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PubMed1996

Age differences in retrieval: further support for the resource-reduction hypothesis.

Age differences in processing resources seem salient to age-related declines in secondary (or "recent") memory. Community-dwelling adults (N = 90, ages 30-80) completed 4 memory tests: Wechsler Memory Scale-Revised (WMS-R) Logical Memory (LM), Cowboy Story (CS), WMS-R Visual Reproductions (VR), and Extended Complex Figure Test (ECFT; Fastenau, in press). Two space-capacity measures (WMS-R Digit Span and Visual Memory Span) and 4 processing speed measures (cancellation and mental-tracking tasks) assessed processing resources. A statistical control procedure was used to isolate retrieval efficiency and measures contributions of age and processing resources to retrieval. A negative relationship between age and retrieval efficiency emerged on all measures (p < .05). The age effect was reduced 60% on LM and CS when processing resources were controlled, eliminated for VR, and unchanged on ECFT. It is possible that visual-spatial retrieval requires fewer processing resources than does verbal retrieval.

Adult↗

PubMedDate not supplied

Toward a research-based assessment of dyslexia: using cognitive measures to identify reading disabilities.

One hundred five participants from a random sample of elementary and middle school children completed measures of reading achievement and cognitive abilities presumed, based on a synthesis of current dyslexia research, to underlie reading. Factor analyses of these cognitive variables (including auditory processing, phonological awareness, short-term auditory memory, visual memory, rapid automatized naming, and visual processing speed) produced three empirically and theoretically derived factors (auditory processing, visual processing/speed, and memory), each of which contributed to the prediction of reading and spelling skills. Factor scores from the three factors combined predicted 85% of the variance associated with letter/sight word naming, 70% of the variance associated with reading comprehension, 73% for spelling, and 61% for phonetic decoding. The auditory processing factor was the strongest predictor, accounting for 27% to 43% of the variance across the different achievement areas. The results provide practitioner and researcher with theoretical and empirical support for the inclusion of measures of the three factors, in addition to specific measures of reading achievement, in a standardized assessment of dyslexia. Guidelines for a thorough, research-based assessment are provided.

Adolescent↗

PubMed2005

Aerobic fitness and neurocognitive function in healthy preadolescent children.

PURPOSE: We investigated the relationship between age, aerobic fitness, and cognitive function by comparing high- and low-fit preadolescent children and adults. METHOD: Twenty-four children (mean age = 9.6 yr) and 27 adults (mean age = 19.3 yr) were grouped according to their fitness (high, low) such that four approximately equal groups were compared. Fitness was assessed using the Fitnessgram test, and cognitive function was measured by neuroelectric and behavioral responses to a stimulus discrimination task. RESULTS: Adults exhibited greater P3 amplitude at Cz and Pz sites, and decreased amplitude at the Oz site compared with children. High-fit children had greater P3 amplitude compared with low-fit children and high- and low-fit adults. Further, adults had faster P3 latency compared with children, and high-fit participants had faster P3 latency compared with low-fit participants at the Oz site. Adults exhibited faster reaction time than children; however, fitness interacted with age such that high-fit children had faster reaction time than low-fit children. CONCLUSION: These findings suggest that fitness was positively associated with neuroelectric indices of attention and working memory, and response speed in children. Fitness was also associated with cognitive processing speed, but these findings were not age-specific. These data indicate that fitness may be related to better cognitive functioning in preadolescents and have implications for increasing cognitive health in children and adults.

Adult↗

PubMed2002

Fractionated simple and choice reaction time in children with prenatal exposure to alcohol.

BACKGROUND: The present study investigated central and peripheral processing speed using simple reaction time (SRT) and choice reaction time (CRT) tasks in children who were exposed to alcohol in utero compared with control subjects. Each RT interval was fractionated into premotor and motor components to assess the central processing of stimulus information and peripheral motor unit recruitment, respectively. METHODS: Eleven children with confirmed prenatal alcohol exposure (ALC) and 13 control subjects (NC), aged 5 to 10 years, completed 20 trials of both SRT and CRT tasks. Muscle activity was recorded from the biceps brachii muscle of each arm using electromyography to facilitate the fractionating of RT into premotor and motor components. RESULTS: ALC children exhibited significantly slower premotor RTs during the CRT task. Motor RTs were also slower for the ALC group during both SRT and CRT tasks. ALC children exhibited greater response variability compared with control subjects; however, the magnitude of this variability was not greater than would be predicted, given their lengthened RTs. In contrast, response variability was greater for young children of both groups even after accounting for mean RT. Significant age-related differences in premotor and motor RTs were also observed. CONCLUSIONS: Alcohol-related increases in CRT were attributable to longer premotor and motor components, reflecting both reduced speed of information processing and peripheral delays in responding. These alterations likely are associated with alcohol-related changes in the central and peripheral nervous systems that could impede or slow neuronal transmission.

Age Factors↗

PubMed1995

Selective influences of age and speed on associative memory.

Data from three studies involving a continuous paired associates task performed by adults of different ages were analyzed in an attempt to identify how processing speed might mediate age-related differences in associative memory. Age differences were found in measures postulated to represent encoding and consolidation processes, but not in a measure presumed to reflect rate of forgetting. It is suggested that increased age is associated with a reduction in the speed of executing processes concerned with establishing a stable internal representation, but not with an alteration in the rate at which encoded information is lost as a function of time or subsequent processing.

Adult↗

PubMed2005

Top-down enhancement and suppression of the magnitude and speed of neural activity.

Top-down modulation underlies our ability to selectively attend to relevant stimuli and to ignore irrelevant stimuli. Theories addressing neural mechanisms of top-down modulation are driven by studies that reveal increased magnitude of neural activity in response to directed attention, but are limited by a lack of data reporting modulation of neural processing speed, as well as comparisons with a perceptual (passive view) baseline necessary to evaluate the presence of enhancement and suppression. Utilizing functional MRI (fMRI) and event-related potential recordings (ERPs), we provide converging evidence that both the magnitude of neural activity and the speed of neural processing are modulated by top-down influences. Furthermore, both enhancement and suppression occur relative to a perceptual baseline depending on task instruction. These findings reveal the fine degree of influence that goal-directed attention exerts upon activity within the visual association cortex. We further document capacity limitations in top-down enhancement corresponding with working memory performance deficits.

Adult↗

PubMed2004

Effects of diffuse axonal injury on speed of information processing following severe traumatic brain injury.

To test the hypothesis that slowed information processing in traumatic brain injury is related to diffuse axonal injury (DAI), the authors compared 10 patients with predominant DAI (diffuse group) and minimal DAI (mixed injury group) on the Symbol Digit Modalities Test, simple and choice reaction time, Trail Making Tests A and B, and the Stroop Neuropsychological Screening Test. The diffuse group was slower than the mixed injury and control groups on basic speed of processing tasks. This difference was not apparent on complex speeded tasks once basic speed of processing was controlled for. The diffuse group's slower speed of processing was not accounted for by differences in injury severity, age, or time postinjury. The diffuse group showed greater recovery over time.

Adolescent↗

PubMed2006

A single motion system suffices for global-motion perception.

Global-motion perception is the perception of coherent motion in a noisy motion stimulus. Thresholds for coherent motion perception were measured for different combinations of signal and noise speeds. Previous research [Edwards, M., Badcock, D. R., & Smith, A. T. (1998). Independent speed-tuned global-motion systems. Vision Research, 38 (11), 1573-1580; Khuu, S. K., & Badcock, D. R. (2002). Global speed processing: evidence for local averaging within, but not across two speed ranges. Vision Research, 42 (28), 3031-3042.] showed that thresholds were elevated when signal and noise speeds were similar, but not when they were different. The regions of increased threshold values for low and high signal speeds showed little overlap. On the basis of this evidence two independent speed-tuned systems were proposed: one for slow and one for fast-motion. However, in those studies only two signal speeds were used. We expanded the results by measuring threshold-curves for four different signal speeds. Considerable overlap of the threshold-curves was found between conditions. These results speak against a bipartite global-motion system. Model simulations indicate that present and previous experimental results can be produced by a single motion system providing that the mechanisms within it are speed-tuned.

Humans↗

PubMed2006

Interference effects in a numerical Stroop paradigm in 9- to 12-year-old children with ADHD-C.

Attention deficit hyperactivity disorder (ADHD) is characterized by deficient self-regulation, poor attentional control, and poor response inhibition. To date, however, the extent to which these deficits affect basic interference control remains a matter of controversy. Secondly, ADHD has been reported to be associated with arithmetic deficits. It remains unclear whether such deficits are a secondary consequence of the above-mentioned characteristics of ADHD or whether basic numerical magnitude representations are also affected. In the present study we attempted to investigate these issues using a basic numerical interference paradigm. Nine- to twelve-year-old children with ADHD-C (attention-deficit hyperactivity-disorder combined type) and control children without ADHD (each n = 16) were presented with two digits of possibly different physical sizes (e.g., 3 7). This numerical Stroop task requires subjects to make a magnitude classification concerning either the physical or the numerical stimulus dimension. The irrelevant dimension can be congruent (same response), incongruent (different response), or neutral (no response association). Children with ADHD-C performed worse than control children in most analyses. The most important finding was a significant interaction of congruity effects with group in the numerical comparison task. Children with ADHD-C tended to show larger congruity and interference effects than controls, and these were not attributable to a speed-accuracy trade-off. The results might reflect differential processing speeds, or a different degree of automatic activation of physical and numerical magnitudes in children with and without ADHD-C. Alternative explanations, such as insufficient inhibition of selective (domain-specific) attention are also discussed.

Attention↗

PubMed2006

The role of sedation tests in identifying sedative drug effects in healthy volunteers and their power to dissociate sedative-related impairments from memory dysfunctions.

The study investigated whether four specified drugs would show similar patterns on tests considered to measure sedation. In addition, their drug-effect patterns on sedation and memory performance were compared to determine whether the sedative effects could be differentiated from the memory effects. Two double-blind, placebo-controlled, crossover studies, each with 16 healthy volunteers, were performed, one testing lorazepam (2.5 mg) and mirtazapine (15 mg) and the other olanzapine (10 mg) and haloperidol (2.5 mg). Subjective sedation was assessed by means of visual analogue scales (VAS) and objective sedation using a simple-reaction-time (SRT) task and a choice-reaction-time (CRT) task, code substitution (symbol digit substitution test (SDST)) and the peak velocity of saccadic eye movements (SEM). A verbal memory test (VMT) was administered to evaluate memory capacity. Apart from haloperidol, all drugs proved to impair performance on all five sedation indices. Contrary to the VAS, the objective measures yielded different response profiles. Two types of drug-effect patterns emerged: one for greater impairments in response speed (SRT, SEM) and one for greater impairments in information processing (CRT, SDST). Lorazepam and olanzapine impeded memory performance, whereas mirtazapine did not. With the use of standardized scores it proved possible to differentiate between the size of the effects of the drugs on the sedation and memory tests. To accurately assess the level and nature of sedation and to differentiate sedation from memory impairments different types of sedation measures are required. Besides studying the subjective effects, it is recommended to also test psychomotor responses and information processing speed.

Adult↗

PubMedDate not supplied

Not all reading disabilities are alike.

In this article, reading disability is defined broadly to refer to below-average achievement in reading comprehension as assessed by a standardized test. With our research we tried to answer the question of whether all children with reading disability share a common etiology of deficient phonology, or constitute heterogeneous groups. The answer to this question was sought in four studies that examined reading disabilities from the perspective of componential skills of reading. In Part 1, the results of the first study are reported. A principal-components analysis of the performance of 139 children from Grades 3, 4, and 6 on reading-related tasks yielded two factors: decoding and comprehension. However, factor analyses conducted for each grade separately indicated that orthographic skill and processing speed could possibly constitute a third component. The orthography-speed factor emerged as a factor only in the 6th grade. Part 2 of this article reports the findings of three studies that analyzed the componential skills profiles of poor readers. It was found that the poor readers constituted heterogeneous groups and that four different types of poor readers could be identified with deficiency in any one of the following skills: (a) decoding only, (b) comprehension only, (c) a combination of decoding and comprehension, and (d) a combination of orthographic processing and reading speed. It was also found that the criteria used in selecting poor readers influenced the distribution of the ratio of the four types of poor readers within any given group.

Auditory Perception↗

PubMed2003

Electrophysiological comparison of grammatical processing and semantic processing of single spoken nouns.

Access to meaning from speech input is a high-speed process. However, models of word comprehension stipulate that words must be analyzed at phonological, grammatical and semantic levels. Here we used event-related potentials (ERPs) to compare on-line semantic categorization (natural/manufactured) and grammatical gender categorization (masculine/feminine) of spoken monosyllabic French noun pairs. Twenty four native French speakers were instructed to spot pairs of nouns in which both stimuli pertained to a category specified prior to each block. They could make a decision either after processing the first noun (i.e., ignore the second, Release condition), or after processing both (Hold condition). Virtually identical N4 components affecting Hold and Release ERPs in relation to category expectations were elicited by the first noun in both the tasks. Their topography was intermediary between that of the N400 and that of the Left Anterior Negativity. Despite shorter Release reaction times (RTs) for gender decisions than semantic ones, Release and Hold ERPs diverged 84 ms earlier in the semantic context than in the gender context, indicating faster onset for the processing of meaning. Conversely, the offset of Hold/Release differences was observed 42 ms earlier in the gender task than in the semantic task, suggesting an earlier completion for gender categorization. In sum, electrophysiological differences induced by semantic operations commenced earlier but recovered later than those relating to grammatical gender analysis. In convergence with previous Lateralized Readiness Potential and N200 studies, our results suggest that conscious semantic access can precede access to other types of lexical information during word comprehension in highly controlled conditions.

Adult↗

PubMed1994

Proportional slowing and addition speed in old and young adults.

An addition and copying task was used to compare processing speed in young and old adults. Consistent with previous studies, no age differences in the problem-size effect were observed (Geary & Wiley, 1991). However, the old adults were slower overall, and an analysis of the distributions of old and young individuals indicated that the form of this slowing was proportional. These analyses also demonstrated that proportional slowing was uniform in the old adults, such that the fastest and slowest old individuals were slowed by the same factor. Because the regression of old-young mean response times can be insensitive to differential age effects, comparisons of old and young distributions are recommended to support claims regarding proportional slowing and uniformity of age effects across individuals. Finally, the results suggest that requiring Ss to initiate a new operation produced a larger age effect than requiring Ss to repeat an operation.

Adult↗

PubMed2003

Timing accuracy in motion extrapolation: reverse effects of target size and visible extent of motion at low and high speeds.

By varying target size, speed, and extent of visible motion we examined the timing accuracy in motion extrapolation. Small or large targets (0.2 or 0.8 deg) moved at either 2.5, 5, or 10 deg s(-1) across a horizontal path (2.5 or 10 deg) and then vanished behind an occluder. Observers responded when they judged that the target had reached a randomly specified position between 0 and 12 deg. With higher speeds, the timing accuracy (the reverse of absolute error) was better for small than for large targets, and for long than for short visible extents. With low speed, these effects were reversed. In addition, while long visible extents yielded a greater accuracy at high than at low speeds, for short extents the accuracy was much better with the low speed. The findings suggest that, when extrapolating motion with targets and visible extents of different sizes, the visual system implements different scaling algorithms depending on target speed. At higher speeds, processing of visible and occluded motion is likely to share a common scaling mechanism based on velocity transposition. Reverse effects for target size and extent of visible motion at low and high speeds converge with the assumption of two distinct speed-tuned motion-processing mechanisms in human vision.

Humans↗

PubMed2006

Global motion mechanisms compensate local motion deficits in a patient with a bilateral occipital lobe lesion.

Successive stages of cortical processing encode increasingly more complex types of information. In the visual motion system this increasing complexity, complemented by an increase in spatial summation, has proven effective in characterizing the mechanisms mediating visual perception. Here we report psychophysical results from a motion-impaired stroke patient, WB, whose pattern of deficits over time reveals a systematic shift in spatial scale for processing speed. We show that following loss in sensitivity to low-level motion direction WB's representation of speed shifts to larger spatial scales, consistent with recruitment of intact high-level mechanisms. With the recovery of low-level motion processing WB's representation of speed shifts back to small spatial scales. These results support the recruitment of high-level visual mechanisms in cases where lower-level function is impaired and suggest that, as an experimental paradigm, spatial summation may provide an important avenue for investigating functional recovery in patients following damage to visually responsive cortex.

Aged↗

PubMed1999

Insulin-like growth factor-I and cognitive function in healthy older men.

The GH/insulin-like growth factor-I (GH/IGF-I) axis is known to be involved in aging of physiological functions. Recent studies indicate that the GH/IGF-I axis may be associated with cognitive functioning. The aim of the present study was to determine whether the age-related decline in circulating levels of IGF-I, as an index of anabolic status, is associated with cognitive functions that are known to decline with aging, but not with cognitive functions not sensitive to aging. Twenty five healthy older men with well-preserved functional ability participated in the study. We also administered neuropsychological tests of general knowledge, vocabulary, basic visual perception, reading ability, visuoconstructive ability, perceptual-motor speed, mental tracking, and verbal long-term memory. Performance on the last four tests decline with aging, whereas the first four of these tests have been shown not to be sensitive to cognitive aging. Mean age of the subjects was 69.1 +/- 3.4 (SD) yr (range 65-76 yr), their mean body mass index was 27.0 +/- 2.4 kg/m2, and their mean IGF-I level was 122 ng/mL (range: 50-220). We found IGF-I levels to be significantly associated with the performances (controlled for education) on the Digit Symbol Substitution test (r = 0.52, P = 0.009) and the Concept Shifting Task (r = -0.55, P = 0.005), which measure perceptual-motor and mental processing speed. Subjects with higher IGF-I levels performed better on these tests, performance on which is known to decline with aging. In conclusion, the results of this study support the hypothesis that circulating IGF-I may play a role in the age-related reduction of certain cognitive functions, specifically speed of information processing.

Aged↗

PubMed1996

Uncoupling learning from initial recall: the relationship between speed and memory deficits in old age.

Nettelbeck & Rabbitt (1992) found that measures of speed of performance with low knowledge requirements (four-choice reaction time, inspection time and coding-substitution) accounted substantially for age-related changes among 104 persons aged from 54 to 85 years in a number of more complex cognitive measures reflecting general fluid ability. However, the numbers of words recalled from a list after either a single brief viewing of each word, or following a cumulative learning procedure across four trials, provided an exception to this general trend, leading to the conclusion that some aspects of memory may be independent of mental speed. A follow-up of 82 of the same people 18-20 months later was designed to partition performance in a similar cumulative learning procedure into an initial first recall component and a subsequent learning component. This was accomplished by fitting individual cumulative learning data with a hyperbolic power function which met the theoretical requirement of defining separate initial recall and learning parameters. These parameters were found to be independent and it was concluded that learning involved rehearsal, whereas first recall did not. The hyperbolic power function provided a good account for 92 per cent of individual cases. Analyses which combined Nettelbeck & Rabbitt's (1992) data with new measures confirmed the reliability of these authors' results. Furthermore, it was found that first recall, but not learning, was mediated by processing speed. Learning was relatively unaffected by age-related slowing in mental speed, suggesting that Nettelbeck & Rabbitt's results were the consequence of a strong rehearsal component in their memory tasks. Thus, while mental slowing is clearly one important aspect of cognitive decline during old age, it does not constitute a sufficient explanation for changes in all areas of cognitive functioning. Specifically, age-decline in rate of learning with rehearsal appeared to be independent of slowing in speed of information processing.

Aged↗

PubMed2006

Sensitometric comparisons of Insight and Ektaspeed Plus films: effects of chemical developer depletion.

The aim of this study was to compare the sensitometric properties of Insight and Ektaspeed Plus radiographic films manually and automatically processed using fresh and depleted chemical solutions. Ten sets of each type of film were obtained (1 set = 5 films), 5 sets being manually processed and 5 sets being automatically processed. A total of 100 films (50 Ektaspeed Plus and 50 Insight film) were exposed and developed. The first two sets of each film type were developed in fresh chemicals (one set per each type of processing), on the first day of the experiment. The other sets were processed in the same progressively depleted solutions once a week until the end of experiment, which was completed within 4 weeks. Characteristic curves were constructed to compare the sensitometric properties of the films: contrast, latitude and speed. Processing solution depletion had different effects on manually and automatically developed films, which was confirmed by the changes in the form of the characteristic curves in the third week of the automatic processing and fourth week of the manual processing. Ektaspeed Plus showed 11% reduction in contrast values for manual processing and 53% for automatic processing, while Insight contrast values showed a reduction of 25% and 59%, respectively. Insight film, however, showed lesser loss of speed and lesser increase of latitude than Ektaspeed Plus. In conclusion, chemical depletion in automatic film processing was faster than in manual developing. In depleted chemicals, both types of films had an increase in latitude values and a decrease in speed and contrast. Insight was more resistant than Ektaspeed Plus to decrease in speed and latitude when processed using older chemicals, whereas contrast in Ektaspeed Plus was comparatively more stable.

Solutions↗