EEG-EMG Zeitschrift fur Elektroenzephalographie, Elektromyographie und verwandte Gebiete最新文献

The second part of this study deals with the behavioral und event-related potential (ERP) findings from the recognition phase of incidental and intentional learning paradigms. Correctly recognized old items were characterized by a significantly more positive ERP in the 400 to 800 ms range when compared to correctly identified new items. Furthermore old words, which had previously been remembered in a free recall test were associated with a more positive ERP when compared to both, correctly recognized and nonrecognized old words. This effect also had an earlier onset latency. The findings are considered in the context of recent results from continuous recognition memory and repetition priming studies. It is concluded that in the present paradigm ERP differences due to recognition can be attributed to unspecific phenomena.

The macro-EMG can be recorded with a modified single fiber or concentric needle. The two needles attain different results with smaller potentials values for the concentric needle type. For the single fiber type normal data are given for the EDC and tibialis anterior muscle. These data are compared with previously published results and their statistical evaluation. The concentric needle type can be used for scanning EMG. In addition potential stability can be examined in different parts of the MU using the unblanketing principle. A further novel use for macro-EMG is simultaneous single motor unit twitch recording to compare mechanical and electrical MU activity. In normal muscle the electrical signal is positively correlated with twitch force. In diseased muscle like ALS twitch is dissociated from electrical potential size. Macro-EMG allows to quantify MU size, a prerequisite to follow up dynamic changes in muscle. Improved computer programs in commercially available EMG-machines will help to introduce this method into clinical EMG laboratories as a useful addition to increase the diagnostic yield of EMG.

In the past, clinically relevant diagnostic procedures using nocifensive reflexes have been restricted mainly to ascertaining the functional status of the efferent or afferent portion of the reflex arc. The method described here, which evoked global nocifensive reflexes, permits differentiated conclusions to be drawn regarding possible supraspinal influences on nocifension. The reflex patterns yielded by the procedure can provide information regarding the functional status of the formatio reticularis, which is subject to modulatory influences of the pallidostriatum and thalamus. The results show that specific, pathohistologically confirmed lesions of the thalamus de-inhibit the formatio reticularis for motor reticulospinal activity and that this is reflected in the nocifensive pattern. Thus, the nocifensive reflex on the contralateral side to the thalamic process is stronger and has a shorter latent time than that on the clinically healthy side. This phenomenon has so far been confirmed on all patients with an impaired thalamus function.

The routine-EEG in premature and term infants with cerebral seizures and its additional information are discussed in comparison to clinical and morphological findings. The clinical, electroencephalographic and echoencephalographic data to all 29 neonates that were treated during a four years period are presented. Three of those infants died, eight of them showed pathological results during developmental and neurological follow-up. EEG's were performed during or short by after seizures. A correlation could be shown between poor prognosis and suppression of background activity consisting in inactivity, burst-suppression pattern or moderate suppression. By contrast a normal or mildly suppressed EEG correlated with good longterm prognosis. Paroxysmal discharges in the EEG were helpful in diagnosing seizures and also for prognosis of cerebral convulsions later on. The echoencephalographic findings especially mild intracranial hemorrhages and increased periventricular echogenicity had less prognostic value. The echoencephalographic follow-up showed ventricular dilatation (e vacuo) in children who later on had developmental and neurological impairment. For assessment of prognosis in premature and term babies with cerebral seizures imaging procedures (echoencephalography and CT-scan) as well as electroencephalography are of mutual importance.

The presented automatic sleep analysis is based on the time courses of the mean amplitudes of EEG (delta, beta and alpha bands), EMG and motility and specific patterns (spindles, REMs, delta waves greater than 40 microV) detected automatically. The interindividual variability of the parameters is taken into consideration by interactively determining the threshold levels. Sleep stages are classified for every epoch using context free decision rules according to the manual of Rechtschaffen and Kales. The resulting cyclograms are smoothed and corrected using context sensitive rules which considers the successive epochs and the probability of stage transitions.

Event-related brain potentials were recorded from healthy young adults during two paradigms calling for recall and recognition of previously presented words. In the first part of the study incidental learning was employed, i.e. the subject was unaware that he participated in a memory test and engaged in a semantic task instead. ERPs from the encoding phase were averaged according to whether a word was 1. subsequently recalled, 2. recognized or 3. neither recalled nor recognized. The intentional paradigm was identical in all respects except for the instructions to remember as many words as possible for subsequent memory testing. No semantic task was employed during intentional encoding. Both paradigms yielded significantly higher positivities for words which were later recalled.

In a prospective randomized study involving 32 male subjects aged 18 to 38, the effects of flunitrazepam (0.25 to 2 mg/70 kg), lormetazepam (0.5 to 4 mg/70 kg), midazolam (1.5 to 12 mg/70 kg) and diazepam (4 to 32 mg/70 kg) on the beta-activity (13 to 20/s) were investigated. Each subject received four benzodiazepine injections of increasing dosage. The doses were selected so that the lowest had only a slight effect on the test person's condition, while the highest resulted in deep sedation. The increase in beta-activity started off with a latency of 30 to 60 s; it was proportional to the dosage and reached its maximum between the 2. and 3. minutes. The subsequent decrease in beta-activity could be represented by an exponential function. The effect could be cancelled temporarily by administering repeated doses of the specific antagonist, flumazenil (0.1, 0.3 and 0.9 mg/70 kg). The method is suited for describing pharmacodynamic processes, determining equipotential doses of benzodiazepines and detecting the interaction between benzodiazepines and specific antagonists.

Transarterial EEG-recording is a complementary method to surface and depth-techniques. In 8 patients having superselective angiography because of diagnosis or therapeutic manoeuvres transarterial EEG-recording was performed. There were only few artefacts and no clinical side effects. The value of this additional information is discussed.

34 ambulatory polygraphic sleep-records of young adults were carried out using the Oxford Medilog 9000 recorder. All of the records underwent automatic evaluation by the Oxford Sleep Stager. 10 cases were, in addition, evaluated visually. 4 records could not be analyzed because of artifacts. Thus, 30 subjects were used in the end for establishing standard values of sleep parameters. Automatic versus automatic comparisons and automatic versus visual comparisons of ten polysomnograms were performed epoch-by-epoch. The automatic versus automatic comparison showed agreement in 85.5% of epochs, and the automatic versus visual comparison in 70.4% of epochs. The Sleep Stager showed the best agreement with the visual evaluation in epoch-by-epoch comparison in the REM-stage (93.9%), the worst in stage 1 (32.4%). In calculating the percentages of total night sleep for the respective sleep stages, the automatic analysis showed strongest disagreement with visual evaluation in the REM-stage (plus 7.5%) and in stage 2 (minus 5.2%).

Macro-EMG records electrical activity from the whole motor unit (MU) as a parameter of its size. The main component of the recording device is a modified single fiber or concentric needle electrode. Different sized uptake areas allow to record with different selectivities from the MU. The teflon insulated shaft surface allows to record with a defined large blank area unselectively macro-signals from the muscle. The conceptual ideas to use a concentric needle in addition to the single fibre electrode is to simplify the trigger-potential recording, which needs to be selective within the MU. In both instances the EMG apparatus has to provide two channels, one for the trigger and the second for an averaging device to record the macro-EMG. The different techniques use the single fiber or concentric EMG-potential as a trigger to average the associated macro-potential from the raw signals. The electrodes different design allow the whole single-fiber-needle to lie within the MU territory whereas the MU is only touched by the concentric needles tip. This implies different recording situations and results. Anatomically macro-EMG size is varied by the recording site of the muscle. The signal is greater close to the endplate zone and declines to stable values about 20 mm apart. For quantitative measurements within a muscle 20 different potentials have to be evaluated for median amplitude, duration and area.