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PubMedDate not supplied

Extent of cognitive decline in traumatic brain injury based on estimates of premorbid intelligence.

Global cognitive impairment following traumatic brain injury (TBI) is common, with some abilities more significantly affected than others. However, due to difficulties in estimating premorbid intelligence, there has been no systematic evaluation of the extent of decline in different cognitive abilities following TBI. Recent studies indicate that the Wide Range Achievement Test-Revised (WRAT-R) Reading subtest is an accurate estimate of premorbid intelligence, suggesting that post-TBI cognitive test scores can be compared to the WRAT-R to estimate the extent of decline that occurs in specific cognitive abilities. The current study estimated the extent of deficit in intelligence, memory, attention, speed of processing, and cognitive flexibility for 97 outpatients with TBI. Extent of decline was calculated by subtracting WRAT-R z-scores from cognitive test z-scores to determine a z-difference score (ZDiff) for each cognitive ability. The results suggest that intelligence is least declined following TBI (WAIS-R 3-4-point decline; VIQ ZDiff = -0.23: FIQ ZDiff = -0.27), followed by attention (WMS-R 5-point decline; ZDiff = -0.31), memory (WMS-R 6-9-point decline; Verbal Memory ZDiff = -0.41; General Memory ZDiff = -0.51; Delay Memory ZDiff = -0.57), speed of processing (Trails A 15-16 second decline; ZDiff = -1.90) and cognitive flexibility (Trails B 35-52 second decline; ZDiff = -2.65). Implications for provision of feedback to individuals with TBI and their families are discussed.

Adolescent↗
PubMed2006

A cost-benefit analysis of risk-reduction strategies targeted at older drivers.

OBJECTIVE: The risk of motor-vehicle collisions increases as driving-related functional abilities decline. These declines can accompany normal or pathological aging and can be identified through driving-related functional screening exams upon license renewal. The objective of this cost-benefit analysis was to determine the utility of four functional screening procedures used to identify drivers at risk for motor-vehicle collisions, as well as an intervention designed to maintain or improve functional abilities. Additionally, this study sought to determine the expected cost per driver if an intervention was designed to target only those drivers who failed the functional ability-based driving screen, versus the expected cost per driver if the intervention was distributed en masse to all drivers 75 years and older. Improving functional abilities in older adults has potential far-reaching health and financial impacts which are broader than their impact of maintaining mobility. METHODS: A decision tree was constructed to evaluate the expected costs and benefits of (a) screening all drivers and intervening when indicated (several screening batteries of varying length were considered), (b) no screening, but intervening with all drivers of older age, or (c) neither screening nor intervening (i.e., re-licensing per usual). Test characteristics and risk probabilities were based on a cohort of drivers aged 75 and older from a previous study (Ball et al., 2006). Relevant sensitivity analyses were conducted. RESULTS: Providing all drivers with the speed-of-processing intervention is the most cost-beneficial option (expected cost per driver = $493.30), even if the cost of the intervention doubles. Sensitivity analysis indicated the effectiveness of the intervention could drop from 86% to 25% and the preventative approach of intervening with all drivers remains the most cost-beneficial strategy. The least cost-beneficial option is almost always re-licensing per usual (expected cost per driver = $1,562.84). CONCLUSION: Screening drivers upon license renewal is not currently beneficial because the available technology cannot consistently identify drivers at risk for a collision. However, the speed-of-processing intervention has demonstrated efficacy in improving driving competence (Roenker et al., 2003) and is a non-invasive, moderate-cost intervention that has the potential to protect the safety and mobility, as well as the financial interests, of older drivers and the community at large.

Accidents, Traffic↗
PubMed1979

Processing determinants of reading speed.

Two groups of university undergraduates differing in reading ability were tested on a number of reaction-time tasks designed to determine the speed of encoding visual information at several different levels. In addition, the subjects were given tests of sensory functions, verbal and quantitative reasoning ability, short-term auditory memory span, and ability to comprehend spoken text. The groups did not differ on the sensory tests. However, the faster reader group had faster reaction times on all of the reaction-time tasks, and the size of the fast-reader advantage increased with the mean reaction time. Faster readers also performed more accurately in verbal and quantitative reasoning, short-term auditory memory, and speech comprehension. Regression analyses suggested that the ability to comprehend spoken material and speed of accessing overlearned memory codes for visually presented letters represented two important independent correlates of reading ability in our sample of subjects. Two variables reflecting these abilities--the percentage of correct answers to a listening comprehension test and the reaction time for correct responses in a letter-matching task--accounted for nearly all of the variance in reading ability tapped by both of our reading tests. In a second experiment, no reaction-time difference was found between fast and average readers in a matching task requiring no long-term memory code access but considerable visual information processing as indexed by overall mean reaction time. The results supported the conclusion that one skill allowing fast readers to capture more information from each reading fixation is faster access to letter codes from print.

Concept Formation↗
PubMed2002

Neuropsychological evaluation of deficits in executive functioning for ADHD children with or without learning disabilities.

This study investigates multiple aspects of executive functioning in children with attention deficit/hyperactivity disorder (ADHD). These areas include attentional components, impulsiveness, planning, and problem solving. The rationale of the study is based on neurophysiological studies that suggest frontal lobe dysfunction in ADHD. As frontal lobe functioning is related to abilities in executive control, ADHD is hypothesised to be associated with deficits in various areas of executive functioning. The specific effect of comorbidity of learning disability (LD) was also investigated. Eighty-three children with ADHD and 29 age-matched controls (age 7-13) participated in the study. A battery of neuropsychological tests was utilized to evaluate specific deficits in speed of processing, selective attention, switching attention, sustained attention, attentional capacity, impulsiveness, planning and problem solving. Findings indicated that children with ADHD have slower verbal responses and sustained attention deficit. Deficits in selective attention and attentional capacity observed were largely related to the presence of LD. No specific deficit associated with ADHD or the comorbidity of LD was identified in switching attention, impulsiveness, planning, and problem solving. These results revealed that ADHD is not associated with a general deficit in executive functioning. Instead, ADHD is related to a specific deficit in regulation for attentional resources. The importance of isolating the deficit related to LDs for examining the specific deficit associated with ADHD is highlighted. Results also emphasised the importance of isolating the effect of lower level of abilities (e.g., speed of processing) and the utilization of specific definition for the examination of executive functions.

Attention↗
PubMed1995

NASA high performance computing, communications, image processing, and data visualization-potential applications to medicine.

High-speed information processing technologies being developed and applied by the Jet Propulsion Laboratory for NASA and Department of Defense mission needs have potential dual-uses in telemedicine and other medical applications. Fiber optic ground networks connected with microwave satellite links allow NASA to communicate with its astronauts in Earth orbit or on the moon, and with its deep space probes billions of miles away. These networks monitor the health of astronauts and or robotic spacecraft. Similar communications technology will also allow patients to communicate with doctors anywhere on Earth. NASA space missions have science as a major objective. Science sensors have become so sophisticated that they can take more data than our scientists can analyze by hand. High performance computers--workstations, supercomputer and massively parallel computers are being used to transform this data into knowledge. This is done using image processing, data visualization and other techniques to present the data--one's and zero's in forms that a human analyst can readily relate to and understand. Medical sensors have also explored in the in data output--witness CT scans, MRI, and ultrasound. This data must be presented in visual form and computers will allow routine combination of many two dimensional MRI images into three dimensional reconstructions of organs that then can be fully examined by physicians. Emerging technologies such as neural networks that are being "trained" to detect craters on planets or incoming missiles amongst decoys can be used to identify microcalcification in mammograms.

Image Interpretation, Computer-Assisted↗
PubMed1990

Motion segregation from speed differences: evidence for nonlinear processing.

This paper examines observers' ability to detect regions delimited by speed differences. Several types of translational motion stimuli, of varying task difficulty, were tested over a wide range of base speeds. The observer's task was to decide whether a region of dots moving at a different speed from the base speed was located to the left or right of the display's center. Both increments (dots within the test region moving faster than the base speed) and decrements (dots within the test region moving slower than the base speed) were examined. When the task was relatively difficult the following asymmetries were found: at slow base speeds, incremental thresholds were lower than decremental thresholds; at fast base speeds, the reverse pattern occurred. When the task was relatively easy, no consistent asymmetries were found. It is proposed that the visual system encodes speed through a sigmoidal nonlinear response function, and it is shown that this one nonlinearity can be used to explain results for both easy and difficult tasks.

Differential Threshold↗
PubMed2000

Evaluation of a new F speed dental X-ray film. The effect of processing solutions and a comparison with D and E speed films.

OBJECTIVE: To compare the properties of a new speed group F intra-oral X-ray film with those of three well established types both from groups D and E, and evaluate the impact of six commercially available processing solutions. METHODS: Four types of dental X-ray film, Flow (Flow X-ray, West Hempstead, NY, USA), speed group F, Ektaspeed Plus (Eastman Kodak, Rochester NY, USA) and M2 Comfort (AgfaGevaert, Morstel, Belgium), both speed group E, and Ultra-speed (Eastman Kodak), speed group D, were exposed under standardised conditions and processed in six different processing solutions. Base plus fog density, characteristic curves, film density, speed, average gradient, contrast and latitude and spatial resolution were calculated. RESULTS: The choice of processing chemistry affected radiographic characteristics including speed grouping. The new F film was consistently the fastest. M2 Comfort could achieve F speed and Ultra-speed achieved E speed using Automat XR chemicals. The speed of Ektaspeed Plus was independent of the automatic processing solution used. Ultra-Speed film had the lowest base plus fog density and the widest latitude. Film contrast was similar irrespective of the film and solution combination. CONCLUSIONS: The choice of processing chemistry can affect radiographic characteristics. The new F film reduces patient exposure by one-half compared with E speed film with no detriment to image quality.

Absorptiometry, Photon↗
PubMed1988

Impulsivity and speed-accuracy tradeoffs in information processing.

Despite its theoretical importance for such areas of research as reflection-impulsivity (Kagan, 1966), there is little evidence to support the assumption that individual differences in the personality trait of impulsivity are associated with differences in the willingness to sacrifice accuracy for speed of information processing. The present studies explored this association further. In Experiment 1, high, medium, and low impulsives (identified by self-report) performed a visual-comparison task under conditions differing in the monetary payoff for speed relative to accuracy. High impulsives were consistently faster and less accurate than other subjects. However, an analysis based on Sternberg's (1969) additive-factor method indicated that high impulsives performed at least one stage of information processing as slowly and accurately as other subjects. In Experiment 2, it was found that high impulsives were actually more accurate than low impulsives when all subjects were required to process information extremely rapidly. Experiment 3 identified the response execution stage as one that high impulsives carry out just as slowly and accurately as other individuals. The data from these experiments pose problems for a simple speed-accuracy tradeoff model of impulsive cognitive functioning.

Adult↗
PubMed2004

A fast low-power optical memory based on coupled micro-ring lasers.

The increasing speed of fibre-optic-based telecommunications has focused attention on high-speed optical processing of digital information. Complex optical processing requires a high-density, high-speed, low-power optical memory that can be integrated with planar semiconductor technology for buffering of decisions and telecommunication data. Recently, ring lasers with extremely small size and low operating power have been made, and we demonstrate here a memory element constructed by interconnecting these microscopic lasers. Our device occupies an area of 18 x 40 microm2 on an InP/InGaAsP photonic integrated circuit, and switches within 20 ps with 5.5 fJ optical switching energy. Simulations show that the element has the potential for much smaller dimensions and switching times. Large numbers of such memory elements can be densely integrated and interconnected on a photonic integrated circuit: fast digital optical information processing systems employing large-scale integration should now be viable.

Journal Article↗
PubMed1993

Frequency-related differences in the speed of human auditory processing.

Three experiments were performed, two comparing the peak latencies of auditory evoked potentials (AEPs) elicited by 250 Hz and 4000 Hz tone pips and a third comparing simple reaction times (RTs) to the same stimuli. In the AEP experiments, the latencies of brainstem, middle and long-latency components were delayed following 250 Hz tone pips in comparison with the latencies of the same components evoked by loudness-matched 4000 Hz tones. Frequency-related latency differences increased with component latency, ranging from less than 1.0 ms for wave V of the brainstem AEP, to more than 20.0 ms for the cortical N1 component. Interpeak latency differences were also significantly lengthened following the 250 Hz tone pips. In the behavioral study, RTs were 14.6 ms slower following 250 than 4000 Hz tone pips. The results suggest that the time required for the sensory analysis of auditory signals varies inversely with their frequency.

Acoustic Stimulation↗
PubMed1981

Impaired speed of visual information processing in marijuana intoxication.

The authors conducted a double-blind crossover study to investigate the effects of marijuana on visual information processing. The authors used a tachistoscopic paradigm, and the results show no marijuana effect on the critical stimulus duration, a measure of stimulus intake. The visual backward masking data are compatible with a marijuana-induced slowness of information processing from labile unconscious iconic memory to more permanent memory processes. These results are discussed in relation to reports of marijuana's effects on perception and early information processing.

Adult↗
PubMed1998

Familiarity norms for the Boston Naming Test stimuli.

Forty-nine young adults (M age = 22 years) and 30 elderly adults (M age = 69 years) rated the 60 pictorial stimuli from the Boston Naming Test (BNT) on familiarity, providing the first such normative data for these stimuli along this dimension. Participants also made speeded lexical decisions about the word item representations of each BNT picture. B NT word frequency values were also examined in relation to BNT familiarity and speeded lexical decision performance. For both young and elderly adults, lexical decision reaction times to the word representations of BNT stimuli were negatively related to word frequency and familiarity of the BNT pictures. These patterns suggest that increases in word frequency and picture familiarity facilitate (i. e., speed up) the processing of BNT word representations. Furthermore, speed of processing appears to be a relevant dimension of BNT performance, at least when young and elderly adults free from clinical aphasia are involved.

Journal Article↗