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PubMed1990

Beyond drug effects and dependent variables: the use of the Poisson-Erlang model to assess the effects of D-amphetamine on information processing.

Several studies have shown that d-amphetamine (DAMP) speeds mean reaction time (RT). However, the use of mean RT may obscure important aspects of the drug response. Therefore we applied the Poisson-Erlang (PE) stochastic model of choice reaction time proposed by Pieters (1985) to the RT distribution. This model proposes that the RT distribution is generated by two states: Processing (P) and Distraction (D). RT represents the sum of the time spent in each of these states. P is the time taken to complete a set of cognitive operations which are required to give a correct response. D represents the time taken by all other activities. RTs were collected using a task (SERS) in which stimulus and response complexity each had two levels, easy and hard. Subjects were tested pre- and postdrug. Drug conditions were: placebo, 10 mg d-amphetamine (DAMP), 4 mg of the dopamine agonist, pimozide, and a combination of DAMP and pimozide (COMBO). Parameters of the model were derived using methods described by Pieters. Four measures were analyzed: Processing Time (PT); Mean Time per distraction (XTD); Distraction Rate (DR); and Total Distraction Time per trial (TDT). Mean RT is also presented. Analyses of the effects of task conditions on the parameters of the model were made using the predrug sessions. Mean RT was increased by both stimulus and response complexities as was PT. TDT was increased by the task conditions. The PE measures did not change over days. DAMP speeded mean RT. However, this effect did not interact with the task factors. DAMP speeded processing and reduced distraction. Processing was speeded only in the hard response condition, distraction time was reduced only in the easy response condition. The results indicate that the PE model can be successfully applied to fast RT tasks. More importantly, the parameters of the model revealed important pharmacological effects that were not apparent in mean RT. DAMP speeds cognitive operations related to motor preparation and reduces the effects of distraction. Consistent with past studies there are no indications that DAMP interacted with stimulus processing. The distraction effect appears to be mediated by an increase in the rate of distraction and a decrease in the average time of these distractions.

Adult↗
PubMed2005

Exercise and cognitive performance in chronic fatigue syndrome.

PURPOSE: To determine the effect of submaximal steady-state exercise on cognitive performance in patients with chronic fatigue syndrome (CFS) alone, CFS with comorbid fibromyalgia FM (CFS + FM), and sedentary healthy controls (CON). METHODS: Twenty CFS-only patients, 19 CFS + FM, and 26 CON completed a battery of cognitive tests designed to assess speed of information processing, variability, and efficiency. Tests were performed at baseline, immediately before, and twice following 25 min of either cycle ergometry set at 40% of peak oxygen capacity or quiet rest. RESULTS: There were no group differences in average percentage of peak oxygen consumption during exercise (CFS = 45%; CFS + FM = 47%; Control = 43%: P = 0.2). There were no significant effects of acute exercise on cognitive performance for any group. At baseline, one-way ANOVA indicated that CFS patients displayed deficits in speed of processing, performance variability, and task efficiency during several cognitive tests compared with healthy controls. However, the CFS + FM patients were not different than controls. Repeated measures ANOVA indicated that across all tests (pre- and postexercise) CFS, but not CFS + FM, were significantly less consistent (F2,59 = 3.7, P = 0.03) and less efficient (F2,59 = 4.6, P = 0.01) than controls. CONCLUSION: CFS patients without comorbid FM exhibit subtle cognitive deficits in terms of speed, consistency, and efficiency that are not improved or exacerbated by light exercise. Importantly, our data suggest that CFS + FM patients do not exhibit cognitive deficits either pre- or postexercise. These results highlight the importance of disease heterogeneity in studies determining acute exercise and cognitive function in CFS.

Adolescent↗
PubMed1997

Standardized technique of transplanting micrografts in hair restoration surgery. A practical approach.

BACKGROUND: The transplantation of a large number of hair-bearing micrografts has become an important method in hair restoration surgery and one that achieves a more natural looking growth of the transplanted hairs than minigrafts or punchgrafts. However, the process of grafting over a hundred micrografts is still tedious, laborious, and time-consuming, and also increases the amount of surgical trauma to the hair follicles of the donor site. OBJECTIVE: To speed up the process of micrografting and minimize surgical trauma to the follicles and the grafts in order to maximize the grafts survival and therefore optimize clinical results. METHODS: The authors describe the standardized micrografting technique used in our unit for hair transplantation, which speeds up the grafting process and minimizes the trauma due to surgery during the various fares of the transplanting procedure of the hair follicles. RESULTS: The described technique significantly speeds up the process of transplanting micrografts with minimal surgical trauma and therefore the best possible graft survival. CONCLUSION: Standardized micrografting is a fast, practical and efficient technique for hair restoration surgery.

Adult↗
PubMed1980

Contextual memory in the molecular domain.

Contextually rich recall of past events and actions indicates the formation of complex memory traces in which many items of information are integrated. The speed of this process and the inference that large numbers of cortical neurons are involved argue against synaptic transmission of all of the information required. The intercellular electromagnetic field giving rise to the EEG may function as an additional carrier of information essential to contextual processing. Recent experiments have led to models of the neural membrane that show very great sensitivities to the intercellular field. Changes of arrayed molecular conformations in this membrane due to cooperative effects in the intercellular field may provide a contextual memory located within the dense dendritic network of the cortex. Integrative effects within the volume structure of complex electromagnetic fields may thus provide a means of high-speed contextual processing and discrimination.

Cell Membrane↗
PubMed2005

Rey Complex Figure Test performance after traumatic brain injury.

The influence of factors such as a cerebral injury characteristics, education, perceptual organization skills, and speed of information processing on performance on the Rey Complex Figure Test & Recognition Trial (RCF) was examined by means of hierarchical regression analyses in 100 consecutively referred persons with traumatic brain injury at a median of 2.5 months post-injury. Patients with premorbid (e.g., psychiatric history) or comorbid (e.g. financial compensation seeking) complicating factors were excluded. Perceptual organization skills and the presence of a diffuse intracranial lesion but not education or speed of processing were statistically significant predictors of the variance in RCF variables. A large proportion of the sample improved by at least a standard deviation from independent delayed recall to multiple-choice recognition, and this was mediated by perceptual organization skills but not by injury parameters. It is concluded that performance on the RCF after traumatic brain injury is affected relatively more by perceptual organization skills than by injury severity characteristics.

Adolescent↗
PubMed2002

Cognition following acute tryptophan depletion: difference between first-degree relatives of bipolar disorder patients and matched healthy control volunteers.

BACKGROUND: Serotonergic circuits have been proposed to mediate cognitive processes, particularly learning and memory. Cognitive impairment is often seen in bipolar disorders in relation to a possible lowered serotonergic turnover. METHODS: We investigated the effects of acute tryptophan depletion (ATD) on cognitive performance in healthy first-degree relatives of bipolar patients (FH) (N= 30) and matched controls (N= 15) in a placebo-controlled, double-blind cross-over design. Performance on planning, memory and attention tasks were assessed at baseline and 5 h after ATD. RESULTS: Following ATD, speed of information processing on the planning task was impaired in the FH group but not in the control group. FH subjects with a bipolar disorder type I relative (FH I) showed impairments in planning and memory, independent of ATD. In all subjects, ATD impaired long-term memory performance and speed of information processing. ATD did not affect short-term memory and focused and divided attention. CONCLUSIONS: The results suggest serotonergic vulnerability affecting frontal lobe areas in FH subjects, indicated by impaired planning. Biological vulnerability in FH I subjects is reflected in impaired planning and memory performance. In conclusion, the cognitive dysfunctions in FH subjects indicate an endophenotype constituting a possible biological marker in bipolar psychopathology. Serotonin appears to be involved in speed of information processing, verbal and visual memory and learning processes.

Administration, Oral↗
PubMed2006

Cognitive functioning in patients with suspected chronic toxic encephalopathy: evidence for neuropsychological disturbances after controlling for insufficient effort.

OBJECTIVES: Chronic toxic encephalopathy (CTE) caused by long term occupational exposure to organic solvents is still a controversial disorder. Neuropsychological testing is the cornerstone for diagnosing the syndrome, but can be negatively influenced by motivational problems. In this nationwide study, we investigated the neuropsychological functioning and psychological symptoms of a large group of patients with suspected CTE, and ruled out alternative explanations for their complaints, including suboptimal performance due to insufficient effort. METHODS: We studied participants with suspected CTE (n = 386) who were referred for further diagnosis to the Netherlands Centre of Occupational Diseases in the period 1998-2003 and who had completed the entire diagnostic protocol. Patients were excluded if there was the slightest suspicion that test performance had been negatively influenced by insufficient effort (n = 221), or if comprehensive assessment identified an alternative diagnosis (n = 80). Insufficient effort was defined by a combination of three indices. The neuropsychological test scores of the patient group (n = 85) were compared with those of a control group of building trade workers matched for sex, age, and educational level (n = 35). RESULTS: The patient group had significantly more psychological complaints and performed significantly worse than the control group on tests of speed of information processing and memory and learning. However, only a small percentage of the patients had clearly abnormal scores for cognitive speed (9%) or memory (8%). Attention, verbal abilities, and constructional functions were not disturbed. Exposure duration and cognitive complaints were significantly correlated, whereas the correlation between exposure duration and neuropsychological domain scores was not significant. CONCLUSIONS: Insufficient effort was present in a substantial part of the patient group. After minimising the likelihood that insufficient effort negatively influenced neuropsychological scores, we still found neuropsychological deficits in speed of cognitive processing and memory; however, these scores were clearly abnormal only in a minority of patients with suspected CTE. Screening instruments should focus on these domains.

Adult↗
PubMed2007

High-speed camera imaging for laser ablation process: for further reliable elemental analysis using inductively coupled plasma-mass spectrometry.

Production of laser ablation-induced sample aerosols has been visualized using a high-speed camera device coupled with shadowgraphy technique. The time resolution of the method is 1 micros, and production of the sample grains was successfully defined by the imaging system. An argon-fluoride excimer laser operated at 193-nm wavelength was used to ablate the solid samples. When the laser was shot onto the sample (Si wafer), a dome-shaped dark area appeared at the ablation pit. This dark area reflects changes in refractive index of ambient He probably due to emission of electrons or ions from the ablation pit. The dark area expanded hemispherically from the ablation pit with a velocity close to the speed of sound (approximately 1000 m/s for He at 300 K). This was followed by the excitation or ionization of the vaporized sample, known as the plasma plume. Immediately after the formation of the plasma plume, sample aerosols were produced and released from the ablation pit along the propagation of the laser-induced shockwave. Production of the sample aerosols was significantly delayed (approximately 4 micros) from the onset of the laser shot. The typical speed of particles released from the ablation pit was 100-200 m/s, which was significantly slower than the reported velocity of the plasma plume expansion (104 m/s). Since the initial measured speed of the sample particles was rather close to the speed of sound, the sample aerosols could be rapidly decelerated to the terminal velocity by a gas drag force with ambient He. The release angle of the sample aerosols from the ablation pit was very shallow (<10 degrees ), which may be due to the downforce produced by the thermal expansion of the ambient gas above the ablation pit. The shallower release angle and the contribution of the downforce probably results in the redeposition of sample aerosols or vapor around the ablation pit. In fact, the degree of sample redeposition around the ablation pit can be effectively minimized by evacuation the sample cell down to 20 kPa. In the case of glass samples, almost no visible laser-induced sample particles could be found using the spatial resolution of our device. This was mainly due to the smaller size distribution of the sample aerosols from the glass materials. Differences in size distribution of the sample aerosols between Si wafers and glass materials can affect analytical sensitivity and precision of elemental analyses using the laser ablation-ICP-mass spectrometry (LA-ICPMS). Although details of the mechanism of production and release of the sample aerosols from the ablation pit are not fully understood, the present imaging device for laser ablation has various implications for further precise elemental and isotopic analyses using LA-ICPMS.

Journal Article↗
PubMed1979

Age-related differences in two stages of central perceptual processes: the effects of short duration targets and criterion differences.

Two experiments investigated age differences in speed of central perceptual processes using a dichoptic backward masking paradigm. Twelve young (mean age = 19.6 years) and 12 old (mean age = 68.5 years) adults served as subjects. Exp. 1 examined age differences in speed of central perceptual processes using an ascending limits procedure and forced-choice responding to control for criterion differences. Target durations from 2 to 30 msec were used to further test the fit of young and elderly masking functions to the additive rule believed to describe masking which arises centrally (Turvey, 1973). Results from Exp. 1 showed a 33% slower speed of processing in the elderly sample. Furthermore, masking functions for both age groups fit the central rule across the wide range of target durations used. Exp. 2 examined the perceptual detectability of a 2- and 20-msec target at 7 stimulus onset asynchronies between target and masking stimuli using a forced-choice procedure. Subanalysis of two different components of the observed masking functions suggested the elderly sample was equally slow in completing both an early and late stage of central perceptual processing.

Adolescent↗
PubMedDate not supplied

Hypertension affects neurobehavioral functioning.

This study compared the neurobehavioral performance of hypertensive and normotensive men and women using neuropsychological, information-processing, and psychometric assessments. One hundred subjects, including 68 hypertensive and 32 normotensive individuals, completed a test battery that yielded scores on measures of speed of information processing, verbal and figural memory, psychosocial functioning, Type A behavior, and locus of control. Results showed that, compared with the normotensive individuals, the hypertensives performed more poorly on a set of tasks that measure speed of information processing and short-term memory (Digit Symbol, Digit Span (Backwards), and Reaction Time (slope)). The hypertensives also reported higher levels of state anxiety relative to their normotensive counterparts. The effects of hypertension on neurobehavioral functioning could not be accounted for on the basis of age or education.

Adult↗
PubMed2006

Effects of pharmacologically induced changes in NMDA receptor activity on human timing and sensorimotor performance.

Unlike processing of time intervals in the range of seconds or more, processing of brief durations in the subsecond range appears to be beyond cognitive control and based on subcortical mechanisms located in the basal ganglia. The present study was designed to evaluate the effects of NMDA receptor activity on temporal processing in the second and subsecond range. In a double-blind crossover design, either 30 mg of the noncompetitive NMDA receptor antagonist memantine or placebo was administered to 32 healthy male volunteers. While memantine induced a marked impairment in temporal processing of intervals in the range of seconds, temporal processing of intervals in the range of milliseconds was not affected. Furthermore, no effect of memantine on speed of information processing could be observed. Speed of motor response execution, however, was significantly enhanced by memantine compared to placebo. The overall pattern of results provides converging evidence for the notion that temporal processing of longer intervals involves higher order working memory functions such as working memory capacity. The absence of an effect on temporal processing of very brief intervals in combination with the beneficial effect on movement time suggests that NMDA receptor activity in the basal ganglia is not directly related to the timing of intervals in the subsecond range.

Adult↗
PubMed1995

Helping to solve problems associated with spina bifida: 1. Presentation of the TRS Project: organizing services for low frequency diagnostic groups and 2. Cognitive deficits often seen in young adults with spina bifida: effects in the school and work place.

1. A Presentation of the TRS Project: Counselling and (Re)habilitation Center. A Model Project in Organizing Services for Low Frequency Diagnostic Groups. Persons with low frequency disabilities often require services from a number of professions. The patient organizations claim that the patients themselves often have to coordinate their own treatment. The TRS project has been established as one of the initiatives under the Norwegian Government's Plan of Action for the Disabled. The project is one of three national projects designed to develop models for the coordination of services for persons with low frequency congenital disabilities. The TRS project deals with the following five diagnoses: Marfan syndrome, arthrogryphosis multiplex congenita, myelomeningocele/spina bifida, osteogenesis imperfecta and congenital limb deficiency. The project is based on patient (user) participation. The five patient organizations are represented on the board where they are in the majority. Patients along with professionals give lectures during group stays. The project offers its services to persons with the diagnosis from all parts of Norway (4.3 mill. inhabitants). Persons with spina bifida over 16 years are included in the project, as well as persons with the other diagnoses at all ages. We present the organization of the project and the repertoire of services that are on offer. 2. Cognitive Deficits Often Seen in Young Adults with Spina Bifida: Effects in the School and Work Place. As survival rates continue to increase with the use of shunting procedures for persons with spina bifida (SB), the need for improved educational and vocational planning also increases. Orbeck and Schanke reported that the cognitive deficits of young adults with SB have not received enough attention in educational and vocational planning. A thorough description of these deficits will aid in developing more effective individualized planning. With improved planning, insight into alternative methods for improving support may also then be investigated. The purpose of this study is to better define and describe the cognitive deficits often encountered while planning support in the school and work place for this group. Neuropsychological examinations are the basis for this description of observed cognitive deficits. The study included 46 young adults with SB aged 15 to 38 living in Norway. All persons were given a neuropsychological test battery which included tests for attention, memory, speed of information processing, visual perception and visual constructive function, arithmetic, fine motor coordination, and verbal functioning. The results indicated deficits in fine motor coordination, speed of information processing, and a slow learning curve. The consequences of these deficits in educational and vocational planning are discussed and guidelines for further studies are suggested.

Abnormalities, Multiple↗
PubMed1976

Application of high-speed liquid chromatography to the analysis of polyoxyethylene surfactants and their decomposition products in industrial process waters.

Complementary high-speed liquid chromatographic techniques have been combined with infrared spectroscopy for the characterization and analysis of polyoxyethylene fatty acid surfactants and their decomposition products in industrial process waters. The combination of molecular sieve chromatography and infrared spectroscopy offers a selective and simple method for the analysis of trace concentrations (detection limit approx. 0.05-0.1 ppm) of these surfactants. Liquid-solid and reversed-phase chromatography have proven useful for the characterization and analysis of free fatty acids. Some of the parameters that affect the reversed-phase separation of fatty acids are discussed.

Chromatography, High Pressure Liquid↗
PubMed2004

3D restoration with multiple images acquired by a modified conventional microscope.

A problem in high magnification microscopy is the blurring in the imaging of an object. In this article, we demonstrate a restoration technique that simultaneously makes use of the confocal image and the wide-field image. These images can be acquired by a modified conventional microscope. In front of the light-source, there is an array of pinholes. There are no pinholes at the detection plane. Instead, one or more pixels from the CCD camera are used, where the pinholes would have been. Using all pixels gives the wide-field image, but using a selected subset can give a confocal image. The array is used to speed up the process of acquiring the image. Note that the speed of acquisition is proportional to the number of pinholes. We show that the restoration from the two images can lead to a better result than using only one of the images. If this is the case, we show that a distance of 5 times the diameter of the pinholes can give the same results as a distance of 20 times after deconvolution. This offers an increase in acquisition time of a factor 16.

Algorithms↗
PubMed1985

Detection of DNA damage induced in vivo by a cross-linking agent with a circular channel crucible oscillating viscometer.

DNA damage induced in vivo by the cross-linking agent mitomycin C (MMC) was investigated with a new oscillating crucible viscometer. Viscosity was measured by lysing rat liver nuclei in an alkaline lysing solution (pH 12.5; 25 degrees C). In control samples the viscosity increased very slowly with time, reaching a plateau only after 10-12 h. The process was accelerated and the maximum viscosity was decreased by alkaline single-stranded breaks arising from methylation and subsequent depurination of DNA in vitro with dimethylsulphate (DMS). MMC, when given alone, had no evident effect on the time needed for reaching plateau viscosity but it induced a small increase in maximum viscosity. When MMC was given in association with DMS, the time of disentanglement remained unchanged (accelerated) but maximum viscosity was increased in a dose dependent way. We conclude that these data clearly confirm that the slow steady increase of the viscosity of control DNA with time reflects mainly the process of unwinding of the two strands. The speed of this process seems to depend only from the number of unwinding points in DNA (breaks).

Animals↗
PubMed1998

Alcohol, cognitive impairment and expectancies.

OBJECTIVE: This experiment tested the hypothesis that differences in subjects' expectations about the impairing effect of alcohol on cognitive performance predict their responses to alcohol and to a placebo. METHOD: Twenty-seven male social drinkers were randomly assigned to one of three treatment groups: alcohol (0.62 g/kg), placebo, or no treatment control. All groups practiced a Rapid Information Processing Task that measured cognitive performance by the speed of information processed. After practice, they rated the degree of impairment they expected alcohol to have on their performance, and then performed the task under their different treatments. RESULTS: Alcohol slowed (i.e., impaired) information processing compared with placebo and no treatment. In addition, those who expected more impairment performed more poorly under alcohol, and under the placebo when alcohol was expected. When no beverage was received, no expectancy-performance relationship was obtained. CONCLUSIONS: The findings call attention to expectancies as an important factor that may contribute to individual differences in cognitive functioning under alcohol and placebo.

Adult↗
PubMed1999

Influence of process variables on physical properties of the pellets using extruder and spheronizer.

Placebo pellets containing lactose and microcrystalline cellulose (Avicel PH101) ratio 60:40 were prepared by the extrusion-spheronization process. The influence of processing variables, including the spheronizer speed, the spheronization time, the binder type, and the concentration and amount of water content on physical properties of the pellets, were studied. The sphericity of pellets was increased with increasing spheronizer speed during wet mass process. When spheronization time was increased, sphericity, smooth surface, and particle size of pellets were increased. Increasing binder concentration will increase particle size. Pellets using HPC-M as a binder at high spheronizer speeds showed spherical shape, narrow size distribution, and good flow properties when compared with Methocel E-15LV, HPC-L, and Methocel A4M. In addition, increasing HPC-M concentration had no effect on shape and particle size of pellets. The amount of water content was found to affect shape, flow rate, and density. In summary, suitable conditions consisted of 2% w/w of HPC-M, 40% w/w of water, and 15 min of spheronization time at 951 rpm of spheronizer speed.

Cellulose↗