羧酸化合物的空间构象和电子结构分析,在α-氨基癸酸中,(1)-αC-C键自由旋转能垒8.425 1kcal/mol,-αC-N键自由旋转能垒14.042 3kcal/mol,高能构象时分子极性较大,为化学反应活性构象;(2)碳原子电荷密度受到氨基的影响,随着氨基取代位置n增加,-αC、-βC、-γC等碳原子负电荷密度减少;(3)氨基酸的体系能E随氨基与羧基有位置n的关系具有E=-594.804-0.005ln(n)(2≤n≤10),给予阐述.  相似文献   

19.
Using time‐frequency analysis techniques to investigate the event‐related low‐frequency (delta: 0.5–4 Hz; theta: 4–8 Hz) activity of auditory event‐related potentials (ERPs) data of highly and average intelligent children, 18 intellectually gifted children, and 18 intellectually average children participated the present study. Present findings show that intellectually gifted children had significantly larger delta activity than their normal peers in mismatch negativity (MMN) component, while in P3a component, which originates from stimulus‐driven frontal attention mechanisms during task processing, intellectually gifted children had both significantly larger delta and theta activities than their normal peers. The present findings further supported that low‐frequency brain activity could be regarded as the basis of intelligence and cognitive functions, and spectral EEG time‐frequency analysis technique should be used to explore some new aspects of brain activity relating to intelligence.  相似文献   

20.
设m、n、p、q是正整数,F是不同构于它自身的真子域的域,Mmn(F)记F上所有m×n矩阵的集合,M1mn(F)记Mm(nF)的包含所有秩1矩阵的子集。若一个映射f:Mm(nF)→Mpq(F)满足f(M1mn(F))哿M1pq(F)且f(A+B)=f(A)+f(B),坌A,B∈Mmn(F),则称f是保持秩1矩阵的加法映射。证明了:若一个保持秩1矩阵的加法映射f:Mm(nF)→Mp(qF)满足存在G,H∈Mm1n(F)使得rank(f(G)+f(H))>1,则存在P∈GL(pF),Q∈GL(qF)和F的域自同构啄使得1)p叟m叟2,q叟n叟2,f:A｜→P(A啄堠0)Q;或者2)p叟n叟2,q叟m叟2,f:A｜→P((A啄)T堠0)Q。  相似文献   

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