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Robin Walker

Publications and source records attributed to Robin Walker.

15 recordsLinked to original sources
PubMed2005

Spatial and temporal aspects of oculomotor inhibition as revealed by saccade trajectories.

The spatial and temporal effect of distractor related inhibition on stimulus elicited (reflexive) and goal driven (voluntary) saccades, was examined using saccade trajectory deviations as a measure. Subjects made voluntary and reflexive saccades to a target location on the vertical midline, while the distance of a distractor from the target was systematically manipulated. The trajectory curvature of both voluntary and reflexive saccades was found to be subject to individual differences. Saccade curvature was found to decrease monotonically with increasing distractor distance from target for some subjects while for others no reduction in curvature or even an increase was found. These results could not be explained by latency differences or landing position effects. The different patterns of distractor effects on saccade trajectories suggest the additional influence of a non-spatial inhibitory mechanism.

Adult↗
PubMed2004

Critical care procedure logging using handheld computers.

INTRODUCTION: We conducted this study to evaluate the feasibility of implementing an internet-linked handheld computer procedure logging system in a critical care training program. METHODS: Subspecialty trainees in the Interdepartmental Division of Critical Care at the University of Toronto received and were trained in the use of Palm handheld computers loaded with a customized program for logging critical care procedures. The procedures were entered into the handheld device using checkboxes and drop-down lists, and data were uploaded to a central database via the internet. To evaluate the feasibility of this system, we tracked the utilization of this data collection system. Benefits and disadvantages were assessed through surveys. RESULTS: All 11 trainees successfully uploaded data to the central database, but only six (55%) continued to upload data on a regular basis. The most common reason cited for not using the system pertained to initial technical problems with data uploading. From 1 July 2002 to 30 June 2003, a total of 914 procedures were logged. Significant variability was noted in the number of procedures logged by individual trainees (range 13-242). The database generated by regular users provided potentially useful information to the training program director regarding the scope and location of procedural training among the different rotations and hospitals. CONCLUSION: A handheld computer procedure logging system can be effectively used in a critical care training program. However, user acceptance was not uniform, and continued training and support are required to increase user acceptance. Such a procedure database may provide valuable information that may be used to optimize trainees' educational experience and to document clinical training experience for licensing and accreditation.

Adult↗
PubMed2004

A new look at Op art: towards a simple explanation of illusory motion.

Vivid motion illusions created by some Op art paintings are at the centre of a lively scientific debate about possible mechanisms that might underlie these phenomena. Here we review emerging evidence from a new approach that combines perceptual judgements of the illusion and observations of eye movements with simulations of the induced optic flow. This work suggests that the small involuntary saccades which participants make when viewing such Op art patterns would generate an incoherent distribution of motion signals that resemble the perceptual effects experienced by the observers. The combined experimental and computational evidence supports the view that the illusion is indeed caused by involuntary image displacements picked up by low-level motion detectors, and further suggests that coherent motion signals are crucial to perceive a stable world.

Fixation, Ocular↗
PubMed2004

Distractor modulation of saccade trajectories: spatial separation and symmetry effects.

The trajectories of saccadic eye movements can be modulated by the presence of a competing visual distractor. In the present study the trajectories of vertical saccades curved away from a single visual distractor presented in one visual field, but tended to be straight when two distractors were presented at mirror symmetric locations in both visual fields. The spatial nature of the mirror distractor effect was examined by presenting a second distractor at mirror and non-mirror locations. Saccade trajectories also tended to be straight with both mirror and non-mirror symmetrical distractors. The relationship between the distractor location and saccade curvature was examined in a third experiment by manipulating the distractor-to-target spatial separation. Although there was a tendency for greater curvature when the distractor was presented in the same hemifield as the target there was no clear relationship between curvature and distractor location. The results show that the distractor modulation of saccade trajectory is not highly spatially specific and that it can be balanced by a second bilateral distractor in the opposite visual field. The results are interpreted in terms of a model in which the initial saccade direction and curvature back towards the saccade goal are controlled by separate processes. Initial saccade direction is modulated by the inhibition of distractor locations within a 'motor map' specifying saccade direction. Curvature back towards the saccade goal may be attributed to a feedback system, with a separate representation of the visual target location, that enables an on-line correction of the saccade during mid-flight.

Adult↗
PubMed2004

Crop protection--what will shape the future picture?

The drivers which influence the types of crop protection most needed by agriculture are changing. A polarisation of approaches has resulted in the needs of organic agriculture and biotechnological agriculture, which can be identified as the current extremes of the spectrum, becoming very different. The main requirements of these two sectors are identified here and used as the basis for questioning future EU research requirements in crop protection. Factors affecting/influencing organic farming and the use of genetically modified crops are discussed in some detail.

Crops, Agricultural↗
PubMed2004

Antifungal activities of four fatty acids against plant pathogenic fungi.

The effect of the fatty acids linolenic acid, linoleic acid, erucic acid and oleic acid on the growth of the plant pathogenic fungi Rhizoctonia solani, Pythium ultimum, Pyrenophora avenae and Crinipellis perniciosa were examined in in vitro studies. Linolenic and linoleic acids exhibited activity against all of the fungi. However, whereas linolenic acid reduced mycelial growth of R. solani and C. perniciosa at 100 microM, the concentration had to be increased to 1000 microM before any effect on mycelial growth of P. ultimum and P. avenae was observed. Linoleic acid only reduced mycelial growth of R. solani, P. ultimum and P. avenae at 1000 microM, but led to a significant reduction in growth of C. perniciosa at 100 microM. In contrast, oleic acid had no significant effect on growth of R. solani or P. avenae, but gave significant reductions in mycelial growth of P. ultimum at 100 microM and reduced growth of C. perniciosa significantly at 1000 microM. All of the fatty acids reduced biomass production by all of the fungi significantly in liquid culture when added to the media at 100 microM. Erucic acid had no effect on fungal growth at any concentration examined. The antifungal activities exhibited by linolenic, linoleic and oleic acids may be useful in the search for alternative approaches to controlling important plant pathogens, such as those examined in this study.

Ascomycota↗
PubMed2003

Multimodal visual-somatosensory integration in saccade generation.

Neurophysiological studies have demonstrated multisensory interaction effects in the neural structures involved in saccade generation when visual, auditory or somatosensory stimuli are presented bimodally. Visual-auditory interaction effects have been demonstrated in numerous behavioural studies of saccades but little is known about interaction effects involving somatosensory stimuli. The present study examined visual-somatosensory interaction effects on saccade generation using a multisensory paradigm, whereby task-irrelevant distractors appeared spatially-coincident with, or remote from the designated saccade target. Somatosensory distractors reduced the latency of saccades when presented before the visual target and the greatest facilitation effect was observed with spatially-coincident stimuli. Visual distractors spatially-coincident with a somatosensory target reduced latency (and increased peak velocity) when presented before and after the target. Visual distractors contralateral to somatosensory targets increased saccade latency and produced high error rates of saccades made to the distractor. The high error rates and latency modulation with visual distractors is consistent with a bias for visual stimuli in the saccadic system. In the visual target condition, saccade latency was modulated by a somatosensory distractor that was entirely task-irrelevant and this effect was always greatest with spatially-coincident distractors. The multisensory distractor effects are discussed in terms of saccades being programmed to the non-target modality, the early triggering of a non-spatial saccade 'when' signal, and multisensory neuronal enhancement effects.

Acoustic Stimulation↗
PubMed2002

Variations in mortality rates among Canadian neonatal intensive care units.

BACKGROUND: Most previous reports of variations in mortality rates for infants admitted to neonatal intensive care units (NICUs) have involved small groups of subpopulations, such as infants with very low birth weight. Our aim was to examine the incidence and causes of death and the risk-adjusted variation in mortality rates for a large group of infants of all birth weights admitted to Canadian NICUs. METHODS: We examined the deaths that occurred among all 19 265 infants admitted to 17 tertiary-level Canadian NICUs from January 1996 to October 1997. We used multivariate analysis to examine the risk factors associated with death and the variations in mortality rates, adjusting for risks in the baseline population, severity of illness on admission and whether the infant was outborn (born at a different hospital from the one where the NICU was located). RESULTS: The overall mortality rate was 4% (795 infants died). Forty percent of the deaths (n = 318) occurred within 2 days of NICU admission, 50% (n = 397) within 3 days and 75% (n = 596) within 12 days. The major conditions associated with death were gestational age less than 24 weeks (59 deaths [7%]), gestational age 24-28 weeks (325 deaths [41%]), outborn status (340 deaths [42%]), congenital anomalies (270 deaths [34%]), surgery (141 deaths [18%]), infection (108 deaths 114%]), hypoxic-ischemic encephalopathy (128 deaths [16%]) and small for gestational age (i.e., less than the third percentile) (77 deaths [10%]). There was significant variation in the risk-adjusted mortality rates (range 1.6% to 5.5%) among the 17 NICUs. INTERPRETATION: Most NICU deaths occurred within the first few days after admission. Preterm birth, outborn status and congenital anomalies were the conditions most frequently associated with death in the NICU. The significant variation in risk-adjusted mortality rates emphasizes the importance of risk adjustment for valid comparison of NICU outcomes.

Canada↗
PubMed2002

Snap-II predicts severe intraventricular hemorrhage and chronic lung disease in the neonatal intensive care unit.

OBJECTIVE: To determine whether the Score for Neonatal Acute Physiology, Version II (SNAP-II), improved prediction of severe (> or = grade III) intraventricular hemorrhage (IVH) and chronic lung disease (CLD) when compared to models using gestational age (GA) and traditional risk factors (e.g., Apgar score, small-for-gestational-age, sex, outborn status). STUDY DESIGN: We examined 4226 infants < or = 32 weeks' GA admitted to 17 Canadian neonatal intensive care units between 1996 and 1997. We compared prediction models for severe IVH and CLD, with and without SNAP-II. RESULTS: SNAP-II was a significant and independent predictor of severe IVH and CLD. Addition of SNAP-II to models using GA and traditional risk variables significantly (p<0.05) improved model prediction (AUC 0.8 for severe IVH; 0.83 for CLD). Models were well calibrated (p>0.05 for Hosmer-Lemeshow goodness of fit test). CONCLUSION: Addition of SNAP-II to models using GA and traditional risk factors significantly improves prediction of severe IVH and CLD.

Cerebral Hemorrhage↗
PubMed2002

Cost-effectiveness and choice of infant transport systems.

OBJECTIVE: To compare cost-effectiveness of three types of infant transport models (Emergency Medical Technicians [EMT], Registered Nurses [RN], or Combined Teams [CT] of RNs and Respiratory Therapists) and to derive a decision model to guide choice of a transport system. RESEARCH DESIGN: A prospective, multicenter, observational study was conducted to compare infant physiologic status before and after transport. Cost-effectiveness analysis from the perspective of the third-party payer, sensitivity analysis and threshold analysis were performed. SUBJECTS: All (n = 1931) out born infants with complete transport data admitted to 11 regional tertiary-level Canadian NICUs from January 1996 to October 1997. MEASURES: Change in Transport Risk Index of Physiologic Stability (TRIPS) Score before and after transport, transport costs. RESULTS: Change in TRIPS was predicted by gestational age at transport, transport duration, and pretransport TRIPS score, but not the type (EMT, RN, CT) of transport team, mode (air/ground) or direction (forward/retrograde) of transport, presence of a physician, and other baseline population risks (sex, small for gestational age, antenatal corticosteroid treatment, Apgar score). The RN model is least costly under most assumptions. At high transport volumes (>2760 transports per year) and long average transport times (>6.8 h per transport), the EMT model was less costly. Cost drivers of transport were volume of transport, relative wages of transport personnel, and percent of waiting time dedicated to infant transport. CONCLUSIONS: A deterministic decision-analytic model can be used to model transport cost-effectiveness and derive a threshold analytic chart for identifying the least costly transport model.

Canada↗
PubMed2002

Extending ventilation duration estimations approach from adult to neonatal intensive care patients using artificial neural networks.

In earlier work, the research group successfully used artificial neural networks (ANNs) to estimate ventilation duration for adult intensive care unit (ICU) patients. The ANNs performed well in terms of correct classification rate (CCR) and average squared error (ASE) classifying the outcome into two classes: whether patients were ventilated for less than/equal to or for more than 8 h (< or >). The objective of new work was to apply this adult model to the estimation of ventilation with neonatal ICU (NICU) patient records. The performance obtained with the neonatal patients was comparable to that previously found with the adult database, again as measured in terms of a maximum CCR and a minimum ASE. The effectiveness of using the weight-elimination technique in controlling overfitting was again validated for the neonatal patients as it had been for our adult patients. It was concluded that the approach developed for ICU adult patients was also successfully applied to a different medical environment: neonatal ICU patients.

Databases, Factual↗
PubMed2002

Community education on preterm birth. Does it change practice?

OBJECTIVE: To evaluate how well physicians and other prenatal care providers educate women about early recognition of and appropriate response to the signs and symptoms of preterm labour (PTL). To assess use of antenatal steroids for babies born at less than 34 weeks' gestation. DESIGN: Before-after study using a population-based approach. SETTING: Health care providers' offices, hospitals, and prenatal classes in Ottawa, Ont. PARTICIPANTS: Prenatal care providers, women in hospital after giving birth, prenatal class participants. INTERVENTIONS: Prenatal care providers received information and educational materials on PTL and preterm birth (PTB). They passed this information on to pregnant women at their 18- to 20-week prenatal visits. Teachers of prenatal classes gave the same information in early-series classes. Clinical practice guidelines were developed, and hospital staff received education on appropriate response to PTL. MAIN OUTCOME MEASURES: Use of educational materials and steroid treatment. RESULTS: Statistically significant increases were seen in the numbers of care providers who had educational material about PTL and PTB, who reported giving the educational material to all women, and who reported discussing signs and symptoms of PTL and PTB with all women; women who reported that their care providers talked with them about PTL and PTB, and women delivering preterm (< 34 weeks) babies who received steroids. CONCLUSION: Providing knowledge and standardized educational materials to health care providers can help improve preventive practice for PTL and educate women about PTL.

Female↗
PubMed2001

Multisensory interactions in saccade target selection: curved saccade trajectories.

In a series of experiments, we examined the change in saccade trajectories observed when distractors are presented at non-target locations. The primary aim of the experiments was to examine multisensory interaction effects between the visual, auditory and somatosensory modalities in saccade generation. In each experiment observers made saccades to visual targets above and below fixation in the presence of visual, auditory or tactile stimuli to the left or right of fixation. In experiment 1 distractor location indicated which of two stimuli was the target for the saccade. Saccade trajectories showed strong leftward curvature following right-side distractors and showed rightward curvature following left-side distractors. The largest effects on trajectories were observed for visual distractors, but significant curvature was observed with auditory and somatosensory distractors. In experiment 2 saccades were made following the onset of a visual target (reflexive) or following presentation of an arrow at fixation (voluntary), and task-irrelevant crossmodal distractors were presented simultaneously with target onset. Both voluntary and reflexive saccades were found to curve away from task-irrelevant visual distractors, but auditory and somatosensory distractors did not modulate saccade trajectories. In experiment 3 task-irrelevant distractors preceded the onset of the target by 100 ms. Reflexive saccades were found to curve away from visual, auditory and somatosensory distractors, but voluntary saccades curved away from visual distractors only. The modulation of saccade trajectories by distractors from different modalities is interpreted in terms of inhibitory processes operating in neural structures involved in saccade generation. Our findings suggest that visual, auditory and somatosensory distractors can all modulate saccade trajectories. Such effects could be related to the inhibition of populations of neurons, in a common motor map, for the selection of a saccade target.

Attention↗