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PubMed1995

NMRPipe: a multidimensional spectral processing system based on UNIX pipes.

The NMRPipe system is a UNIX software environment of processing, graphics, and analysis tools designed to meet current routine and research-oriented multidimensional processing requirements, and to anticipate and accommodate future demands and developments. The system is based on UNIX pipes, which allow programs running simultaneously to exchange streams of data under user control. In an NMRPipe processing scheme, a stream of spectral data flows through a pipeline of processing programs, each of which performs one component of the overall scheme, such as Fourier transformation or linear prediction. Complete multidimensional processing schemes are constructed as simple UNIX shell scripts. The processing modules themselves maintain and exploit accurate records of data sizes, detection modes, and calibration information in all dimensions, so that schemes can be constructed without the need to explicitly define or anticipate data sizes or storage details of real and imaginary channels during processing. The asynchronous pipeline scheme provides other substantial advantages, including high flexibility, favorable processing speeds, choice of both all-in-memory and disk-bound processing, easy adaptation to different data formats, simpler software development and maintenance, and the ability to distribute processing tasks on multi-CPU computers and computer networks.

Magnetic Resonance Spectroscopy↗

PubMed1999

The relation between psychometric test performance and physical performance in older adults.

BACKGROUND: The relationship between cognitive function and physical disability in nondemented older adults is not well characterized. The purpose of this study was to determine the relationship between performance on psychometric measures and a modified Physical Performance Test (modified PPT) in older men and women. METHODS: One hundred twenty-five men and women aged 75 years and older, who were enrolled in randomized, controlled trials of exercise or hormone replacement therapy, were recruited from the community-at-large and from congregate living sites. Measures obtained included Trailmaking A and B tests, Cancellation Random Figure tests, Weschler Associate Learning and 20-minute Delayed Recall, Verbal Fluency test, a modified PPT, and self-reports about performance of activities of daily living, medication use, and hospitalization in the previous year. RESULTS: Simple regression analysis demonstrated that speed of performance on the Trailmaking B and Cancellation Random Figure tests was significantly associated with total modified PPT score (r = .29, p < .001 and r = .36,p < .001, respectively). A factor analysis of the psychometric test battery demonstrated that two factors, a cognitive speed factor and a memory factor, accounted for 55% of the variance in cognitive test performance. Hierarchical multiple regression analyses demonstrated that age, number of medications, and the cognitive speed factor were independent predictors of total modified PPT score. CONCLUSIONS: Cognitive processing speed is a significant component of physical frailty in this population, although it accounts for a small percentage of variance on a standardized physical performance test.

Activities of Daily Living↗

PubMedDate not supplied

Neurobehavioural sequelae following cranial irradiation and chemotherapy in children: an analysis of risk factors.

Neurobehavioural deficits are commonly reported following treatment for childhood cancers. This study examined the impact of cranial irradiation (CRT) and chemotherapy in children, aiming to identify factors detrimental to long-term outcome. The study compared survivors of acute lymphoblastic leukemia (ALL), treated with CRT and chemotherapy (CRT group: n = 100), survivors of cancers treated with chemotherapy only (n = 50) and healthy controls (n = 100) for intelligence, academic achievement, information processing, learning, and executive function. CRT and chemotherapy in combination were associated with reduced intelligence, educational skill, immediate memory, processing speed, and executive function. Children treated with chemotherapy alone exhibited subtle information processing deficits. Within the CRT group, younger age at treatment was predictive of deficits in non-verbal ability, educational skills and executive functions. High dose CRT was associated with poorer information processing and lower arithmetic ability.

Achievement↗

PubMed2005

Effects of processing bias on the recognition of composite face halves.

Research has shown that face recognition accuracy can be improved by prior global processing and impaired by prior local processing (Macrae & Lewis, 2002). The aim of this study was to test the processing bias account of face recognition, using the composite face task (Young, Hellawell, & Hay, 1987), a test of featural recognition. Undergraduate volunteers (N = 75) participated in a between-subjects design that tested their ability to recognize face halves within a composite, following either global or local Navon processing or a control task. Results showed that, as compared with the control task, local processing speeded ability to recognize face halves. These results provide support for the processing bias account of face recognition.

Cognition↗

PubMed1991

The genetic correlation between intelligence and speed of information processing.

This study examined the contributions of genetic and environmental factors to the observed correlation between intelligence test scores and speed of information processing, based on data for same-sex adult twin pairs (age, 15-57). Verbal and performance IQ scores from the Multidimensional Abilities Battery, as well as 11 reaction-time measures derived from a battery of information-processing tasks, were available for 50 monozygotic and 32 dizygotic pairs of twins. Multivariate biometrical analyses were used to estimate genetic and environmental parameters underlying observed variances and covariances among intelligence test scores and a general speed of information-processing factor (based on a linear composite of the 11 reaction-time scores). A common-factor model with loadings on general speed of processing, verbal IQ, and performance IQ fit the data well. The common factor was influenced primarily by additive genetic effects, such that the observed relationships among the speed and IQ measures are mediated entirely by hereditary factors. There was additional specific genetic variance for Verbal IQ and specific shared-twin environmental variance for Performance IQ. However, twin similarity for general speed of processing was explained entirely by genetic factors related to intelligence. The results emphasize the importance of common, heritable, biological mechanisms underlying the speed-IQ association.

Adolescent↗

PubMed2004

Further investigation of harmonic priming in long contexts using musical timbre as surface marker to control for temporal effects.

Harmonic priming studies have reported facilitated processing for chords that are harmonically related to the prime context. Responses to the target (the last chord of an 8-chord sequence) were faster and more accurate when the target was strongly related, i.e., a tonic chord, to the preceding prime context than when it was less related, i.e., a subdominant chord. Results have been interpreted in terms of musical expectations and processing speed: the prime allows listeners to develop expectations for future events which lead to facilitated processing of the most strongly expected event. The present experiment investigated an alternative hypothesis suggesting that the harmonic structure of the prime context might create an ambiguity about "when" to respond that is stronger in contexts ending on less related targets than in contexts ending on strongly related targets. A change of musical timbre was used as surface marker indicating without ambiguity the temporal occurrence of the target. Participants made speeded intonation judgments of the target, i.e., judging whether targets are acoustically consonant or dissonant. The findings replicate the previously reported priming effect and rule out that processing differences are solely due to ambiguities about when in time the target will occur.

Humans↗

PubMed2006

A single system explains human speed perception.

Motion is fully described by a direction and a speed. The processing of direction information by the visual system has been extensively studied; much less is known, however, about the processing of speed. Although it is generally accepted that the direction of motion is processed by a single motion system, no such consensus exists for speed. Psychophysical data from humans suggest two separate systems processing luminance-based fast and slow speeds, whereas neurophysiological recordings in monkeys generally show continuous speed representation, hinting at a single system. Although the neurophysiological findings hint at a single system, they remain inconclusive as only a limited amount of cells can be measured per study and, possibly, the putative different motion systems are anatomically separate. In three psychophysical motion adaptation experiments, we show that predictions on the basis of the two-motion system hypothesis are not met. Instead, concurrent modeling showed that both here-presented and previous data are consistent with a single system subserving human speed perception. These findings have important implications for computational models of motion processing and the low-level organization of the process.

Adaptation, Physiological↗

PubMed1998

Visual processing impairment and risk of motor vehicle crash among older adults.

CONTEXT: Motor vehicle crash risk in older drivers has been associated with visual acuity loss, but only weakly so, suggesting other factors contribute. The useful field of view is a measure that reflects decline in visual sensory function, slowed visual processing speed, and impaired visual attention skills. OBJECTIVE: To identify whether measures of visual processing ability, including the useful field of view test, are associated with crash involvement by older drivers. DESIGN: Prospective cohort study with 3 years of follow-up, 1990-1993. SETTING: Ophthalmology clinic assessment of community-based sample. PATIENTS: A total of 294 drivers aged 55 to 87 years at enrollment. MAIN OUTCOME MEASURE: Motor vehicle crash occurrence. RESULTS: Older drivers with a 40% or greater impairment in the useful field of view were 2.2 times (95% confidence interval, 1.2-4.1) more likely to incur a crash during 3 years of follow-up, after adjusting for age, sex, race, chronic medical conditions, mental status, and days driven per week. This association was primarily mediated by difficulty in dividing attention under brief target durations. CONCLUSION: Reduction in the useful field of view increases crash risk in older drivers. Given the relatively high prevalence of visual processing impairment among the elderly, visual dysfunction and eye disease deserve further examination as causes of motor vehicle crashes and injury.

Accidents, Traffic↗

PubMed2001

Generalized approach for accelerated maximum likelihood based image restoration applied to three-dimensional fluorescence microscopy.

For deconvolution applications in three-dimensional microscopy we derived and implemented a generic, accelerated maximum likelihood image restoration algorithm. A conjugate gradient iteration scheme was used considering either Gaussian or Poisson noise models. Poisson models are better suited to low intensity fluorescent image data; typically, they show smaller restoration errors and smoother results. For the regularization, we modified the standard Tikhonov method. However, the generic design of the algorithm allows for more regularization approaches. The Hessian matrix of the restoration functional was used to determine the step size. We compared restoration error and convergence behaviour between the classical line-search and the Hessian matrix method. Under typical working conditions, the restoration error did not increase over that of the line-search and the speed of convergence did not significantly decrease allowing for a twofold increase in processing speed. To determine the regularization parameter, we modified the generalized cross-validation method. Tests that were done on both simulated and experimental fluorescence wide-field data show reliable results.

Algorithms↗

PubMed1997

Fast detection of venous air embolism in Doppler heart sound using the wavelet transform.

The introduction of air bubbles into the systemic circulation can result in significant morbidity. Real-time monitoring of continuous heart sound in patients detected by precordial Doppler ultrasound is, thus, vital for early detection of venous air embolism (VAE) during surgery. In this study, the multiscale feature of wavelet transforms (WT's) is exploited to examine the embolic Doppler heart sound (DHS) during intravenous air injections in dogs. As both humans and dogs share similar physiological conditions, our methods and results for dogs are expected to be applicable to humans. The WT of DHS at scale 2j (j = 1, 2) selectively magnified the power of embolic, but not the normal, heart sound. Statistically, the enhanced embolic power was found to be sensitive (P < 0.01 at 0.01 ml of injected air) and correlated significantly (P < 0.0005, r = 0.83) with the volume of injected air from 0.01 to 0.10 ml. A fast detection algorithm of O(N) complexity with unit complexity constant for VAE was developed (processing speed = 8 ms per heartbeat), which confirmed the feasibility of real-time processing for both humans and dogs.

Algorithms↗

PubMed1996

Speed of information processing as a mediator between age and free-recall performance.

A combined experimental and individual differences approach was used to investigate the mediating role of task-specific and task-independent speed of information processing measures in the relationship between age and free-recall performance. Thirty-six younger adults (mean age = 21 years) and 36 older adults (mean age = 73 years) participated. Participants were required to encode 3 lists of words for immediate recall, by rehearsing the words aloud, twice, and 3 times. Participants' speed of information processing was assessed by 3 measures: rehearsal time, articulation speed, and scores on the Digit Symbol Substitution Test (DSST; Wechsler, 1981). Working memory was also assessed by a backward word-span measure. As predicted, younger adults recalled more words after rehearsing words 3 times rather than once, whereas older adults' recall did not increase with increasing numbers of rehearsals. Younger adults were faster on all speed-of-processing measures and had higher backward word span than did older adults. Task-independent speed of processing, measured by DSST scores and articulation speed, mediated the relationship between age and free recall. Scores on the DSST appear to reflect a fundamental difference between younger and older adults that influences recall performance.

Adolescent↗

PubMed2006

Cognitive functioning in the early course of first-episode schizophrenia spectrum disorders: timing and patterns.

OBJECTIVE: The aim of this study was to examine possible cognitive changes throughout the early course of schizophrenia spectrum disorders. METHOD: Forty-two patients, aged 15-50 years, admitted to a first episode psychosis program (PAFIP) serving to the community of Cantabria (Spain) and 43 healthy volunteers completed a brief battery of five neurocognitive tests at four time-points over 3 months. The cognitive testing comprise five domains: attention, visuomotor speed, declarative memory, working memory and executive function. Baseline assessment occurred within 72 hour after the initiation of standard pharmacological treatment, and after then parallel forms of the tests were applied at week-2, week-6, and month-3. RESULTS: Patient scores showed a significant impairment compared to healthy volunteers in the five cognitive domains at baseline and week-2 assessments. After the first 3 months of antipsychotic treatment, the patient group performance reached healthy volunteers level on executive function (Stroop interference) and immediate verbal memory tests. In contrast, performance on working memory, sustained attention, visuomotor speed, and verbal memory delayed recall domains still remained below healthy volunteers, although visuomotor processing speed showed a significant improvement. CONCLUSION: Schizophrenia spectrum patients show heterogeneous patterns and degrees of cognitive changes that contribute to stress the importance of when, what, and how neurocognitive functioning in the early phases of the illness is evaluated.

Adolescent↗

PubMed1999

Assessment of long-chain polyunsaturated fatty acid nutritional supplementation on infant neurobehavioral development and visual acuity.

The aims of this paper are (i) to consider how best to examine effects of long-chain polyunsaturated fatty acid nutritional supplementation or deficiency on infant neurobehavioral development, after controlling for other factors that might influence outcome, including maternal demographic, intellectual, and personality characteristics, and (ii) to present new findings on the relation between visual acuity and processing speed and the effects of prenatal alcohol exposure and visual acuity on infant information processing. The following topics are also addressed: (i) breastfeeding and intelligence, (ii) criteria for the selection and control of potential confounding variables, and (iii) new infant information processing measures.

Ethanol↗

PubMed2004

Temporal processing in poor adult readers.

The aim of this study was to investigate the relationships between two different temporal processing tasks and word identification performance in skilled, dyslexic and poor adult readers. In Experiment 1 spatial and temporal sequencing tasks were conducted. It was found that adult dyslexics were significantly less accurate than skilled readers across all conditions in the temporal sequencing task, and when higher numbers of stimuli were presented in the spatial task. Experiment 2 replicated Experiment 1 in the temporal sequencing task and also found that poor readers had significantly higher motion coherence thresholds than those found in the skilled reader group. Ten percent of the variance in coherence thresholds was accounted for by performance on the temporal sequencing task. Multiple regression analyses determined that performance on the two temporal tasks could explain seventy percent of the variance in word identification scores, with the temporal sequencing task making the larger independent contribution. Experiment 3 replicated the findings of Experiment 2, while taking into account IQ, verbal memory and processing speed. Three things were concluded. First, the temporal tasks measure different aspects of temporal processing. The contribution to performance of higher-level perceptual and attentional components of the temporal sequencing task accounts for the relatively weak correlation found between the two measures. While sensory sensitivity to motion is measured at MT, the involvement of this area and PPC in higher-level perceptual and attentional processes is suggested by the findings of this study. Second, the association between temporal sequencing and reading skills may provide a stronger link between neural processing and poor reading skills than basic sensory processing measures alone, suggesting that a sensory magnocellular (M) system deficit cannot fully explain the relationship found between reading and visual neural processing. Third, problems with rapid sequential processing are predicted to be a generalised problem in poor adult readers, whether they are formally classified as dyslexic, or are poor performers on measures of word identification. Temporal processing may follow a distribution similar to that found for word identification skills.

Adolescent↗

PubMed2000

Mechanisms of speed-accuracy tradeoff: evidence from covert motor processes.

Speed-accuracy tradeoff (SAT) refers to the inverse relation between speed and accuracy found in many tasks. The present study employed reaction times (RTs) and movement-related brain potentials arising during the RT interval (lateralized readiness potentials; LRPs) to examine the mechanisms by which people control their position along an SAT continuum. Many models of SAT postulate that changes in position across conditions (macro-tradeoffs) and trial-by-trial variations within conditions (micro-tradeoffs) are mediated, at least in part, by the same mechanisms. These include: (1) all models that postulate mixtures of guesses and accurate responses and (2) some models postulating decision criterions applied to accumulating evidence or response tendencies. Such models would seem to be rejected for conditions under which macro- and micro-tradeoffs can be shown to involve no stages of RT in common. Under the present conditions, the two types of SAT produced additive effects on RT, with the macro-tradeoff involving only that portion of the RT interval occurring after LRP onset and the micro-tradeoff involving only that portion before LRP onset. These findings imply that the two types of SAT arose during different serial stages of RT and that the macro-tradeoff involved only stages occurring after differential preparation of the two hands had begun.

Brain↗

PubMed2001

Structural effects of the Azospirillum lipopolysaccharides in cell suspensions.

The structural influence of Azospirillum lipopolysaccharides (LPS) and lipopolysaccharide-protein complexes (LPPC) on carrot, erythrocyte, and bacterial cell suspensions was explored. The structural potentialities of O-specific polysaccharide fragments of LPS and protein fractions of LPPC were also evaluated. An ability to induce the formation of three kinds of structures in the cell suspensions was revealed depending on the chemical composition of the preparations used. The first and the second ones were connected with effects of cell aggregation (a relatively fast process) and agglutination (a relatively slow process). The third one resulted in phase separation of erythrocyte suspensions (a medium-speed process), with segregating the cells to a separate homogeneous liquid phase.

Agglutination↗

PubMed1984

A quality control program for cine radiography.

We describe a ciné processing quality control program aimed at the consistent production of high quality angiograms. A year's experience with this protocol has demonstrated the difficulty and importance of maintaining a constant on-frame optical density to ensure consistently high quality. We monitored film processing, speed of the emulsion and the automatic brightness control of the angiographic imaging system several times a day. Variations in film speed and their causes observed in our institution demonstrate that parameters other than film processing should be carefully controlled. The cost of applying this protocol is about +190.00/month and it requires no additional personnel. The cost is offset by the improved quality of the angiograms, reduced repeat examinations, and the improved monitoring of the system making for more effective preventative and corrective maintenance.

Cineangiography↗

PubMed2003

Effects of temporal and/or spatial instructions on the speed-accuracy trade-off of pointing movements in children.

The present experiment examined in a visuo-manual task the effects of verbal instructions on the speed/accuracy trade-off across children aged 6, 8 and 10 years and adults. Three different verbal instructions (speed, accuracy and speed-accuracy) had to be respected to perform a pointing task. Analysis of reaction time (RT), movement time (MT) and percentage of targets reach showed that: (1) whatever the age, children were able to comply with the verbal instructions to adapt the velocity and/or the precision of their response (initiation and movement execution); (2) the main age-related difference of the speed-accuracy trade-off concerned the temporal (MT) but not the accuracy (targets reach) characteristics of the pointing movements; and (3) in the older children and even more precisely in adults, a temporal deficit was observed when the accuracy of aiming was required. This deficit increased as accuracy increased. These results were discussed within the theoretical frameworks of the developmental speed processing model proposed by Kail [Psychol. Bull., 109(3) (1991) 490-501] for RT data, and the speed-accuracy trade-off model proposed by Pachella [Pachella, R.G., The interpretation of reaction time in information-processing research, in, Kantowitz, B. (ed) Human Information Processing: Tutorial in Performance and Recognition, Erlbaum, (1974) 41-82] for MT and targets reach data.

Acceleration↗