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Biomedical subjects

J J Downes

Publications and source records attributed to J J Downes.

At least 19 recordsLinked to original sources
PubMed1992

Preserved implicit memory for lexical information in Alzheimer's disease.

Recent studies have suggested that there is a specific impairment of implicit memory for lexical priming in Alzheimer's Disease. However, there are problems in accepting data from the word-stem completion paradigm as evidence of pure implicit-memory performance. To assess whether Alzheimer's Disease patients are relatively impaired on implicit memory for lexical information an anagram-solution task was adopted. A group of 16 early stage Alzheimer's Disease patients and a group of 16 normal elderly subjects were presented a list of 40 target words. Subsequent free recall was significantly poorer in the former group, but while both groups were significantly better at solving anagrams for words they had previously seen, there was no difference between the two groups in the amount of priming. The data are consistent with the view that previous reports of an implicit deficit in Alzheimer's Disease may not generalise to implicit tasks independent of explicit-memory performance.

Aged↗
PubMed1992

The historical evolution, current status, and prospective development of pediatric critical care.

This article describes the multiple historic origins of pediatric critical care medicine and the evolution of the subspecialty, from the late 1950s with the first units dedicated to the care of critically ill and injured infants and children, to the present status as a recognized medical subspecialty. Also discussed are current major issues and future challenges that flow from both this historic background and a commitment to critically ill children. Presented are specific considerations for physicians in this subspecialty to address as they plan for the future.

Anesthesiology↗
PubMed1990

Sparing of attentional relative to mnemonic function in a subgroup of patients with dementia of the Alzheimer type.

Patients with dementia of the Alzheimer type (DAT) received two tests of visual selective attention, together with tests of spatial and visual recognition memory and visuospatial conditional learning previously used to show deficits early in the course of DAT. One set of attentional tests compared visual discrimination learning along intra- and extra-dimensional shifts, using a "total change" design. In the 12 DAT patients capable of attempting the extra-dimensional shift (subgroup 1), performance was equivalent to that of controls. This subgroup was also unimpaired at simple and compound discrimination learning and reversal and an intra-dimensional shift. They were as accurate as controls on a visual search task requiring matching of stimuli on two dimensions with variable numbers of alternatives, but were significantly impaired in the tests of recognition memory and learning. By contrast, the other 13 patients showed marked impairments in the attentional tasks. This subgroup was also significantly worse than subgroup 1 in performance on the visual recognition and conditional learning tasks, and showed greater severity on most of the clinical ratings of dementia. The sparing of attentional shifting in patients early in the course of DAT is contrasted with the impairments previously described in patients with Parkinson's disease with only mild or absent memory loss. The implications of this double dissociation of deficits for understanding the neural bases of the cognitive deficits in these two neurodegenerative diseases are discussed and their significance for the staging of DAT is considered.

Aged↗
PubMed1990

Planning and spatial working memory following frontal lobe lesions in man.

Twenty-six patients with unilateral or bilateral frontal lobe excisions were compared with age and IQ matched controls on a computerized battery of tests of spatial working memory and planning. A computerized test of spatial short term memory capacity revealed no significant impairment in the patients' ability to execute a given sequence of visuo-spatial moves. In contrast, a paradigm designed to assess spatial working memory capacity, revealed significant impairments in the patient group in both possible types of search errors. Furthermore, additional analysis showed that the frontal lobe patients were less efficient than controls in their usage of a strategy for improving performance on this test. Higher level planning was also investigated using a test based on the "Tower of London" problem [SHALLICE, T. Phil. Trans. R. Soc. Lond. B. 298, 199-209, 1982]. Patients with frontal lobe damage required more moves to complete the problems and a yoked motor control condition revealed that movement times were significantly increased in this group. Taking both of these factors into consideration, initial thinking (planning) time was unimpaired in the patient group although the thinking time subsequent to the first move was significantly prolonged. These data are compared to previous findings from patients with idiopathic Parkinson's disease and are discussed in terms of an impairment of higher cognitive functioning following frontal lobe damage.

Attention↗
PubMed1989

Impaired extra-dimensional shift performance in medicated and unmedicated Parkinson's disease: evidence for a specific attentional dysfunction.

Groups of patients with Parkinson's disease, either medicated, or unmedicated and early in the course, together with age- and IQ-matched control subjects were tested in two paradigms measuring different aspects of selective attention. The first set of tests compared visual discrimination learning following intra- and extra-dimensional shifts, using a "total change" design in which each shift was made in the presence of novel exemplars of the compound stimuli used as discriminanda. The second test consisted of a visual search task in which the number of alternatives was varied. The results of the first experiment showed a selective deficit in both groups of Parkinsonian subjects in their ability to perform an extra-dimensional shift. In the visual search task, the patients were less accurate, but responded with equivalent choice reaction times to those of controls. The results are discussed in terms of the nature of the attentional dysfunction that occurs in Parkinson's disease.

Aged↗
PubMed1988

Global ratings of stress in the elderly.

The properties of four global ratings of life stress were investigated using data from 237 elderly subjects interviewed using the Brown & Harris life event and difficulties schedule. The global ratings had high one-year test-retest reliability and inter-rater reliability agreement. A summary measure of Adversity (based on contextual rating of all events and difficulties) may be reliably derived when a single index of life stress is desired. In the elderly sample Adversity was more closely related to chronic difficulties than to life-events.

Adaptation, Psychological↗
PubMed1988

Planning and spatial working memory in Parkinson's disease.

The higher level cognitive function of planning was studied in a group of medicated Parkinson's disease patients and a group of matched control subjects, using a computerised version of Shallice's Tower of London task. Baseline measurement of the ability to execute a given plan of action, to generate low level strategies required for efficient searching, and spatial working memory capacity, all of which contribute to performance on the planning task, established that the Parkinson's disease group was unimpaired on any of these measures. On the Tower of London task, the Parkinson's disease group was also unimpaired in terms of the average number of moves required to solve a problem. However, a specific planning deficit was evident when "thinking" times were analysed, and this was after the confounding influence of motor initiation and execution times had been carefully extracted from total performance times. This finding is discussed in relation to putative functions of the frontal lobes and basal ganglia, and an attention-switching hypothesis is developed to account for it.

Aged↗
PubMed1987

Chronic respiratory failure in infants with prolonged ventilator dependency.

One hundred one infants with chronic respiratory failure (CRF) who required prolonged mechanical ventilation were cared for in the pediatric intensive care unit at The Children's Hospital of Philadelphia between January 1967 and December 1984. Chronic respiratory failure of infancy is a condition that requires mechanical ventilation for more than 28 days in the first year of life. Thirty-six children had severe bronchopulmonary dysplasia, 50 had congenital anomalies, and 15 had neuromuscular disorders. The mean duration of mechanical ventilation for the 101 patients was 12.3 months. Seventy-one children were alive, and 53 (75%) of the 71 had been weaned from mechanical ventilation as of Dec 31, 1984. Pulmonary insufficiency and cardiac failure were the predominant causes of death in 17 of 22 infants in the first two years after the onset of CRF; four of eight deaths that occurred beyond two years were caused by airway- and ventilator-related accidents. Mechanical ventilatory support was emphasized for as long as necessary to provide normal blood gas tensions, nutrition, growth, and development rather than weaning as rapidly as possible. This clinical experience demonstrates that it is feasible to save over 70% of infants with the severest forms of CRF and prolonged ventilator dependency.

Bronchopulmonary Dysplasia↗
PubMed1987

Postoperative apnea in preterm infants.

Preterm infants may become apneic during the immediate post-operative period. To define this risk, the authors studied prospectively the breathing patterns of 47 preterm infants less than 60 weeks postconception with pneumocardiograms before and after general inhalational anesthesia. Eighteen infants (37%) had prolonged apnea (greater than 15 s) postoperatively, and an additional seven infants (14%) had short apnea (6-15 s) postoperatively. An infant's risk of prolonged and short postoperative apnea was related to a young postconceptional age (P less than 0.05) and to a history of necrotizing enterocolitis (P less than 0.01). Furthermore, as the postconceptional age of the infant increased, the risk of postoperative apnea decreased proportionately (P less than 0.025). Among the 18 infants with prolonged apnea, 83% experienced multiple apneic episodes. Manual stimulation was required in order for breathing to return in 13 (72%) of the infants. Breathing resumed spontaneously in four (22%) of the infants, and one infant required mechanical ventilation due to repeated prolonged apnea. The first apneic event occurred within 2 h postoperatively in 13 of the infants (72%); the remaining five infants (28%) had their initial apneic episode as late as 12 h after operation. The postoperative time to the last prolonged apneic event was inversely related to the postconceptional age (P less than 0.01, r = -0.70) and extended up to 48 h postoperatively. The preoperative pneumocardiogram was not a reliable test for predicting postoperative apnea (sensitivity 56%, specificity 83%).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1976

Optimum levels of CPAP for tracheal extubation of newborn infants.

Arterial oxygen tension and functional residual capacity were studied in 16 intubated, spontaneously breathing newborn infants recovering from respiratory disease. Studies were made at 2 cm H2O continuous positive airway pressure, at zero end expiratory pressure, and following extubation. The study showed that PaO2 and FRC at 2 cm H2O CPAP were the same as observed following extubation, but that both values were significantly lower at ZEEP.

Humans↗