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Biomedical subjects

C Heywood

Publications and source records attributed to C Heywood.

10 recordsLinked to original sources
PubMed2003

EEG biofeedback vs. placebo treatment for attention-deficit/hyperactivity disorder: a pilot study.

METHOD: Seven children diagnosed with attention-deficit hyperactivity disorder (ADHD) were trained using a standard EEG biofeedback treatment protocol designed to alter SMR/theta ratios and reduce behavioral symptomatology diagnostic of ADHD. During alternate periods they were also trained using a placebo protocol that was identical to the treatment protocol, save that the association between EEG patterns and feedback to the participants was random. Single-case design elements were used to control for the effects of internal validity threats such as maturation, history, and treatment order. Two participants failed to complete all training sessions, and the effects of training on behavior were analyzed both including and excluding these non-completers. RESULTS: When all participants were included in analyses that controlled for overall trend, EEG biofeedback was found to be no more effective than the placebo control condition involving non-contingent feedback, and neither procedure resulted in improvements relative to baseline levels. When overall behavioral trends unrelated to training were not controlled for and non-completers were excluded from the analysis, it could be mistakenly concluded that EEG biofeedback is significantly more effective than placebo and that the effect sizes involved are moderate to large. These results indicate that many previous reports of the efficacy of EEG biofeedback for ADHD, particularly those presenting series of single cases, might well have been based on spurious findings.

Attention Deficit Disorder with Hyperactivity↗
PubMed1998

Discrimination of cone contrast changes as evidence for colour constancy in cerebral achromatopsia.

One proposed mechanism for underpinning colour constancy is computation of the relative activity of cones within one class--cone ratios, or cone contrasts--between surfaces in a fixed scene undergoing a change in illuminant. Although there is evidence that cone ratios do determine colour appearance under many conditions, the site or sites of their computation is unknown. Here, we report that a cerebrally achromatopsic observer, MS, displayed evidence of colour constancy in asymmetric colour matching tasks and was able to discriminate changes in cone ratios for simple, but not complex scenes. We hypothesise that the site of local cone-ratio computation is therefore early in the visual system, probably retinal.

Color Perception↗
PubMed1996

Now you see it, now you don't. Colour vision.

Studies of patients who are colour blind as a result of brain damage show that colour contributes much more to our perception of the visual world than merely the registration of hue.

Color Perception↗
PubMed1989

Selective deficit of visual search in moving displays after extrastriate damage.

A visual cue that is often associated with significant stimuli, such as those provided by prey and predators, is movement relative to the observer. An efficient visual system should be able to direct attention to those parts of the visual field that contain such stimuli. What is needed is a system that can filter by movement difference. This could direct attention to a moving item among stationary items, or an item moving in one direction against a background moving in a different direction. Visual search experiments have shown that people are indeed able to filter by movement; that is, they can attend to just the moving items in arrays of moving and stationary stimuli. Single-cell recordings from monkey visual cortex show that the medial temporal cortical area (MT) has some of the properties required to filter by movement. We have now linked these two observations by showing that a patient with bilateral lesions to the presumed human homologue of MT cannot restrict visual attention to the moving items in arrays of both moving and stationary items. This suggests that MT is the site of a movement filter used in normal visual processing.

Animals↗
PubMed1979

Lung function in healthy British women.

The forces expiratory volume, total lung capacity, transfer factor (diffusing capacity), and their subdivisions have been measured in 113 healthy British women aged 27 to 74 years of whom 47 were current smokers and 66 were lifetime non-smokers. The results have been analysed in terms of age, stature, mass, body fat, and smoking. In addition to their relation to stature and to age, the inspiratory capacity was positively correlated with indices of body muscle while the residual volume, expiratory reserve volume, and total lung capacity were inversely correlated with the percentage of body mass that is fat or with mass divided by the square of stature. The inverse correlation between total lung capacity and age was apparently due to the quantity of body fat increasing with age. The transfer factor and its subdivisions were inversely correlated with smoking. In this study the forced expiratory volume and vital capacity were independent of both fat and smoking; the transfer factor was independent of the physiological response to exercise. The results provide reference values for lung function in British women.

Adipose Tissue↗
PubMed1977

Ventilatory capacity if healthy Chinese children: relation to habitual activity.

Ventilatory capacity, including forced expiratory volume (FEV 1-0) and forced vital capacity (FVC), and selected anthropometric indices have been obtained for 36 boys and 19 girls aged 5-10 years from a working class district in Kowloon. The ventilatory capacity is related to stature and is 13 per cent larger for boys than girls. After allowing for stature and sex the residual variation is significantly reduced by also allowing for the children's habitual activity. The ventilatory capacity of the more active children, including those who have lived all their lives in squatter huts on the hillsides, is on average 8 per cent larger than for the inactive children including those who have lived all their lives in tenement flats with lifts. The groups are apparently similar with respect to income, dietary pattern, intelligence and disease incidence, so that findings provide independent support for the hypothesis that the level of habitual activity during childhood contributes to the ventilatory capacity. The absolute level of ventilatory capacity resembles that of Nepalese children and differs from that of some other groups.

Activities of Daily Living↗
PubMedDate not supplied

Sitting height, fat-free mass and body fat as reference variables for lung function in healthy British children: comparison with stature.

The ventilatory capacity, total lung capacity and transfer factor with their respective subdivisions have been measured on 254 healthy British boy and girl twins aged 8-16 yrs. The logarithmic regression relationships of lung function on stature have been compared with those on sitting height and on stature plus indices of body muscle and fat. The regressions on stature and on sitting height describe the results with similar precision, but stature is marginally better; either index may be used as the reference variable. For the description of inspiratory capacity and of all indices which include this volume (e.g. vital capacity, total lung capacity and transfer factor), additional precision is secured by adding to the regression equation on stature a term for fat-free mass or body mass divided by the square of the stature; for the description of functional residual capacity, the inclusion of a term for % body fat similarly reduces the variance about the regression equation. The difference in lung function between boys and girls is smaller when the function is related to stature than to sitting height. It is further reduced when fat-free mass/sature and % body fat are also included in the prediction equations. The equations may be used to obtain reference values for indices of lung function in similar subjects.

Adipose Tissue↗
PubMedDate not supplied

Genetic and environmental determinants of the cardio-respiratory response to submaximal exercise--a six-year follow-up study of twins.

The fat-free mass and the ventilatory and cardiac frequency responses to submaximal exercise have been assessed longitudinally over six years in a total of 65 identical and non-identical boy and girl twin pairs. Exercise ventilation at rates of work below the anaerobic threshold was independent of the genetic and environmental factors which were investigated. The anaerobic threshold increased with age. The fat-free mass and the exercise cardiac frequency were subject to both genetic and environmental control with the genetic component predominating initially. The subsequent environmental component was larger for non-identical than for identical twin pairs and for boys than for girls. It is concluded that in identical twin boys by the time they reach adolescence the performance during submaximal exercise has a material environmental component. There appears to be interaction between the genetic and environmental components.

Adolescent↗