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PubMed1999

Age-related differences in global-local processing: stability of laterality differences but disproportionate impairment in global processing.

Visual processing of global and local features differentially engages the right and left hemispheres and requires different allocations of spatial attention. To further understand the decline in visual cognition and visual attention with age, we studied the performance of healthy young subjects and healthy elders on a global-local figures task. The results showed that elders processed global images more quickly when presented in the left visual field and local images in the right visual field, similarly to the young controls. However, we did observe a significant impairment in the elders' ability to process global figures compared with local figures, despite there being no overall difference between global and local processing speed among the young. It is thought that this age-related decline in global processing is related to the narrowed attentional field that can be demonstrated in other age-related visual processing declines such as visual search and useful field of view.

Adult↗

PubMed1990

A study of humor and the right hemisphere.

65 male and 65 female subjects rated 32 jokes for funniness and solved 14 visually displayed mental-rotation problems. Subjects with faster mental-rotation times tended to rate the jokes as funnier, which is consistent with previous evidence implicating the right hemisphere in the processing of humor. The hypothesis that right-hemisphere processing speed or problem-solving ability are the common factors in mental rotation and humor processing is discussed. Furthermore, sex differences suggest that gender-differentiating preferences for type of humor and mental-rotation abilities may involve basic cognitive functions.

Adult↗

PubMed1990

The speed of mental rotation as a function of problem-solving strategies.

40 subjects solved seven identical and seven mirror image visually-displayed mental-rotation problems, a measure of right hemisphere processing. Subjects who indicated that they had inferred that, if two objects were not identical, then they must be mirror images showed faster rotation times. This evidence supports the hypothesis that expedient problem-solving strategies may contribute to right-hemisphere processing speed as measured by mental rotation. That mental rotation and humor processing may draw on the same right hemisphere processes is also discussed.

Adult↗

PubMed1992

On estimating processing variance: commentary and reanalysis of Kail's "Developmental functions for speeds of cognitive processes".

A recent paper by Kail (1988) in this journal appears to contain a significant error in the data analysis. The "goodness-of-fit" coefficients reported which suggest that overall about 94% of the variance can be accounted for by the model seem to be a substantial overestimation as a result of inappropriate procedures for statistical modeling. Using the data made available to us by Kail, we have reanalyzed these results. The corrected values range from 0.9 to 92.1% for the individual tasks with an overall average between 40 and 60%. We suggest that the support for the original conclusions is considerably weaker than reported.

Aptitude↗

PubMed1996

Working memory and supervisory control after severe closed-head injury. A study of dual task performance and random generation.

Survivors of severe closed-head injury (CHI) frequently suffer from slowed information processing. Whether supervisory strategies are additionally impaired remains a point of debate. The first part of this study employed a self-paced dual task; the second part, a random generation task, performed at a paced rate, under single and dual task conditions. A measure of information processing speed was used as a covariate in statistical analysis. In the first experiment, in addition to slow processing, patients performed slightly poorer than controls on each task. In the second experiment, patients' performance (one randomness index in single task condition, and processing of dual task) was impaired even after statistical control of slow processing. These results suggest that there is at least some degree of impairment in supervisory strategies in addition to, but independent of, slowed processing. The clinical significance of this finding is discussed.

Adolescent↗

PubMed1997

Attention deficits in stroke patients with aphasia.

Attentional capacity and sustained attention were investigated in 21 aphasic stroke patients and 21 non-brain-damaged patients. Attentional capacity was assessed using a series of reaction time (RT) tasks. The aphasic patients demonstrated impaired attentional capacity as shown by slower processing speed than the non-brain-damaged group (p < .01) and greater increases in RT with increased processing load (p < .05). Similar patterns were found for both verbal and spatial material. There was no significant relationship between severity of auditory comprehension deficits and attentional capacity. Sustained attention was assessed using a cognitive vigilance task requiring identification of a target letter presented infrequently over 32 minutes. Both the aphasic and the non-brain-damaged group demonstrated a decline in performance with time on task as shown by a steady increase in RTs (p < .0001), but the decline was equivalent across the groups. Thus, the aphasic group did not show a specific deficit in the ability to sustain attention.

Aphasia↗

PubMed2000

Inhibitory control in children with traumatic brain injury (TBI) and children with attention deficit/hyperactivity disorder (ADHD).

The behavioural and cognitive sequelae of traumatic brain injury (TBI) have features in common with attention deficit/hyperactivity disorder (ADHD), best characterized by deficits in response inhibition.The performance was, therefore, examined of 27 children with TBI, 31 children with developmental ADHD, and 26 matched controls aged 8-12, on two inhibition tasks: the Stop-Signal Task and a Delayed-Response-Task. Children with TBI and children with ADHD showed a pervasive deficit in their inhibitory control processes with respect to inhibition of both pre-potent and on-going responses. In addition, children with TBI were found to suffer from a general slowing of their information processing, which was not correlated with the inhibition deficit. TBI children with and without a secondary ADHD differed only tendentially in their Mean Go-Reaction time in the stop-task. However, subdividing TBI children according to actigraph data into hypo-, hyper- and normokinetic subgroups revealed that the hyperactive TBI children had inhibitory deficit patterns that were similar to children with developmental ADHD. It is concluded that slowing of information processing speed seems to be a general consequence of TBI in childhood, whereas slowing of the stop-processes or inhibitory deficits, specifically, are associated with post-injury hypo- or hyperactivity.

Attention Deficit Disorder with Hyperactivity↗

PubMed2006

Digitally reconstructed radiograph generation by an adaptive Monte Carlo method.

Digitally reconstructed radiograph (DRR) generation is an important step in several medical imaging applications such as 2D-3D image registration, where the generation of DRR is a rate-limiting step. We present a novel DRR generation technique, called the adaptive Monte Carlo volume rendering (AMCVR) algorithm. It is based on the conventional Monte Carlo volume rendering (MCVR) technique that is very efficient for rendering large medical datasets. In contrast to the MCVR, the AMCVR does not produce sample points by sampling directly in the entire volume domain. Instead, it adaptively divides the entire volume domain into sub-domains using importance separation and then performs sampling in these sub-domains. As a result, the AMCVR produces almost the same image quality as that obtained with the MCVR while only using half samples, and increases projection speed by a factor of 2. Moreover, the AMCVR is suitable for fast memory addressing, which further improves processing speed. Independent of the size of medical datasets, the AMCVR allows for achieving a frame rate of about 15 Hz on a 2.8 GHz Pentium 4 PC while generating reasonably good quality DRR.

Algorithms↗

PubMed2004

Association between visual attention and mobility in older adults.

OBJECTIVES: To examine the association between visual attention/processing speed and mobility in older adults. DESIGN: Cross-sectional. SETTING: Clinical research unit of a department of ophthalmology. PARTICIPANTS: Three hundred forty-two older adults (aged 55-85) living independently in the community recruited from primary eye care practices. MEASUREMENTS: In addition to demographic, health, and functional information, the following variables were collected at the second annual visit of a prospective study on mobility: a test of visual attention/processing speed; a performance mobility assessment; and self-reported measures of falls, falls efficacy, mobility/balance, and physical activity. RESULTS: Lower scores on visual attention/processing speed were significantly related to poorer scores on the performance mobility assessment, even after adjustment for age, sex, race, education, number of chronic medical conditions, cognitive status, depressive symptoms, visual acuity, and contrast sensitivity (P=.04). Scores on the visual attention/processing speed test were unrelated to the self-reported measures of mobility. CONCLUSION: Results imply that visual attention impairment/slowed visual processing speed in older adults is independently associated with mobility problems. Interventions to reverse or minimize the progression of mobility dysfunction in older adults should take this common aging-related deficit in visual processing into account.

Activities of Daily Living↗

PubMed1997

Mild head injury and speed of information processing: a prospective study of professional rugby league players.

The sensitivity of several short tests of speed of information processing to the effects of mild head injury in rugby league football was investigated. The measures used were the Symbol Digit Modalities Test, the Digit Symbol Substitution Test, and the Speed of Comprehension Test. Two studies were conducted, the first to examine the effect of practice, the second to determine sensitivity to cognitive impairment immediately following injury. The first study established alternate form equivalence and demonstrated that performance on the Speed of Comprehension and Digit Symbol Substitution tests improved with practice, whereas the Symbol Digit Modalities test remained stable. A second study of 10 players who subsequently sustained mild head injuries showed that measures of speed of information processing were sensitive to impairment in the postacute phase, whereas an untimed task of word recognition (Spot-the-Word) was not. Speed of Comprehension was more sensitive to postinjury impairment than either the Digit Symbol Substitution or Symbol Digit Modalities tests. A repeated baseline assessment before injury using the higher score to reflect a player's potential, allowed measurement of impaired performance on sensitive tests.

Acute Disease↗

PubMed1994

A method for studying the generalized slowing hypothesis in children with specific language impairment.

The present work was conducted to demonstrate a method that could be used to assess the hypothesis that children with specific language impairment (SLI) often respond more slowly than unimpaired children on a range of tasks. The data consisted of 22 pairs of mean response times (RTs) obtained from previously published studies; each pair consisted of a mean RT for a group of children with SLI for an experimental condition and the corresponding mean RT for a group of children without SLI. If children with SLI always respond more slowly than unimpaired children and by an amount that does not vary across tasks, then RTs for children with SLI should increase linearly as a function of RTs for age-matched control children without SLI. This result was obtained and is consistent with the view that differences in processing speed between children with and without SLI reflect some general (i.e., non-task specific) component of cognitive processing. Future applications of the method are suggested.

Adolescent↗

PubMed2005

A speeded coding task using a computer-based mouse response.

This study assessed whether a speeded coding task that used a computer-based mouse response (CBMR) format was a measure of general processing speed (Gs). By analyzing the task within a network of tasks representing both traditional Gs tests and reaction time tasks, it was shown that a CBMR test can be used to measure the same construct as traditional paper-and-pencil (PP) tests and that this response format does not introduce variance associated with psychomotor performance. Differences between PP and CBMR formats were observed, and it is argued that these may provide information on individual differences in performance not available from traditional coding tests.

Adult↗

PubMed2005

Fabrication of DNA microarrays onto polymer substrates using UV modification protocols with integration into microfluidic platforms for the sensing of low-abundant DNA point mutations.

We describe the microfabrication and operational characteristics of a simple flow-through biochip sensor capable of detecting low abundant point mutations in K-ras oncogenes from genomic DNA, which carry high diagnostic value for colorectal cancers. The biochip consisted of an allele-specific ligase detection reaction (LDR) coupled to a universal array for interrogating multiple mutations simultaneously from a clinical sample. The integrated sensing platform was micro-manufactured from two different polymers, polycarbonate, PC, which was used for the LDRs, and poly(methyl methacrylate), PMMA, which was used to build the microarray. Passive elements were hot embossed into the PC and PMMA microchips and then, the chips assembled into a three-dimensional architecture with the interconnect fabricated from an elastomer, poly(dimethylsiloxane), PDMS, to produce a leak-free connection between the biochips. The array in PMMA was produced using a photomodification process, which involved three steps; (1) UV (254 nm) exposure of the polymer surface; (2) EDC coupling of amine-terminated oligonucleotide probes to the surface (via an amide bond) and; (3) washing of the surface. The LDR/hybridization flow-through biochip performed the entire assay at a relatively fast processing speed: 6.5 min for on-chip LDR, 10 min for washing, and 2.6 min for fluorescence scanning (total processing time=19.1 min) and could screen multiple mutations simultaneously for high throughput applications at a level of one mutant sequence in 100 wild-type sequences.

Biosensing Techniques↗

PubMedDate not supplied

Modeling and analysis of the affinity filtration process, including broth feeding, washing, and elution steps.

Affinity filtration is a developing protein purification technique that combines the high selectivity of affinity chromatography and the high processing speed of membrane filtration. In this work a lumped kinetic model was developed to describe the whole affinity filtration process, including broth feeding, contaminant washing, and elution steps. Affinity filtration experiments were conducted to evaluate the model using bovine serum albumin as a model protein and a highly substituted Blue Sepharose as an affinity adsorbent. The model with nonadjustable parameters agreed fairly to the experimental results. Thus, the performance of the affinity filtration in processing a crude broth containing contaminant proteins was analyzed by computer simulations using the lumped model. The simulation results show that there is an optimal protein loading for obtaining the maximum recovery yield of the desired protein with a constant purity at each operating condition. The concentration of a crude broth is beneficial in increasing the recovery yield of the desired protein. Using a constant amount of the affinity adsorbent, the recovery yield can be enhanced by decreasing the solution volume in the stirred tank due to the increase of the adsorbent weight fraction. It was found that the lumped kinetic model was simple and useful in analyzing the whole affinity filtration process.

Adsorption↗

PubMed1995

Speaking rate, articulatory speed, and linguistic processing in children and adolescents with severe traumatic brain injury.

Two studies were conducted to examine speaking rate following traumatic brain injury (TBI) in childhood and adolescence. Study 1 focused on longitudinal changes in speaking rate in 9 subjects with severe TBI and their age-matched control subjects. Physical measurements of speaking rate (in syllables/sec) were made from spontaneous speech samples obtained from each subject during three sampling sessions over a 13-month period. Although the average speaking rate of the group with TBI was slower than that of the control group at all three sampling sessions, an examination of the data from individual subject pairs revealed markedly slower speaking rates in only 5 of the 9 subjects with TBI at the final sampling session. The perceptual significance of slowed speaking rates in these 5 subjects was confirmed through subjective ratings by naive listeners. In Study 2, the contributions of two potential causes of slowed speaking rate were explored: reduced articulatory speed and increased pausing believed to be associated with linguistic processing difficulties. It is hypothesized that articulatory speed and linguistic processing speed may contribute independently to slowed speaking rates more than 1 year after TBI.

Adolescent↗

PubMed2006

Balancing and pointing tasks in dyslexic and control adults.

Developmental dyslexia may affect as much as 15% of the population, but the aetiology of the disorder is still being debated. The cerebellar theory of dyslexia proposes that cerebellar dysfunction could lead to the myriad of symptoms seen in dyslexic individuals, both in literacy and non-literacy domains. The cerebellum is crucial to the fluent performance of motor skills. Previous studies have found that dyslexic children are worse than control children on certain motor and balancing tasks. Here the performance of 28 dyslexic compared to 26 control adults on rapid pointing and balancing measures, tasks which are thought to reflect cerebellar function, was investigated. There were no significant differences between the dyslexic and control participants on the balancing tasks or when the speed and accuracy of pointing were analysed separately. However, when the speed and accuracy of pointing were combined, the dyslexic participants showed poorer performance than the controls (p = 0.045). Furthermore, there were significant relationships between performance on the pointing task and literacy skills, and regression analysis showed that the error and speed of pointing contributed significantly to the variance in literacy skill. The implications for the role of the cerebellum and processing speed in dyslexia are discussed.

Adolescent↗

PubMed2001

Walking or talking? Behavioral and neurophysiological correlates of action verb processing.

Brain activity elicited by visually presented words was investigated using behavioral measures and current source densities calculated from high-resolution EEG recordings. Verbs referring to actions usually performed with different body parts were compared. Behavioral data indicated faster processing of verbs referring to actions performed with the face muscles and articulators (face-related words) compared to verbs referring to movements involving the lower half of the body (leg-related words). Significant topographical differences in brain activity elicited by verb types were found starting approximately 250 ms after word onset. Differences were seen at recording sites located over the motor strip and adjacent frontal cortex. At the vertex, close to the cortical representation of the leg, leg-related verbs (for example, to walk) produced strongest in-going currents, whereas for face-related verbs (for example, to talk) the most in-going activity was seen at more lateral electrodes placed over the left Sylvian fissure, close to the representation of the articulators. Thus, action words caused differential activation along the motor strip, with strongest in-going activity occurring close to the cortical representation of the body parts primarily used for carrying out the actions the verbs refer to. Topographically specific physiological signs of word processing started earlier for face-related words and lasted longer for verbs referring to leg movements. We conclude that verb types can differ in their processing speed and can elicit neurophysiological activity with different cortical topographies. These behavioral and physiological differences can be related to cognitive processes, in particular to lexical semantic access. Our results are consistent with associative theories postulating that words are organized in the brain as distributed cell assemblies whose cortical distributions reflect the words' meanings.

Adolescent↗

PubMed1978

Methamphetamine and diphenhydramine effects on the rate of cognitive processing.

Three cognitive tasks in which performance depends primarily on the rate of cognitive processing were given to 24 male subjects before and after oral doses of methamphetamine (10 mg), diphenhydramine hydrochloride (100 mg), and placebo. Each subject was tested on Monday, Wednesday, and Friday of one week with drug orders balanced across subjects. Compared with placebo and diphenhydramine, methamphetamine increased the rate at which a visual display was scanned for a target stimulus. Methamphetamine affected neither a time-production task nor a divided attention task that required the subject to perform two cognitive tasks in a limited amount of time. This suggests that methamphetamine can increase cognitive processing speed on tasks involving familiar cognitive operations but that an increase is not likely in tasks involving more complicated decision processes. Compared with placebo and methamphetamine, diphenhydramine caused subjects no experience geophysical time as passing more slowly, but the drug had no significant effects on the visual search or divided-attention tasks. This suggests that time perception is more likely to be altered by diphenhydramine than is performance on tasks requiring short periods of rapid cognitive processing.

Adolescent↗