轻度认知功能障碍患者工作记忆中 脑电能量及皮质联络功能的变化特征

探讨轻度认知功能障碍患者（MCI）工作记忆状态下脑电能量及皮质联络功能的变化特征。被试为从社区选取的35名轻度认知功能障碍患者和34名健康志愿者。采用简单计算回忆方法,结果发现工作记忆加工过程中会引起4.0~18.0Hz范围内功率值的改变,且MCI组高于正常对照组;MCI患者在中央、顶、颞叶的半球间相干系数均显著高于正常对照组。研究结果提示MCI患者可能存在中央、顶、颞叶皮层的功能减退,工作记忆状态下通过代偿机制仍能维持加工的有效性     

Relationship between automatically analyzed quantitative EEG data and psychological performance parameters in patients with epilepsy

A report is given on results of comprehensive studies in which significant positive correlations between automatically analysed parameters reflecting the frequency behaviour of the EEG background activity and psychometrically recorded relatively complex psychic and psychomotoric tempo performances as well as some partial aspects of the re-adjustment capability in epileptics were found. EEG indicator values could be ascertained which point to psychic performance disturbances in epileptics.     

Quantitative EEG Assessment During Neuropsychological Task Performance in Adults with Attention Deficit Hyperactivity Disorder

This study evaluated the neuropsychological performance of adults with and without Attention Deficit Hyperactivity Disorder (ADHD) during the Paced Auditory Serial Addition Test (PASAT), Wisconsin Card Sorting Test: Computerized Version 3 (WCST), and the Integrated Visual and Auditory Continuous Performance Test (IVA). Quantitative electroencephalographic (QEEG) data were also collected during task performance to examine differences in cortical activity between groups and tasks. Results suggest that adults with ADHD demonstrated lower levels of performance on the PASAT and IVA, tasks that involve working memory and processing speed, and sustained attention, respectively. Adults with ADHD also had more upper alpha activity during the IVA. Lastly, for the ADHD group, an increased theta/beta ratio during the IVA was significantly related to poorer attentional performance. The current results support reinforcing specific types of cortical activity though EEG operant conditioning (neurofeedback) as a treatment option in adults with ADHD. This paper is based largely in part on a dissertation by J. Noland White in partial fulfillment of the requirements of his doctoral program at The University of Tennessee. Portions of this study have been presented in summary form at several professional conferences.     

Phase-locking and amplitude modulations of EEG alpha: Two measures reflect different cognitive processes in a working memory task

It has been demonstrated in numerous experiments that oscillatory EEG responses in the alpha frequency band (8-12 Hz) increase with memory load during the retention interval in working memory tasks. However, the findings diverge with respect to which measurement of alpha activity is influenced by memory processes. Here, we differentiate between evoked and total alpha activity in order to separate effects of phase-locking and amplitude modulation. We present data from a delayed-matching-to-sample task (S1-S2 paradigm) for which we compared EEG alpha responses between a perception and a memory condition. Increased total alpha activity was found in the retention interval for the memory as compared to the perception condition. Evoked alpha activity, however, did not differentiate between memory and perception conditions but, instead, was increased for the more complex condition of processing non-Kanizsa figures as compared to Kanizsa figures. Thus, our results demonstrate a functional differentiation between evoked and total alpha activity. While alpha phase locking seemed to be influenced mainly by task complexity, alpha amplitude clearly reflected memory demands in our paradigm.     

Intellectual disabilities and developmental EEG transition to alpha band: a comment on Shibagaki, et al. (2006)

In 2006 Shibagaki, et al. estimated mean chronological age at which dominant EEG frequency reached alpha band in 11 children with intellectual disabilities (M age, 15 yr.). Consistent with previous studies, the results showed a delay in the critical age relative to healthy children and earlier maturation at posterior scalp sites, with the exception of several children who persistently showed EEG slower than alpha band. A flaw in the study might be that having only 2 children younger than 10 yr. was insufficient. A remaining problem for researchers would be to identify whether the developmental delay in EEG correlates with IQ in intellectually disabled children.     

The relationship between psychological test results and EEG patterns in healthy children

222 children (112 girls and 110 boys) aged 5–16 years with different types of EEG pattern, selected according to well defined normal criteria in order to exclude cerebral lesion elements, were investigated by current child-psychiatric diagnostic methods, including the Wechsler Intelligence Scale for children (WISC), which gave a mean IQ of 116.5. With two so-called tests of organicity (Bender Gestalt Test and Benton's Revised Visual Retention Test) poor performances indicating brain damage were shown in 22% and 24% of the children respectively. Various EEG patterns showed few significant correlations with the test variables. According to clinical judgement "slight symptoms of cerebral dysfunction" was found in some children, but no correlation appeared between such symptoms and poor performance in the psychological tests. The high frequency of defective scores in the Bender and Benton tests in this selected material of healthy children means that these tests cannot be used in clinical work for diagnosing brain injury in individual children. Nor can they be used to throw light on the clinical significance of the different EEG variables studied.     

Primed word-fragment completion and successive memory test performance in normal aging

Young and old subjects were investigated to examine whether: the effects of priming are influenced by aging; there is independence between primed word-fragment completion and recognition performances; and the dependence between different tests is influenced by aging. A successive test paradigm was employed involving repeated assessment of to-be-remembered words by means of recognition and primed word-fragment completion. The results show that implicit memory declines with increasing age, and that correlations between different memory tests decrease with age. The outcome suggests that age-related memory decline involves several forms of memory, including primed word-fragment completion, and is reflected in correlations between measures of implicit and explicit memory.     

Stimulus complexity, EEG abundance gradients, and detection efficiency in a visual recognition task.

Occipital EEG was monitored while subjects inspected 27 projected patterns. The number (N) and variety (V) of elements in the patterns were varied systematically. There were three levels of N (6, 12 or 24 elements) and three levels of V (circles, squares or hexagons occupying all, one half or one third of the element locations for all levels of N). Subjects were instructed that they would be required in a post-test to recognize the patterns, among patterns which had not appeared; they were also informed that the patterns had been constructed according to a set of simple rules, but the nature of these rules was not made fully explicit. The EEG was quantified by means of low-frequency analysis, yielding measures of abundance (theta, alpha and beta) and mean dominant frequency. For the recognition task, nine stimulus items were embedded among 45 items. Recognition efficiency was measured by means of the signal detection theory discrimination index (d'). The results were as follows: (i) Both N and V were inversely related to alpha abundance (P less than 0-01); (ii) the strongest relationship between stimulus parameters and the EEG held for N and EEG beta activity (13-5-19-5 Hz;P less than 0-001), where again the EEG and N were inversely related; (iii) there was a significant (P less than 0-05) direct relationship between N and theta activity; (iv) contrary to prediction, mean dominant alpha frequency decreased as N increased; (v) d' correlated significantly with a number of effects for N, i.e. subjects who exhibited greatest EEG discriminability of items during exposure of the patterns, subsequently obtained the higher detection scores in the recognition task. The work described therefore demonstrates that only only do stimulus parameters have systematic effects upon brain activity as measured by the EEG, but that such effects have functional value and reflect aspects of efficiency. The results are fully compatible with arousal theory constructs relating physiological reactivity and performance.     

Assessing declarative memory in 12-month-old infants: A test – retest reliability study of the deferred imitation task

This study examined whether declarative memory in infants can be reliably assessed using the deferred imitation task. Twenty-four infants at the age of 12 months were given the same deferred imitation task twice within a short period of time (week-to-week assessment). Replicating the results of former studies the second memory test yielded better memory performances on the group level than the first one, indicating a memory benefit as is typically found in older children as well as in adults. Stability of memory performance level was analysed using two indicators, namely test – retest correlations assessing stability of individual memory performances for the whole sample, as well as corrected test – retest correlations using individual consistency scores. Test – retest reliability was highly significant (r = .52, p = .009), as well as corrected test – retest reliability (r = .62, p = .001), thus demonstrating that the individual memory performance level in infants can reliably be assessed using the deferred imitation task.     

Relations between subjective evaluations of memory and objective memory performance.

Several explanations for the weak relations between subjective memory judgements and objective memory performance were investigated in two groups of normal older adults. Group 1 sampled a general population (mean age 61.6 yr., range 46-89), while Group 2 sampled subjects who were on a waiting list for memory training (mean age 63.0 yr., range 45-85 years). In both groups, subjective memory judgments were assessed with global ratings of memory capacity and with ratings of frequency of forgetting in specific memory situations. Memory performance was assessed with several well-known tests and with recently developed tests for domain-specific aspects of memory. Most tests concerned episodic memory. Study 1 also included measures of semantic, incidental and working memory. Study 2 further examined the influence of the domain-specificity of objective and subjective measures for remembering names, intentions, and texts. Relations between memory self-reports and performance were weak in both groups and for all kinds of tests. Against expectations, the low correlations could not be explained by differences between ecological and laboratory tests or incidentally and intentionally remembered information, or by differences between specific failures compared to global, stereotyped judgments. Surprisingly, correlations did not increase when subjective and objective measures assessed the same ability, like remembering names. Also noncognitive variables (mood and lifestyle) did not influence the relations. The (weak) relations between subjective and objective memory measures were comparable for subjects over and under 65 years of age. Furthermore, relations were comparable for the general population sample and the memory compliant group.     

Use of automatic frequency analysis in the therapy of patients with acute ischemic insults

A series of EEG reading by automatic frequency analysis by means of Fast-Fourier transformation was taken, with a total of thirteen patients with acute ischemic infarction. Of the parameters under test, the total power-parameters, the relative performances of the delta and alpha wavebands, the delta/alpha index, and the alpha peak frequency variation proved their suitability in assessing clinical progress and in lateral localisation. Automatic frequency analysis adds to the range of tools available for EEG diagnosis, and can play its part in trend analysis during intensive therapy.     

Interindividual differences in alpha and theta power reflect memory performance

Previous research from our laboratory has shown that phasic or event-related changes in alpha and theta band power are related to memory performance. In this study, we test the hypothesis, whether tonic or ‘baseline’ power too is related to memory performance. The ongoing EEG was analyzed for a sample of 60 subjects during five experimental conditions: eyes closed, eyes open, memorizing words and counting backward in steps of 3 and 7. The results show that subjects with good memory performance have significantly larger upper alpha, but less theta and lower alpha power. In contrast to memory, good calculation performers have more beta and theta power than bad performers. These findings were obtained during actual task performance, but in a similar way also during the resting conditions eyes closed and open.     

Changes in the EEG frequency spectrum in various phases of mental stress

To obtain evidence about the relationship between spontaneous EEG activity and mental activity, an experiment was designed and executed with EEG recordings during a concept-learning task. We varied task performance (self-paced vs. machine-paced) and distinguished different stages of information processing during task performance. Using factor analysis calculated on all spectral coefficients, we found two orthogonal variables in the clinical alpha band. Alpha 2 power (10.5-12 Hz) seems to reflect the overall processing demands imposed on the individuals. Furthermore, there are different EEG frequency patterns during perceptual-central- compared with response-related processing as well as during processing of positive vs. negative feedback. The results suggest using (1) conservative procedures in hypothesis testing and (2) procedures to reduce between subject variability (a posteriori defined frequency variables, relative power values, scaling of reaction values) in further studies relating EEG activity to mental activity during task performance.     

Intra- and interindividual differences in lateralized cognitive performance and asymmetrical EEG activity in the frontal cortex

The study shows that changes in relative verbal vs. figural working memory and fluency performance from one session to a second session two to 3 weeks apart covary with spontaneously occurring changes of cortical asymmetry in the lateral frontal and central cortex, measured by electroencephalography (EEG) in resting conditions before the execution of tasks. That is, it was examined whether the current state of cortical asymmetry predicts verbal vs. figural performance. The findings complete the circle from studies showing correlations between changes of EEG asymmetry in the lateral frontal cortex and changes of mood to studies showing correlations between changes of mood and changes of relative verbal vs. figural working memory and fluency performance. The study suggests that state-dependent changes of lateralized cortical activity may underlie certain cognitive-emotional interactions observed in previous studies, and supports the assumption of reciprocal influences of specific emotional and specific cognitive processes.     

Arousal and memory: phasic measures of arousal in a free recall task.

EEG alpha activity and skin potential were monitored during word presentation in a single trial free recall task. Phasic changes in EEG alpha and skin potential, co-occurring with word onset, were positively related to recall at an immediate retention interval (2 min) but not after a delay (45 min). The results were interpreted as supporting the extension of Routtenberg's (1968) two-arousal system hypothesis to human memory. Arousal was viewed as affecting memory during the attribute encoding stage of memory storage.     

发散性思维的年龄差异及“位置法”记忆训练的作用

该研究的目的是探讨发散性思维的年龄差异以及“位置法”记忆训练对发散性思维的迁移作用。训练组为经过记忆训练的青年人24名,老年组20名,对照组为相匹配的青年人24名、老年人19名。结果表明:(1)在图形、符号、语义三方面的流畅性、变通性和独特性上,老年组均很显著地比青年组差。青年组的个别差异较大,老年组的更大,尤其是独特性。(2)青年训练组的图形流畅性、独特性及语义的独特性成绩显著优于其对照组,老年训练组图形的变通性有优于其对照组的趋势(P=.052),说明“位置法”记忆训练对发散性思维有一定的间接迁移作用,尤其是对青年人。(3)发散性思维与想象力、数字符号、训练前和训练后词的记忆以及图形的记忆成绩均有很显著正相关。而词汇成绩只与训练组两项发散性思维有显著相关。     

Working memory training: improving intelligence--changing brain activity

The main objectives of the study were: to investigate whether training on working memory (WM) could improve fluid intelligence, and to investigate the effects WM training had on neuroelectric (electroencephalography - EEG) and hemodynamic (near-infrared spectroscopy - NIRS) patterns of brain activity. In a parallel group experimental design, respondents of the working memory group after 30 h of training significantly increased performance on all tests of fluid intelligence. By contrast, respondents of the active control group (participating in a 30-h communication training course) showed no improvements in performance. The influence of WM training on patterns of neuroelectric brain activity was most pronounced in the theta and alpha bands. Theta and lower-1 alpha band synchronization was accompanied by increased lower-2 and upper alpha desynchronization. The hemodynamic patterns of brain activity after the training changed from higher right hemispheric activation to a balanced activity of both frontal areas. The neuroelectric as well as hemodynamic patterns of brain activity suggest that the training influenced WM maintenance functions as well as processes directed by the central executive. The changes in upper alpha band desynchronization could further indicate that processes related to long term memory were also influenced.     

On the electrophysiology of effective visual memory as measured by QEEG

An investigation into the QEEG parameters of effective cognitive functioning of visual memory for six Korean figures was conducted employing 69 normal subjects. Subjects studied the figures for 1 minute, engaged in an immediate 30-second quiet recall period, which was then followed by the subjects drawing the figures. A delayed recall of 45 minutes later followed the same methodology. The recall performances were correlated with the QEEG variables. For the input stage, total memory was determined predominantly by specific patterns of left frontal (F7, F3, Fpl) projections (phase and coherence activity) and left central/posterior (T3, C3, P3) phase (Alpha and Betal( 13–32 Hz)) projections. Success during immediate silent recall was determined by left frontal (F7, Fpl, F3) projections and left central/posterior (T3, T5, Ol, P3) projections in the Beta frequencies. Long term-delayed recall was determined by Ol coherence Alpha projection activity and Symmetry of Beta2 (32–64 Hz) at F8. Degree of activation variables (from visual attention and eyes closed) showed different patterns of successful activations.     

On the electrophysiology of effective visual memory as measured by QEEG

An investigation into the QEEG parameters of effective cognitive functioning of visual memory for six Korean figures was conducted employing 69 normal subjects. Subjects studied the figures for 1 minute, engaged in an immediate 30-second quiet recall period, which was then followed by the subjects drawing the figures. A delayed recall of 45 minutes later followed the same methodology. The recall performances were correlated with the QEEG variables. For the input stage, total memory was determined predominantly by specific patterns of left frontal (F7, F3, Fpl) projections (phase and coherence activity) and left central/posterior (T3, C3, P3) phase (Alpha and Betal( 13–32 Hz)) projections. Success during immediate silent recall was determined by left frontal (F7, Fpl, F3) projections and left central/posterior (T3, T5, Ol, P3) projections in the Beta frequencies. Long term-delayed recall was determined by Ol coherence Alpha projection activity and Symmetry of Beta2 (32–64 Hz) at F8. Degree of activation variables (from visual attention and eyes closed) showed different patterns of successful activations.     

Maturation of EEG power spectra in early adolescence: a longitudinal study

This study investigated the fine-grained development of the EEG power spectra in early adolescence, and the extent to which it is reflected in changes in peak frequency. It also sought to determine whether sex differences in the EEG power spectra reflect differential patterns of maturation. A group of 56 adolescents were tested at age 10 years and then at two further time-points approximately 18 months apart. The EEG was recorded during both eyes-closed and eyes-open conditions and Fourier transformed to provide estimates of absolute and relative spectral power at 0.5 Hz intervals from 0.5 to 40 Hz. The peak alpha frequency for each individual at each time-point was also determined for relative spectral power. Partial Least Squares (PLS) analysis was used to determine the combination of electrodes and frequencies that showed developmental change, or differed between the sexes. As a function of age, absolute delta and theta frequencies power decreased, and relative alpha2 and beta frequencies increased, replicating the standard findings of a decrease in lower, and increase in higher, frequencies with age. A small but significant increase in peak alpha frequency with age was detected. Moreover PLS analysis performed with individual alpha frequencies aligned to 10 Hz suggested that the age-related increase seen in alpha2 relative power was driven by changes in the peak frequency. Although males demonstrated higher alpha power than females, there were no sex differences in peak frequency, suggesting that there may be more to sex differences in EEG power than simply different rates of maturation between the two sexes.