Removal of visual feedback alters muscle activity and reduces force variability during constant isometric contractions

The purpose of this study was to compare force accuracy, force variability and muscle activity during constant isometric contractions at different force levels with and without visual feedback and at different feedback gains. In experiment 1, subjects were instructed to accurately match the target force at 2, 15, 30, 50, and 70% of their maximal isometric force with abduction of the index finger and maintain their force even in the absence of visual feedback. Each trial lasted 22 s and visual feedback was removed from 8–12 to 16–20 s. Each subject performed 6 trials at each target force, half with visual gain of 51.2 pixels/N and the rest with a visual gain of 12.8 pixels/N. Force error was calculated as the root mean square error of the force trace from the target line. Force variability was quantified as the standard deviation and coefficient of variation (CVF) of the force trace. The EMG activity of the agonist (first dorsal interosseus; FDI) was measured with bipolar surface electrodes placed distal to the innervation zone. Independent of visual gain and force level, subjects exhibited lower force error with the visual feedback condition (2.53 ± 2.95 vs. 2.71 ± 2.97 N; P < 0.01); whereas, force variability was lower when visual feedback was removed (CVF: 4.06 ± 3.11 vs. 4.47 ± 3.14, P < 0.01). The EMG activity of the FDI muscle was higher during the visual feedback condition and this difference increased especially at higher force levels (70%: 370 ± 149 vs. 350 ± 143 μV, P < 0.01). Experiment 2 examined whether the findings of experiment 1 were driven by the higher force levels and proximity in the gain of visual feedback. Subjects performed constant isometric contractions with the abduction of the index finger at an absolute force of 2 N, with two distinct feedback gains of 15 and 3,000 pixels/N. In agreement with the findings of experiment 1, subjects exhibited lower force error in the presence of visual feedback especially when the feedback gain was high (0.057 ± 0.03 vs. 0.095 ± 0.05 N). However, force variability was not affected by the vastly distinct feedback gains at this force, which supported and extended the findings from experiment 1. Our findings demonstrate that although removal of visual feedback amplifies force error, it can reduce force variability during constant isometric contractions due to an altered activation of the primary agonist muscle most likely at moderate force levels in young adults.     

Power spectral EEG analysis and EEG variability in obsessive-compulsive disorder

Spectral EEG characteristics of thirteen patients with severe Obsessive-Compulsive Disorder (OCD) were investigated topographically. The finding of predominantly left posterior frontal to mid-temporal theta-2 is discussed in light of previous EEG studies and recent neuroradiologic findings.     

脑电反馈控制系统的研制

本文介绍了基于IBM PC/XT计算机的新型双闭环脑电反馈控制系统的研制及在系统中抑制噪声干扰、使系统具有临床实用性的具体措施。该系统将脑电生物反馈和物理刺激的反馈控制加以结合,能有效地进行脑电反馈控制,并具备多种脑电指标的CRT显示和打印机输出。     

Procaine-lnduced increases in limbic rCBF correlate positively with increases in occipital and temporal EEG fast activity

Summary Previous independent EEG and PET studies suggest that administration of intravenous procaine hydrochloride selectively activates limbic brain structures. To further elucidate procaine's effects and explore the relationship between quantitative EEG (qEEG) and regional cerebral blood flow (rCBF), we simultaneously recorded qEEG and sampled rCBF using O-15 water PET in 20 healthy volunteers during single-blind injections of saline (baseline condition) followed by intravenous procaine (1.84 mg/kg). After thorough screening of EEG records, a subgroup of 7 subjects with EEG data relatively free of both muscle and movement artifacts was selected for analysis. Quantitative spectral EEG data from right occipital and temporal leads were then correlated with each subject's PET rCBF values on a pixel by pixel basis, both at baseline and after procaine. The most striking finding was that the increases in occipital and temporal omega activity from baseline to procaine positively correlated with rCBF increases in the amygdala and its efferents (p<.05), in a pattern very similar to the rCBF increases seen after procaine administration. This suggests that omega activity may reflect activation of deeper brain limbic structures. Also, the convergence of EEG and PET data further supports procaine's selective limbic activation.     

Creativity and cortical activation during creative, intellectual and EEG feedback tasks.

Thirty-two male subjects were divided into four groups based on their performance on the remote associates test and alternate uses test, two measures of creativity. Right EEG alpha presence was monitored under basal conditions, while subjects took tests of creativity and intelligence, and while they attempted to enhance and suppress the amount of alpha in a feedback situation. High scorers on the alternate uses test operated at a high percentage of basal alpha during all tests while high scorers on the remote associates test showed differential amounts of alpha presence across tests, with the highest percentage of basal alpha during tests of creativity and the lowest percentage during an intellectual test. Both high creative groups tended to show increases in amount of alpha across trials when trying to suppress alpha as well as when trying to enhance it, but did not differ in overall control from the low creative groups.     

Interindividual variability in EEG correlates of attention and limits of functional mapping.

In this study, we analyzed the EEG oscillatory activity induced during a simple visual task, in search of spectral correlate(s) of attention. This task has been previously analyzed by conventional event-related potential (ERP) computation, and Slow Potentials (SPs) were seen to be highly variable across subjects in topography and generators [Basile LF, Brunetti EP, Pereira JF Jr, Ballester G, Amaro E Jr, Anghinah R, Ribeiro P, Piedade R, Gattaz WF. (2006) Complex slow potential generators in a simplified attention paradigm. Int J Psychophysiol. 61(2):149-57]. We obtained 124-channel EEG recordings from 12 individuals and computed latency-corrected peak averaging in oscillatory bursts. We used current-density reconstruction to model the generators of attention-related activity that would not be seen in ERPs, which are restricted to stimulus-locked activity. We intended to compare a possibly found spectral correlate of attention, in topographic variability, with stimulus-related activity. The main results were (1) the detection of two bands of attention-induced beta range oscillations (around 25 and 21 Hz), whose scalp topography and current density cortical distribution were complex multi-focal, and highly variable across subjects (topographic dispersion significantly higher than sensory-related visual theta induced band-power), including prefrontal and posterior cortical areas. Most interesting, however, was the observation that (2) the generators of task-induced oscillations are largely the same individual-specific sets of cortical areas active during the pre-stimulus baseline. We concluded that attention-related electrical cortical activity is highly individual-specific, and possibly, to a great extent already established during mere resting wakefulness. We discuss the critical implications of those results, in combination with results from other methods that present individual data, to functional mapping of cortical association areas.     

SPECT changes and their correlation with EEG changes in tuberculous meningitis

OBJECTIVE: In tuberculous meningitis (TBM) blood flow may be altered due to associated vasculitis, hydrocephalus and raised intracranial pressure. Electroencephalography (EEG) and single photon emission computed tomography (SPECT) provide information about electrical activity and regional cerebral blood flow respectively. This study aims at the correlation of EEG and SPECT changes in patients with TBM. METHOD: Sixteen patients with TBM whose age ranged between 5 and 62 years and 3 of whom were females were subjected to clinical, radiological (CT and/or MRI), EEG and SPECT studies using 99mTc ethylene cystine dimer (ECD). Ten patients were in stage III and 3 each in stage II and stage I meningitis. Cranial CT scan was carried out in 15 and MRI in 4 patients. Hydrocephalus was present in 9, infarction in 7 and tuberculoma in 5 patients. RESULTS: SPECT studies were abnormal in all except 2 patients revealing basal ganglionic hypoperfusion in 14 and focal cortical hypoperfusion in 9 patients. The EEG was abnormal in 11 patients which included delta slowing in 5, theta slowing in 6, frontal intermittent rhythmic delta activity (FIRDA) in 3 and epileptiform discharges in 2 patients. All the patients with abnormal EEG had abnormal SPECT study except 1. In 4 patients, EEG was normal although there was subcortical hypoperfusion on SPECT. In spite of high frequency of focal cortical hypoperfusion (9 patients), EEG revealed focal abnormality in 3 patients only. CONCLUSION: It can be concluded that the SPECT reveals more frequent abnormalities compared to EEG and CT scan. Cortical hypoperfusion with or without basal ganglia hypoperfusion is associated with FIRDA and diffuse delta slowing on EEG.     

Circadian and seasonal variability of resting frontal EEG asymmetry

Asymmetrical frontal cortical activity at resting baseline relates to important aspects of personality and psychopathology. However, some research has failed to replicate these relationships, perhaps because of situational influences. The present research investigates two situational variables, circadian and seasonal variability. These variables affect basal cortisol levels and mood, which have also been found to relate to resting asymmetrical frontal activity. Results of two correlational studies revealed that relative right frontal activity was greatest during fall mornings. These results suggest the importance of assessing time of day (TOD) and time of year (TOY) effects on resting frontal EEG asymmetry, which could reflect circadian and seasonal influences, but also selection effects when participants are free to select among study session times.     

Reaction-time variability, periodicities in reaction-time distributions, and the EEG gating-signal hypothesis.

Variability in a person's reaction time (RT) was investigated in relation to a model which hypothesized that the speed of information processing is a function of two factors, namely, the time characteristics of a cortical gating signal, and the recovery period of the events activated by the gating signals. A total of 280 RTs were obtained from each of six young adult subjects while electroencephalograms (EEGs) were simultaneously recorded. Half of the trials were performed under conditions which yielded short, low variability RTs while the other 140 trials were obtained under conditions which produced longer, highly variable RTs. Distributions of RTs from the two conditions were examined in relation to distributions of EEG half waves - which were assumed to define the period of the cortical gating signal - taken from the interval between stimulus and response. Findings were consistent with the model under investigation, namely: (1) the two different conditions produced periodicities or multiple peaks in the RT distributions; (2) the magnitude of the time intervals between consecutive peaks in the subjects' RT distributions was correlated with the duration of the most frequently occurring half waves in their EEGs; and (3) inter-subject differences in variability of the RT distributions were associated with differences in variability of the EEG distributions.     

Effects of performance feedback on cardiovascular reactivity and frontal EEG asymmetry

The process of goal-setting may be captured by psychophysiological variables, such as cardiovascular reactivity (representative of effort mobilisation) and frontal EEG asymmetry (motivational disposition). The current study exposed 32 participants to false performance feedback in order to manipulate goal-setting and mental effort investment. Participants performed five consecutive blocks of the n-back task and received false performance feedback. One group received repeated positive feedback (i.e. performance steadily improved over the five blocks) whilst a second group were exposed to repeated negative feedback (i.e. performance deterioration over five blocks). Blood pressure, power in the mid-frequency and high-frequency component of Heart Rate Variability (HRV), heart rate, frontal EEG asymmetry and subjective self-assessment data were collected. Sustained and repeated positive feedback led to increased systolic blood pressure reactivity and a suppression of the 0.1 Hz component of HRV. Increased relative left hemisphere activation was observed at F3/F4 and FC1/FC2 over successive task blocks in the presence of feedback regardless of positive or negative direction. It is argued that upward goal adjustment accounted for the psychophysiological changes observed in the positive feedback condition.     

Effects of feedback control on EEG alpha asymmetry during covert mental tasks

EEG alpha (8-12 Hz) was recorded bilaterally from O1-P3 and O2-P4 during two eyes-closed sessions in 40 women. During one session subjects performed two covert right-hemisphere activation tasks and two covert left-hemisphere activation tasks (no-biofeedback condition). During the other session subjects performed the same tasks while trying to control their EEG asymmetries, being provided with EEG asymmetry auditory feedback (biofeedback condition). The ratios of integrated EEG alpha amplitudes were calculated as measure of hemispheric asymmetry, and the number of times that the right and left alpha had the same phase angle was determined as index of hemispheric synchrony (alpha phase index). In both conditions, subjects rated orally after each task their degree of subjective fullfilment of the task. There were significant differences between the EEG asymmetry during right- and left-hemisphere tasks. Significant differences of integrated alpha amplitudes and ratios between the no-biofeedback and biofeedback condition were also found. There was more hemispheric asymmetry in the biofeedback than in the no-biofeedback condition, and a significantly higher alpha phase index. There was no correlation between fullfilment ratings and alpha ratios in the no-biofeedback condition, but there was such correlation during right and left hemisphere tasks in the biofeedback condition. The study demonstrated that biofeedback regulation and covert mental activity can have effects on EEG alpha asymmetry which are cumulative.     

儿童癫痫发作间期SPECT高灌注灶与EEG致痫区之间的关系

目的：观察早期儿童癫痫病例单光子发射计算机层体摄影（SPECT）高灌注灶与脑电图（EEG）致痫灶之间的相关性。方法：对30例儿童癫痫SPECT高灌注显像病例进行同步录像脑电图（V-EEG）进行12h长程监测,分析这两种方法结果的相关性。结果：发作间期SPECT显像高灌注灶者29例（97％）,高低灌注灶者1例（3％）;单灶者13例（43％）13个灶,多灶者17例（57％）41个灶,共54个灶。EEG30例均异常,有痫样放电者29例（97％）,其中局限性异常18例（60％）,广泛性异常11例（37％）,另有慢波异常者1例。SPECT高灌注灶与EEG的致痢灶相符者7例（23％）,相近者7例（23％）,不相符者16例（54％）。结论：早期儿童癫痫病例SPECT的高灌注灶与EEG的致痫灶的相关性较低。     

Sensory feedback prosthesis reduces phantom limb pain: proof of a principle

Background

Constrained functionality and phantom limb pain (PLP) are major concerns for forearm amputees. Neuroscientific investigations of PLP suggest that behaviorally relevant stimulation of the stump can decrease PLP. Furthermore the prosthesis user could use feedback information of the prosthesis hand for optimizing prosthesis motor control when handling soft and fragile objects. Somatosensory feedback information from a prosthetic hand may therefore help to improve prosthesis functionality and reduce phantom limb pain.

Objectives

We wanted to find out whether a two weeks training on a hand prosthesis that provides somatosensory feedback may help to improve prosthesis functionality and reduce phantom limb pain.

Methods

Eight forearm amputees with phantom limb pain were trained for two weeks to use a hand prosthesis with somatosensory feedback on grip strength.

Results

The current study demonstrates a significant increase of functionality of the prosthesis in everyday tasks. Furthermore, the study shows that usage of a prosthesis that provides somatosensory feedback on the grip strength is effective to reduce phantom limb pain.

Conclusions

A prosthesis with a feedback function appears to be a promising therapeutic tool to reduce phantom limb pain and to increase functionality in everyday tasks. Future studies should further investigate the scope of application of that principle.     

90例围产期异常的癫痫患者的临床、SPECT、EEG与影像学研究

目的：探讨围产期异常癫痫患者的临床特征、发作间期SPECT、V-EEG及CT和（或）MRI特点。方法：对90例围产期异常的癫痫患者进行发作间期SPECT、V-EEG和影像学检查并分析其与临床的关系。结果：本组90例中存在16种围产期高危因素,起病年龄≤14岁者占88％。V-EEG异常81例（90％）,呈痢样放电74例,定位率为37％。SPECT异常78例（87％）;低灌注38例（49％）,高灌注33例（42％）,高-低灌注7例（9％）,总异常灌注灶120个,其中颞叶占54个（45％）。影像学异常45％。结论：围产期异常的癫痫患者多在儿童期发病;V-EEG痴样放电以广泛性多见。发作间期SPECT异常灌注多见于颞叶。影像学表现以颞叶萎缩和脑发育障碍多见。     

Spatial resolution of visual feedback affects variability and structure of isometric force

The purpose of this study was to examine the effect of spatial resolution of visual feedback on the variability and structure of isometric force. We manipulated spatial resolution of the display by changing the number of possible feedback dot positions. Twelve healthy young adults (5 men, 7 women) attempted to apply a constant level of force normal to a load cell with the index finger using two types of visual displays. One display provided high spatial resolution visual feedback by allowing feedback dot take any position from the 440 pixels along the vertical dimension of the screen. This display provided precise information about the current level of force relative to the target and to a range of allowable force deviation around the target. The other display provided low spatial resolution visual feedback by depicting applied force as taking on only three discrete values—below, within, or above the target range. Participants produced less variable and more complex (higher approximate entropy) force output with the displays that had higher spatial resolution. Recurrence quantification analysis of the force time series revealed that the display with low visual feedback resolution promoted a more intermittent, discontinuous force-production performance.     

青少年肌阵挛癫痫的临床、EEG与SPECT的研究

目的：探索青少年肌阵挛癫痫（JME）的临床、脑电图（EEG）和发作间期单光子发射断层扫描（SPECT）的特点.方法：总结40例JME病例的临床、EEG和 SPECT显像等资料.结果：年龄6～32岁.病程2周至19年,平均（4.12±3.95）年.病因：家族史7例.临床表现：有肌阵挛发作性抽动40例（100%）,兼有全面性强直阵挛发作36例（90%）,兼有失神发作12例（30%）.常规EEG检查13例,正常5例,异常8例 长程EEG监测27例（V-EEG 21例,AEEG 6例）均异常,总体异常35例（87%）.异常者中,广泛性31例（89%）,局灶性异常4例（11%） 多棘慢波31例（89%）,高波幅慢波2例（6%）.发作间期SPECT正常11例（28%）,异常29例（72%）.低灌注12例（41%）,高灌注17例（59%）.异常灌注部位41个,额叶占40%.影像学异常5%.结论： 有关JME的诊断,在把握好临床表现的基础上,长程EEG监测显得很重要,SPECT显像的额叶异常灌注灶的证据也具有重要意义.