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Biomedical subjects

M Rodenburg

Publications and source records attributed to M Rodenburg.

At least 19 recordsLinked to original sources
PubMed1993

Therapeutic advantage of bifrontal electrode placement in ECT.

Fifty-nine patients suffering from a major depressive episode, for whom electroconvulsive therapy (ECT) was clinically indicated, were randomly assigned to one of three electrode placement groups for treatment with brief pulse, threshold-level ECT: bitemporal (BT), right unilateral (RU) or bifrontal (BF). Comparison of these groups in terms of number of treatments, duration of treatment, or incidence of treatment failure, showed that the bilateral placements were superior to the unilateral; comparison of Hamilton, Montgomery-Asberg, and visual analogue scale scores showed that the bifrontal placement was superior to both bitemporal and unilateral treatment. Bitemporal treatment showed therapeutic results intermediate between BF and RU. Because BF ECT causes fewer cognitive side effects than either RU or BT, and is independently more effective, it should be considered as the first choice of electrode position in ECT.

Adult↗
PubMed1990

Electrode placement in ECT: cognitive effects.

Forty patients suffering from a major depressive disorder, for whom electroconvulsive therapy (ECT) was clinically indicated, were assigned to one of three electrode placement groups: bitemporal (BT), right unilateral (RU) or bifrontal (BF). Comparisons of these groups in terms of cognitive status showed that the BF placement, which avoided both temporal regions, spared both verbal and nonverbal functions. These differential effects, which were independent of the degree of clinical depression, were not, however, evident three months after the last ECT.

Adult↗
PubMed1990

The ward milieu and its effect on the behaviour of psychogeriatric patients.

Research relating environment and behaviour indicates that relatively minor changes in the environment, such as restructuring a dayroom, can result in significantly improved psychosocial functioning in psychogeriatric patients. A project introducing multiple changes designed to improve the quality of life on a geriatric ward in a provincial mental hospital is described and discussed in the light of that research and suggestions are made regarding its replication under more rigorous experimental conditions.

Accidental Falls↗
PubMed1988

Correlations between cis-platinum dosage and toxicity in a guinea pig model.

A guinea pig model was used to study correlations between cis-platinum dosage and level of hearing loss, hair cell loss in the cochlea. Other parameters measured included weight loss and serum urea, creatinine, and cis-platinum levels. The damage to the inner ear expressed as hearing loss and hair cell loss demonstrated a highly positive correlation with the dosage of cis-platinum, and only a moderately positive correlation with the cis-platinum serum levels. Weight loss correlated well with hearing loss.

Animals↗
PubMed1988

Contrast sensitivity for oscillating sine wave gratings during ocular fixation and pursuit.

The influence of pursuit eye movements on the visibility of sine wave gratings was investigated by the simultaneous measurement of eye movements and contrast thresholds under different viewing conditions. It was concluded that: 1. with moving gratings contrast sensitivity during ocular pursuit was equal to contrast sensitivity during maintained fixation on a stationary target, provided that the magnitude of retinal image motion (0-20 deg/sec) was equal in both cases; 2. accurate pursuit eye movements led to a paradoxical suppression of the visibility of low spatial frequency gratings; 3. the visibility of high spatial frequency gratings remained unchanged during accurate pursuit eye movements; 4. iso-contrast-sensitivity resulting from both pursuit and non-pursuit conditions could be used to quantify the ocular pursuit performance.

Contrast Sensitivity↗
PubMed1988

Gain of the adaptation mechanism in the human vestibulo-ocular reflex system.

The response of the vestibulo-ocular reflex to constant angular acceleration was investigated in healthy subjects using various stimulus amplitudes and stimulus durations. For stimulus amplitudes of 1.06 and 2.13 degrees/s2 the peracceleratory response maximum at 43 s was always followed by a decline in response. This decay was less pronounced for the longer stimulus duration suggesting a nonreturn to the zero baseline. From a comparison with the theoretical model it can be deduced that the gain of the adaptation mechanism is less than unity.

Acceleration↗
PubMed1987

Development of cis-platinum-induced hearing loss in guinea pigs.

The resultant hearing loss can be variable if cis-dichlorodiammineplatinum is given to guinea pigs. In order to find out more about these differences, we used brainstem audiometry to study the start and development of hearing loss over time for several frequencies. Our results confirmed previous observations that hearing loss starts at the higher frequencies but can also occur at lower frequencies. Furthermore, there were great differences in the start and the rate of the increase of hearing loss found in the individual animals. The individual differences in susceptibility can not be explained by one factor alone, but by the combination of three factors, namely deviation point, slope and length of survival.

Animals↗
PubMed1985

Psychiatric and nonpsychiatric facilities in the care of psychogeriatric patients.

The care of elderly patients who are mentally impaired requires reorganization in the delivery of mental health services to these patients. In this paper recommendations are made for the improvement of such services. These include the development of comprehensive psychogeriatric assessment services, which should be based mainly in general hospitals, the rationalization of the roles of facilities that provide nonpsychiatric long-term care, the development of specialized facilities for demented elderly patients, and a focus on education in psychogeriatrics for both undergraduate and postgraduate students in medicine and in other health care professions.

Aged↗
PubMed1985

Comparison of the adaptation time constants of the vestibulo-ocular reflex and of the sensation of rotation during sinusoidal stimulation.

The influence of adaptation on the phase characteristic of both the vestibular-ocular reflex and the sensation of rotation is investigated. The experimental data can be described by a second-order model with an adaptation term. The adaptation time constant Ta is found to be 135 s for the vestibulo-ocular reflex while it has a much lower value, 47 s, for the sensation of rotation. The difference is only found in the low-frequency region.

Adaptation, Physiological↗
PubMed1984

Analysis of hearing loss due to cis-diamminedichloroplatinum-II.

The difference in the hearing threshold before and after treatment with cis-diaminnedichloroplatinum (DDP) is analysed in 69 patients. Hearing loss due to DDP treatment is mainly limited to 8,000 Hz and the incidence is about 40%. The effect of DDP is dose-related, although even at the lowest dose 20% of the patients are affected. The age of the patients is not an important factor. Loss of hearing due to DDP treatment occurs independent of any pre-existent hearing loss although those patients with great pre-existent hearing loss do not show a further loss. Of the patients with hearing loss, 39% show a difference of 20 dB or more between the left and the right ear. Hearing loss due to DDP is of minor importance compared with many of the other side-effects of DDP.

Auditory Threshold↗
PubMed1983

Influence of adaptation upon the impulsive time constant of the human vestibulo-ocular reflex system. I. Theoretical study.

From the impulse response of the human vestibulo-ocular reflex system the value of the long time constant T1 can be calculated in two different ways: (a) by plotting the decay of the response on log-linear graph paper; (b) by plotting the duration of the response against the logarithm of the impulse amplitude for various impulse amplitudes, i.e. the cupulometric method. Using mathematical models, with and without adaptation, we studied the effect of the two methods of calculation on the value of the response T1. The adaptation term was demonstrated to give a distinct reduction in the value of the response T1, compared with that of the cupular T1, especially when the cupulometric method (b) was used. The extent of this reduction was calculated.

Adaptation, Physiological↗
PubMed1983

Influence of adaptation upon the impulsive time constant of the human vestibulo-ocular reflex system. II. Experimental investigation.

The response of the vestibulo-ocular reflex (VOR) system was measured after a start or stop in angular velocity around the vertical axis. All determinations were carried out six times for 5 subjects. In a previous study, the mean value of the response T1 was calculated from the slope of the decay of the slow phase eye velocity (method a) and found to be 13.2 +/- (SD) 1.4 s for CW stimulation, and 12.8 +/- 1.7 s for CCW stimulation. Using the cupulometric method (b) with a fixed threshold for the slow phase eye velocity, these values are 12.1 +/- 2.0 and 11.2 +/- 1.4 s, respectively. The difference between the values calculated by method (a) and those calculated by method (b) is in line with the theoretical predictions as formulated in section I of this paper.

Adaptation, Physiological↗
PubMed1983

Frequency response of the human vestibulo-ocular reflex system at low frequencies: the effect of adaptation. I. Theoretical study.

From the mathematical model of the human vestibulo-ocular reflex (VOR) system, the frequency response has been calculated for harmonic sinusoidal acceleration. The addition of an adaptation term to the second order model, describing the cupular behaviour, results in considerable changes in the response characteristics in the low frequency region. An attempt has been made to quantify the influence of the cupular time constant T1 and the adaptation time constant Ta on the amplitude and phase characteristics of the transfer function, which represents the human VOR system. The results of this theoretical study will be employed in the following paper.

Acoustic Stimulation↗
PubMed1983

Frequency response of the human vestibulo-ocular reflex system at low frequencies: the effect of adaptation. II. Experimental investigation.

The frequency response of the human vestibulo-ocular reflex (VOR) system was investigated by determining its amplitude and phase characteristics. The angular head velocity and the resulting angular eye velocity were measured in 7 healthy subjects using a rotation room. Rotations about a vertical axis were carried out at frequencies ranging from 0.0025 to 0.1 Hz; peak head velocity was 50 degrees/s. From the experimental data, the gain and the phase relationship were calculated. The results appear to be in agreement with the frequency response of the theoretical transfer function which represents the VOR system. This is based on a second order differential equation for cupular behaviour, modified by an adaptation term. According to the experimental phase characteristic the cupular restoration time constant T1 was 16.6 s, and the adaptation time constant was 114 s. Linearity of the VOR system, both for amplitude and phase, was demonstrated at frequencies of 0.05 and 0.005 Hz.

Acoustic Stimulation↗
PubMed1983

Response of the human vestibulo-ocular reflex system to constant angular acceleration. I. Theoretical study.

The response of the human vestibulo-ocular reflex system to a constant angular acceleration is calculated using a second order model with an adaptation term. After first reaching a maximum the peracceleratory response declines. When the stimulus duration is long the decay is mainly governed by the adaptation time constant Ta, which enables to reliably estimate this time constant. In the postacceleratory period of constant velocity there is a reversal in response. The magnitude and the time course of the per- and postacceleratory response are calculated for various values of the cupular time constant T1, the adaptation time constant Ta, and the stimulus duration, thus enabling their influence to be assessed.

Acceleration↗
PubMed1983

Response of the human vestibulo-ocular reflex system to constant angular acceleration. II. Experimental investigation.

The vestibulo-ocular reflex (VOR) response to a constant angular acceleration was investigated in a small group of subjects by varying the stimulus amplitude and the stimulus duration. Various parameters of the response were determined and compared with the results of the theoretical study. This form of stimulation yields a rather high value for the adaptation time constant Ta, which perhaps indicates that there is an adaptation gain of less than unity. This supposition is supported by finding of non-linearity within the VOR system at high stimulus amplitudes.

Acceleration↗