Improved Working Memory Performance Research Articles

Working Memory, Strategy Knowledge, and Strategy Instruction in Children With Reading Disabilities

Two experiments investigated the effects of strategy knowledge and strategy training on the working memory (WM) performance in children (ages 10—11) with and without reading disabilities (RD). Experiment 1 examined the relationship between strategy knowledge (stability of strategy choices) and WM performance as a function of initial, gain (cued), and maintenance conditions. WM performance was significantly improved for both groups under cued conditions; however, the performances of children with RD were inferior to those of children without RD across all memory conditions. Measures of WM capacity rather than strategy stability or processing efficiency best predicted reading comprehension performance. Experiment 2 assessed the effects of strategy training on WM performance by randomly assigning children to strategy instruction or control conditions. Significant improvements in WM performance occurred as a function of training conditions, but the residual WM differences between the reading groups remained. Although the results showed that stable strategy choices, cued performance, and strategy instruction significantly bolstered WM performance in children with RD, their overall WM performance, however, was constrained by capacity limitations.

Effects of age and contextualized material on working memory span performance.

The present research explores the effects of contextualized material on age-related working memory performance. Two experiments examining younger and older adults are reported. ANOVA results of the first experiment showed age effects in both a standard operation span and a contextual task of parallel structure (air travel task). The second experiment also revealed a significant age effect in a standard operation span task. However, there was no age difference in a contextual task providing additional visual context (rail travel task), mainly due to older adults being unaffected by task type manipulation and younger adults performing worse in the contextual than in the standard task. The present research suggests that contextual task material may not necessarily lead to improved working memory performance in older adults. Several methodological and conceptual conclusions for future research are discussed.

Sleep Accelerates the Improvement in Working Memory Performance

Working memory (WM) performance, which is an important factor for determining problem-solving and reasoning ability, has been firmly believed to be constant. However, recent findings have demonstrated that WM performance has the potential to be improved by repetitive training. Although various skills are reported to be improved by sleep, the beneficial effect of sleep on WM performance has not been clarified. Here, we show that improvement in WM performance is facilitated by posttraining naturalistic sleep. A spatial variant of the n-back WM task was performed by 29 healthy young adults who were assigned randomly to three different experimental groups that had different time schedules of repetitive n-back WM task sessions, with or without intervening sleep. Intergroup and intersession comparisons of WM performance (accuracy and response time) profiles showed that n-back accuracy after posttraining sleep was significantly improved compared with that after the same period of wakefulness, independent of sleep timing, subject's vigilance level, or circadian influences. On the other hand, response time was not influenced by sleep or repetitive training schedules. The present study indicates that improvement in n-back accuracy, which could reflect WM capacity, essentially benefits from posttraining sleep.

α2A-Adrenoceptors Strengthen Working Memory Networks by Inhibiting cAMP-HCN Channel Signaling in Prefrontal Cortex

Spatial working memory (WM; i.e., "scratchpad" memory) is constantly updated to guide behavior based on representational knowledge of spatial position. It is maintained by spatially tuned, recurrent excitation within networks of prefrontal cortical (PFC) neurons, evident during delay periods in WM tasks. Stimulation of postsynaptic alpha2A adrenoceptors (alpha2A-ARs) is critical for WM. We report that alpha2A-AR stimulation strengthens WM through inhibition of cAMP, closing Hyperpolarization-activated Cyclic Nucleotide-gated (HCN) channels and strengthening the functional connectivity of PFC networks. Ultrastructurally, HCN channels and alpha2A-ARs were colocalized in dendritic spines in PFC. In electrophysiological studies, either alpha2A-AR stimulation, cAMP inhibition or HCN channel blockade enhanced spatially tuned delay-related firing of PFC neurons. Conversely, delay-related network firing collapsed under conditions of excessive cAMP. In behavioral studies, either blockade or knockdown of HCN1 channels in PFC improved WM performance. These data reveal a powerful mechanism for rapidly altering the strength of WM networks in PFC.

Attentional Modulation of Object Representations in Working Memory

We investigated the role of object-based attention in modulating the maintenance of faces and scenes held online in working memory (WM). Participants had to remember a face and a scene, while cues presented during the delay instructed them to orient their attention to one or the other item. Event-related functional magnetic resonance imaging revealed that orienting attention in WM modulated the activity in fusiform and parahippocampal gyri, involved in maintaining representations of faces and scenes respectively. Measures from complementary behavioral studies indicated that this increase in activity corresponded to improved WM performance. The results show that directed attention can modulate maintenance of specific representations in WM, and help define the interplay between the domains of attention and WM.

Effect of Methamphetamine on Cognition and Repetitive Motor Behavior of Mice Deficient for Dopamine D2 and D3 Receptors

Mice deficient for dopamine D2 and D3 receptors exhibit blunted D(1)-receptor responses to agonist stimulation. This blunted D1-receptor activity is prominent in the medial prefrontal cortex (mPFC) and results in a significantly impaired performance of the mutants in a test for spatial working memory. A single dose of methamphetamine (METH; 5 mg/kg i.p.), however, elicits a long-lasting increase in agonist-stimulated D1 receptor activity in the mPFC. In D2 mutants, this increase reaches wild-type levels, and the working memory of METH-treated mutants is completely rescued. In D3 mutants, however, the METH-induced increase in D1-receptor activity remains below wild-type levels and does not result in improved working memory performance. D2 and D3 mutants also differ in their locomotor responses to METH. Repeated administration of this drug (5 mg/kg administered three times at 2-h intervals) leads to a transition from horizontal hyperlocomotion to excessive orofacial stereotypy (taffy pulling) only in wild type and D3 mutants. In both genotypes, this transition is accompanied by a change in the relative ratios of striatal neuronal activation in two neurochemically distinct compartments, with striosomal neuronal activation exceeding that of the striatal matrix during stereotypy. Both the stereotypic response to METH and the associated predominant activation of neurons located in striosomes require D2-receptor expression. These studies indicate a differential requirement for D1- and D2-like receptor activation in mediating the effects of METH on cognitive and motor function.

The effect of musical training on the neural correlates of math processing: a functional magnetic resonance imaging study in humans

The neural correlates of the previously hypothesized link between formal musical training and mathematics performance are investigated using functional magnetic resonance imaging (fMRI). FMRI was performed on fifteen normal adults, seven with musical training since early childhood, and eight without, while they mentally added and subtracted fractions. Musical training was associated with increased activation in the left fusiform gyrus and prefrontal cortex, and decreased activation in visual association areas and the left inferior parietal lobule during the mathematical task. We hypothesize that the correlation between musical training and math proficiency may be associated with improved working memory performance and an increased abstract representation of numerical quantities.

Chronic nicotinic stimulation and blockade effects on working memory

Acute and chronic nicotine treatment has been found to improve learning and memory function in a variety of tasks. In several studies we have found that chronic nicotine infusion improves working memory performance. Replicating these results, the current study showed that chronic nicotine treatment (12mg/kg/day) significantly improved working memory performance in the radial-arm maze. The nicotine effect did not diminish during the 2 weeks following withdrawal. The nicotine-induced improvement was eliminated when the nicotinic antagonist mecamylamine (3mg/kg/day) was given concurrently, suggesting that the nicotine effect was mediated via actions on the nicotinic receptor. Surprisingly, when this chronic dose of mecamylamine was given alone, it caused a transient improvement in choice accuracy during the first week of administration. This improvement subsequently became attenuated and was not evident at all by the third and fourth weeks of administration.