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Biomedical subjects

W Hofman

Publications and source records attributed to W Hofman.

12 recordsLinked to original sources
PubMed1995

Early symptoms and neurological findings in demented subjects from a community survey.

The prevalence of the symptoms at disease onset reported by close informants, in an unselected group of demented elderly, is presented in this study. Of the 174 dementia cases, 98 were Alzheimer disease (AD), 41 were vascular dementia (VaD), and 35 were other dementias. In 42% of AD subjects, single memory deficit was the earliest problem, while in 56% of VaD cases, the tendency was to present two or more disturbances in the early stages. Slightly younger mean age at onset was reported in VaD than in AD cases. Our results support the hypothesis that the debut of the dementia is variable with any combination of symptoms. However, when memory problems start, assessment is needed. Among the neurological findings in the clinical examination, extrapyramidal signs were present in 25% of all dementia cases and in 20% of AD cases. A higher frequency of extrapyramidal signs was present in more severe cases, confirming previous reports of the unfavorable prognostic value of these signs.

Age Distribution↗
PubMed1993

EEG spectral power analysis of phasic and tonic REM sleep in young and older male subjects.

EEG spectral power was studied during periods of rapid eye movements (REMs) and tonic intervals in REM sleep of 7 young and 7 older male subjects. Significant symmetrical decreases in alpha and beta1 power at central and occipital sites, concurrent with an increase in frontal theta power, were observed during the production of REMs. The former findings are discussed as sleep analogues to changes in alpha and beta1 during waking, showing increased information processing and behavioural activation, and that of theta is tentatively presented as reflecting an increase in afferent thresholds. Independent of the phasic-tonic REM distinction, total EEG power markedly decreased as a function of time of night and did not interact with age. Significant age differences in the overall spectral composition of the EEG were obtained, namely, a lower level of delta power and a relative shift towards more power in frequencies above 12 Hz for the older group. Further, older subjects also demonstrated a more uniform topographical distribution of alpha and sigma power.

Journal Article↗
PubMed1992

Removal of ocular artifacts from the REM sleep EEG.

The present report concerns the first study in which electrooculographic (EOG) contamination of electroencephalographic (EEG) recordings in rapid eye movement (REM) sleep is systematically investigated. Contamination of REM sleep EEG recordings in six subjects was evaluated in the frequency domain. REM-active and REM-quiet series were obtained for each subject. Transfer coefficients and power spectra of EOG and EEG indicated that (a) increases in transfer coefficients beyond 4.5 Hz are brought about by residual EEG in the EOG, and (b) EOG-EEG contamination in the delta band is most pronounced in frontal, intermediate in central and negligible in occipital leads. It was found that correction of the REM-active series resulted in significant (c) reductions in power, (d) increases in interhemispheric coherences and (e) reductions in degree of lateral asymmetry. These effects were largest for frontal leads, but still marked for central ones. The results are discussed in the light of previous findings concerning models of hemispheric functioning during REM sleep.

Adult↗
PubMed1992

Effects of delta sleep-inducing peptide on sleep of chronic insomniac patients. A double-blind study.

The influence of delta sleep-inducing peptide (DSIP) on sleep was studied in 16 chronic insomniac patients according to a double-blind matched-pairs parallel-groups design. Subjects slept for 5 consecutive nights in the laboratory. Night 1 was used for adaptation, night 2 for baseline measurements. In the afternoon before the 3rd, 4th and 5th night, half of the patients received intravenously 25 nmol/kg body weight DSIP, and half of the patients a glucose solution (placebo). Measures for sleep structure, objective (polysomnography) and subjective sleep quality and for subjective tiredness were assessed. The results for objective sleep quality indicated higher sleep efficiency and shorter sleep latency with DSIP as compared to placebo. One measure of subjectively estimated tiredness decreased within the DSIP group. Data analysis suggested, however, that the statistically significant effects were weak and in part could be due to an incidental change in the placebo group. As none of the other measures, including subjective sleep quality, showed any change, it was concluded that short-term treatment of chronic insomnia with DSIP is not likely to be of major therapeutic benefit.

Adult↗
PubMed1986

ATP binding and crossbridge structure in muscle.

Thick filaments extracted from insect flight muscle were used in examining whether the dependence of actin-myosin crossbridge structure on nucleotide, generally presumed to underlie the power-stroke, is exhibited by myosin alone. The strongly periodic crossbridge arrangement seen in the presence of ATP (corresponding to relaxed muscle) is reversibly lost in conditions that induce rigor in intact muscle fibres. These observations suggest that the power-stroke may involve changes in the steric relation of the myosin head to the thick as well as to the thin filament.

Actin Cytoskeleton↗
PubMed1980

Human and automatic validation of a phase-locked loop spindle detection system.

A further test of a phase-locked loop spindle detector is described. On the basis of comparison with both human visual scoring and with a second automatic system employing complex demodulation techniques, the detector's performance would appear to be adequate for most laboratories' needs. The errors in detection were largely shared by the two automatic systems.

Adult↗
PubMedDate not supplied

An automatic spindle analysis and detection system based on the evaluation of human ratings of the spindle quality.

An evaluation of the spindle quality ranked by experienced human raters is described. The pattern discriminating criteria obtained from this evaluation are used for an automatic system based on the complex demodulation method. The performance of this automatic system is compared with both the human visual scoring and with a second automatic system employing phaselocked loop techniques. The performance of the complex demodulation is satisfactory. It also detects spindles buried in slow waves. It is not sensitive to the age of the subject. This method opens possibilities for research of either temporal or chemical (drugs etc.) effects on the characteristics of rhythmic activity, without being hampered by the arbitrary EEG jargon "alpha" or "sigma".

Adult↗