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Biomedical subjects

A D Milner

Publications and source records attributed to A D Milner.

At least 73 records · Page 4Linked to original sources
PubMed1996

The perception and prehension of objects oriented in the depth plane. I. Effects of visual form agnosia.

Previous studies have reported that the visual form agnosic D.F. is able to use information about visual targets for the control of motor acts, but has great difficulty in using the same visual information for perceptual report. This intact visuomotor performance may be mediated by relatively intact parieto-frontal cortical mechanisms. The present study investigated the ability of D.F. to use binocular and monocular information about the orientation of an object in the depth plane for perceptual and visuomotor purposes. A square plaque was presented at seven different orientations in depth to D.F. and to three age- and sex-matched control subjects. Subjects were required to reach out and grasp the plaque using a precision grip (index finger and thumb) under binocular and monocular viewing conditions, and in separate trials to match the orientation of a hand-held plaque to the perceived orientation of the target object, also under both binocular and monocular conditions. D.F.'s performance in grasping trials was found to be normal under binocular conditions, but was substantially worsened by removal of binocular vision. She was severely impaired at matching the orientation of the test square, although under binocular conditions her performance rose clearly above chance. The data suggest that the separation of cortical processing for visuomotor and visual perceptual purposes also applies, at least in part, to information about the orientation in depth of an object. The impaired performance under monocular viewing conditions on the visuomotor task is in agreement with recent physiological data and suggests that posterior parietal systems depend critically on binocular input for the processing of orientation in depth when ventral-stream information is unavailable.

Adult↗
PubMed1996

Treatment of recurrent acute wheezing episodes in infancy with oral salbutamol and prednisolone.

UNLABELLED: The aim of this study was to investigate the role of oral salbutamol and prednisolone in the treatment of acute episodes of wheezing in infants under 15 months of age. Sixty-two acute episodes of wheezing were studied in 59 babies (age range 3-14 months; mean 7 months), who had all suffered at least one previous wheezy episode. Patients were randomised to receive either salbutamol and prednisolone, salbutamol and placebo or double placebo. Parents were requested to keep a diary card record of twice daily scoring of their baby's symptoms over the next 14 days. A significantly greater number of treatment failures occurred in the placebo group compared to babies treated with oral salbutamol (relative risk 2.51; 95% confidence intervals for relative risk 1.09-5.79). There was no difference in the number of treatment failures between babies treated with a combination of salbutamol and placebo and those treated with salbutamol and prednisolone (relative risk 0.71; 95% confidence intervals for relative risk 0.18-2.80). CONCLUSION: This study demonstrates that oral salbutamol is beneficial in the treatment of acute episodes of wheezing in infancy. A combination of oral salbutamol and oral prednisolone appeared to have no additional benefit over treatment with oral salbutamol alone.

Administration, Oral↗
PubMed1996

Visuomotor sensitivity for shape and orientation in a patient with visual form agnosia.

We have previously demonstrated that a patient with visual form agnosia (DF), who is unable to report the orientation or size of visual targets, can nevertheless use these same visual attributes to control motor acts. In the first of three new experiments, we found that DF is able to grasp everyday tools and utensils proficiently (i.e. with a well-formed hand posture) but has difficulty in visually selecting the correct part of the object to grasp (e.g. the handle) for subsequent use of that object. A second experiment revealed that DF's visuomotor system is able to adjust concurrently to variations in both the size and orientation of target objects; when these visual attributes were both varied, she adjusted both her grip aperture and the orientation of her hand well in advance of target contact. These spared visuomotor abilities do not seem to extend to shape processing per se, however. In the final experiment we found that DF was insensitive to changes in the orientation of a cross-shaped object, where no single principal axis could be extracted to control orientation of the grasp. These observations extend our knowledge of DF's residual visuomotor abilities, and suggest limitations on the visual processing capacities of the human dorsal stream.

Adult↗
PubMed1996

Estimation of fetal lung volume using enhanced 3-dimensional ultrasound: a new method and first result.

OBJECTIVE: To measure fetal lung volume using a computer based, enhanced, 3-dimensional ultrasound imaging system. DESIGN: An observational study. SETTING: The Fetal Medicine Unit at Guys Hospital, London. PARTICIPANTS: Twenty healthy women with a singleton pregnancy between 24 and 36 weeks of gestation were scanned on one occasion during pregnancy using an ultrasound based 3-dimensional imaging system. All delivered at term with weights above the 10th centile for gestation. RESULTS: Total lung volume increased exponentially with gestational age. Right lung volume measured consistently greater than left lung volume. CONCLUSIONS: The use of this new enhanced 3-dimensional imaging system allows for estimations of fetal lung volume. Preliminary data confirm that fetal lung volume, measured by a computerised 3-dimensional ultrasound imaging system increased exponentially with gestational age. The use of this system has obvious application in the further study of lung growth in utero and possible clinical application in disease states where fetal lung growth may be impaired.

Female↗
PubMed1995

Distortion of size perception in visuospatial neglect.

BACKGROUND: A number of studies have shown that most patients with symptoms of unilateral (left-sided) visuospatial neglect make consistently rightward errors when attempting to bisect a horizontal line at its midpoint. One possible interpretation of this impairment is that such patients misperceive the left half of the line: that is, that they underestimate its extent relative to the right half. RESULTS: We have carried out direct tests for such a perceptual distortion in three neglect patients by asking them to make matching judgements on pairs of horizontal rectangles, vertical rectangles or nonsense shapes, of varying relative size, presented on a computer screen. We report here that all of the patients tested showed a significant and substantial relative underestimation of the horizontal extent or area of stimuli presented on the left side of their egocentric space. There was no such misperception of vertical extent. CONCLUSIONS: It is suggested that size perception may be partially determined by a representational system that is anatomically centred in the parieto-temporal region of the brain. The results are interpreted in terms of damage to this system in neglect patients.

Attention↗
PubMed1995

Effective argon-FRC with a rebreathing technique in children with acute asthma.

In children with asthma the measurement of functional residual capacity (FRC) with standard dilution techniques requires long rebreathing times of the inert gas, i.e., helium, to reach alveolar units with long time constants. A modification of the argon-freon-22 rebreathing technique enables argon to dilute in the readily accessible lung volume and potentially can give a measurement of FRC. However, the rebreathing tests cannot be prolonged for more than 1 min thus allowing argon to reach only the rapidly accessible lung units which are grossly useful in gas exchange (effective FRC, EFRC). The aim of this study was to measure the EFRC and standard lung function in children with acute severe asthma, assess their response to nebulized salbutamol, and evaluate the relations of the EFRC response to baseline spirometric measurements. Twenty-four asthmatic children who were admitted to the hospital with an acute asthma attack had spirometry and triplicate EFRC measurements before and after treatment with nebulized salbutamol. Eighteen patients had repeated the respiratory tests 50 days later when they had fully recovered. A significant proportion (28.9%) of the argon traces obtained at baseline before treatment did not equilibrate. However, in the great majority of these tests the oscillation of the argon traces over the last 3 breaths of the test was < 5% of the simultaneous argon concentration. The EFRC values derived from the argon traces with minimal oscillation (< 5%) were reduced during the acute asthma attack when compared with the paired values obtained after recovery (P = 0.03). The administration of salbutamol caused a fall from the baseline EFRC (P = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1995

Lung sounds in neonates with and without an added dead space.

Previous studies have reported great difficulty in recording lung sounds from neonates and have found conflicting results. We studied lung sounds in neonates during the inspiratory phase of the respiratory cycle as monitored by inductive plethysmography (A) and by a pneumotachograph and a face mask (B) which added a dead space of 12 mL. Sixteen term babies were tested 12 hr to 6 days (median 45 hours) after birth. Lung sounds were recorded and then analysed using overlapping and non-overlapping fast Fourier transforms. The two methods of analysis showed a difference in intensity but not in frequency. Fourteen babies provided enough breaths for comparison; a total of 596 inspirations were analysed. The intensity of lung sounds on occasion B was higher in all but two babies with a mean B/A ratio of 2.4. The mean (SD) power on occasions A and B was 13.9 (8.5) mW and 26.9 (21.0) mW, P = 0.02, respectively. In all but 4 babies the B/A ratios of the median (f50) and 90th centile (f90) frequencies were scattered randomly within 20% of unity. The mean (SD) f50 on occasions A and B was 205.5 (51.1) Hz and 225.8 (32.3) Hz, P = 0.10, respectively; the mean f90 was 370.3 (91.0) Hz and 396.1 (67.8) Hz, P = 0.25, respectively. Linear regression showed that there is a third-order polynomial relationship between sound intensity and air flow at the mouth. A weaker positive association exists between frequency and air flow, showing that the median and 90th centile frequencies approach an asymptote as flow increases.(ABSTRACT TRUNCATED AT 250 WORDS)

Auscultation↗
PubMed1995

An investigation of hemispatial neglect using the Landmark Task.

The "Landmark Task" is designed to tease apart two major factors in determining line bisection errors in spatial neglect: one whose general nature is perceptual, the other whose nature is motor. On critical test trials, the subject is required to point to whichever end of a mid-transected line is judged as nearer to the transection. Seven out of eight neglect patients pointed consistently to the left end of such lines. Thus their misjudgments were made in the direction opposite to any putative "directional hypokinesia." One patient, however, pointed predominantly rightward on these test trials. Normal controls and unilateral stroke patients were also tested on the Landmark Task. Cueing of one end of a line led to a relative perceptual overestimation of that half of the line in all of these groups.

Aged↗
PubMed1995

Lung volume and pulmonary blood flow measurements following exogenous surfactant.

UNLABELLED: Lung function in eight infants with clinical and radiological features of surfactant deficiency treated with exogenous porcine surfactant was studied before and at 15 min, 2h and 6h after the intratracheal administration of porcine surfactant. We measured alveolar-arterial oxygen tension difference, dynamic lung compliance, lung volume and effective pulmonary blood flow in all infants. The alveolar-arterial oxygen tension difference fell from a mean (SD) 43.3 (14.5) kPa before treatment to 8.8 (8.8) kPa at 1 h and 12.2 (6.8) kPa 6h after treatment (P < 0.001). There was no change in mean (SD) dynamic compliance (0.39 [0.10] ml/cmH2O/kg pre dose; 0.36 [0.13] ml/cmH2O/kg 6h post treatment). Accessible functional residual capacity and effective pulmonary blood flow were measured using an adaptation of the argon/freon rebreathing method and showed an increase in mean (SD) functional residual capacity from 7.5 (1.4) ml/kg predose to 10.8 (3.3) ml/kg within 15 min of treatment, 11.4 (3.4) ml/kg 2h later and 12.7 (3.1) ml/kg 6h after treatment (P = 0.009). Mean (SD) effective pulmonary blood flow values did not differ significantly, changing from 78.2 (20.9) ml/kg per min predose to 88.7 (24.1) ml/kg per min 15 min post dose, 87.6 (21.7) ml/kg per min 2h post dose and 90.0 (22.7) ml/kg per min 6h post dose (P = 0.711). CONCLUSION: The improvement in oxygenation after surfactant treatment is associated with an increase in lung volume but is not related to an improvement in dynamic lung compliance or effective pulmonary blood flow. The change in lung volume is detectable within 15 min of administration of the surfactant.

Analysis of Variance↗
PubMed1995

How does exogenous surfactant really work?

The finding of a lag of up to 24 h between the response to exogenous surfactant in infants with respiratory disease syndrome as assessed by blood gases and improvements in respiratory system compliance has generated considerable interest. Studies have shown that there is rapid increase in functional residual capacity after natural surfactant and a less dramatic rise in effective pulmonary blood flow. These changes in blood flow are not associated with a sustained fall in pulmonary artery flow or pressure indicating that the main improvement in oxygenation results from a reduction in intrapulmonary shunting. Recent studies have shown that natural surfactant does produce rapid increases in lung compliance but only if the expired gases are vented to ambient rather than to positive end expiratory pressures. Thus the mechanical effects of natural surfactant are initially largely limited to the part of the tidal volume which is close to the functional residual capacity.

Humans↗
PubMed1995

Cerebral correlates of visual awareness.

While it may be a long time before we can specify the mechanisms through which a brain process achieves awareness, it may be possible to determine as a first step whether awareness is limited to the products of certain kinds of processing. In the domain of vision, for example, perceptual awareness might only be attainable in association with object-centred coding, configural representations of space, and other such forms of abstracted (non-retinocentric) coding. It appears that these forms of visual coding are anatomically restricted to telencephalic structures, and indeed it has been argued that they may be peculiar to, or at least visually dependent upon, the 'ventral stream' of visual areas with the cortex. It is suggested here that such a brain process would still not be able to enter visual awareness unless it was selectively amplified through neuronal gating of the kind that has been shown to be correlated with selective spatial attention. The present paper explores the extent to which this putative dual requirement for visual consciousness might form a basis for understanding the various phenomena of "covert vision" seen in patients suffering from hemianopia, apperceptive agnosia, and unilateral spatial neglect.

Agnosia↗
PubMed1995

Differential effects of line length on bisection judgements in hemispatial neglect.

Recent studies have shown that certain symptoms of spatial neglect are co-determined by two major factors: one whose general nature is perceptual, the other whose nature is directional and/or motor. In the present study, patients whose neglect was classified as predominantly 'perceptual' or 'directional' through use of the Landmark task (Milner, Brechmann and Pagliarini, 1992) were asked to bisect lines ranging in length from 20 to only 2.5 cm. It was found that the one patient with predominantly directional neglect showed large rightward errors at all line lengths. In contrast, those with perceptual neglect made very small (usually leftward) errors on short lines. It is argued that it is essential to separate these different subtypes of neglect patient if we are to understand the causation of their behaviour in tasks such as line bisection.

Aged↗
PubMed1995

Tryptase and IgE concentrations in the respiratory tract of infants with acute bronchiolitis.

It has been proposed that a specific IgE response contributes to the immunopathology of acute respiratory syncytial virus (RSV) bronchiolitis but previous work has been difficult to replicate. Indirect evidence that might support this contention was sought by measuring total IgE concentrations in bronchoalveolar lavage (BAL) samples obtained from intubated infants and by attempting to detect mRNA for IgE in cells obtained from both the upper and lower respiratory tract. Evidence of significant mast cell activation was sought by measuring tryptase concentrations in BAL fluid and serum. Detectable concentrations of IgE were found in two of seven BAL samples obtained more than five days after intubation and mRNA for IgE was demonstrated in three of six BAL samples and three of six samples obtained from the upper respiratory tract. Tryptase was detectable in 11 of 12 BAL samples with the two highest values detected on day 1. These values were raised compared with control samples but were not such to suggest that mast cell degranulation is the major contributor to the inflammatory process. These results suggest that IgE may be produced in the airways of infants in response to RSV infection. The relationships between IgE production, RSV infection, and symptoms of acute bronchiolitis remain obscure.

Acute Disease↗
PubMed1994

Bilirubin and ascorbate antioxidant activity in neonatal plasma.

Extremely low birth weight premature infants have been known for many years to have limited antioxidant protective capacity, especially with reference to those antioxidant components which do not cross the placenta until the third trimester of gestation. In this study the total antioxidant activity and the concentrations of individual antioxidants in plasma from premature neonates (27 +/- 2 weeks gestation) compared to term babies (38-41 weeks gestation) have been examined. The results show elevated levels of ascorbate at birth in the plasma of premature neonates compared with those of term babies, but the total plasma antioxidant status of the premature babies is significantly lower than that of term babies. At 5 days post-partum the ascorbate levels are within the normal adult range and plasma bilirubin levels are considerably enhanced in both groups, while the total plasma antioxidant status of the premature neonates has increased. Analysis of the relationship between the total plasma antioxidant activity and the bilirubin concentration show a direct, highly significant correlation for the term group, r2 = 0.774, consistent with significance of bilirubin as a plasma antioxidant.

Antioxidants↗
PubMed1994

Effective pulmonary blood flow in children with acute asthma attack requiring hospitalization.

In children with acute obstructive lung disease gas exchange is affected by ventilation-perfusion mismatch and the degree of bronchoconstriction. Standard lung function measurements do not reflect the impairment in gas exchange. Alternatively, the effective pulmonary blood flow (EPBF), that is, the proportion of the cardiac output that is supplying well-ventilated lung units, can give accurate and noninvasive estimates of ventilation-perfusion mismatch. We measured EPBF with the argon freon-22 rebreathing technique in children with acute severe asthma to assess their response to nebulized salbutamol and to determine whether induced changes in the EPBF could be predicted from baseline measurements. Twenty-four children admitted with an acute asthma attack had spirometry and triplicate EPBF measurements before and after nebulized salbutamol. Eighteen patients had repeated tests 50 days later when fully recovered; 4 patients were taking methylxanthines on at least one occasion. The mean forced expiratory volume in 1 sec (FEV1) rose from 55% of predicted to 66% after salbutamol and to 83% with recovery. The mean coefficients of variation for EPBF measurements on the three test occasions were 11.3%, 8.2%, and 9%. Except in children on methylxanthines, the EPBF values were reduced during the acute asthma attack (median, 2.53 L/min/m2; range, 1.99-3.60 L/min/m2) compared with paired values obtained after recovery (median, 2.89 L/min/m2; range, 2.28-4.04 L/min/m2) (P = 0.009). Salbutamol caused a highly significant increase in EPBF from 2.88 L/min/m2 (range, 1.86-3.80) before treatment to 3.34 L/min/m2 (range, 2.26-4.65) immediately afterwards (P = 0.0003).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1994

The Hering-Breuer deflationary reflex in the newborn infant.

Initial observations on healthy term infants using the forced partial expiratory flow-volume technique with an inflatable jacket suggested that this technique was stimulating the Hering-Breuer deflationary reflex, a reflex which has not been systematically studied in man. To investigate this fully, esophageal pressure, jacket pressure, flow and volume at the mouth were recorded during the forced partial expiratory flow-volume maneuver on 10 infants (mean age, 3.1 days; birth weight, 3533 g; gestation, 39.8 weeks). A total of 186 measurements were performed at different points in the respiratory cycle. In 159 (85%) recordings inspiratory effort was evident with a fall in esophageal pressure within 166 msec; in some cases this occurred before the jacket was fully inflated. This was associated with a reduction of 23.4 cm H2O in mean intrathoracic pressure, which was 2.5 times that occurring during normal tidal breathing. In the remaining 27 measurements a plateau pressure was associated with closure of the upper airway. When the squeeze was applied at low lung volumes (end-expiration) the inspiratory effort occurred significantly earlier (133 msec) and stronger (reducing peak intrathoracic pressure to 15.8 cm H2O) than when applied at end-inspiration (181 msec with a reduction in intrathoracic pressure to 25.2 cm H2O). The observed inspiratory response was highly consistent, representing the deflationary reflex as described by Hering and Breuer in 1868. The stronger and more rapid onset of inspiration at low lung volume supports the claim made by Breuer that it has a protective role on functional residual capacity (FRC) in young infants.

Female↗