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PubMed2003

Latent change models of adult cognition: are changes in processing speed and working memory associated with changes in episodic memory?

The authors used 6-year longitudinal data from the Victoria Longitudinal Study (VLS) to investigate individual differences in amount of episodic memory change. Latent change models revealed reliable individual differences in cognitive change. Changes in episodic memory were significantly correlated with changes in other cognitive variables, including speed and working memory. A structural equation model for the latent change scores showed that changes in speed and working memory predicted changes in episodic memory, as expected by processing resource theory. However, these effects were best modeled as being mediated by changes in induction and fact retrieval. Dissociations were detected between cross-sectional ability correlations and longitudinal changes. Shuffling the tasks used to define the Working Memory latent variable altered patterns of change correlations.

Aged↗
PubMed2006

A processing speed deficit in dyslexic adults? Evidence from a peg-moving task.

Developmental dyslexia is diagnosed when literacy skills are not commensurate with a person's general cognitive ability and education. While the most common difficulty found in dyslexia is poor phonological processing, many dyslexics are reported to be clumsy, with poor handwriting, suggesting that there may be a motor deficit in dyslexia. To establish whether the motor difficulties described in dyslexic children persist into adulthood, we tested 18 dyslexic adults and 22 control participants on Annett's peg-moving task. The dyslexic participants performed significantly slower than control adults on the peg-moving task with their dominant hands (p=0.004). Furthermore, response times (RTs) during tasks testing component literacy skills correlated with peg-moving ability in the dominant hand in the entire group (orthographic r=0.448, p=0.005; phonological r=0.383, p=0.025). These results indicate that a motor speed deficit in dyslexia may not be simply a sign of developmental delay, but may persist into adulthood. Furthermore, motor speed may be related to the speed at which literacy information is processed.

Adult↗
PubMed2003

Both processing speed and semantic memory organization predict verbal fluency in schizophrenia.

We systematically examined the relationship of both lexical retrieval and semantic memory organization to categorical verbal fluency performance in 40 outpatient schizophrenic subjects and 16 healthy controls. Mean choice reaction time (RT) on a lexical decision task was used as a measure of lexical retrieval efficiency. The complexity of semantic memory organization was measured using a Pathfinder semantic network analysis (calculated as the number of inter-node links obtained from a similarity rating task). In the schizophrenia group only, RT and semantic network links were each significantly negatively correlated with fluency and, together, accounted for 23% of the variance in fluency. RT and links were not significantly correlated with one another. Findings were unrelated to age, sex, education, or medication dose. Controlling for IQ reduced but did not abolish the relationship between fluency and network links. We conclude that the restricted verbal output of schizophrenic subjects is related both to impaired lexical retrieval and to variation in semantic memory organization, which partly reflects general intelligence. The statistical independence of the retrieval speed and organizational factors suggests that individuals with schizophrenia differ in the underlying processes that contribute to their reduced verbal fluency.

Adult↗
PubMedDate not supplied

Processing speed and adult age differences in activity memory.

Immediate and delayed recall of performed cognitive activities was examined in 136 adults aged 20 to 85. Hierarchical regression analyses were used to assess the association between perceptual speed and age differences in activity memory. The age-related variance in delayed activity recall was reduced by 52% by the statistical control of perceptual speed, and the age-related variance in immediate activity recall was reduced by 91%. Thus, adult age differences in delayed and immediate activity memory were found to be associated with limitations in perceptual speed. The cognitive effort that is required to perform cognitive activities may tax the processing resources of older adults, prohibiting successful encoding of the activities.

Adult↗
PubMed1975

Visual information-processing speed in reflective and impulsive children.

A backward-masking procedure was used to measure the rate of visual information processing in 8- and 10-year-old reflective and impulsive children. The test stimulus (TS) and the masking stimulus (MS) which followed it were presented tachistoscopially. The subject's information-processing threshold was defined as the next highest TS-MS interval above the interval where at least 3 of the 4 TSs were incorrectly identified. Reflective children were significantly faster than impulsive children at processing information. This finding was related to research indicating that reflective and impulsive children employ similar cognitive strategies; it was suggested that performance differences between these children might be related to reflective children employing their strategies with more adequate information.

Age Factors↗
PubMed2004

Cerebral hemodynamics and processing speed during category learning.

The Wisconsin Card Sorting Test (WCST) is a commonly used paradigm of category learning with two alternating and distinct processes, maintaining set and set shifting that have been characterized by functional transcranial Doppler sonography (fTCD) of the basal cerebral arteries. Further, repeated WCST administrations resulted in improved speed of solution. This study addressed the question of whether optimised speed during maintaining set or set shifting is associated with changes of cerebral hemodynamics as measured by bilateral fTCD. During maintaining set, improved speed was associated with increased peak mean cerebral blood flow velocity (CBFV) of the anterior cerebral arteries. These results suggest a common functional substrate between optimised speed of solution and cerebral hemodynamics during maintaining set.

Adult↗
PubMed2006

Spatial scale of stereomotion speed processing.

To examine the spatial scale of the mechanisms supporting the perception of motion in depth defined by binocular cues, we measured stereomotion speed discrimination thresholds as a function of stimulus size using a two-interval speed comparison task. Stimuli were either random dot stereogram (RDS) bars featuring both the changing disparity (CD) and the interocular velocity difference (IOVD) cues to motion in depth or dynamic random dot stereogram (DRDS) bars featuring the CD cue alone. Monocular speed discrimination performance was also assessed, using half-images of the RDS stimulus. In addition, subjects' stereoacuity for stationary versions of the binocular stimuli was measured. Stimuli ranged in vertical extent from 1.25 to 40 min. Sensitivity to speed differences was strongly related to stimulus height for DRDS stimuli. Performance decreased rapidly as stimulus size was reduced, becoming nearly random for heights below 5 min. However, for RDS stimuli, speed discrimination performance declined with reductions in stimulus size at a far slower rate, providing superior performance at every stimulus size used. Monocular performance was superior still for the majority of subjects, yet showed a similar rate of decline to binocular RDS stimuli. We conclude that the spatial resolution of the CD mechanism and its static disparity inputs is, on average, nearly nine times more coarse than the IOVD system and its monocular motion inputs. Static stereoacuity controls show that this finding cannot be explained by differences in the disparity signals available in our RDS and DRDS stimuli.

Cues↗
PubMed1989

Information processing speed in patients with multiple sclerosis.

We have recently proposed that the cognitive deficits of patients with multiple sclerosis (MS) share numerous characteristics associated with the syndrome of subcortical dementia. One such characteristic, slowness of mental processing, was evaluated in the present study. Thirty-six MS patients were compared to 26 normal controls of equivalent age, education, and verbal intelligence on the Sternberg memory scanning test. As anticipated, the motor-involved MS patients had an overall slower reaction time than did controls. Their scanning rate, a measure of pure cognitive speed, was also significantly slower than controls. These results suggest that MS patients exhibit a slowing of mental processing independent of motor involvement.

Adult↗
PubMed2003

Processing speed and timing in aging adults: psychoacoustics, speech perception, and comprehension.

Age-related differences are observed on many measures of both perceptual and cognitive processing. Indeed, strong correlations between basic measures of hearing and vision and age-related variations in intelligence have highlighted the powerful links between perception and cognition. In this paper, links between age-related differences in auditory temporal processing and slowing in cognitive processing are explored in an effort to illuminate how older adults listen to language spoken in challenging everyday conditions. Experiments in which the signal-to-noise condition is varied to equate listening difficulty for younger and older adults and experiments that simulate auditory aging in younger listeners provide evidence that at least some of the apparent age-related differences in cognitive performance during spoken language comprehension may be secondary to auditory temporal processing differences.

Adult↗
PubMed1985

Differences in semantic processing speed of mentally retarded and nonretarded persons.

A modified Sternberg choice-reaction time procedure was used to compare differences in the speed with which mentally retarded and nonretarded adults were able to retrieve recently stored information from short-term memory and process permanently stored semantic information. Results revealed that the retarded adults were slower than were the nonretarded adults in both domains of processing; the relative magnitude of "processing inefficiency" exhibited by the retarded subjects was quite similar across the two domains (47% and 57% as efficient as the nonretarded subjects in short-term and long-term memory processing, respectively). This similarity suggests that inefficient processing may represent a fundamental deficiency of retarded individuals resulting from the inefficient execution of some central processing mechanism.

Adult↗
PubMed1996

An automatic sleep-stage analysis system with off-line high-speed processing using a super mini-computer.

An automatic sleep analysis system using a super mini-computer was developed. The system improved and expanded the data processed by the mini-computer. It had the following features: 1) wave-forms were collected and analyzed at a high speed (reproduced at 10 or 20 times the speed of a data recorder) by an off-line procedure to utilize the computer resources more efficiently; 2) all information and the original wave-forms were output to a laser printer because of the lower cost and more efficient arrangement of the data; 3) various wave-form parameters were measured by wave-form analysis; 4) the application program was based on general-purpose language; and 5) wave-form reanalysis and reconstruction of the logic was easily implemented for automatic evaluation of the sleep stages. Automatic analysis of the sleep stages was impossible for 15 of 1484 periods (20 sec per period) with one of the cases analyzed, and 142 of 1484 periods had to be corrected because of erroneous identification.

Adult↗
PubMed2006

Trauma-related deficits in working memory.

INTRODUCTION: The aim of the study was to evaluate trauma-related impairments of working memory in psychiatric outpatients, and the mediating role of processing speed, anxiety and depression in the cognitive decrements. METHODS: This research applied a comprehensive assessment protocol including an evaluation of psychopathological and neuropsychological functioning in psychiatric outpatients. Patients with trauma history (n = 33) were compared to patients without such a history (n = 30). We collected information regarding age, gender, culture level, profession level, alcohol abuse, anxiety, and depression symptoms. Working memory and speed processing were assessed with standardised neuropsychological instruments. Data analysis was accomplished using parametric statistics, and a hierarchical multiple regression model was used to regress working memory performance scores against the trauma variable, anxiety-depression scores, and speed processing. RESULTS: The groups differed by gender, not by age, education level, socioeconomic status and alcohol abuse. Analysis of cognitive data revealed specific trauma-related deficits in working memory. Moreover, the trauma-exposed subjects scored higher on anxiety/depression scales, and lower on processing speed tests. The regression revealed significant impairment in working memory partially mediated by speed processing, but not by anxiety or depression. CONCLUSIONS: These findings confirmed the trauma-related impairments in working memory and the paramount importance for these impairments of reduced processing speed rather than emotional factors.

Adolescent↗
PubMed2005

Rapid categorization of natural scenes in monkeys: target predictability and processing speed.

Three monkeys performed a categorization task and a recognition task with briefly flashed natural images, using in alternation either a large variety of familiar target images (animal or food) or a single (totally predictable) target. The processing time was 20 ms shorter in the recognition task in which false alarms showed that monkeys relied on low-level cues (color, form, orientation, etc.). The 20-ms additional delay necessary in monkeys to perform the categorization task is compared with the 40-ms delay previously found for humans performing similar tasks. With such short additional processing time, it is argued that neither monkeys nor humans have time to develop a fully integrated object representation in the categorization task and must rely on coarse intermediate representations.

Animals↗
PubMed1992

Influence of processing speed on adult age differences in working memory.

Two studies are reported in which adults ranging from 18 to 80 years of age performed tasks designed to measure working memory functioning and perceptual comparison speed. The results from both studies indicated that statistical control of the measures of perceptual comparison speed greatly attenuated the age-related variance in measures of working memory even when working memory was assessed under self-paced conditions. Additional results in the second study supported the hypothesis that the speed influence was manifested in the rate of activating information rather than in the rate at which it was lost as a function of time or other processing.

Adolescent↗
PubMed1997

Backward masking of words and faces: evidence for different processing speeds in the hemispheres?

Two tachistoscopic experiments with a lateralized presentation of function words and faces were carried out to investigate the influence of temporal factors and type of masking on visual field asymmetries. Accuracy, represented by signal detection measures (d' and beta), was calculated separately for the two visual fields, for various interstimulus intervals, and for noise and pattern masking. In both experiments, d' increased with prolonged temporal delay between target and mask. In the lexical decision task, visual field interacted with mask type confirming that only in the pattern mask condition did an advantage of the right visual field emerge. In the facial decision task, however, visual field interacted with interstimulus interval, confirming that, in the left visual field, the facial information escaped the masking effect earlier than in the right visual field. In the facial task, there was a higher response criterion (beta) in the left visual field. By applying different types of masks, visual processing of lexical stimuli can be disrupted at distinct stages where perceptual asymmetries are present to a varying extent. The results of both experiments suggest that words and faces are differentially affected by masking procedures.

Adult↗
PubMed2001

Cigarette smoking and attention: processing speed or specific effects?

RATIONALE: It has been evidenced that nicotine acts on some dimensions of human attention. OBJECTIVE: This study was carried out to test whether the positive effects of nicotine usually observed on the posterior system are specific or should rather be explained in terms of an effect of nicotine on eye movement velocity. METHODS: Ten participants were submitted to four tasks assessing attention. The tasks were borrowed from Zimmermann and Fimm's Battery for the Assessment of Attention: alert, eye movements, visual search and incompatibility. The order of the different tasks was balanced among participants. A within-subjects repeated-measure design was used. Participants received a 0.9-mg or 0.1-mg nicotine cigarette. The 0.1-mg cigarette was used as control. The order of administration of doses over sessions was counterbalanced. During the testing day, volunteers smoked their own cigarette and then waited 3 h without smoking. At the end of this abstinence period, participants completed the baseline tests before smoking an experimental cigarette ad libitum. They were then tested again. RESULTS: Participants who received nicotine appeared to respond faster in an eye movement task--a task associated with a non-elaborated attentional process. Similarly, their alert state improved. On the contrary, no effect of nicotine was observed in the incompatibility task and in the visual search task depending on elaborated attentional process. CONCLUSIONS: Data support previous observations and suggest that, first, non-elaborated information processing appeared to be more sensitive to nicotine and, second, this effect is not due to a velocity factor.

Adult↗