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Biomedical subjects

F Foerster

Publications and source records attributed to F Foerster.

At least 19 recordsLinked to original sources
PubMed2001

Development of prosaccade and antisaccade task performance in participants aged 6 to 26 years.

There are few studies on the development of oculomotor functions during childhood. B. Fischer, M. Biscaldi, and S. Gezeck (1997) reported improvement of antisaccade task performance between ages 6 and 16 years. The present study is a replication and extension of those results. In three age groups (6-7, 10-11, 18-26 years), saccades during pro- and antisaccade tasks with 200-ms gap and overlap and during a fixation task were measured. Adults exhibited faster saccades and less prosaccades during the antisaccade tasks than 10-11-year-old children; these two groups had faster saccades during all tasks and less prosaccades during the anti- and the fixation task than 6-7-year-old subjects. Both children groups made more express saccades than adults. Results suggest different degrees of age-related improvement for different saccadic parameters, the effects being greatest for prosaccade inhibition during the antisaccade task and in line with the assumed protracted development of prefrontal functions.

Adolescent↗
PubMed2000

The gap effect in pro-saccades and anti-saccades in psychometric schizotypes.

Schizophrenic patients and their first-degree relatives exhibit deficits in the anti-saccade task. In the present study, anti-saccade task performance was examined in subjects with 'high' and 'low' expressions of the schizotypal personality trait. For that purpose, the SPQ-G, the German adaptation of the Schizotypal Personality Questionnaire (SPQ; Raine, 1991), was filled in by 489 university students. Twenty and 21 participants with 'high' and 'low' SPQ-G scores, respectively, were compared with respect to saccadic eye movements elicited under the overlap and 200 ms gap conditions of the pro- and anti-saccade tasks. Each task block comprised 150 trials, 75 to either side in random order. The order of presentation of the task blocks was counterbalanced across the participants of each group. Saccadic reaction times were slower during the anti- as compared to the pro-saccade task and under the overlap as compared to the gap condition. Direction errors occurred almost exclusively during the anti-saccade task, express saccades mainly under the pro-saccadic gap condition. High-schizotypal participants did not differ significantly from low-schizotypal participants in any of these measures. While these results might suggest normal anti-saccade task performance in schizotypal personality as defined by the SPQ-G, the sampling strategy adopted in the present study is the more plausible explanation for the lack of group differences.

Adult↗
PubMed2000

Motion pattern and posture: correctly assessed by calibrated accelerometers.

Basic motion patterns and posture can be distinguished by multichannel accelerometry, as recently shown. A refinement of this method appeared to be desirable to further increase its effectiveness, especially to distinguish walking and climbing stairs, and body rotation during sleep. Recordings were made of 31 subjects, according to a standard protocol comprising 13 motions and postures. This recording was repeated three times with appropriate permutation. Five uni-axial sensors and three sites of placement (sternum with three axes, right and left thigh) were selected. A hierarchical classification strategy used a standard protocol (i.e., individual reference patterns) to distinguish subtypes of moving behaviors and posture. The analysis method of the actometer signals reliably detected 13 different postural and activity conditions (only 3.2% misclassifications). A minimum set of sensors can be found for a given application; for example, a two-sensor configuration would clearly suffice to differentiate between four basic classes (sitting, standing, lying, moving) in ambulatory monitoring.

Adult↗
PubMed1997

Assessment of posture and motion by multichannel piezoresistive accelerometer recordings.

Modern assessment of posture and motion involves the use of wide bandwidth piezoresistive accelerometers. The direct current (DC) component allows for assessment of slow motion and change in position referring to the gravitational axis: the alternating current (AC) component, calibrated in g. represents acceleration along the sensitive axis of the device. A method study was designed to evaluate the division in DC and AC components, reliabilities, discrimination between conditions, and detection of types of physical activities. Recordings were made in 26 student participants for eight conditions: sitting, standing, lying supine, sitting and typing on a PC keyboard, walking, climbing stairs, walking downstairs, and cycling. This procedure was repeated in reversed order. A classification of physical activities according to the eight conditions (first trial) and based on four parameters, that is DC components trunk, thigh, and lower leg and AC component trunk, was correct in almost 100% of patterns, when applied to the second trial.

Acceleration↗
PubMed1995

Is elevated blood pressure level associated with higher cardiovascular responsiveness in laboratory tasks and with response specificity?

Cardiovascular responsiveness and response specificity were investigated in male students, 48 with moderately elevated blood pressure (systolic blood pressure [SBP] > 140 mmHg and/or diastolic blood pressure [DBP] > 90 mmHg), 31 with mildly elevated blood pressure, and 57 with normal blood pressure. The behavioral tests and physically demanding tasks in the laboratory included mental arithmetic, free speech condition, cold pressor test, upright tilt, and ergometer exercise. Subjects with elevated blood pressure differed in baseline, task, and recovery levels of SBP, DBP, and heart rate. There were no significant effects in task-baseline differences or in residualized change scores. However, a positive initial-value dependency (LIV) in blood pressure responses was found: elevated blood pressure is associated with a larger increase under task conditions. Response scaling that employed reliability estimates and true difference scores indicated higher responsiveness in subjects with moderately elevated blood pressure and, thus, are in accordance with the positive LIV as compared with response measures based on task-baseline differences or residualized change scores. Findings from the specificity analysis indicated a higher incidence of SBP responders, that is, subjects with maximum response in SBP, among subjects with elevated blood pressure. Some of the inconsistencies in the literature with respect to blood pressure responsiveness and heart rate level in individuals with borderline hypertension may be attributed to the specific method of response scaling and to insufficient habituation to the setting and measurement.

Adult↗
PubMed1993

Covariation of physiological sleep parameters in coronary patients and their relationships to sleep quality.

Relationships between the time series of five physiological sleep parameters were examined and related to sleep quality. Twenty-eight male coronary patients participated in the investigation. Recordings were carried out with a mobile device consisting of two Medilog 4-24 recorders and one DMI-recorder assessing five biosignals: EEG, EOG, EMG, ECG and body movements. Relationships between the time series of physiological sleep parameters were obtained by partitioning of covariance. The investigation showed that substantial relationships exist between the time series of the EEG, the number of eye movements and heart rate. Moreover, the time series of body movements showed substantial relationships to the time series of the EMG and heart rate. High correlations between the time series of the EEG and heart rate were related to a better sleep quality.

Adult↗
PubMed1992

Development of a new dynamic method for quantitative evaluation of in vitro hemocompatibility of biomedical materials.

In this study a new dynamic method is introduced allowing the estimation of blood cell adhesion on flat test surfaces by measuring the cell loss in the bulk phase of surface contacting test blood under defined rheological conditions. This was achieved by constructing a novel test chamber permitting the contact of small amounts of blood with a large geometrical test surface. The construction consists of a spiral-shaped flow channel of 0.3 cm width, 0.02 cm height and 78 cm length covered with the biomaterials to be tested from both sides. Laminarity of blood flow in the conduit was confirmed theoretically by the calculation of an equivalent to the Reynolds number for curved systems the so-called Dean number. Furthermore, flow laminarity was proved experimentally finding that the flow rate of blood with different hematocrit values was proportional to the hydrostatic pressure applied. The applicability of the novel 'spiral method' for the estimation of hemocompatibility was demonstrated by evaluation of platelet adhesion onto different polymers in comparison to siliconized and fibrinogen coated glass as reference surfaces. Additionally, it was possible under distinct conditions to determine the adhesion of leucocytes and the detachment of platelet aggregates. Therefore, it was concluded that the spiral method can be used for the assessment of the hemocompatibility of flat biomedical polymers. As main advantages of the new method can be considered the high time efficiency and accuracy without labelling or optical detection of adherent cells.

Acrylic Resins↗
PubMed1991

A model of cardiovascular activation components for studies using autonomic receptor antagonists.

Alpha-adrenergic, beta-adrenergic, and cholinergic responses are often considered important activation components when conceptual and empirical analyses are made of single physiological variables and of patterns of cardiovascular reactivity; these autonomic distinctions are also of particular significance in autonomic blockade studies. A Model of Cardiovascular Activation Components is introduced that relates these components to both the measured cardiovascular variables and the protocol of autonomic blockade studies. It is pointed out that a restricted form of the complete model is often implicitly used in cardiovascular psychophysiology. The differential consequences of an erroneous employment of the restricted model are discussed for single and dual blockade protocols. Critical evaluations of autonomic blockade as a tool in cardiovascular psychophysiology are examined and are proposed to be often the consequence of the restricted model assumptions. Lastly, the utility of the Activation Components Model for a componential description of tasks and for componential intertask relationships is illustrated with data from the literature.

Arousal↗
PubMed1988

Detection of emotionally induced ECG changes and their behavioural correlates: a new method for ambulatory monitoring.

Heart rate is a well-established indicator of emotional arousal and can serve to detect emotional events. One difficulty, however, is in separating emotional heart rate increases from those increases due to physical activity. On-line analysis of both heart rate and physical activity (recorded with motion detectors) with a portable minicomputer may be able to solve this problem. We have developed a special algorithm that compares the values for heart rate and activity of a particular minute with the values of the previous minutes. If heart rate of a specific minute exceeds the rate of the previous minutes without an accompanying increase of activity, an emotional event may possibly be assumed. In such a case, the patient is requested by a beep signal to answer relevant questions about what he is doing, how he feels, etc. Moreover the patient is allowed to activate the system for himself for special events, e.g. chest pain. Methodological results of a first feasibility study with 32 cardiac patients are presented.

Affective Symptoms↗
PubMed1986

The law of initial value: a rare exception.

The well-known negative correlation between initial value and difference score, referred to as the law of initial value (LIV), is analyzed in the present study. It is shown that whenever the correlation between the initial and final values is less than 1.00, the negative correlation is influenced by the a(a - b) effect. By relating values to the first principal component axis, this spurious effect can be eliminated, thus allowing analysis of any real dependency on initial values. Data collected in a psychophysiological experiment were used to test this hypothesis. A subject sample of 125 male students experienced various challenges (Cold Pressor Test, breath holding, reaction time measurement, digit-series test) while several physiological variables (e.g. blood pressure, stroke volume, electrodermal activity) were monitored. Results fail to support the LIV as originally advanced by Wilder. On the contrary, after eliminating the a(a - b) effect, a positive dependency as indicated by the slope of the first principal component axis (anti-LIV) was observed. The reciprocal relationship between the LIV and anti-LIV is discussed with respect to the measures employed. Advantages and disadvantages of various methods to correct for the initial value dependency are presented.

Adult↗
PubMed1985

Psychophysiological response specificities: a replication over a 12-month period.

A sample of 58 students was subjected to four stress conditions (mental arithmetic, reaction time, free speech, cold-pressor test). Eight physiological variables (skin conductance, heart rate, pulse amplitude, Heather index, eye blinking, horizontal eye movements, respiration rate, blood pressure) and five psychological variables (self-rated anger, irritability, tenseness, motivation, indifference) were monitored. Proportions of variance in a three-factor ANOVA (subjects, situations, variables) accounted for by individual specific response patterns (ISR) amounted to 33-40% for physiological and 9-13% for psychological variables. Stimulus specific response patterns (SSR) accounted for 11-19% for physiological and 8-14% for psychological variables, and motivation specific response patterns (MSR) for 17% for physiological and 14-16% for psychological variables. About one-fourth of the subjects showed a rather stable ISR in physiological variables when tested again after two months, and about 14% when tested again after twelve months. Overall, the results replicated earlier findings from this laboratory.

Adaptation, Physiological↗
PubMed1983

The differentiation of individual-specific, stimulus-specific, and motivation-specific response patterns in activation processes: an inquiry investigating their stability and possible importance in psychophysiology.

The role of specific response patterns obtained by means of psychophysiological activation and their temporal stability are meeting with an increasing interest in the literature because of a low correlation between psychophysiological variables and of possible implications with regard to pathogenetic mechanisms in psychosomatic disease. Two empirical studies are presented that were conducted under similar stress conditions (mental arithmetic, free speech, cold-pressor test, blood-taking) and have been monitoring similar activation variables (seven physiological and four or five psychological variables) - one of which using a large sample of 125 students, the other one consisting of 47 students, who were tested three times week- by-week. Findings reveal that substantial proportions of variance in the three-factorial ANOVA (subjects, situations, variables) may be considered on the basis of individual-specific (23-29% for physiological variables, 6-11% for psychological variables), stimulus-specific (5-19% for physiological variables, 1-11% for psychological variables), and motivation-specific (21% for physiological variables, 10% for psychological variables) response patterns. Five evaluation procedures on nominal, ordinal, and interval data levels as well as various definitions of similarity found in the reaction patterns are used in a comprehensive approach to the analysis of specificities. Estimation of variance components, global tests, and individual tests are applied. The results prove to be reliable and rather stable, at least over a period of several weeks. In total, about one fourth of the subjects show a stable individual-specific response pattern on physiological variables. The results are discussed with respect to data and sampling problems as well as to various methods of data analysis.

Adult↗
PubMed1978

[Biochemical measures in cardiac patients: an analysis of change during rehabilitation (author's transl)].

210 male patients hospitalized for cardiac rehabilitation have been studied. As a result of age matching the sample was reduced to 190 patients: 72 patients with myocardial infarction, 90 patients with functional cardiovascular diseases, and 28 patients with angina pectoris. At the beginning and at the end of the 4 to 6 week rehabilitation program total lipids, cholesterol, triglycerides, phosphatides, GOT, GPT, LDH, HBDH, cholinesterase, aldolase, blood sugar, creatinine, electrolytes, hemoglobin, erythrocytes, leukozytes, and catecholamines were measured. In addition to the statistical comparison of the three groups and their specific change patterns, effects of body weight reduction and improvement of physical fitness were analyzed. The decrease of lipids is especially associated with weight reduction, whereas the decrease of enzyme activity and electrolyte concentration is accompanied as well with weight reduction as with the improvement of physical fitness.

Adult↗
PubMedDate not supplied

Covariation and consistency of activation parameters.

Individual differences in activation processes, as well as the consistency and predictability of these differences, constitute a classical issue eliciting much theoretical discussion in this field and as such poses an essential question for any practical application of psychophysiological methods. A typical activation experiment assessing 125 male students on four self-report and 21 physiological measures under five conditions (rest, mental arithmetic, interview, anticipation and blood taking) was performed supplying an empirical basis for a multivariate analysis. A partition of covariance, factor analyses, item analyses and scale construction procedures as well as models engaging an increasing number of components were used to study the covariation and consistency of these activation parameters. Several biometric problems that are generally thought to complicate the evaluation of such data (i.e. non-linear relations, the problem of initial values, differing sensibility curves of physiological response systems, individual response specificities) are considered and tested empirically. Findings suggest that the use of a single variable or a composite measure as an 'indicator' of individual differences in state or reaction aspects of activation is inadequate, due to empirical inconsistency and the lack of predictability between functional subsystems. A multicomponent model or a set of marker variables, having empirically derived discriminative efficiency as well as reliability estimates, seem to be preferable.

Analysis of Variance↗