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Biomedical subjects

E Pöppel

Publications and source records attributed to E Pöppel.

At least 19 recordsLinked to original sources
PubMed2001

Conscious control of movements: increase of temporal precision in voluntarily delayed actions.

The variability of simple actions with response to auditory stimuli was studied under different delay conditions. Subjects reacted as fast as possible or with a defined time delay (from 250 to 750 ms) to a tone switching off by pressing a response-key with the left index finger (controlled by the right hemisphere) or with the right one (left hemisphere). For short delays (requested response times below 350 ms) variability of responses was much larger then for longer delays (above 350 ms), especially for the right hand. Thus, precise temporal control on consciously mediated actions sets only in after a rather long delay (in some cases after half a second). Neuronal mechanisms underlying conscious temporal control of actions appear to be different for the two hemispheres.

Adult↗
PubMed1999

Daily rhythm of temporal resolution in the auditory system.

Over a period of 24 hours, fusion thresholds (click durations 100 micros) were assessed in 7 subjects. Over the same period, order thresholds (click duration of 1 ms) were measured in 10 subjects (12 independent sessions). Auditory fusion thresholds showed a diurnal rhythm with a maximum performance (shortest intervals) around midnight. In contrast, order thresholds appear to be independent on the time of day. Sex specific differences in threshold levels were only observed in order thresholds but not in fusion thresholds.

Acoustics↗
PubMed1999

[How, when and what can we learn? Temporal and spatial characteristics of sensorimotor coordination].

On the basis of an account on elementary processes of spatio-temporal control of movements and on findings on motor learning, we propose in this article the employment of test and training procedures for motor skills in the training of surgeons. Elementary temporal and spatial factors of motor performance control underly the very precise complex motor behaviour of the activity of a surgeon. An established diagnosis of individual competence in this domain could help the doctors' decisions on whether to take up surgery. Training devices could improve the efficiency of the surgeons' motor functions. The inclusion of knowledge of motor abilities and learning processes could complement the present-day training of surgeons.

Clinical Competence↗
PubMed1998

Temporal integration in a subjective accentuation task as a function of child cognitive development.

We have previously shown that temporal integration in the domain of a few seconds may be studied using a subjective accentuation paradigm. Here we report developmental effects on the limits of this temporal integration in 9-10-year-olds in comparison with 13-14-year-olds. The task was to listen to a string of identical metronome beats and mentally bind the presented beats by subjectively accentuating every second, third or nth beat. The integration interval length was defined as the number of stimuli mentally connected multiplied by the temporal interval between two successive beats. For the lowest stimulus frequency integration intervals were approximately 3 s for the older and 2.2 s for the younger children. For higher frequencies integration intervals got systematically shorter, but being always longer for the older age group. It is suggested that the prefrontal region is responsible for this developmental effect. The expansion of temporal integration correlates with cognitive development in the investigated phase of ontogenesis.

Adolescent↗
PubMed1997

Temporal processing disorders in patients with Broca's aphasia.

We report an association between a language deficit following brain lesion and a new strategy in temporal integration. Patients with different brain lesions mentally grouped sequences of identical acoustic stimuli generated at various frequencies. They were asked while listening to the stimuli to accentuate every second, third or other stimulus to create an individual rhythmic pattern. After each sequence patients reported how many stimuli they had united into a perceptual unit. The integration interval was defined as the number of reported stimuli multiplied by the temporal interval between two successive stimuli. Results indicate different integration strategies depending on the lesion site, i.e. Broca's aphasics behaving differently than all other patient groups. At lower frequencies they showed longer, at higher frequencies they displayed shorter integration. From this observation we conclude that the Broca's patients acquired a new strategy because of the lesion; they relied on mental counting and less on automatic temporal integration, which is usually the case.

Adult↗
PubMed1996

Midlatency auditory evoked potentials during anaesthesia with increasing endexpiratory concentrations of desflurane.

BACKGROUND: Under general anaesthesia with the volatile anaesthetics halothane, enflurane and isoflurane, midlatency auditory evoked potentials (MLAEP) are suppressed dose-dependently. Therefore, MLAEP have been used to measure depth of anaesthesia and to indicate intraoperative awareness. Desflurane is a new volatile anaesthetic and its effect on MLAEP have not been studied previously. METHODS: We have studied MLAEP during general anaesthesia with increasing endexpiratory concentrations of desflurane in 12 patients scheduled for elective gynaecological surgery. Auditory evoked potentials were recorded in the awake state and during anaesthesia with endexpiratory steady state concentrations of 1.5, 3.0, 4.5 and 6.0 vol % of desflurane on vertex (positive) and mastoids on both sides (negative). Latencies of the peaks V, Na, Pa, Nb, Pl (ms) and amplitudes Na/Pa, Pa/Nb and Nb/Pl (micro V) were measured. RESULTS: In the awake state, MLAEP had high peak-to-peak amplitudes and a periodic waveform. During general anaesthesia with increasing endexpiratory concentration of desflurane, the latency of the brainstem response V increased only slightly. In contrast, MLAEP showed a marked dose-dependent and statistically significant increase in latencies of Na, Pa, Nb and Pl and decrease in amplitudes of Na/Pa, Pa/Nb and Nb/Pl. Under 6.0 vol % of desflurane MLAEP were severely attenuated or even abolished. CONCLUSION: Based on these observations, endexpiratory concentrations of > or = 4.5 vol % desflurane should suppress awareness phenomena such as auditory perceptions during anaesthesia.

Adult↗
PubMed1996

Temporal constraints in processing of nonverbal rhythmic patterns.

This study investigates the effect of a mental content of presented stimuli, normal aging and individual differences in cognitive abilities on temporal limits of an integration mechanism. Younger and older subject grouped together the beats generated by a metronome. Subjects were asked to listen to the beats of a metronome and to accentuate mentally every second, third, fourth...etc. beat, to create a subjective rhythm. This rhythm exists, in fact, only in subjects' mind and not objectively. Subjects reported verbally how many clicks they were able to integrate into a perceptual unit. On this basis, the time interval during which subjects were able to integrate temporally separated stimuli was calculated (number of beats reported as being integrated x time distance between beats) for different metronome frequencies. The results show, firstly, that the length of integration periods significantly depends on the frequency of presented metronome beats. When the frequency of metronome beats is high, the time interval during which the subjects integrate beats into a single perceptual unit is shorter. Secondly, older adults integrate information during a longer time interval than younger ones. Thirdly, the length of an integration period is related to a subjects' level of cognitive ability. These results suggest that the length of an integration period is not a constant, stable feature, but varies across the life span depending on the mental content of the information presented and individual factors.

Acoustic Stimulation↗
PubMed1995

[Awareness during general anesthesia. Definition, incidence, clinical relevance, causes, avoidance and medicolegal aspects].

The possibility that a patient during general anaesthesia is aware of the operation going on and aware of severe pain that might be remembered postoperatively must be very alarming to patients and anaesthetists alike. Furthermore, there is experimental evidence showing that conscious recall of intraoperative events is only the tip of an iceberg; it seems very probable that there is even a higher incidence of unconscious perception during general anaesthesia. Therefore, the following stages of intraoperative awareness must be distinguished: (1) conscious awareness with explicit recall and with severe pain; (2) conscious awareness with explicit recall but no complaints of pains; (3) conscious awareness without explicit recall and possible implicit recall; (4) subconscious awareness without explicit recall and possible implicit recall; (5) no awareness. The incidence of conscious awareness with explicit recall and severe pain has been estimated at less frequent than 1/3000 general anaesthetics. Conscious awareness with explicit recall but no complaints of pain has been reported in the literature with an incidence of 05-2%. With 7-72%, conscious awareness without explicit recall and possible implicit recall shows a very wide range of variation and its occurrence probably depends on the anaesthetic drugs used. Subconscious awareness with possible implicit recall has an incidence of up to 80%, but there are many methodological problems in demonstrating implicit memory of intraoperative events. Reports of intraoperative awareness do not come exclusively from cardiac surgery and obstetrics, but also from all other operative specialties. Postoperatively, patients who experience intraoperative awareness may develop a so-called post-traumatic stress syndrome. Symptoms involve re-experiencing the event awake or in dreams, sleep disturbances, depression, avoidance of stimuli associated with the event. The probability of the development of the post-traumatic stress syndrome seems to coincide with the experience of severe pain. When a patient complains of intraoperative awareness postoperatively the anaesthesiologist should discuss the event frankly with the patient. When the symptoms of the post-traumatic stress syndrome persist a psychotherapy should follow. Causes for intraoperative awareness may be: equipment failure, too-light anaesthesia, e.g. for a caesarean section or for emergency surgery in severely injured or polytraumatized patients, during cardiac surgery, bronchoscopy of difficult intubation. There is interindividual variability in anaesthetic effect; for example, chronic drug or alcohol abuse or overweight may make increased anaesthetic doses necessary. They are at risk for intraoperative awareness. Some general anaesthetics or anaesthetic procedures, e.g. the combination of a relaxant and N2O, opioid mono-anaesthetics, or opioids combined with benzodiazepines, seem to involve a higher risk of intraoperative awareness than do volatile anaesthetics. The bases of litigation are medical malpractice, breach of contract by the anaesthesiologist or lack of informed consent from the patient. Therefore, patients who are at risk of intraoperative awareness should be given detailed information on this special risk before the operation.

Anesthesia, General↗
PubMed1995

Anesthesia with increasing doses of sufentanil and midlatency auditory evoked potentials in humans.

Our interest focused on the question whether sufentanil differs from alfentanil, fentanyl, and morphine with regard on its effects on midlatency auditory evoked potentials (MLAEP). Therefore, we studied MLAEP during general anesthesia with increasing doses of sufentanil in 16 patients scheduled for elective major urologic surgery. Anesthesia was induced with sufentanil (1 microgram/kg every 7 min to a total dose of 3 micrograms/kg). In 8 of 16 patients, further incremental doses of sufentanil were given to a total dose of 5 micrograms/kg. Auditory evoked potentials were recorded before and 5 min after every sufentanil dose on vertex (positive) and mastoids on both sides (negative). Latencies of the peaks V, Na, Pa, Nb, and P1 (ms), and amplitudes Na/Pa, Pa/Nb, and Nb/P1 (microV) were measured. In the awake state, MLAEP had high peak-to-peak amplitudes and a periodic waveform. During general anesthesia the brainstem response V was stable to increasing doses of sufentanil. There was a marked statistically significant increase in latency and decrease in amplitude of Nb and P1 after 1-2 micrograms/kg sufentanil, which remained stable under further sufentanil application. In contrast, the early cortical potentials Na and Pa increased only slightly in latencies. This increase was statistically significant at 4 micrograms/kg for Na and at 3 and 4 micrograms/kg for Pa. For the amplitudes Na/Pa and Pa/Nb there was only a slight and statistically insignificant reduction. After the largest dose of sufentanil (3-5 micrograms/kg) Na and Pa showed a similar pattern as in awake patients. We conclude that sufentanil does not differ essentially from alfentanil, fentanyl, and morphine with regard on its effects on MLAEP.

Anesthesia, General↗
PubMed1995

The effects of anesthesia with increasing end-expiratory concentrations of sevoflurane on midlatency auditory evoked potentials.

We studied midlatency auditory evoked potentials (MLAEP) during general anesthesia with increasing end-expiratory concentrations of sevoflurane in 12 patients scheduled for elective gynecologic surgery. After oral premedication with 20 mg clorazepate dipotassium, anesthesia was induced with etomidate (0.2 mg/kg intravenously [IV]). Vecuronium (0.1 mg/kg) was given for neuromuscular block, and controlled ventilation with sevoflurane in 100% O2 was instituted. Auditory evoked potentials were recorded in the awake state and during anesthesia with end-expiratory steady-state concentrations of 0.5, 1.0, 1.5, and 2.0 vol% of sevoflurane on vertex (positive) and mastoids on both sides (negative). Latencies of peaks V, Na, Pa, Nb, and P1 (ms) and amplitudes of Na/Pa, Pa/Nb, and Nb/P1 (microV) were measured. In the awake state, MLAEP had high peak-to-peak amplitudes and a periodic waveform. During general anesthesia with increasing end-expiratory concentrations of sevoflurane, the latency of the brainstem response V increased slightly. In contrast, MLAEP showed marked dose-dependent, statistically significant increases in the latencies of Na, Pa, Nb, and P1 and decreases in the amplitudes of Na/Pa, Pa/Nb, and Nb/P1. Under 2 vol% of sevoflurane, MLAEPs were severely attenuated or abolished. Based on these observations, > or = 1.5 vol% sevoflurane should suppress phenomena such as auditory perceptions, intraoperative wakefulness, and awareness.

Adult↗
PubMed1995

Mid-latency auditory evoked potentials and wakefulness during caesarean section.

We investigated intra-operative wakefulness and mid-latency auditory evoked potentials (MLAEP) in 20 patients undergoing elective Caesarean section under general anaesthesia. Anaesthesia was induced with thiopentone 5 mg kg-1 i.v. and succinylcholine 1-1.5 mg kg-1 i.v. After delivery, a balanced anaesthetic technique was maintained using fentanyl 0.2-0.3 mg i.v., enflurane 0.4-1.0 vol% end-expired concentration and 50% N2O in oxygen. Purposeful movements were interpreted as signs of inadequate anaesthesia and intra-operative wakefulness. They were recorded as either spontaneous movements or in response to one of two audio tapes (tape A: sound of a crying baby; tape B: classical music). Post-operatively, intra-operative dreams, hallucinations and detailed reports about intra-operative events were evaluated. Auditory evoked potentials were recorded online before and during general anaesthesia. Twenty spontaneous purposeful movements were observed in 12 patients, seven before or during delivery and 13 after delivery. Four purposeful movements were observed after presentation of the sound of a crying baby but only one after classical music. Dreams and hallucinations were reported by nine patients. Two patients reported experiencing surgical manipulations. In the awake state MLAEPs had great peak-to-peak amplitudes and a periodic waveform. Under adequate levels of general anaesthesia MLAEPs showed a marked increase in latency and decrease in amplitude or were even suppressed completely. This increase in latencies and decrease in amplitude of MLAEP was absent in patients who reported intraoperative events and during spontaneous or provoked motor reactions.

Anesthesia, General↗
PubMed1994

[Anesthesia with flunitrazepam/fentanyl and isoflurane/fentanyl. Unconscious perception and mid-latency auditory evoked potentials].

There is a high incidence of intraoperative awareness during cardiac surgery. Mid-latency auditory evoked potentials (MLAEP) reflect the primary cortical processing of auditory stimuli. In the present study, we investigated MLAEP and explicit and implicit memory for information presented during cardiac anaesthesia. PATIENTS AND METHODS. Institutional approval and informed consent was obtained in 30 patients scheduled for elective cardiac surgery. Anaesthesia was induced in group I (n = 10) with flunitrazepam/fentanyl (0.01 mg/kg) and maintained with flunitrazepam/fentanyl (1.2 mg/h). The patients in group II (n = 10) received etomidate (0.25 mg/kg) and fentanyl (0.005 mg/kg) for induction and isoflurane (0.6-1.2 vol%)/fentanyl (1.2 mg/h) for maintenance of general anaesthesia. Group III (n = 10) served as a control and patients were anaesthetized as in I or II. After sternotomy an audiotape that included an implicit memory task was presented to the patients in groups I and II. The story of Robinson Crusoe was told, and it was suggested to the patients that they remember Robinson Crusoe when asked what they associated with the word Friday 3-5 days postoperatively. Auditory evoked potentials were recorded awake and during general anaesthesia before and after the audiotape presentation on vertex (positive) and mastoids on both sides (negative). Auditory clicks were presented binaurally at 70 dBnHL at a rate of 9.3 Hz. Using the electrodiagnostic system Pathfinder I (Nicolet), 1000 successive stimulus responses were averaged over a 100 ms poststimulus interval and analyzed off-line. Latencies of the peak V, Na, Pa were measured. V belongs to the brainstem-generated potentials, which demonstrates that auditory stimuli were correctly transduced. Na, Pa are generated in the primary auditory cortex of the temporal lobe and are the electrophysiological correlate of the primary cortical processing of the auditory stimuli. RESULTS. None of the patients had an explicit memory of intraoperative events. Five patients in group I, one patient in group II, and no patients in group III showed implicit memory of the intraoperative tape message. They remembered Robinson Crusoe spontaneously when they were asked their associations with Friday. In the awake state AEP peak latencies were in the normal range. During general anaesthesia in group I, the peaks Na, Pa did not increase in latency or decrease in amplitude before and after the audiotape presentation. The primary cortical complex Na/Pa could be identified as in the awake state. In contrast, in group II Na, Pa showed a marked increase in latency and a decrease in amplitude or were completely suppressed. CONCLUSIONS. During general anaesthesia auditory information can be processed and remembered postoperatively by an implicit memory function, when the electrophysiological conditions of primary cortical stimuli processing is preserved. Implicit memory can be observed more often when high-dose opioid analgesia is combined with receptor-binding agents like the benzodiazepines than under non-specific anaesthetics like isoflurane. Non-specific anaesthetics seem to provide a more effective suppression of auditory stimuli processing than receptor-specific agents.

Adult↗
PubMed1994

Mass-action view of single-cell responses to stimulation of the receptive field and/or beyond: exemplification with data from the rabbit primary visual cortex.

Whereas single cells in the visual cortex prefer moving light bars, mass-action responses are evoked better by diffuse luminance changes. This discrepancy was investigated by quantitatively comparing the response properties of individual cells with those of a representative group of cells. The latter responses were derived from the single-cell responses, which were obtained from recording in the rabbit. These quantitative estimates of mean responses resolve the discrepancy between the single-cell domain and the mass-action domain: from the single-cell point of view, a properly oriented moving-bar stimulus is much more effective than a diffuse-light stimulus. The corresponding mass-action response to one common moving-bar stimulus, however, is as small as the mean response to a diffuse-light stimulus (which may even be presented at retinotopically non-corresponding sites). The peak intensities of these mass responses are even much stronger with the diffuse-light stimuli. The same conclusions are valid for the cat, as could be verified from published data. The restrictions of the local receptive field concept that may be implied by the mass-action view of cortical activity and the potential functional relevance of mass activities are discussed.

Animals↗
PubMed1994

Mid-latency auditory evoked potentials and circulatory response to loud sounds.

We investigated in 60 patients scheduled for elective aorto-coronary bypass grafting if loud sounds by themselves can induce cardiovascular responses and if these could be related to mid-latency auditory evoked potentials (MLAEP). Anaesthesia was induced in group I (n = 20) with flunitrazepam-fentanyl 0.01 mg kg-1 and maintained with flunitrazepam-fentanyl 1.2 mg h-1. Patients in groups II (n = 20) and III (n = 20) received etomidate 0.25 mg kg-1 and fentanyl 0.005 mg kg-1 for induction and 0.6-1.2 vol% isoflurane and fentanyl 1.2 mg h-1, or propofol 4-8 mg kg-1 h-1 and fentanyl 1.2 mg h-1 for maintenance of general anaesthesia. After preparation of the sternum the operation was stopped for several minutes. Then, as a loud auditory stimulus, the sound of the running sternotomy saw was presented to the patients by putting the saw inverted on the sternum for several seconds. Heart rate (HR), arterial pressure (SAP), pulmonary capillary wedge pressure (PCWP), cardiac index, systemic vascular resistance and MLAEP were measured in the awake state, before and after presentation of the sound. Latencies of the peak V, Na, Pa, Nb and P1 were measured. In group I there were statistically significant increases in HR (63.5-70.2 beat min-1), SAP (123.9-146-5 mm Hg) and PCWP (9.2-11.7 mm Hg) after presentation of the sound. These haemodynamic changes were not observed in patients in groups II and III. In the awake state, AEP had high peak -to-peak amplitudes and a periodic waveform.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1994

Midlatency auditory evoked potentials and explicit and implicit memory in patients undergoing cardiac surgery.

BACKGROUND: A high incidence of intraoperative awareness during cardiac surgery has been reported. Midlatency auditory evoked potentials (MLAEP) have been used recently as an indicator of awareness. In the current study, memory for information presented during anesthesia was investigated using MLAEP as one experimental indicator in 45 patients scheduled for elective cardiac surgery. METHODS: In all patients general anesthesia was maintained using high-dosage fentanyl (1.2 mg.h-1). In addition, the patients of group 1 (n = 10) received flunitrazepam (1.2 mg.h-1), the patients of group 2 (n = 10) isoflurane (0.6-1.2 vol%), and the patients of group 3 (n = 10) propofol (4-8 mg.kg-1.h-1). Group 4 (n = 15) served as a control, and those patients were assigned randomly to one of the anesthetic regimes. After sternotomy and before cardiopulmonary bypass, an audiotape, which included an implicit memory task, was presented to the patients of groups 1-3. Auditory evoked potentials were recorded while the patients were awake and during general anesthesia immediately before and after the audiotape presentation. Latencies of the brain stem peak V and the early cortical potentials Na and Pa were measured. RESULTS: Three to 5 days postoperatively no patient had a clear explicit memory of intraoperative events. However, there were statistically significant differences in the incidence of implicit recall among the groups. Five patients in the flunitrazepam-fentanyl group, 1 patient in the isoflurane-fentanyl group, 1 patient in the propofol-fentanyl group, and no patient in the control group showed an implicit memory of the intraoperative tape message. In the awake state, MLAEP showed high peak-to-peak amplitudes and a periodic waveform. In the patients with implicit memory postoperatively, MLAEP continued to show this pattern during general anesthesia. The early cortical potentials Na and Pa did not increase in latency or decrease in amplitude before or after the audiotape presentation. In contrast, in the patients without implicit memory, MLAEP waveform was severely attenuated or abolished. Na and Pa showed marked increases in latencies and decreases in amplitudes or were completely suppressed. In 9 patients, including all patients (7 of 9) with implicit memory, Pa latency increased less than 12 ms, and 21 of 23 patients without implicit memory showed a Pa latency increase of greater than 12 ms during anesthesia and the audiotape presentation. Therefore, the Pa latency increase of greater or less than 12 ms may provide sensitivity of 100% and specificity of 77% in distinguishing patients with implicit memory from patients without implicit memory postoperatively. CONCLUSIONS: When the early cortical potentials of MLAEP are preserved during general anesthesia, auditory information may be processed and remembered postoperatively by an implicit memory task.

Aged↗
PubMed1994

Midlatency auditory evoked potentials and purposeful movements after thiopentone bolus injection.

The effect of thiopentone on the middle latency auditory evoked potentials was investigated in 12 patients during induction of anaesthesia with thiopentone 5 mg.kg-1. 100% oxygen was administered throughout the induction, and when the patient moved purposefully a further bolus (2 mg.kg-1) was given, and anaesthesia continued in the normal way. The middle latency auditory evoked potentials were elicited before and during the induction. Binaural clicks (70 dB above normal hearing threshold) were presented at a rate of 9.3 per s. Averages of 1000 responses were analysed off line, and a fast Fourier transformation of the middle latency auditory evoked potentials were used to calculate the power spectrum of the averages. Awake, the patients had large peak to peak amplitudes and a normal waveform. The power spectra showed a high energy between 30-40 Hz. After induction the latencies of waves Na, Pa, Nb and P1 and the amplitudes of the waves Na/Pa, Pa/Nb, and Nb/P1 were decreased or completely attenuated. Both effects lasted for 4 min. When movement occurred (after 4-6 min), the values returned to awake. The second bolus repeated the changes.

Adult↗