Factors contributing to attentional impairments after traumatic brain injury.

The aim of the present study was to investigate the contribution of impaired information processing speed and strategic control of attention to performance on attentional tasks after traumatic brain injury (TBI). Forty moderately to severely injured rehabilitation inpatients and 40 healthy controls completed a selection of attentional tasks. Slowed processing speed in the TBI group was identified on the Symbol Digit Modalities Test (SDMT), 2&7 Selective Attention Test (2&7), Selective Attention (SAT), and Four Choice Reaction Time (4CRT) tasks. Impaired working memory was evident on the Letter Number Sequencing (LNS) task. Structural equation modeling revealed that the group difference in RT on the complex SAT was accounted for by slowed speed of processing on the simple SAT, and not working memory. TBI participants made more errors and missed responses on the complex version of the SAT, suggesting impairment in some aspects of strategic control of attention, and appeared unable to benefit from the automatic condition of the 2&7 Test. There was little evidence of deficit on the Sustained Attention to Response Task (SART). The present study provides evidence for a significant contribution of slowed processing speed to impaired performance on attentional tasks after TBI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relationship between processing speed and working memory demand in systemic lupus erythematosus: Evidence from a visual n-back task.

Objective: Working memory (WM) deficits have been reported previously in systemic lupus erythematosus (SLE), but the relationship between information processing speed (PS) and WM deficits in SLE is unknown. This study examined whether or not PS slowing could account for the WM deficits observed in SLE. Method: A visual n-back task was used to measure simple and complex PS and WM in 40 SLE patients and 36 healthy controls. Simple PS was defined as reaction time (RT) to correct responses under a very low WM load condition (0-back), while complex PS was defined as RT to correct responses under moderate and high WM load conditions (1 and 2-back). Results: The results showed that SLE patients performed as well as the controls at the lower WM load conditions but had fewer correct responses than controls under the highest WM load condition (2-back). SLE patients had slower RTs than controls under all conditions, but they had relatively greater RT slowing than controls under the higher WM load conditions. Further, when RT for simple PS was subtracted from complex PS, SLE patients still showed slower complex PS for the 1- and 2-back compared with controls. Both simple and complex PS slowing were related to poorer accuracy scores on the 2-back condition, only for the SLE group. Conclusions: The n-back task provides a sensitive measure of PS and WM. The results suggest that PS deficits alone could not account for the WM deficits in SLE. Disease duration, disease activity, and depression did not appear to account for the observed PS and WM deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Growth in working memory and mathematical problem solving in children at risk and not at risk for serious math difficulties.

The influence of cognitive growth in working memory (WM) on mathematical problem solution accuracy was examined in elementary school children (N = 353) at risk and not at risk for serious math problem solving difficulties. A battery of tests was administered that assessed problem solving, achievement, and cognitive processing (WM, inhibition, naming speed, phonological coding) in children in 1st, 2nd, and 3rd grade across 3 testing waves. The results were that (a) children identified as at risk for serious math problem solving difficulties in Wave 1 showed less growth rate and lower levels of performance on cognitive measures than did children not at risk; (b) fluid intelligence and 2 components of WM (central executive, visual-spatial sketchpad) in Wave 1 (Year 1) predicted Wave 3 word problem solving solution accuracy; and (c) growth in the central executive and phonological storage component of WM was related to growth in solution accuracy. The results support the notion that growth in WM is an important predictor of children's problem solving beyond the contribution of reading, calculation skills, and individual differences in phonological processing, inhibition, and processing speed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Context processing in older adults: Evidence for a theory relating cognitive control to neurobiology in healthy aging.

A theory of cognitive aging is presented in which healthy older adults are hypothesized to suffer from disturbances in the processing of context that impair cognitive control function across multiple domains, including attention, inhibition, and working memory. These cognitive disturbances are postulated to be directly related to age-related decline in the function of the dopamine (DA) system in the prefrontal cortex (PFC). A connectionist computational model is described that implements specific mechanisms for the role of DA and PFC in context processing. The behavioral predictions of the model were tested in a large sample of older (N = 81) and young (N = 175) adults performing variants of a simple cognitive control task that placed differential demands on context processing. Older adults exhibited both performance decrements and, counterintuitively, performance improvements that are in close agreement with model predictions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)