Biomedical subjects

W H Brouwer

Publications and source records attributed to W H Brouwer.

At least 19 recordsLinked to original sources

PubMed2005

[Is the Activities-specific Balance Confidence Scale suitable for Dutch older persons living in the community?].

BACKGROUND: In ageing populations fear of falling is an important issue. International studies and collaborations require scales suitable to more cultures. Scales developed in one culture require adaptation and additional investigation of psychometric properties for use in other countries. OBJECTIVE: To investigate the psychometric properties of a Dutch version of the Activities-specific Balance Confidence scale (ABC-NL) and whether adding questions about complex/dual tasks improves the discriminatory power. METHOD: Subjects were 106 men and 140 women aged 65-92 years. Measures were the 16-item ABC-NL and seven additional more complex items, fall history, general and physical self-efficacy, a functional reach test and a balance platform test. RESULTS: The ABC-NL had a weak ceiling effect. Internal consistency (Cronbachs alpha) was high. The relationship between ABC-NL and physical self-efficacy was significantly stronger than between the ABC-NL and general self-efficacy. Relationships with performance-based measures of balance were moderate. Differences between fallers and non-fallers and between activity avoiders and non-avoiders were significant. Adding questions about complex tasks hardly improved discriminatory power, reliability and validity. CONCLUSION: Psychometric properties of the ABC-NL were satisfactory. Further research is needed for use in high-functioning older persons.

Accidental Falls↗

PubMed2002

Grey scales uncover similar attentional effects in homonymous hemianopia and visual hemi-neglect.

Multi-component models of visual hemi-neglect have postulated that visual hemi-neglect is characterised by various attentional deficits. A grey scales task has been developed to quantify the early, automatic, (perhaps obligatory) ipsilesional orienting of visual attention, frequently assumed as the first of these attentional deficits. Explanations for this attentional imbalance are up until now mainly formulated in terms of right hemisphere activation. This lateral attentional bias has also been demonstrated in controls, in whom it is expressed as a leftward perceptual asymmetry. We reproduced previous literature findings on a grey scales task, considering controls and neglect patients. Three patients with neglect showed an extreme ipsilesional lateral bias. This bias did not change during or after cognitive rehabilitation. Additionally, we presented this grey scale task to 32 patients with left- and right-sided homonymous hemianopia (HP). HP is the loss of sight in one visual hemi-field. The HH patients had no clinical signs of impaired lateralised attention. Results revealed that HH patients showed a similar ipsilesional bias, albeit to a lesser degree than in neglect. Left-sided HH patients presented a quantitatively similar, but qualitatively opposite bias than the right-sided HH patients. We suggest that sensory effects can be an alternative source of attentional imbalance, which can interact with the previously proposed (right) hemispheric effects. This suggests that the perceptual asymmetry in the grey scales task is not necessarily an indicator of impaired right hemisphere attention. It rather suggests a pattern of functional cerebral asymmetry, which can also be caused by asymmetric sensory input.

Adolescent↗

PubMed2002

Hemianopic visual field defects elicit hemianopic scanning.

Previous explanations for the variability in success of compensating for homonymous hemianopia (HH) has been in terms of extent of the brain injury. In using on-line eye movement registrations, we simulated HH in 16 healthy subjects and compared their scanning performance on a dot counting task to their own "normal" condition and to real HH patients' performance. We evidenced clear parallels between simulated and real HH, suggesting that hemianopic scanning behaviour is primarily visually elicited, namely by the visual field defect, and not by the additional brain damage. We further observed age-related processes in compensating for the HH.

Adolescent↗

PubMed2001

[Cognitive impairments among older drivers: medical examination and driving test].

The aim of this study was to gain insight in the prevalence of cognitive impairments among active older drivers and in driving performance of cognitively impaired ones. The study was implemented in the existing Dutch relicensing procedure for older drivers and consisted of three evaluation moments: a medical screening (for all subjects), a neuropsychological assessment and a test-drive (for candidates with cognitive impairments). In total, 2992 drivers were medically evaluated. In 4% of cases indications for impaired cognitive functioning were observed that could be evaluated and confirmed with neuropsychological tests. Eighty subjects performed an on-road test. Of these subjects, 57% were allowed to renew their driver's license, while in the remaining 43% no new licenses or restricted licenses were issued. During the test-drive, slow reactions and attention deficits were the most important causes for impaired fitness to drive.

Age Factors↗

PubMed2000

Fitness to drive in older drivers with cognitive impairment.

This paper is a literature review on assessment of fitness to drive in older drivers with cognitive impairment. Early studies on dementia and driving generally failed to distinguish between safe and unsafe drivers on the basis of cognitive test performance. Predictive studies demonstrated that cognitively impaired persons as a group perform significantly worse than controls on both neuropsychological and driving measures. A high prevalence of cognitive impairment was found in groups of older drivers involved in traffic accidents and crashes. However, a large range in neuropsychological test scores has been found. Low to moderate correlations could be established between neuropsychological test results and on-road driving performance, making it difficult to discriminate between cognitively impaired subjects who are fit or unfit to drive. The review concludes with a discussion of methodological difficulties in the field of dementia and driving, including participant selection, the choice of neuropsychological tests, and the operationalization of driving performance.

Accidents, Traffic↗

PubMed1999

Slow information processing after very severe closed head injury: impaired access to declarative knowledge and intact application and acquisition of procedural knowledge.

As an explanation of the pattern of slow information processing after closed head injury (CHI), hypotheses of impaired access to declarative memory and intact application and acquisition of procedural memory after CHI are presented. These two hypotheses were tested by means of four cognitive reaction-time tasks, a semantic memory task, a memory comparison task, a mental rotation task and a mirror reading task. These tasks were administered on two different days to 12 survivors of a CHI tested more than 5 years after injury and a healthy control group of comparable age and education. In three tasks the difficulty of access to declarative knowledge was varied and it was expected that this would slow the CHI group more than the controls. In two tasks opportunities for procedural learning were provided by repeatedly presenting the same cognitive tasks and in one task, the difficulty of access to procedural memory was varied. It was expected that the CHI group would profit as much from this as would the control group. Both hypotheses were supported.

Adolescent↗

PubMed1998

[Memory and learning abilities in everyday life of the elderly].

Self-evaluations by adults (varying in age from 45-92 years) of their memory and learning abilities were investigated and related to performance on laboratory and ecological memory tasks. Hardly any association was found between subjective and objective measures. Self-evaluations were strongly influenced by (systematically varied) frames of reference: optimistic in comparisons with other people, pessimistic in comparisons with their own previous level of functioning. The most frequent problems were 'learning something new' and 'remembering names'. In contrast to external memory aids, cognitive strategies were rarely used spontaneously. Strategy training led to significant improvement of performance, that remained stable at follow-up. A further opportunity for improving performance was realized by ergonomic adaptations of computerized systems (teleshopping). Problems in learning to use such systems were strongly reduced by decreasing the load on working memory and by adapting the system to existing knowledge and skills of the users. A general observation in the different projects was that age-differences could explain only a small percentage of the variance in subjective and objective memory measures.

Adaptation, Psychological↗

PubMed1997

Dementia and driving: an attempt at consensus.

The number of older drivers in Sweden will be rapidly increasing during the next decades. A possible relationship exists between the increased relative crash risk of older drivers and the prevalence of age-related diseases such as dementia. However, a clear-cut policy for evaluating driving competence in demented persons is still lacking. In recognition of this fact, the Swedish National Road Administration invited a group of researchers to formulate a consensus on the issue of driving and dementia. This consensus document is aimed at providing primary care physicians with practical advice concerning the assessment of cognitive status in relation to driving. Suggestions are based on a review of existing research and discuss the use of general and driving-specific sources of information available to the physician. Consensus was reached on the statement that a diagnosis of moderate to severe dementia precludes driving and that certain individuals with mild dementia should be considered for a specialized assessment of their driving competence.

Aged↗

PubMed1995

Motor function in a patient with bilateral lesions of the globus pallidus.

This study describes the long-term deficits of a patient who, after a toxic encephalopathy, sustained extensive bilateral damage to both segments of the globus pallidus (GP) and the right substantia nigra (SN). There were no signs of lesions of the pyramidal tracts or of other motor structures. The most obvious deficits were an abnormal gait with an exaggerated knee extension and a tendency to fall slowly, especially when pushed backward. In contrast, Romberg's test on an unstable platform was normal, as were long-latency leg reflexes induced by perturbations. Inadequate anticipatory and compensatory postural responses, in particular across the hip and knee joints, and slow movements seemed responsible for the falls. Muscle tone was normal but reflex studies showed signs of abnormal facilitation and inhibition at various levels of the neuraxis. We conclude that the GP and SN lesions caused defective input to premotor cortical and brain stem target zones. Dysfunctioning of these zones leads to improper control of the descending ventromedial motor system responsible for locomotion, postural control, and reflex status. The deficits in upper extremity motor performance included delayed and slow movements, inaccurate amplitudes of ballistic responses, a lack of predictive control, and deficits in bimanual coordination. Sensory feedback, proprioceptive more than visual, played a powerful compensating role in rapid aiming movements. Regional blood flow (studied using 15(O)2) was reduced in multiple frontal cortical regions, among which are the hand areas of the supplementary and premotor cortex. We hypothesize that this reflected impaired functioning of these areas, caused by defective bilateral output from GP and SN, and resulting in the motor deficits of the arm and hand.

Adult↗

PubMed1991

Divided attention in experienced young and older drivers: lane tracking and visual analysis in a dynamic driving simulator.

A simulated driving task that required the simultaneous execution of two continuous visual tasks was administered to 12 healthy young (mean age 26.1 years) and 12 healthy older (mean age 64.4 years) experienced and currently active drivers. The first task was a compensatory lane-tracking task involving a three-dimensional road display. The second task was a timed, self-paced visual analysis task involving either a vocal or manual binary response to dot patterns projected within the road display. Using adaptive tasks, single-task difficulty was individually adjusted for each subject. To control for individual differences in attention allocation strategy, the dual task was performed according to three different sets of instructions based on the relative importance of each task. Compared with young adults, older adults showed a significantly decreased ability to divide attention. This effect was apparent in lane tracking and in the accuracy of visual analysis. The impairment of divided attention was less pronounced in the vocal condition than in the manual one. This suggests that difficulty in integrating responses may be an important determinant of poor dual-task performance in old age.

Adult↗

PubMed1991

[Planning ability of older and younger adults].

This investigation was aimed at the effects of ageing on planning. The investigation was carried out with young adults, middle-aged adults and elderly. Because of a suggested resemblance of problems described in elderly with impairments in patients with prefrontal cortical damage, and because the prefrontal cortex is important for planning, a test specifically sensitive to planning deficits in left prefrontal patients, the Tower of London test, was administered. On this test, the elderly solved significantly less problems in the allotted time than the two younger groups. However, the elderly did not show the same type of problem as that described in prefrontal patients. Such patients perform significantly worse on first attempts (problems correctly solved in one attempt). On this variable the elderly in our study equalled the younger adults in performance. However, they less often succeeded when the first attempt was not correct. To check whether this result could be explained simply by decreased mental and psychomotor speed and visuo-spatial function, regression functions between age and Tower score were computed, partialing out scores on tests of these more elementary abilities. A significant effect of age remained, which we tentatively interpret as an effect on planning ability.

Adult↗

PubMed1991

[Physical symptoms of Parkinson's disease and the score on Beck's Depression Inventory].

In patients with Parkinson's disease high prevalence of depression has been estimated. This prevalence may be overestimated since the commonly used assessment of depressive complaints neglects the correspondence with physical symptoms of Parkinson's disease and psychosomatic symptoms in depression. To evaluate the effect of this contamination, we presented a frequently used questionnaire for assessing depressive complaints, Beck's Depression Inventory (BDI), to eight neurologists specialized in Parkinson's disease. We asked them to select those items on which Parkinson patients might receive high scores merely because of the physical symptoms of their disease. Based on their consistent judgments, a BDI-version corrected for somatic items was constructed. Next, the scores of the original and the corrected version were computed for 27 outpatients with Parkinson's disease (from mild to very severe) and 52 psychiatric inpatients who were being treated for depression. Prevalence of depression were 74% (original BDI) and 48% (corrected BDI) for the Parkinson group and 75% and 81% respectively for the psychiatric group. Results indicate that great care should be taken in interpreting scores on depression inventories in patients with Parkinson's disease. In general, the results raise doubts on the validity of somatic complaints as indicators of depression in patients with Parkinson's disease.

Adult↗

PubMed1990

Age-related differences in timing of position and velocity identification.

The aim of this investigation was to study age-related differences in timing of position and velocity identification in a laboratory task. The skills required for performing this task are thought to be similar to those needed in real traffic situations. From this perspective, the results of this study may be taken into account in studies on accident analysis and prevention. To control for differences in the conscious experience of time and for simple reaction time to visual stimuli, young (25-34) and old (58-70) adults had to produce timed periods of 20 seconds and to time the arrival of a visible moving object at its goal. In these simple tasks no differences were found between young and old subjects. In the proper, more complex experiment, timing of position and velocity identification of a moving object were assessed with or without feedback on timing and velocity in the same old and young group. The object, moving from left to right at a constant velocity, was shown on a video screen during the first 40% of its trajectory. The moving object could have any of four (fixed) velocities which were presented in blocks with a regular or a mixed order. By pushing a button subjects estimated at which time the object would have reached the marked end of a trajectory. In a condition without feedback on timing of position, the timing error of older adults was higher than that of young adults and particularly with higher object velocities.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Divided attention 5 to 10 years after severe closed head injury.

The ability to divide attention of persons who had sustained a severe Closed Head Injury 5 to 10 years before (chronic CHI patients), was examined in a dual-task experiment administered to 15 CHI patients and 34 control subjects. Both the patient group and the control group consisted of active licenced drivers at the time of the investigation. One task was a compensatory tracking task requiring lane tracking, a basic skill or car driving. The other task was a self-paced visual choice reaction time task. Single-task difficulty was individually adjusted by adaptive task procedures (on both tasks CHI patients reached significantly lower performance levels in single task conditions). With individual differences in single-task performance thus controlled, the ability to divide attention was found to be approximately equal in the chronic CHI patients and the control group. A surprising finding in this light, however, was the significant positive correlation between severity of injury (PTA duration) and divided attention costs in the patient group.

Adult↗

PubMed1988

Age differences in divided attention in a simulated driving task.

The ability of young, middle-aged, and old adults to divide attention was examined using a dual task experiment involving two continuous performance tasks. The first task was a compensatory tracking task modeled after the important everyday activity of car driving. The second task was a self-paced visual choice-reaction time task requiring analysis of a small visual display presented in such a way that no eye movements were required when the two tasks had to be performed simultaneously. Single-task difficulty was individually adjusted for each subject. Performance-Operating-Characteristics were used to control for individual differences in attention allocation strategies. Even when individual differences in single task performance were adequately controlled for, elderly adults showed a significantly decreased ability to divide attention when compared with young and middle-aged adults. Young and middle-aged adults did not differ in the ability to divide attention.

Adult↗

PubMed1988

Fitness to drive a car after recovery from severe head injury.

Driving skills in relation to residual psychologic impairments were studied in a sample of patients who had survived severe head injuries several years earlier. Daytime driving was studied in an instrumented car that recorded lateral position control on a highway track and during rides in the subjects' own cars with a professional observer. In comparison with a control group matched by age and driving experience, the patients performed worse on both driving tasks. In addition, the patient group showed clear impairments on a neuropsychologic test battery, despite the long intervals since their injuries. However, the only relationships found between test performance and driving involved visuomotor ability and lateral position control. No relationship was found between neurologic status and driving skill. The results are discussed in terms of patients' compensatory potential.

Acute Disease↗

PubMed1987

Acquired brain damage and driving: a review.

Five issues in evaluating driving ability after brain damage were addressed through a review of the literature. Some preliminary conclusions were reached: (1) about half of all subjects studied still hold a valid driver's license; (2) brain-damaged drivers could not, in general, be seen as risky drivers, although some individuals show decreased driving skill and risky behavior in traffic; and (3) statistics show no increase in traffic violations or accidents in groups of neurologic patients with acquired brain lesions or diseases. Frequently noted problems of brain-damaged drivers include poor judgment of traffic situations, impulsivity, and visuospatial impairments. Traditional psychologic tests have insufficient predictive value regarding fitness to drive. It is suggested that new techniques be developed to enable more valid statements about the skills needed for safe traffic participation. These assessment techniques should emphasize the higher cognitive levels in driving, ie, the tactical and strategic levels. At the moment, driver training programs in rehabilitation focus mainly on the operational level, with emphasis on handling the car, use of controls and mirrors, and technical adaptation of the vehicle.

Activities of Daily Living↗

PubMed1985

Sustained attention and sustained effort after closed head injury: detection and 0.10 Hz heart rate variability in a low event rate vigilance task.

In closed head injury patients impaired sustained attention has been used to explain poor performance of complex tasks. However, this basic capacity was never adequately investigated. We investigated sustained attention in an auditory vigilance task and found no evidence at all for an impairment. With an interval of about three months 8 patients, tested in the first half year after closed head injury, and 8 healthy control subjects were confronted twice with a low event rate vigilance task. This yielded measures of signal detection and response latency. Also the amplitude of 0.10 Hz Heart Rate Variability, a power spectral measure, was calculated to indicate sustained effort. Hypotheses that patients would manifest stronger effects of time-on-task on performance and effort were not supported. Independent of sustained attention patients differed from controls in terms of response latencies and sensitivity of discriminating small differences of loudness especially on the first occasion.

Adolescent↗