Working memory and inhibition across the adult life-span

Research has shown that age-related changes in cognitive performance are due mostly to the decline of general factors such as working memory and inhibition. The present study is aimed at investigating age-related changes in these mechanisms across the adult life-span from 20 to 86 years of age. Results indicate a linear relationship between each working memory measure and age, independently of the nature of the task, and a quadratic relationship between the single inhibitory measures and age. Moreover, hierarchical regression analyses show that inhibition accounts for a significant, but modest, part of the age-related variance in working memory. Taken together, these results suggest that inhibition is not as crucial a contributor of age-related changes in the functional capacity of working memory across the adult life-span as previously thought.     

The role of age and inhibitory efficiency in working memory processing and storage components

In this study, we examined the extent to which inhibitory efficiency accounted for age-related decline in the processing and storage components of working memory. Older and younger adults performed a sequential task, which served as an index of deletion-type inhibition (the ability to suppress no-longer-relevant information). The reading span task was used to measure working memory components by examining processing accuracy, processing time, and end-word recall of sentences presented. Reduced inhibitory efficiency, which was poorer in older adults, predicted age-related decline in recall, over and above the effects of processing speed. Similar results were observed for processing accuracy, although the age effect in this component was marginal. These results highlight the important role of deletion-type inhibition in explaining age-related decline in working memory performance, particularly in the storage component, and extend previous research by examining this relationship at a componential level.     

Updating in working memory: a comparison of good and poor comprehenders

In this research, we examined the relation between reading comprehension and success in a working memory updating task. We tested the hypotheses that poor comprehenders' deficiencies are associated with a specific difficulty in the working memory updating process, particularly in controlling for information that is no longer relevant. In the first experiment, groups of poor and good comprehenders, ages 8-11 years, were administered a working memory updating task. In the second experiment a year later, a subgroup of participants involved in the first experiment was tested with a different updating task. In both experiments, poor comprehenders had less accurate recall performance and made more intrusion errors than did good comprehenders. Moreover, distinguishing intrusion errors on the basis of their permanence in memory, we found that poor comprehenders were more likely to intrude items that were maintained longer in memory than were good comprehenders. This type of error predicted reading comprehension abilities better than did working memory recall. This suggests that the relation between reading comprehension and working memory is mediated by the ability to control for irrelevant information.     

Influence of response prepotency strength, general working memory resources, and specific working memory load on the ability to inhibit predominant responses: a comparison of young and elderly participants

One conception of inhibitory functioning suggests that the ability to successfully inhibit a predominant response depends mainly on the strength of that response, the general functioning of working memory processes, and the working memory demand of the task (Roberts, Hager, & Heron, 1994). The proposal that inhibition and functional working memory capacity interact was assessed in the present study using two motor inhibition tasks (Go/No-Go and response incompatibility) in young and older participants. The strength of prepotency was assessed with a short or long training phase for the response to be inhibited. The influence of working memory resources was evaluated by administering the tasks in full vs. divided attention conditions. The effect of working memory load was manipulated by increasing the number of target and distracter items in each task. Results showed no effect of prepotency strength, whereas dividing attentional resources and increasing working memory load were associated with greater inhibitory effects in both groups and for both tasks. This deleterious effect was higher for older participants, except in the working memory load condition of the Go/No-Go task. These results suggest an interactive link between working memory and response inhibition by showing that taxing working memory resources increases the difficulty of inhibiting prepotent responses in younger and older subjects. The additional detrimental effect of these factors on healthy elderly subjects was related to their decreased cognitive resources and to their shorter span size.     

A dissociation between the sense of familiarity and access to semantic information concerning familiar people

In the current study we examined the relationship between working memory capacity, inhibition/susceptibility to interference and fluid intelligence, measured by the Raven's Progressive Matrices (PM38), comparing groups of young (aged 18–35), young-old (aged 65–74), and old-old (aged 75–86) participants. Groups were administered two working memory tasks tapping into different mechanisms involved in working memory. The ability to control for irrelevant information was measured both considering memory errors (intrusion errors) in a working memory task and an index of susceptibility to interference obtained with a variant of the Brown-Peterson task. Regression analyses showed that the classical working memory measure was the most potent predictors of the Raven's score. Susceptibility to interference and intrusions errors contributed, but to a lower extent, to the Raven explained variance. These results confirm that working memory shares cognitive aspects with the fluid intelligence measure considered, whereas the role of inhibition to Raven scores is still in need of better evidence.     

Integrating working memory capacity and context-processing views of cognitive control

Individuals low in working memory capacity (WMC) exhibit impaired performance on a variety of cognitive control tasks. The executive-attention theory of WMC (Engle & Kane, [2004[) accounts for these findings as failures of goal maintenance and response conflict resolution. Similarly, the context-processing view (Braver et al., [2001]) provides an explanation of cognitive control deficits observed in schizophrenia patients and older adults that is based on the ability to maintain context information. Instead of maintenance deficits, the inhibition view (Hasher, Lustig, & Zacks, [2007]) states that older adults and individuals low in WMC primarily have an impairment in the ability to inhibit information. In the current experiment, we explored the relationships among these theories. Individuals differing in performance on complex span measures of WMC performed the AX-Continuous Performance Test to measure context-processing performance. High-WMC individuals were predicted to maintain the context afforded by the cue, whereas low-WMC individuals were predicted to fail to maintain the context information. Low-WMC individuals made more errors on AX and BX trials and were slower to respond correctly on AX, BX, and BY trials. The overall pattern of results is most consistent with both the executive-attention and context-processing theories of cognitive control.     

Motor planning between 4 and 7 years of age: Changes linked to executive functions

In the present study, we adopted the conceptual frameworks of Miyake et al. (2000) (organization of executive functions) and Sergeant (2000) (linking executive function to motor behaviour) to assess developmental changes in executive functions and motor behaviour, using a planning task with a sample of 4–7-years old children. More precisely, the aim of the study was to characterize the development of motor response planning between the ages of 4 and 7 as a measure of the integration of multiple executive function processes, namely inhibition, shifting and working memory, and to gain insight into the concurrent developmental contributions of these processes. Participants were divided into two groups: group 1 was composed of 24 children aged 4–5 years and group 2 was composed of 20 children aged 6–7 years. Each participant took tests for shifting, inhibition, working memory and motor planning (the egg-planning task). Our results suggest that the egg-planning task requires the inhibition of a pre-potent but inappropriate response, and to a lesser extent the manipulation of working memory strategies. These results are discussed in relation to the development of each executive function component.     

Training working memory: Limits of transfer

In two experiments (totaling 253 adult participants), we examined the extent to which intensive working memory training led to improvements on untrained measures of cognitive ability. Although participants showed improvement on the trained task and on tasks that either shared task characteristics or stimuli, we found no evidence that training led to general improvements in working memory. Using Bayes Factor analysis, we show that the data generally support the hypothesis that working memory training was ineffective at improving general cognitive ability. This conclusion held even after controlling for a number of individual differences, including need for cognition, beliefs in the malleability of intelligence, and age.     

Is working memory necessary for implementation intentions to enhance prospective memory in older adults with cognitive problems?

Implementation intentions are an effective strategy for improving prospective memory in older adults. However, their efficacy has never been assessed in older individuals with cognitive problems (i.e., individuals with subjective memory complaints or objective memory impairments). Furthermore, although most authors consider implementation intentions to depend on automatic processes, some studies have shown the necessity of residual preserved controlled processes for implementation intentions to be efficient. We examined the efficacy of implementation intentions in prospective memory in 45 older participants consulting a memory clinic. Half of the participants were instructed to form an implementation intention, the other half receiving standard instructions. Analyses showed that working memory moderated the efficacy of implementation intentions, which were efficient only in individuals with better working memory. These results corroborate the claim that a minimal level of cognitive resources is required for the technique, although implementation intentions might depend principally on automatic processes.     

The immediate and sustained effects of acute exercise on planning aspect of executive function

ObjectiveThe purpose of this study was to clarify the immediate and sustained effects of an acute bout of exercise on the planning aspects of executive function.DesignThis study used a 2 × 4 true experimental design.MethodForty participants were randomly assigned to either the exercise or control groups and completed the Tower of London task prior to, immediately following, 30 min after, and 60 min after cessation of a 30 min, moderate intensity cycling exercise.ResultsAcute exercise positively impacted the total move score, which reflects planning efficiency, immediately after the cessation of exercise. Acute exercise also led to longer total initiation times, which were linked to better response inhibition of planning at 30 and 60 min after the cessation of exercise.ConclusionAcute exercise benefits planning, and the types of planning and the time points at which they were assessed modulate the relationship between acute exercise and executive function. Exercise-induced physiological and biological fluctuations have been proposed to explain the effects present immediately after exercise, and the mechanisms of such effects warrant further exploration.     

Working memory capacity predicts the beneficial effect of selective memory retrieval

Selective retrieval of some studied items can both impair and improve recall of the other items. This study examined the role of working memory capacity (WMC) for the two effects of memory retrieval. Participants studied an item list consisting of predefined target and nontarget items. After study of the list, half of the participants performed an imagination task supposed to induce a change in mental context, whereas the other half performed a counting task which does not induce such context change. Following presentation of a second list, memory for the original list's target items was tested, either with or without preceding retrieval of the list's nontarget items. Consistent with previous work, preceding nontarget retrieval impaired target recall in the absence of the context change, but improved target recall in its presence. In particular, there was a positive relationship between WMC and the beneficial, but not the detrimental effect of memory retrieval. On the basis of the view that the beneficial effect of memory retrieval reflects context-reactivation processes, the results indicate that individuals with higher WMC are better able to capitalise on retrieval-induced context reactivation than individuals with lower WMC.