High resolution quantitative EEG analysis

Summary High resolution spectral methods are explored as an alternative to broad band spectral parameters (BBSP) in quantitative EEG analysis. In a previous paper (Valdes et al. 1990b) regression equations (Developmental surfaces) were introduced to characterize the age-frequency distribution of the mean and standard deviation of the log spectral EEG power in a normative sample. These normative surfaces allow the calculation of z transformed spectra for all derivations of the 10/20 system and z maps for each frequency. Clinical material is presented that illustrates how these procedures may pinpoint frequencies of abnormal brain activity and their topographic distribution, avoiding the frequency and spatial smearing that may occur using BBSP. The increased diagnostic accuracy of high resolution spectral methods is demonstrated by means of receiver operator characteristic (ROC) curve analysis. Procedures are introduced to avoid type I error inflation due to the use of more variables in this type of procedure.     

Time course of EEG background activity level before spontaneous awakening in infants

This research aimed to investigate the time course of the cortical activity level preceding spontaneous awakening as a function of age and state. Two groups of infants (1-4 and 9-14 weeks of age) were continuously monitored by polygraphic recording and behavioural observation during the night. The electroencephalographic (EEG) activity recorded by the C3-O1 lead was analysed through an automatic analysis method which provides, for each 30-s epoch, a single measure, time domain based, of the EEG synchronization. The EEG parameter values were computed in the 6 min preceding each awakening out of non-rapid eye movement (NREM) sleep and out of rapid eye movement (REM) sleep. The EEG background activity level did not change in the minutes preceding awakening out of REM sleep. Awakening out of NREM sleep was preceded by a change of EEG activity level in the direction of higher activation with different time course according to the age. Both REM and NREM sleep results suggest that a high level of EEG activity is a prerequisite for the occurrence of a spontaneous awakening.     

Posture, Place, and Mood Effects on Ambulatory Blood Pressure

Ambulatory blood pressure was studied as a function of posture, place, and mood in 131 subjects classified according to race, gender, and hypertensive status. The effect of posture was significant and explained a substantial proportion of within-subject variability. After controlling for posture, significant place and mood effects were observed when subjects were sitting but not when they were standing. Home vs. work differences in both systolic and diastolic blood pressure were significantly greater in Whites than in Blacks. Similar differences in systolic blood pressure were greater in mild hypertensive than in normotensive subjects. The results of this study underscore the need to control for effects of posture when interpreting ambulatory blood pressure readings.     

高血压急诊患者降压前后脑电图变化及临床意义

目的:观察高血压急诊快速降血压对大脑功能的影响情况。方法:监测56例病人含服 降压药前后的脑电活动和血压情况,并对所获资料进行分析。结果:2 h内收缩压(SBP)下降>5.33 kPa (40 mmHg)或舒张压(DBP)下降>4.00 kPa(30 mmHg)时,脑电图异常程度增加,θ及δ频段功率值明 显升高(P<0.01)。结论:降压急骤,可能会造成大脑功能损害     

EEG enhancement during electrosurgery using an optical fibre

The paper considers the limiting factors in EEG enhancement in the presence of electrosurgery interference and presents a design for a useful fibre-optic EEG monitoring instrument which is free from such problems as electrical shock (micro and macroshock), patient burns and susceptibility to electrosurgery interference associated with conventional EEG monitors.     

Effect on EEG responses of removing ocular artefacts by proportional EOG subtraction

Work undertaken to investigate the effect on EEG responses of ocular artefact removal by proportional electro-oculogram subtraction using the least-squares method is reported. The ocular artefact model and the least-squares approach to estimation of the model parameters and hence of the EEG waveform, including the response, are described. Results are presented to show that the response shapes become modified if ocular artefact removal is implemented recursively. This happens because the response is incorrectly treated as part of the random background EEG. The solution is to incorporate a model of the response within the ocular artefact removal algorithm. The results of tests on simulated data confirm these conclusions. The results of the incorporation of response models in removing ocular artefacts from CNV recordings are presented. Even with modelling recursive ocular artefact removal is found to modify the shape of the CNV, and so reliable results can only be obtained if the removal is implemented nonrecursively. Evidence is given that it is advisable to remove DC levels from the recorded data.     

90例小儿发热惊厥脑电图与临床预后关系

本文报告了90例发热惊厥(FC)患儿的脑电图检查结果,认为对FC患儿的脑电图检查时间应在退热至少2周后进行;FC起病年龄低者再发率高,且脑发育成熟前起病的FC患儿脑损伤轻严重;对于某些患者,引起FC的体温逐渐降低,这些患儿转为无热惊厥(癫痫)的可能性明显增高;家族史不仅会影响FC的发病倾向而且会影响FC的复发及转归。     

Potent depressant effects of adenosine analogs on hippocampal slow-wave activity in the unanesthetized rat

Summary Adenosine and its analogs have previously been shown to exert a depressant effect on several measures of hippocampal excitability in the hippocampal slice and intact anesthetized preparation. In the present report, we examined the effects of intraventricular injections of adenosine analogs on hippocampal slow-wave activity in the freely moving rat. Each of three adenosine analogs— 5-N-ethylcarboxamidoadenosine (NECA) and N⁶-(phenylisopropyl) adenosine (L- and D-PIA) — were found to strongly suppress hippocampal electroencephalographic (EEG) activity. For instance, low doses of NECA (0.5 g) produced an 80–90% decrease in the amplitude of the hippocampal EEG. NECA was approximately 20-fold more potent than L-PIA, and L-PIA was twice the potency of D-PIA. In separate experiments in the anesthetized rat, NECA and L-PIA were found to block completely the activation of the hippocampal theta rhythm elicited with brainstem stimulation. The effects of adenosine analogs on both the hippocampal EEG and theta rhythm were very effectively reversed with methylxanthine, 8-para-sulphophenyl-theophylline (8-PSPT). The present findings demonstrate that adenosine analogs exert a powerful depressant effect on the hippocampal EEG in the natural unanesthetized state, and suggest that changes in the levels of endogenous adenosine may play a significant role in modulating the normal activity and function of the hippocampus.This work was supported in part by National Science Foundation grant BNS-8403544 to RPV     

Influences of Subject Self-Selection on the EEG Alpha-Hypnotizability Correlation

To determine the effect of subject self-selection on the alpha-hypnotizability correlation, the correlations between volunteer and invited subject groups were compared. For 8 volunteers the correlation between baseline eyes-closed occipital alpha and the Harvard Group Scale of Hypnotic Susceptibility score was r=.72; for 12 invited subjects, that correlation was r=-.02. The significant difference in these correlations gives support to a previously published paper which hypothesized, on the basis of a literature review, that sampling modifications generated by subject self-selection were responsible for the occurrence of significant alpha-hypnotizability correlations.     

Design of a multichannel solid-state recorder and its application to temperature measurement

The development of a multichannel unconstrained memory system for monitoring physiological information is described. The system comprises a portable recorder, worn by the subject, to detect and store data in memory and a readout unit for transferring the data to a microcomputer. Using the microcomputer, the physiological data are displayed, retrieved and analysed. The portable recorder consists of a memory control unit, an instrumentation unit, an LCD timer and batteries. In the memory-control unit the data are transferred to EPROM (erasable programmable read-only memory), which is a nonvolatile memory. This memory, removed from the protable recorder, can be delivered to the laboratory and its contents analysed without interrupting the field experiment. In connection with the instrumentation unit, an 8-channel skin thermometer was designed and tested. It was accurate to within ±0.08°C compared with a standard thermometer.