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At least 793 records · Page 44Linked to original sources

PubMed2006

BRUTUS: optimization of a grid-based similarity function for rigid-body molecular superposition. II. Description and characterization.

Finding novel lead molecules is one of the primary goals in early phases of drug discovery projects. However, structurally dissimilar compounds may exhibit similar biological activity, and finding new and structurally diverse lead compounds is difficult for computer algorithms. Molecular energy fields are appropriate for finding structurally novel molecules, but they are demanding to calculate and this limits their usefulness in virtual screening of large chemical databases. In our approach, energy fields are computed only once per superposition and a simple interpolation scheme is devised to allow coarse energy field lattices having fewer grid points to be used without any significant loss of accuracy. The resulting processing speed of about 0.25 s per conformation on a 2.4 GHz Intel Pentium processor allows the method to be used for virtual screening on commonly available desktop machines. Moreover, the results indicate that grid-based superposition methods could be efficiently used for the virtual screening of compound libraries.

Algorithms↗

PubMed2001

The neuropsychology of multiple sclerosis: contributions of neuroimaging research.

Multiple sclerosis (MS) is often associated with cognitive and emotional changes that affect daily activities and quality of life. Deficits in memory, executive function, processing speed, and other cognitive domains are frequently reported. In addition, mood disturbances and fatigue are common. In this article, the authors highlight research on individual differences in the neuropsychology of MS, and emphasize neuroimaging studies that help elucidate the basis of the deficits.

Brain↗

PubMed1996

Uncertainty and processing routes in the selection of a response: an S-R compatibility study.

Stimulus-response (S-R) pairs are usually processed faster when-they are presented in a series that consists entirely of compatible relations rather than incompatible relations. A mixture of the two pairs in a series, which induces uncertainty, increases processing speed for both pairs, but more so for compatible S-R pairs. The results of three choice reaction time (RT) tasks showed that presentation of a precue that only indicated either compatible or incompatible S-R pairs reduced the detrimental effect of mixing pairs more for the former than for the latter pairs. A similar asymmetric reduction was observed in the third experiment when either pair was preceded by the same pair or the same class of pairing. Analyses of RT bins revealed that decreases in RT for the mixed compatible S-R pairs occurred only for the faster responses. It was shown further that errors consisted primarily of a correct application of an incorrect S-R transformation rule. The results are interpreted within the framework of the dimensional overlap model of Kornblum et al. (1990) suggesting two sources of the S-R compatibility effect; interference of primed responses and the need to suppress response priming.

Adolescent↗

PubMed1993

Lack of evidence for Huntington's disease-like cognitive dysfunction in obsessive-compulsive disorder.

Cognitive deficits in patients with structural lesions of the basal ganglia (e.g., Huntington's disease) commonly include slowed processing, reduced verbal fluency, difficulty switching set, impaired egocentric spatial ability, poor recall, and impaired acquisition of motor skills. The goal of this study was to determine if patients with obsessive-compulsive disorder (OCD) would have a similar pattern of cognitive dysfunction. A battery of neuropsychological tests, including reaction time-based measures of cognitive processing speed and a test of procedural, motor-skill learning, was administered to 17 unmedicated OCD patients and 16 age-and education-matched normal controls. Eleven individuals with trichotillomania, matched with the OCD patients on age, education, age at symptom onset, depression, and anxiety were also tested. Contrary to expectation, neither the OCD nor trichotillomania patients were impaired on any of the measures in the battery. The essentially normal performance by these patients suggests that the brain regions responsible for cognitive dysfunction in patients with Huntington's disease may differ from those associated with OCD.

Adolescent↗

PubMed1985

Computer-assisted analysis of two-dimensional electrophoresis images using an array processor.

The CLIP4 machine has been used to analyze two-dimensional electrophoresis gel images. The architecture of the CLIP4 machine allows high-speed processing of gel images unavailable on conventional machines. The paper gives a brief review of the CLIP system followed by a detailed description of the segmentation and comparison algorithms. The segmentation algorithm makes full use of methods already designed for other gel analysis systems, but optimized for use on the highly parallel CLIP4 machine. The comparison algorithm is a totally new method using, to the full, the parallel efficiency of the CLIP4 computer. The algorithm attempts to match each spot on one gel with a corresponding spot on a second gel, operating simultaneously on all pairs of spots.

Biometry↗

PubMed1986

Multilead ECG analysis.

This paper describes the results of our recent research in computer-assisted ECG/VCG interpretation. It comprises new developments which were initiated by the advent of relatively inexpensive microcomputers. Our previous systems performed an off-line analysis of ECGs. Currently, there is a trend to move computer power near to the patient and to provide on-line analysis of ECGs. Besides the advantage of the direct availability of the ECG interpretation, quality control will reduce the number of uninterpretable ECGs and hence the number of repeated recordings. This paper describes the requirements that were established for a system for on-line ECG analysis. The system is based on our modular approach, just like our off-line system, Modular ECG ANalysis System (MEANS). Changes in the methods and software had to be made mainly because of the simultaneity of all ECG leads and the concurrency of the processing tasks. Other modifications and extensions of the algorithms necessary to meet the requirements of on-line ECG interpretation especially those related to processing speed, are discussed, and evaluation results are presented.

Electrocardiography↗

PubMed1993

A multiparametric investigation of daytime sleepiness and psychomotor functions in epileptic patients treated with phenobarbital and sodium valproate: a comparative controlled study.

Subjective and objective measures of daytime sleepiness and psychomotor function were determined in normal control subjects and in epileptic patients on chronic monotherapy with phenobarbital or valproate (n = 10 in each group). All patients had primary generalized epilepsy with a normal resting EEG and were seizure-free for at least 1 year. After nocturnal polysomnographic recording, each subject was evaluated at 2 h intervals between 10:00 and 16:00 h by using multiple sleep latency tests (MSLT), a visual analogue rating scale for alertness (VARS), an anxiety scale (STAI-X1) and a battery of psychomotor tests. Nocturnal sleep parameters before daytime assessment were comparable in the 3 groups. At MSLT, patients on phenobarbital showed a shorter mean sleep latency (9.0 +/- 1.7 min) compared with the valproate group (12.5 +/- 1.3 min) and controls (12.9 +/- 1.2 min), though within-group variability was considerable. Compared with controls, patients on phenobarbital showed longer motor movement times, impaired attention (cancellation test, CT), reduced processing speed (digit-symbol substitution, DSS) and a trend towards lower critical flicker fusion threshold. Patients on valproate showed some impairment in attention and a trend towards longer motor movement time. In patients, no correlation was found between assessed parameters and serum drug concentrations, which were 19.3 +/- 1.7 micrograms/ml for phenobarbital and 85.7 +/- 4.7 micrograms/ml for valproic acid.

Adult↗

PubMed1995

Visual attention mechanisms show a center-surround organization.

The sudden onset of a cue triggers visual attention, which then enhances visual processing in the zone near the cue. This enhancement causes a motion illusion in subsequent stimuli presented near the cue. At greater separations from the cue, the illusory motion reverses direction, indicating prolonged processing speed. Measurements of the strength and direction of illusory motion at increasing separations from the cue reveal an attentional 'perceptive field' with an excitatory center at the locus cued and an inhibitory surround subtending the remaining visual field. These findings help explain the traditional attentional 'benefits' and 'costs' of attention.

Adult↗

PubMed1996

Global-motion perception: interaction of chromatic and luminance signals.

A global dot-motion stimulus was employed in order to investigate the interaction between luminance and chromatic signals in motion processing. Thresholds are determined by measuring the minimum number of dots which need to move in a coherent fashion in a field of randomly moving dots in order for the observers to be able to determine the direction of coherent motion. We found that: (1) observers could not track an achromatic signal-dot which changes its luminance polarity between frame transitions. The addition of a consistent chromatic signal allowed observers to track such a dot when the dot contained low- (8%) luminance contrast but this ability was impaired as the luminance contrast was increased; (2) the addition of chromatic contrast to a dot which contained consistent low-luminance contrast could result in threshold elevation. For fixed contrast chromatic and luminance signals, the presence and degree of threshold elevation depended upon the spatiotemporal properties of the dot motion; (3) the ability of observers to extract a global-motion signal carried by a group of dots of one colour was impaired by the addition of a number of additional-noise dots of a different colour. These results are interpreted as indicating that: (1) the motion-selective cells that are sensitive to chromatic signals are also sensitive to luminance signals; (2) the combined chromatic and luminance and purely luminance motion cells are pooled to form a single pathway prior to global-motion extraction; and (3) the negative interaction observed between the chromatic and luminance signals is likely to be due to the differences in the processing speeds of the combined luminance and chromatic and the purely luminance sensitive motion cells.

Color↗

PubMed1992

Active and passive P3 latency and psychometric performance: influence of age and individual differences.

The relationship of P3 latency of the event-related potential (ERP) to psychometric performance was investigated in 41 subjects who ranged in age from 20 to 88 years. P3 responses were recorded from subjects using an auditory oddball paradigm with and without task-demands. Subjects also received psychometric tests of verbal performance, visuospatial performance, concentration, and immediate, recent and remote memory. Factor analysis was used to reduce the set of psychometric measures to four factors (Verbal learning, general intelligence, narrative recall/fluency, and concentration). Both passive and active P3 latency showed a linear increase with age. Age was inversely correlated with verbal learning performance. After accounting for the influence of age, passive P3 latency correlated with the psychometric factor associated with narrative recall and verbal fluency. Active P3 latency was correlated with factors reflecting general intelligence and concentration. These findings suggest that cognitive processing speed contributes to psychometric performance in adults. The psychological or biological basis for this relationship remains to be identified.

Adult↗

PubMed1994

The affinity technology in downstream processing.

The quality criteria imposed on several biochemicals are stringent, thus, high-separation purification technology is important to downstream processing. Affinity-based purification technologies are regarded as the finest available, and each one differs in its purifying ability, economy, processing speed and capacity. The most widely used affinity technology is classical affinity chromatography, however, other chromatography-based approaches have also been developed, for example, perfusion affinity chromatography, hyperdiffusion affinity chromatography, high-performance affinity chromatography, centrifugal affinity chromatography, affinity repulsion chromatography, heterobifunctional ligand affinity chromatography and the various chromatographic applications of 'affinity tails'. On the other hand, non-chromatographic affinity technologies aim at high throughput and seek to circumvent problems associated with diffusion limitations experienced with most chromatographic packings. Continuous affinity recycle extraction, aqueous two-phase affinity partitioning, membrane affinity filtration, affinity cross-flow ultrafiltration, reversible soluble affinity polymer separation and affinity precipitation are all non-chromatographic technologies. Several types of affinity ligands are used to different extents; antibodies and their fragments, receptors and their binding substances, avidin/biotin systems, textile and biomimetic dyes, (oligo)peptides, antisense peptides, chelated metal cations, lectins and phenylboronates, protein A and G, calmodulin, DNA, sequence-specific DNA, (oligo)nucleotides and heparin. Likewise, there are several support types developed and used; natural, synthetic, inorganic and composite materials.

Affinity Labels↗

PubMed1987

CGP 11.952: an experimental benzodiazepine derivative. Effects on cognitive functioning in patients with epilepsy.

1. In two open studies using patients with intractable epilepsy, the effects of CGP 11.952, a triazolyl benzophenone, on cognitive functioning were assessed by means of a computerized neuropsychological battery. 2. In the first study CGP 11.952 turned out to have a positive effect on information processing speed, perceptual sensitivity and preciseness of responses. 3. Negative effects were found on reaction time. 4. In the second study this latter effect was less clear. 5. A striking result was the less negative effect on memory consolidation under influence of CGP 11.952 in comparison with other benzodiazepines.

Adolescent↗

PubMed1996

The effect of stimulus-response incompatibility on P3 latency depends on the task but not on age.

To help identify the loci of age-related slowing of cognitive processing, the effects of stimulus-response (S-R) incompatibility and stimulus degradation on P3 latency and reaction time (RT) were assessed in ten young and ten elderly women. Subjects saw the words right, left, RIGHT, or LEFT in tasks which required responses to (1) the meaning of the word (WORD) (2) its case (CASE) and (3) both (CASE/WORD). Each task was tested with regular and degraded stimuli. On half the trials, the stimulus and response were incompatible. Although RTs and P3s of elderly subjects were slower, especially RTs in CASE/WORD, stimulus degradation and S-R incompatibility did not differentially affect the two groups, suggesting that cognitive processing of older subjects is not especially prolonged in perceptual and response-related stages. For both groups RTs and P3s were task dependent and were prolonged by degradation and S-R incompatibility. Incompatibility delayed RTs in WORD and CASE/WORD but P3s in WORD only. Thus, young and elderly subjects show qualitatively similar psychophysiological and behavioral indicators of processing speed.

Adult↗

PubMed2005

Assessing the enduring residual neuropsychological effects of head trauma in college athletes who participate in contact sports.

The present study examined the enduring residual neuropsychological effects of head trauma in college athletes using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), Postconcussion Syndrome Checklist, and the Stroop task. Based on a brief self-report concussion history survey, male and female athletes who participated in ice hockey, field hockey, lacrosse, and/or soccer were assigned to one of three concussion-history conditions: Non-concussed, Non-recent concussed (i.e., more than 2 years since last concussion), or Recent concussed (i.e., 2 years or less since last concussion). A fourth group of subjects consisting of non-concussed/non-athletes served in the control condition. Group differences emerged on the RBANS when immediate memory, delayed memory, and total scores were analyzed. Specifically, recent concussed athletes and, surprisingly, non-concussed athletes scored lower than control subjects in the two memory domains, whereas all three athlete groups had lower total RBANS scores than those of control subjects. Moreover, recent concussed athletes not only had lower immediate memory scores than control subjects, but also were impaired relative to non-recent concussed athlete subjects in this memory domain. No group differences were detected on the Stroop task or on the Postconcussion Syndrome Checklist. Interestingly, however, the severity of the Postconcussion Syndrome Checklist scores for the two athlete-concussed groups, taken in aggregate, correlated negatively with RBANS scores for attention (r = -.65) and delayed memory (r = -.61), and with the total RBANS score (r = -.59). In recent concussed athletes, lower delayed memory scores correlated with more severe Postconcussion Symptom Checklist scores (r = -.90), while more severe/higher number of concussions correlated with increased processing speed on the Stroop interference task (r = .90). These findings indicate that recent head injury produces alterations in neuropsychological function, especially that of memory, that resolve with time. More provocatively, the data also suggest that participation in contact sports may produce sub-clinical cognitive impairments in the absence of a diagnosable concussion presumably resulting from the cumulative consequences produced by multiple mild head trauma.

Adult↗

PubMed2005

WAIS-III General Ability Index in neuropsychiatry and forensic psychiatry inpatient samples.

The purpose of this study is to examine the WAIS-III General Ability Index (GAI) in a sample of 33 neuropsychiatry inpatients and 47 forensic psychiatry inpatients. The GAI is comprised of the six subtests that form the Verbal Comprehension and the Perceptual Organization Indexes. The GAI, although highly correlated with the FSIQ, was on average 5.3 points higher in the neuropsychiatry sample and 4.2 points higher in the forensic psychiatry sample. The GAI was significantly higher than the Working Memory and the Processing Speed Indexes in both groups. The GAI, a composite measure of verbal and nonverbal intellect, appears to be an appropriate measure for use in day-to-day clinical practice in neuropsychology. To facilitate clinical use, statistically reliable difference scores between the GAI and the WMI and PSI, for the 95% confidence interval, are presented.

Adolescent↗

PubMed2005

Sensitivity and specificity of the ImPACT Test Battery for concussion in athletes.

This study explored the diagnostic utility of the composite scores of Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) and Post Concussion Symptom Scale scores (PCSS). Recently concussed high school athletes (N=72) were tested within 72 h of sustaining a concussion, and data were compared to non-concussed high school athletes with no history of concussion (N=66). Between-groups MANOVA revealed a significant multivariate effect of concussion on test performance (p<.001); univariate ANOVAS revealed all six measures contributed to the between-groups differences. A discriminant function analyses was conducted to measure the ability of the five ImPACT composite scores, as well as the PCSS to classify concussion status. One discriminant function was identified that consisted of the Visual Memory, Processing Speed, and Impulse Control composite scores PCSS, which correctly classified 85.5% of the cases. Approximately 82% of participants in the concussion group and 89% of participants in the control group were correctly classified. Using these data, the sensitivity of ImPACT was 81.9%, and the specificity was 89.4%. As part of a formal concussion management program, ImPACT is a useful tool for the assessment of the neurocognitive and neurobehavioral sequelae of concussion, and can also provide post-injury cognitive and symptom data that can assist a practitioner in making safer return to play decisions.

Adolescent↗

PubMed2006

Concurrent validity of abbreviated WAIS-III index scores in geriatric outpatients with suspected dementia.

Assessments of older adults with suspected dementia can be time limited and clinicians might consider using abbreviated versions of measures. The present study examined the concurrent validity of abbreviated WAIS-III index scores in a sample of geriatric patients referred for assessment of suspected dementia (N=43; mean age=63.8 years). All 2-subtest estimates of the Verbal Comprehension, Perceptual Organization, and Working Memory index scores accurately estimated more than 80% of cases within +/-2 standard errors of measurement (S.E.M.), and in most cases, more than 90% of cases were accurate at this level. While none of the 1-subtest estimates of these index scores were as accurate, both of the 1-subtest estimates of the Processing Speed index had high clinical accuracy. Abbreviated versions of the four index scores can be substituted in situations with this clinical population where testing time is limited or a patient fatigues easily.

Aged↗

PubMed2006

Baseline cognitive function predicts rate of decline in basic-care abilities of individuals with dementia of the Alzheimer's type.

Decline in basic self-care abilities is an important risk factor for institutionalization in individuals with dementia. The ability to predict such decline would be of clinical importance in working with families of dementia patients. Research has suggested that cognitive decline may precede loss of functional capacity. This paper utilized a large sample of probable Alzheimer's disease patients (N=150) who were evaluated longitudinally to assess the pattern of neuropsychological functioning predictive of rapid decline in self-care. The findings indicated that despite initial equality of Lawton Physical Self-Maintenance (PSM) scores, patients showing rapid decline of PSM function displayed significantly more impaired performance on neuropsychological measures at diagnosis. They also exhibited a statistically significant difference in the pattern of scores from patients who remained stable. The pattern of the rapid declining group included more severe impairment in visual spatial skills, processing speed, and concept formation. Difficulties in using individual patients' cognitive profiles to make predictions about future rate of PSM decline are discussed.

Activities of Daily Living↗