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PubMed2006

Laser induced multi-scale textured zirconia coating on Ti-6Al-4V.

A textured coating of zirconia on Ti-6Al-4V alloy was produced using pulsed laser based processing technique. Scanning electron microscope observations coupled with fractal analysis revealed the multi-scale nature of the textured coating. Both stylus based profilometric measurements and fractal analysis indicated non-linear nature of the relationship between laser processing speed at constant pulse frequency (10 kHz) and roughness of the textured coating. The textured coatings produced with all the three processing speeds (40, 160, 290 cm/min) were fractal over certain length scales. Processing at 40 cm/min resulted in structures that are fractal across a large number of length scales where as higher processing speeds resulted in fractality over fewer length scales. The processing speed influenced the zirconia content in the coating and the phase transformation within Ti-matrix of the coating. Within the coating, while zirconia content decreased the amount of retained beta-Ti increased with increase in processing speed. Such physical and chemical transformations are desired in a titanium bio-implant for effective contact with protein, cells and tissues at various length scales and its effective chemical performance in bio-environment.

Alloys↗

PubMed2005

Cognitive impairment as marker of diffuse brain abnormalities in early relapsing remitting multiple sclerosis.

OBJECTIVES: To establish the frequency of cognitive impairment in a population based sample of patients with recently diagnosed relapsing-remitting multiple sclerosis (RRMS), and to determine the relation between cognitive abnormalities and the extent of macroscopic and microscopic tissue damage revealed by magnetic resonance imaging (MRI) and magnetisation transfer (MT) imaging. METHODS: 58 patients with RRMS consecutively diagnosed in the previous six months in Aquitaine and 70 healthy controls underwent a battery of neuropsychological tests. Lesion load and atrophy indices (brain parenchymal fraction and ventricular fraction) were measured on brain MRI. MT ratio (MTR) histograms were obtained from lesions, normal appearing white matter (NAWM), and normal appearing grey matter (NAGM). Gadolinium enhanced lesions were counted. RESULTS: 44 RRMS patients could be individually matched with healthy controls for age, sex, and education. Patients performed worse in tests of verbal and spatial memory, attention, information processing speed, inhibition, and conceptualisation. Measures of attention and information processing speed were correlated with lesion load, mean NAWM MTR, and the peak location of the NAGM MTR histogram in the patients. Multivariate regression analysis showed that lesion load and mean NAWM MTR were among the MR indices that were most significantly associated with impairment of attention and information processing speed in these early RRMS cases. CONCLUSIONS: Cognitive impairment appears to be common in the early stages of RRMS, mainly affecting attention, information processing speed, memory, inhibition, and conceptualisation. The severity of these deficits reflects the extent of the lesions and the severity of tissue disorganisation outside lesions.

Adult↗

PubMed2001

Genetics of cognition: outline of a collaborative twin study.

A multidisciplinary collaborative study examining cognition in a large sample of twins is outlined. A common experimental protocol and design is used in The Netherlands, Australia and Japan to measure cognitive ability using traditional IQ measures (i.e., psychometric IQ), processing speed (e.g., reaction time [RT] and inspection time [IT]), and working memory (e.g., spatial span, delayed response [DR] performance). The main aim is to investigate the genetic covariation among these cognitive phenotypes in order to use the correlated biological markers in future linkage and association analyses to detect quantitative-trait loci (QTLs). We outline the study and methodology, and report results from our preliminary analyses that examines the heritability of processing speed and working memory indices, and their phenotypic correlation with IQ. Heritability of Full Scale IQ was 87% in the Netherlands, 83% in Australia, and 71% in Japan. Heritability estimates for processing speed and working memory indices ranged from 33-64%. Associations of IQ with RT and IT (-0.28 to -0.36) replicated previous findings with those of higher cognitive ability showing faster speed of processing. Similarly, significant correlations were indicated between IQ and the spatial span working memory task (storage [0.31], executive processing [0.37]) and the DR working memory task (0.25), with those of higher cognitive ability showing better memory performance. These analyses establish the heritability of the processing speed and working memory measures to be used in our collaborative twin study of cognition, and support the findings that individual differences in processing speed and working memory may underlie individual differences in psychometric IQ.

Adolescent↗

PubMedDate not supplied

Timed instrumental activities of daily living tasks: relationship to cognitive function and everyday performance assessments in older adults.

BACKGROUND: We live in a world where information is presented in a time-limited fashion and successful adaptation is dependent on time-limited responses. Slowed visual-processing speed is common among older adults. Its impact on everyday task performance is not clearly understood. OBJECTIVE: The goal was to determine whether visual-processing speed, as well as memory and inductive reasoning, are independently associated with the time required by older adults to complete instrumental activities of daily living typical of everyday life. METHODS: Five timed instrumental activities of daily (TIADL) tasks were administered to 173 older adults (ages 65-90 years) along with assessments of visual-processing speed, memory, and inductive reasoning. The dependent variable was the time required to perform the task (e.g., finding a telephone number, making change, finding and reading the ingredients on a can of food, finding food items on a shelf, reading instructions on medicine container). Medical and functional comorbidities known to affect task performance were measured in order to adjust for their impact on the dependent variable. Other measures of everyday task competence (Everyday Problems Test, Observed Tasks of Daily Living, questionnaire on IADL difficulties) were also administered in order to determine to what extent existing measures of everyday performance are associated with TIADL performance. Test-retest reliability of the TIADL score was assessed in a separate sample. RESULTS: Although memory and reasoning were crudely related to the time needed to perform the TIADL tasks, only processing speed was independently associated with TIADL scores. Those older adults with slow processing speed were more likely to require longer times to complete everyday tasks. Previously developed measures of everyday task competence (e.g., Everyday Problems Test, Observed Tasks of Daily Living) based on accuracy scoring did not strongly predict TIADL performance. CONCLUSION: These results suggest a unique role for an everyday competence test that focuses on the timely completion of everyday tasks, rather than on an assessment of accuracy alone. TIADL measures may prove useful in evaluating the everyday effectiveness of cognitive interventions targeted at increasing information-processing speed.

Activities of Daily Living↗

PubMed2006

Central executive system impairment in traumatic brain injury.

PRIMARY OBJECTIVE: This study investigated whether cognitive impairment after traumatic brain injury (TBI) can be considered a consequence of (1) a speed processing deficit or (2) an impairment of the Central Executive System (CES) of working memory. METHODS AND PROCEDURES: Thirty-seven TBI patients underwent a standardized battery of neuropsychological tests evaluating speed processing, sustained attention, short-term memory, working memory, divided attention, executive functions and long-term memory. MAIN OUTCOMES AND RESULTS: Patients showed severe deficits in working memory, divided attention, executive functions and long-term memory. Divided attention, long-term memory and executive functions deficits significantly correlated with working memory, but not with speed processing deficits. Moreover, multiple regression analyses showed that a CES impairment and not a speed processing deficit predicted divided attention, executive functions and long-term memory deficits. The severity and the site of brain lesions did not predict the level of CES or speed processing impairment. CONCLUSIONS: The cognitive impairment following TBI seem to be caused by an impairment of the Central Executive System, rather than a speed processing deficit.

Adolescent↗

PubMedDate not supplied

The role of IQ in a component model of reading.

The purpose of this study was to test the role of visual processing speed and IQ in a model of reading. This study investigated whether the processes involved in reading differ between a group of children with and a group without reading disability. These two groups of children completed tests of reading comprehension, listening comprehension, decoding, processing speed, and intelligence. The results indicated that processing speed explains a significant amount of variance in reading comprehension over that accounted for by the simple view of reading. Also, IQ accounts for a significant amount of variance in reading over that accounted for by the simple view of reading and processing speed. Path analyses indicated that the effect of IQ on reading is partially mediated by decoding in the children with reading disability. The results point to the importance of the role of IQ in predicting reading comprehension.

Achievement↗

PubMed1983

Factors affecting developmental changes in the speed of processing.

Although many studies have found developmental changes in the speed of various processes, they have potentially confounded the subject's age with his knowledge of the task domain and use of strategies. In this study, the strategies used by the subject and his domain knowledge were independently assessed by a number of tasks. Subsequently, processing rate measures were obtained for a task (the "same/different" judgment task of simultaneously presented stimuli) in which domain knowledge was manipulated independently of age while controlling for strategy usage. It was found that the usual adult superiority in speed of processing could be markedly reduced if children possessed equivalent amounts of domain knowledge and this effect was domain specific. Further, it was found that differences in knowledge affected processing rates in both knowledgeable adults and children and to about the same extent. It was concluded that some part of the typical adult superiority in processing rate was due to knowledge differences.

Adult↗

PubMed1986

Sources of age differences in speed of processing.

3 experiments were conducted to study developmental change in the speed of cognitive processes. In Experiment 1, subjects ranging in age from 8 to 21 years were tested on a mental rotation task in which they judged whether pairs of letters presented at different orientations were identical or mirror images, and on a name retrieval task in which they judged if pairs of pictures were identical physically or had the same name. Increases with age in the speed of mental rotation and speed of name retrieval were both well described by exponential functions, and the rate of developmental change was comparable for the 2 tasks. Experiment 2 confirmed that age changes in rate of mental rotation are well described by an exponential function. Experiment 3 demonstrated, on a mental rotation task, a perfect correlation across conditions between children's mean response times and adults' mean response times for corresponding conditions. These results are interpreted as indicating that age differences in speed of processing are due, at least in part, to a central limiting mechanism that increases with age.

Adolescent↗

PubMed2003

Cognitive effects of long-term benzodiazepine use in older adults.

This study examined the potential for cognitive morbidity associated with the long-term use of benzodiazepine (BZ) sedative-hypnotics in a sample of healthy older adults. Tests of memory, attention and processing speed were conducted prior to and 1 month after drug discontinuation for 25 BZ-users and at similar intervals for 26 healthy control subjects. After controlling for differences in affective status between BZ-users and controls, there were no significant group differences in cognitive performance. However, BZ-users showed greater gains on tests of attention and speed of processing at repeat testing compared with controls this improvement was not attributable to a change in affective status. These findings suggest that there may be subtle and reversible effects of long-term BZ use on speed-dependent tasks in older adults. However, the magnitude of these effects is quite small and may be of little clinical significance in the healthy elderly.

Aged↗

PubMed2001

Measuring central executive functioning: what's in a reading span?

Although variations of Daneman and Carpenter's (1980) Reading Span Test (RST) have seen increasing use in both cognitive and neuropsychological research, the specific mental operations involved in performing it remain unclear. We tested 80 undergraduates to examine the extent to which speed of processing, manipulation capacity, and susceptibility to interference contributed to RST performance. The results suggest that, rather than unitary central executive or processing speed functions underlying RST performance, at least two factors, manipulation capacity and susceptibility to interference, underlie the task. Further study of RST operations may lead to a better understanding of the nature of the central executive itself.

Cognition↗

PubMed2006

Visual search for change in older adults.

Previous research has demonstrated that younger adults are surprisingly poor at detecting substantial changes to visual scenes. Little is known, however, about age differences in this phenomenon. In the 2 experiments reported here, older adults were slower than younger adults in detecting changes to simple visual stimuli. This age difference was beyond what would be expected given known age-related changes in processing speed. Examination of eye movement behavior during the search for change suggested that age-related changes in the useful field of view and degree of cautiousness play a significant role. Speed of processing and 3 age-related eye movement behaviors explained 85% of the variance in change detection latency, eliminating the effect of age.

Adolescent↗

PubMed2006

Computed tomography findings and early cognitive outcome after traumatic brain injury.

PRIMARY OBJECTIVE: To examine the relationship between CT abnormalities and early neuropsychological outcome following traumatic brain injury (TBI) using quantitative CT analyses, data reduction methods for neuropsychological results and specific hypotheses based on literature review. RESEARCH DESIGN: Observational, prospective cohort study using acute (emergency) CT data and neuropsychological test data from 89 participants with TBI who were hospitalized for rehabilitation. METHODS AND PROCEDURES: Principal components analysis with varimax rotation was used to reduce data from a standard battery of eight neuropsychological tests administered after clearance of post-traumatic amnesia (1 month post-TBI on average). Bivariate correlations were used to examine relationships of three factors (verbal memory, cognitive processing speed and verbal working memory) to quantitative volumetric analysis of CT scan abnormalities (size, number and location). Specific hypotheses as to CT predictors of poor performance on each factor were tested using multivariable linear regression that included injury severity and demographic variables. MAIN RESULTS: Eighty-nine per cent of participants had some pathology on initial CT. Age, education and time to follow commands (TFC), an index of overall injury severity, were significantly associated with the neuropsychological factors. However, none of the specific hypotheses about CT scan variables and cognitive outcome were strongly supported by the data. There was a trend for any CT abnormality to predict slower speed of processing and for higher number of brain lesions to predict worse memory performance. CONCLUSIONS: Despite the precision added by quantitative CT analysis, CT findings did not improve on demographic factors and TFC in predicting early cognitive outcome of TBI. Imaging methods that are more sensitive to white matter integrity may be needed to develop pathophysiologic predictors of TBI outcome.

Adult↗

PubMed1998

The effects of normal ageing on neuropsychological functioning following traumatic brain injury.

Increasing age is associated with greater absolute neuropsychological impairment (e.g. slower processing speed, diminished memory), although it is unclear if older individuals with traumatic brain injury (TBI) show greater relative impairment than younger individuals with TBI. The current study evaluated the effects of normal ageing on TBI by using age-based normative data to calculate indices of relative decline from pre-morbid levels (expressed as z-deficit scores) for different age groups (20-39 years, 40-59 years, 60+ years). The sample included 279 individuals with TBI between the ages of 20 and 65 who were assessed in a department of rehabilitation neuropsychology laboratory over a 4-year period. Spearman correlations and ANOVAs did not show age-related differences in relative memory, attention or speed of processing abilities, although results did indicate that increasing age is associated with relatively less impairment in intelligence. The results suggest that the greater neuropsychological impairment noted in older individuals with TBI is most likely related to normal ageing. The importance of considering both absolute and relative degrees of impairment is discussed.

Achievement↗

PubMed2005

Appearances are deceptive? Long-term cognitive and central auditory sequelae from closed head injury.

The purpose of the present study was to examine possible signs of long-term cognitive and/or central auditory sequelae seven to eleven years after a closed head injury (CHI) of sufficient severity to cause scull fracture and/or brain contusion. Another purpose was that this investigation should be carried out in a group of recovered trauma victims with, to the individual, no known or minimal sequelae. A computer-based set of five cognitive tests and three central auditory tests were used in a group of formerly brain-injured patients who considered themselves as well recovered. Most of the participants did not report any signs of cognitive or auditory impairment. Tests of working memory capacity, verbal information processing speed, phonological processing and verbal inference-making ability were used. Auditory brain response (ABR), distorted speech audiometry (interrupted speech), and phase audiometry were used to test central auditory function. The initial severity of brain damage, i.e. status when the patient arrived at the emergency ward, was estimated with Swedish Reaction Level Scale (RLS). Cognitive shortcomings after CHI were demonstrated in a high percentage (59%, 13/22) of the cases seven to eleven years after the injury. Central auditory processing disorders (APD) were also demonstrated in a fairly high percentage (58%, 11/19) of the subjects. None of the correlations between RLS and the results on cognitive and central auditory tests reached statistical significance. However, there was a correlation between cognitive performance and the results on the central auditory tests used in this investigation. Eighty percent (8/10) of those participants with pathologies on ABR and/or phase audiometry and/or IS also failed on one or more of the cognitive tasks, compared to 44% (4/9) among those with no signs of APD. It is possible, many years after CHI, to observe cognitive shortcomings and APD in a relatively high percentage of CHI cases that are subjectively considered to be fairly well recovered. The cognitive tasks used in the study have proved to be a sensitive method to discover cognitive impairments. Long-term cognitive sequelae and APD could not be predicted from RLS scores.

Adolescent↗

PubMed1992

Cognition and immune function in HIV-1 infection.

OBJECTIVES: To determine (1) whether there were differences in cognition between HIV-1-seropositive and HIV-1-seronegative homosexual men and (2), if so, whether these differences could be explained by the degree of immunosuppression [i.e., CD4 cell count and immunoglobulin A (IgA) levels]. DESIGN: A cross-sectional design was used to compare 66 HIV-1-seropositives (Centers for Disease Control stages II and III, n = 56; stages IVA and IVC-2, n = 10) and 37 HIV-1-seronegatives. The HIV-1-seropositives were classified into three immune groups based on their CD4 cell count (x 10(6)/l) and serum IgA level (mg/dl): (1) moderate [(n = 35) CD4 greater than 400, IgA less than 300]; (2) mixed [(n = 22) either CD4 greater than 400 and IgA greater than 300 or CD4 less than 400 and IgA less than 300] and (3) poor [(n = 9) CD4 less than 400, IgA greater than 300]. HIV-1-seronegatives formed the 'good' immune group (CD4 greater than 400 and IgA less than 300). METHODS: The four groups were compared on tests of verbal and visual memory, information-processing speeds, visuospatial skills, language processes, attention, psychomotor reaction time, and mental status. Factors other than HIV-1 sero-status that can influence cognitive performance were tested as covariates. RESULTS: HIV-1-seropositives had slower information-processing speeds and decreased verbal and visual memory, compared with HIV-1-seronegatives. These differences in cognition were not due to differential immunosuppression or to clinical status among the HIV-1-seropositives. CONCLUSIONS: Cognitive alterations occur in HIV-1-infected individuals before AIDS and appear to be independent of clinical status and degree of immunosuppression as measured by CD4 cell count and IgA levels.

Adult↗

PubMedDate not supplied

Cognitive rehabilitation of mildly impaired Alzheimer disease patients on cholinesterase inhibitors.

OBJECTIVE: The authors evaluated the efficacy of a new cognitive rehabilitation program on memory and functional performance of mildly impaired Alzheimer disease (AD) patients receiving a cholinesterase inhibitor. METHODS: Twenty-five participants in the Cognitive Rehabilitation (CR) condition participated in two 45-minute sessions twice per week for 24 total sessions. CR training included face-name association tasks, object recall training, functional tasks (e.g., making change, paying bills), orientation to time and place, visuo-motor speed of processing, and the use of a memory notebook. Nineteen participants in the Mental Stimulation (MS) condition had equivalent therapist contact and number of sessions, which consisted of interactive computer games involving memory, concentration, and problem-solving skills. RESULTS: Compared with the MS condition, participants in CR demonstrated improved performance on tasks that were similar to those used in training. Gains in recall of face-name associations, orientation, cognitive processing speed, and specific functional tasks were present post-intervention and at a 3-month follow-up. CONCLUSION: A systematic program of cognitive rehabilitation can result in maintained improvement in performance on specific cognitive and functional tasks in mildly impaired AD patients.

Activities of Daily Living↗

PubMed1988

Theory-based ability measurement: the learning abilities measurement program.

This paper briefly describes the U.S. Air Force Learning Abilities Measurement Program (LAMP), which is devoted to the development of a science-based system of ability measurement. A short history is given of ability testing and research in the military services, along with a statement of the value of ability testing for making personnel selection and classification decisions. Although few advances in ability measurement have been made in the last two decades, the present availability of micro-computers and recent progress in our understanding of human cognition create possibilities for a major breakthrough in the state-of-the-art. Examples are provided of recent LAMP studies on processing speed and processing capacity which hold promise for forecasting individual differences in learning efficiency, performance capabilities, and susceptibility to information overload. Also discussed is a program which encourages university scientists working toward the same goals to make use of U.S. Air Force subjects and testing facilities.

Aptitude Tests↗

PubMed2000

Speed of information processing in traumatic brain injury: modality-specific factors.

OBJECTIVE: To assess speed of information processing by two serial addition tests (one visual, one auditory) in individuals with moderate-to-severe traumatic brain injuries (TBIs) and in a healthy, normal control group (NC). The tasks were designed to equate and control for accuracy of performance across the TBI and NC groups, thus allowing for quantification of information processing speed. DESIGN: Performance across groups and tasks were compared using 2 x 2 repeated measure analyses of variance (ANOVAs). In addition, each individual's processing speed was used to adjust rate of stimulus presentation on a subsequent "rehabilitation" trial to determine further whether this adjustment equated accuracy of performance. SETTING: Rehabilitation hospital. PATIENTS: 22 outpatients with moderate-to-severe TBI (6 women, 16 men; mean age = 34.6 years; duration of loss of consciousness = 22.6 days) and 20 age- and education-matched healthy controls. RESULTS: Processing speed was slower in TBI subjects, relative to controls and was significantly related to measures of executive functioning for those with TBI. Relative to controls, speed of processing in the TBI group was disproportionately slower when information was presented in the auditory, relative to the visual, modality. CONCLUSIONS: Speed of information processing is a major impairment in those with TBI when unconfounded by performance accuracy. The modality-specific impairment observed in the TBI group may, in part, be due to a greater within-modality interference effect created by the auditory version of the task. By manipulating information at a pace customized for an individual through compensatory strategies and environmental modifications, information-processing performance of TBI participants can be enhanced significantly.

Adult↗