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Results for “processing speed”

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PubMed2004

Algorithms for calculation of kinetic parameters from T1-weighted dynamic contrast-enhanced magnetic resonance imaging.

PURPOSE: To quantify the errors involved in calculating dynamic parameters (K(trans) and ve) from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) scans, and to develop alternative analyses to improve accuracy or increase processing speed. MATERIALS AND METHODS: This paper presents three different ways of handling the discrete samples of the arterial input and tissue response data with increasing fidelity, with which this continuous arterial input function (AIF) is represented. Also, a new noniterative approach to parameter estimation was developed from one used previously for analysis of radioactive tracer concentrations in radioangiography. The analysis methods were tested using simulated data. RESULTS: The more sophisticated schemes for data processing give more accurate parameter estimates when data are sparsely sampled, at least for the AIF that we modeled. The noniterative algorithm is very rapid in execution, but was more susceptible to measurement errors. CONCLUSION: The improved algorithms presented should be useful when the AIF and tissue response are sparsely sampled. The noniterative approach may be suitable for semiquantitative visualization, or where the AIF and tissue response are sampled accurately and with a small time interval between samples.

Algorithms↗

PubMed1989

[The use of lekozim phonophoresis for the treatment of eye burns].

Experimental investigations concerning the influence of lecozyme phonophoresis on the development of a burn process in the eye have shown that lecozyme phonophoresis has a positive action on the development of a burn process, speeds up the stoppage of inflammatory signs, epithelialization and vascularization of the cornea, stimulates the formation of its less intensive opacifications. The most favourable term to use lecozyme phonophoresis is the second day after the moment of a burn trauma. To achieve a positive effect, 5 procedures are enough, while a longer course or treatment or later terms for its usage (7, 14, 21 days after burn) impairs the development of the burn process. The usage of lecozyme phonophoresis in two stages (5 sessions within the first day and 10 sessions after epithelialization of the cornea) allows to achieve the best results--stoppage of inflammatory signs, reduction of vascularization and opacifications of the cornea.

Animals↗

PubMed1996

Speed, noise, information and the graded nature of neuronal responses.

How the firing rate of a neuron carries information depends on the time over which rates are measured. For very short times, the amount of information conveyed depends, in a universal way, on the mean rates only (trial-to-trial variability is irrelevant) and the cell response can be taken to be binary (although an ideal binary response would convey more). For longer times, noise as well as the graded nature of the response come into play, with opposite effects. Which times can be considered 'short' varies with the brain area considered and, possibly, with the processing speed it is required to operate at.

Journal Article↗

PubMed2006

Cognition in the early stage of multiple sclerosis.

OBJECTIVE: Cognitive dysfunctions may contribute to limitation of everyday activities of patients with multiple sclerosis (MS). Recent studies have demonstrated that 45 to 65% of MS-patients are cognitively impaired. The profile of MS-related cognitive dysfunctions varies greatly. It includes memory and learning deficits, attention deficits, executive dysfunctions and visuo-spatial deficits. Most studies of cognition in MS examined patients in later stages, often including MS-patients with marked physical disabilities. Studies of cognitive dysfunctions in the early stage of the disease are rare. This study specifically aimed at evaluating and characterizing cognitive impairments in the early stage of MS, and determining specific patterns of cognitive dysfunction. METHODS: 21 MS patients, experiencing their first neurological symptoms not more than two years previously, and 22 healthy controls were compared. A comprehensive neuropsychological test-battery was used to evaluate MS-related cognition. The battery consisted of memory and learning tests, executive functioning tests and a visuo spatial functioning test. A computerized attention test-battery was also included, which assess accuracy and speed of test responses. In addition depression and intellectual capabilities were assessed. RESULTS: Compared with healthy controls, MS-patients in the early stage of the disease performed significantly lower on each neuropsychological assessment, except for verbal short-term memory. In particular, MS-patients showed a lengthened reaction time for simple and focused attention (19-38%), impaired non-verbal memory function (RVDLT recognition: 33%) and a planning deficit (24%). Associations between information processing speed and disease course and the employment situation were additionally found. However, patients did not have clinically relevant depression rates on the ADS-L and visuo spatial abilities remain preserved. CONCLUSION: Our findings revealed discrete cognitive dysfunction in MS-patients within the early stage of the disease.

Adult↗

PubMed2000

Strategic control in word reading: evidence from speeded responding in the tempo-naming task.

To investigate strategic control over response initiation in word reading, the authors introduce the tempo-naming task. Relative to baseline performance in the standard-naming task, participants were induced to respond with faster latencies, shorter durations, and lower levels of accuracy by instructing them to time response initiation with an experimentally controlled tempo. The tempo response cue attenuated stimulus effects, and as faster tempos reduced latencies, the number of spelling-sound errors remained constant, whereas the number of word, nonword, and articulatory errors increased. To explain these results, the authors propose input gain as a mechanism of control over processing speed. The experimenters sketch how input gain could account for the current results as well as for the results from stimulus-blocking experiments testing the route emphasis and time criterion hypotheses of strategic control.

Adult↗

PubMed2000

Working memory deficits in current and previous users of MDMA ('ecstasy').

Current and previous users of the drug MDMA ('ecstasy') were tested on measures of central executive functioning, information processing speed, and on self-report measures of arousal and anxiety. The results were compared with those for a control group who did not use MDMA. Relative to the control group, both user groups were found to be impaired in some aspects of central executive functioning. Also, there were significant group differences on the measures of anxiety (users were more anxious) and on arousal (previous users scoring higher on the arousal measure relative to current users). Users processed information as quickly as non-users but less accurately. Some possible mediators of the above group differences are discussed.

Adult↗

PubMed1993

An adaptable microcomputer program for monitoring behavior.

We describe an improvement of a flexible and easy to use program for monitoring and recording behavior durations with IBM-compatible microcomputers and a companion program that provides additional versatility for handling data. Up to 35 behaviors or events can be monitored, and processing speed is fast enough to measure even very rapidly performed behaviors. No specialized hardware is required, and the data files that are created are compatible with commercially available software packages for statistical analysis.

Animals↗

PubMed2005

Cognitive consequences of cannabis use: comparison with abuse of stimulants and heroin with regard to attention, memory and executive functions.

This review aims to compare cognitive consequence between cannabis, and stimulants and heroin with regards to attention, memory and executive functions. The available studies using brain imaging techniques and neuropsychological tests show that acutely, all drugs create a disharmony in the neuropsychological network, causing a decrease of activity in areas responsible for short-term memory and attention, with the possible exception of heroin. Cannabis induces loss of internal control and cognitive impairment, especially of attention and memory, for the duration of intoxication. Heavy cannabis use is associated with reduced function of the attentional/executive system, as exhibited by decreased mental flexibility, increased perserveration, and reduced learning, to shift and/or sustain attention. Recent investigations on amphetamine/methamphetamine have documented deficits in learning, delayed recall, processing speed, and working memory. MDMA users exhibit difficulties in coding information into long-term memory, display impaired verbal learning, are more easily distracted, and are less efficient at focusing attention on complex tasks. The degree of executive impairment increases with the severity of use, and the impairments are relatively lasting over time. Chronic cocaine users display impaired attention, learning, memory, reaction time and cognitive flexibility. Heroin addiction may have a negative effect on impulse control, and selective processing.

Amphetamine-Related Disorders↗

PubMed2000

Data explosion: the challenge of multidetector-row CT.

The development of multi detector-row CT has brought many exciting advancements to clinical CT scanning. While multi detector-row CT offers unparalleled speed of acquisition, spatial resolution, and anatomic coverage, a challenge presented by these advantages is the substantial increase on the number of reconstructed cross-sections that are rapidly created and in need of analysis. This manuscript discusses currently available alternative visualization tecvhniques for the assessment of volumetric data acquired with multi detector-row CT. Although the current capabilities of 3-D workstations offer many possibilities for alternative analysis of MCDT data, substantial improvements both in automated processing, processing speed and user interface will be necessary to realize the vision of replacing the primary analysis of transverse reconstruction's with alternative analyses. The direction that some of these future developments might take are discussed.

Angiography↗

PubMed2002

Psychomotor and cognitive effects of piribedil, a dopamine agonist, in young healthy volunteers.

Piribedil is a dopamine agonist acting on D2 and D3 central nervous system dopamine receptors. This drug has been administered to 12 young healthy male volunteers (age 22 +/- 2 years) according to a single center randomized, double-blind, two ways cross-over, placebo controlled trial, including a washout period of one week. Placebo and piribedil were administered by a single intravenous infusion over 2 h (3 mg). Psychomotor performance and cognitive functions were assessed through a standardized and computerized psychometric tests battery and a continuous electroencephalogram (EEG) mapping. Piribedil improved simple reaction time (P=0.02), immediate (P=0.045 and 0.004), and delayed free recall (P=0.05), dual coding test (P=0.02) and increased theta and fast beta waves on the EEG (P < 0.05 and 0.001, respectively). No deleterious effect was observed on the tests exploring attention and concentration via the other procedures. It is concluded that a single intravenous perfusion of piribedil 3 mg improves alertness and the information processing speed within the central nervous system, in healthy volunteers.

Adult↗

PubMed1990

Magnetic resonance imaging and neuropsychological findings in human immunodeficiency virus infection.

Neurobehavioral functioning and magnetic resonance imaging (MRI) were investigated in 25 patients with various Centers for Disease Control (CDC) stages of human immunodeficiency virus (HIV) infection and in a control group of seven normal subjects. Unequivocal slowing of information processing speed and cerebral atrophy were related to the stage of HIV infection, with patients in CDC group IV exhibiting the most abnormal findings. Slowing of response speed was directly related to the severity of cerebral atrophy.

Adult↗

PubMed1998

Perceiving topological structure of 2-D patterns.

Four experiments investigated observers' sensitivity to the topological structure of visual stimuli. Three factors were taken to capture the topological structure of 2-D patterns: The number of disconnected components, the number of holes (connections), and inclusion relationships. If studied in isolation, any given topological property is typically confounded with the presence of particular features such as line terminations and contour length, or with Gestalt principles of perceptual organization. We went beyond existing studies and attempted to systematically remove potential confounds from the stimulus displays. Results showed that processing speeds for two-dimensional patterns are a function of their topological properties. The more patterns differ in their topological structure the easier they can be discriminated. Not only do all three topological factors contribute to pattern discriminability, they also can be combined to provide an overall measure of structural complexity. Forced choice comparison techniques agreed well with similarity judgments. Topological structure thus contributed to discriminability above and beyond many confounding variables. Claims suggesting a general topological analyzer in visual processing are discussed.

Adult↗

PubMed2005

Perinatal anoxia degrades auditory system function in rats.

Little is known about the neural bases of the reduced auditory and cortical processing speeds that have been recorded in language-impaired, autistic, schizophrenic, and other disabled human populations. Although there is strong evidence for genetic contributions to etiologies, epigenetic factors such as perinatal anoxia (PA) have been argued to be contributors, or causal, in a significant proportion of cases. In this article, we explored the consequences of PA on this elementary aspect of auditory behavior and on auditory system function in rats that were briefly perinatally anoxic. PA rats had increased acoustic thresholds and reduced processing efficiencies recorded in an auditory behavioral task. These rats had modestly increased interpeak intervals in their auditory brainstem responses, and substantially longer latencies in poststimulus time histogram responses recorded in the primary auditory cortex. The latter were associated with degraded primary auditory cortex receptive fields and a disrupted tonotopy. These processing deficits are consistent with the parallel behavioral and physiological deficits recorded in children and adults with a history of language-learning impairment and autism.

Acoustic Stimulation↗

PubMedDate not supplied

Real time measurement of RR intervals using a digital signal processor.

The accurate measurement of beat to beat intervals is essential for subsequent heart rate variability analysis. Where the ECG is used to derive the intervals, timing can be affected by artefacts such as muscle noise, electrode instability and also shape changes in the QRS complex. Identifying the QRS time by correlation methods can minimize the uncertainty but the method is computationally intensive. We have developed a real time RR interval measurement system using a correlation technique running on a low cost digital signal processor (TMS320C31). Sampling rate is 1 KHz. Timing resolution is +/- 1 ms. The correlation process uses an averaged complex from the actual ECG and has an adaptive noise threshold. The high processing speed of a DSP has proved ideal for accurate RR interval measurement. The system is described and test results with various signal to noise ratios and different types of noise are presented.

Algorithms↗

PubMed1993

Speed of memory scanning is not affected in early HIV-1 infection.

Thirty-seven nondemented HIV-seropositive and 17 seronegative control subjects were administered the Sternberg speed of memory scanning task, a procedure frequently employed to study mental slowing in patients with subcortical dementing disorders. Experimental and control subjects did not differ in speed of memory scanning, as indexed by the slopes of set size-reaction time functions, nor on mean 0-intercepts for the RT functions, which index stimulus detection and motor response time. Intercept values were significantly greater for subjects with a positive alcohol abuse history and for subjects with greater self-reported depression, but slopes were not significantly correlated with substance abuse history or psychological distress. Cognitive slowing in early HIV-1 infection is not a nonspecific effect observed across all measures of information processing speed. Underlying component functions measured must be carefully considered when selecting reaction time tasks for study with HIV-seropositive subjects. The term "subcortical" dementia may be too general a descriptor, and RT task performance may provide an alternative basis for classification of dementia types.

Acquired Immunodeficiency Syndrome↗

PubMed2006

Cognitive function is not impaired in people with a long history of migraine: a blinded study.

Little is known about the long-term consequences of migraine for cognitive functioning. This study compared older migraine patients with matched controls on four measures of cognitive ability, in a blinded design. Migraine patients and case-matched controls were recruited from the database records of a pre-existing study of ageing. Data were available from four tests of cognitive ability: verbal/arithmetic problem solving, spatial problem solving, processing speed, and vocabulary. There were no significant differences between the mean scores of migraine and control groups on any of the four cognitive tests. In addition, there were no significant differences between migraine and control groups in the effect of age on any of the four tests. A long history of migraine does not compromise scores on the four cognitive tests used in this study. These tests are predictive of memory and executive functioning in cognitive ageing, but it remains possible that lower-level cognitive processes, particularly as assessed by visual tasks, may be vulnerable to migraine.

Adult↗

PubMed2000

Age-related differences in supervisory attentional system functions.

The authors explored the effect of age on executive functions by using 3 tasks (Tower of London, Hayling, and Brixton tests) designed to assess specific executive processes (planning, inhibition, and abstraction of logical rules) that were also sensitive to frontal dysfunction. The performance of elderly participants (n = 48) was significantly poorer than that of young participants (n = 47) in all 3 tasks. Processing speed, measured by means of a color-naming task, explained some but not all of the age-related differences. These results are discussed in terms of general and specific factors in cognitive aging.

Adaptation, Psychological↗

PubMed1997

Executive functions in multiple sclerosis: an analysis of temporal ordering, semantic encoding, and planning abilities.

Previous studies have consistently demonstrated impairments in conceptual reasoning and set-shifting abilities in patients with multiple sclerosis (MS). Other executive functions have been less frequently examined. We compared 44 MS patients and 48 demographically matched controls on a temporal-ordering and semantic-encoding task and on a test of planning (Tower of Hanoi). Compared with controls, MS patients experienced deficient semantic encoding and planning but unimpaired temporal-order memory. For both tasks, post hoc analyses indicated that chronic-progressive MS patients contributed most to the group differences. A combination of poor planning and slowed information-processing speed was hypothesized to have contributed to MS patients' impaired Tower of Hanoi performance. Further research is needed to explore the possible relationship between semantic-encoding and planning deficits in MS and social and occupational disabilities.

Cues↗