An automated version of the operation span task

We present an easy-to-administer and automated version of a popular working memory (WM) capacity task (operation span; Ospan) that is mouse driven, scores itself, and requires little intervention on the part of the experimenter. It is shown that this version of Ospan correlates well with other measures of WM capacity and has both good internal consistency (alpha=.78) and test-retest reliability (.83). In addition, the automated version of Ospan (Aospan) was shown to load on the same factor as two other WM measures. This WM capacity factor correlated with a factor composed of fluid abilities measures. The utility of the Aospan was further demonstrated by analyzing response times (RTs) that indicated that RT measures obtained in the task accounted for additional variance in predicting fluid abilities. Our results suggest that Aospan is a reliable and valid indicator of WM capacity that can be applied to a wide array of research domains.     

Interactive effects of APOE and CHRNA4 on attention and white matter volume in healthy middle-aged and older adults

In the present study, we investigated age-related changes in interactions between efficiency of neuronal repair mechanisms and efficiency of cholinergic neurotransmission in the context of attentional orienting. In addition, we explored white matter volume changes as possible neuronal underpinnings. A sample of 230 healthy middle-aged (53–64 years) and older (65–75 years) adults was genotyped for polymorphisms of APOE and CHRNA4, a nicotinic receptor subunit gene. Participants were administered a visuospatial attention task involving letter discrimination with location cues of varying validity. Genotype effects on white matter volume were also investigated in a subset of participants who received MRI scans. APOE interacted with CHRNA4, such that APOE-ε4 carriers who were also CHRNA4 TT homozygotes showed disproportionately slowed reaction time (RT) following invalid location cues. The interaction was stronger in the middle-aged participants than in the older participants. There was also a trend for individuals with combined APOE-ε4/CHRNA4 TT genotypes to show both lower white matter volume and slower overall RT on the attention task. The interaction of a neurotransmission gene (CHRNA4) and a susceptibility gene (APOE) suggests that the efficiency of neuronal repair mechanisms may modulate the cholinergic system to influence attentional function.     

Memory scanning of described images and undescribed images: Hemispheric differences

Seamon (1972) has found that reaction times (RTs) to memory probes do not increase with memory set size (M) for words encoded in mental images in a memory scanning task. Rothstein and Atkinson (1975) have failed to replicate Seamon’s results. Experiment 1 investigated this discrepancy by manipulating one methodological difference (whether images were or were not described) between the two investigations. Results revealed that described images produced typical linear increases in RT with M. Undescribed images, however, revealed no change in RT with M for positive probes (i.e., the word presented was contained in the current memory set). Experiment 2 manipulated to which visual field probes were presented (RVF — right visual field; LVF = left visual field). Results showed that the imagery group showed no relation between RT and M for probes presented to the LVF, but a linear relation for probes presentedto the RVF. Described-image and repetition groups revealed a linear relation between RT and M no matter which visual field received the probe.     

Classifying retrieval strategies as a function of working memory

Strategy selection may help explain performance differences between individuals with high working memory capacity (HWMs) and low working memory capacity (LWMs) (Budd, Whitney, & Turley, (Memory & Cognition, 23, 735–748 1995); Cokely, Kelley, & Gilchrist, (Psychonomic Bulletin & Review, 13, 991–997 2006). We compared the independent and spontaneous strategy use of HWMs and LWMs during a category fluency (retrieval) task that required participants to retrieve animal names. HWMs were more successful at the fluency task under normal conditions, but under increased cognitive load, there were no WM-related performance differences. One strategy (i.e., retrieving animals according to their scientific classification) significantly aided performance, irrespective of cognitive load. Under normal conditions, HWMs were more likely to use the effective strategy; however, under load, WM did not predict strategy use. Use of the classification strategy was more strongly related to retrieval performance than was WM. These results suggest that retrieval strategy use is related to WM capacity, and that employing a successful strategy may make up for WM disadvantages during a demanding retrieval task.     

Dissociating effects of stimulus identity and load on working memory attentional guidance: Lengthening encoding time eliminates the effect of load but not identity

Effects of the identity and load of items in working memory (WM) on visual attention were examined. With a short interval between the WM item and a subsequent search task, there were effects of both load (slowed overall reaction times, RTs, in a WM condition relative to a mere repetition baseline) and identity (search RTs were affected by re-presentation of the item in WM in the search display). As the time to encode the initial display increased, the effects of load decreased while the effect of identity remained. The data indicate that the identity of stimuli in WM can affect the subsequent deployment of attention even when time is allowed for consolidation of the stimuli in WM, and that the WM effects are not causally related to the presence of cognitive load. The results are consistent with the identity of stimuli in WM modulating attention post the memory consolidation stage.     

Working memory in the oldest-old: evidence from output serial position curves

In the present study, we examined adult age differences in short-term and working memory performance in middle-aged (45–64 years), young–old (65–74 years), old–old (75–89 years), and oldest–old adults (90 years and over) in the Louisiana Healthy Aging Study. Previous research suggests that measures of working memory are more sensitive to age effects than are simple tests of short-term memory Bopp and Verhaeghen (Journal of Gerontology: Psychological Sciences 60:223–233, 2005), Myerson, Emery, White, and Hale, (Aging, Neuropsychology, and Cognition 10:20–27, 2003). To test this hypothesis, we examined output serial position curves of recall data from three span tasks: forward and backward digit span and size judgment span. Participants’ recall patterns in the size judgment span task revealed that the two oldest groups of adults showed the largest decreases in recall performance across output serial positions, but did not differ significantly from each other. Correlation analyses indicated the strongest negative correlation with age occurred with the size judgment span task. Implications of these findings for understanding strategic processing abilities in late life are discussed.     

Dissociating effects of stimulus identity and load on working memory attentional guidance: Lengthening encoding time eliminates the effect of load but not identity

Effects of the identity and load of items in working memory (WM) on visual attention were examined. With a short interval between the WM item and a subsequent search task, there were effects of both load (slowed overall reaction times, RTs, in a WM condition relative to a mere repetition baseline) and identity (search RTs were affected by re-presentation of the item in WM in the search display). As the time to encode the initial display increased, the effects of load decreased while the effect of identity remained. The data indicate that the identity of stimuli in WM can affect the subsequent deployment of attention even when time is allowed for consolidation of the stimuli in WM, and that the WM effects are not causally related to the presence of cognitive load. The results are consistent with the identity of stimuli in WM modulating attention post the memory consolidation stage.     

An electrophysiological comparison of visual categorization and recognition memory

Object categorization emphasizes the similarities that bind exemplars into categories, whereas recognition memory emphasizes the specific identification of previously encountered exemplars. Mathematical modeling has highlighted similarities in the computational requirements of these tasks, but neuropsychological research has suggested that categorization and recognition may depend on separate brain systems. Following training with families of novel visual shapes (blobs), event-related brain potentials (ERPs) were recorded during both categorization and recognition tasks. ERPs related to early visual processing (N1, 156–200 msec) were sensitive to category membership. Middle latency ERPs (FN400 effects, 300–500 msec) were sensitive to both category membership and old/new differences. Later ERPs (parietal effects, 400–800 msec) were primarily affected by old/new differences. Thus, there was a temporal transition so that earlier processes were more sensitive to categorical discrimination and later processes were more sensitive to recognition-related discrimination. Aspects of these results are consistent with both mathematical modeling and neuropsychological perspectives.     

N-backer: an auditory n-back task with automatic scoring of spoken responses

The n-back task is commonly used to load working memory (WM) in dual-task and neuroimaging experiments. However, it typically involves visual presentation and buttonpress responses, making it unsuitable for combination with primary tasks that involve vision and action, such as sequential object use and other tasks of daily living. The N-backer software presented here will automatically present and score auditory–verbal n-back sequences utilising the standard speech synthesis and recognition facilities that come with Microsoft Windows. Data are presented from an experiment in which 12 student participants carried out three tasks from the Naturalistic Action Test (NAT) while their attention was divided between the primary task and a continuous auditory–verbal 2-back secondary task. The participants’ 2-back performance was scored in two ways: by hand, from video recordings, and automatically, using the software, allowing us to evaluate the accuracy of N-backer. There was an extremely high correlation between these scores (.933). The videos were also used to obtain a comprehensive error score for the NAT. Significantly more errors were made in the more complex NAT tasks when participants were 2-backing, as compared with when they were not, showing that the auditory–verbal n-back task can be used to disrupt sequential object use. This dual-task method may simulate the attentional deficits of patients with brain injury, providing insights into the difficulties they face in tasks of daily living.     

Memory guidance in distractor suppression is governed by the availability of cognitive control

Information stored in the memory systems can affect visual search. Previous studies have shown that holding the to-be-ignored features of distractors in working memory (WM) could accelerate target selection. However, such facilitation effect was only observed when the cued to-be-ignored features remained unchanged within an experimental block (i.e., the fixed cue condition). No search benefit was obtained if the to-be-ignored features varied from trial to trial (i.e., the varied cue condition). In the present study, we conducted three behavioral experiments to investigate whether the WM and long-term memory (LTM) representations of the to-be-ignored features could facilitate visual search in the fixed cue (Experiment 1) and varied cue (Experiments 2 and 3) conditions. Given the importance of the processing time of cognitive control in distractor suppression, we divided visual search trials into five quintiles based on their reaction times (RTs) and examined the temporal characteristics of the suppression effect. Results showed that both the WM and LTM representations of the to-be-ignored features could facilitate distractor suppression in the fixed cue condition, and the facilitation effects were evident across the quintiles in the RT distribution. However, in the varied cue condition, the RT benefits of the WM-matched distractors occurred only in the trials with the longest RTs, whereas no advantage of the LTM-matched distractors was observed. These results suggest that the effective WM-guided distractor suppression depends on the availability of cognitive control and the LTM-guided suppression occurs only if sufficient WM resource is accessible by LTM reactivation.     

The reaction-time task-rule congruency effect is not affected by working memory load: further support for the activated long-term memory hypothesis

Previous studies claimed that task representation is carried out by the activated long-term memory portion of working memory (WM; Meiran and Kessler in J Exp Psychol Human Percept Perform 34:137–157, 2008). The present study provides a more direct support for this hypothesis. We used the reaction-time task-rule congruency effect (RT-TRCE) in a task-switching setup, and tested the effects of loading WM with irrelevant task rules on RT-TRCE. Experiment 1 manipulated WM load in a between-subject design. WM participants performed a color/shape task switching, while having 0, 1 or 3 numerical task rules as WM load. Experiment 2 used a similar load manipulation (1 or 3 rules to load WM) in a within-subject design. Experiment 3 extended these results by loading WM with perceptual tasks that were more similar to the shape/color tasks. The results show that RT-TRCE was not affected by WM load supporting the activated long-term memory hypothesis.     

Visual working memory is disrupted by covert verbal retrieval

If working memory (WM) depends on a central resource—as is posited in some theories, but not in others—it should be possible to observe interference between tasks that share few features with each other. We investigated whether interference with WM for visual arrays would occur, even if the interfering task required neither visual processing nor overt responding. In an auditory-verbal interfering task, a response was to be made if a word was recognized as having come from one of two prelearned lists, but not from the other list. As compared with nonretrieval control conditions, even covert verbal memory retrieval disrupted the storage of visual items held in WM. A second experiment ruled out verbal recoding of the visual arrays as the basis of interference. The results indicate that visual WM and verbal long-term retrieval share a central resource (e.g., attention).     

Working memory improvement with non-invasive brain stimulation of the dorsolateral prefrontal cortex: A systematic review and meta-analysis

Recent studies have used non-invasive brain stimulation (NIBS) techniques, such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), to increase dorsolateral prefrontal cortex (DLPFC) activity and, consequently, working memory (WM) performance. However, such experiments have yielded mixed results, possibly due to small sample sizes and heterogeneity of outcomes. Therefore, our aim was to perform a systematic review and meta-analyses on NIBS studies assessing the n-back task, which is a reliable index for WM. From the first data available to February 2013, we looked for sham-controlled, randomized studies that used NIBS over the DLPFC using the n-back task in PubMed/MEDLINE and other databases. Twelve studies (describing 33 experiments) matched our eligibility criteria. Active vs. sham NIBS was significantly associated with faster response times (RTs), higher percentage of correct responses and lower percentage of error responses. However, meta-regressions showed that tDCS (vs. rTMS) presented only an improvement in RT, and not in accuracy. This could have occurred in part because almost all tDCS studies employed a crossover design, possibly due to the reliable tDCS blinding. Study design was also associated with no improvement in correct responses in the active vs. sham groups. To conclude, rTMS of the DLPFC significantly improved all measures of WM performance whereas tDCS significantly improved RT, but not the percentage of correct and error responses. Mechanistic insights on the role of DLPFC in WM are further discussed, as well as how NIBS techniques could be used in neuropsychiatric samples presenting WM deficits, such as major depression, dementia and schizophrenia.     

视觉空间工作记忆组间差异的神经机制

为考察视觉空间工作记忆（working memory, WM）维持和操作的组间差异及其神经机制,本研究记录了高、低WM组完成延迟再认（维持）任务和心理旋转（操作）任务时的行为和事件相关电位数据。结果发现,在操作任务中,高WM组比低WM组的反应时显著更短;高WM组的中前额叶慢波显著更正、双侧后顶区慢波显著更负,并且两者的波幅显著负相关。在维持任务中,两组被试的反应时无显著差异;高WM组的中前额叶慢波显著更正。结果表明,高WM组的执行注意能力可能更强,能通过有效调节和分配加工资源来表征视觉信息。     

颜色凸显条件下基于工作记忆内容的视觉注意

采用记忆任务与视觉搜索任务相结合的实验范式,通过操纵背景颜色与刺激颜色,考察了工作记忆内容对视觉注意的引导是否存在强自动性。实验一通过操作背景颜色以突显记忆项目,结果发现即使工作记忆内容在匹配分心物的情况下仍然自动地捕获视觉注意。实验二通过操作背景颜色以突显目标项目,结果发现工作记忆内容对视觉注意的自动引导作用消失。说明了与工作记忆内容匹配的刺激能够自动地引导视觉注意,但是这种引导并非完全自动化,具有一定的条件性。     

The Effect of modality specific interference on working memory in recalling aversive auditory and visual memories*

Both auditory and visual emotional memories can be made less emotional by loading working memory (WM) during memory recall. Taxing WM during recall can be modality specific (giving an auditory [visuospatial] load during recall of an auditory [visual] memory) or cross modal (an auditory load during visual recall or vice versa). We tested whether modality specific loading taxes WM to a larger extent than cross modal loading. Ninety-six participants undertook a visual and auditory baseline Random Interval Repetition task (i.e. responding as fast as possible to a visual or auditory stimulus by pressing a button). Then, participants recalled a distressing visual and auditory memory, while performing the same visual and auditory Random Interval Repetition task. Increased reaction times (compared to baseline) were indicative of WM loading. Using Bayesian statistics, we compared five models in terms of general and modality specific taxation. There was support for the model describing the effect on WM of dual tasking in general, irrespective of modality specificity, and for the model describing the effect of modality specific loading. Both models combined gained the most support. The results suggest a general effect of dual tasking on taxing WM and a superimposed effect of taxing in matched modality.     

Working memory load and distraction: dissociable effects of visual maintenance and cognitive control

We establish a new dissociation between the roles of working memory (WM) cognitive control and visual maintenance in selective attention as measured by the efficiency of distractor rejection. The extent to which focused selective attention can prevent distraction has been shown to critically depend on the level and type of load involved in the task. High perceptual load that consumes perceptual capacity leads to reduced distractor processing, whereas high WM load that reduces WM ability to exert priority-based executive cognitive control over the task results in increased distractor processing (e.g., Lavie, Trends in Cognitive Sciences, 9(2), 75–82, 2005). WM also serves to maintain task-relevant visual representations, and such visual maintenance is known to recruit the same sensory cortices as those involved in perception (e.g., Pasternak & Greenlee, Nature Reviews Neuroscience, 6(2), 97–107, 2005). These findings led us to hypothesize that loading WM with visual maintenance would reduce visual capacity involved in perception, thus resulting in reduced distractor processing—similar to perceptual load and opposite to WM cognitive control load. Distractor processing was assessed in a response competition task, presented during the memory interval (or during encoding; Experiment 1a) of a WM task. Loading visual maintenance or encoding by increased set size for a memory sample of shapes, colors, and locations led to reduced distractor response competition effects. In contrast, loading WM cognitive control with verbal rehearsal of a random letter set led to increased distractor effects. These findings confirm load theory predictions and provide a novel functional distinction between the roles of WM maintenance and cognitive control in selective attention.     

Chewing gum moderates the vigilance decrement

We examine the impact of chewing gum on a Bakan‐type vigilance task that requires the continual updating of short‐term order memory. Forty participants completed a 30‐min auditory Bakan‐task either with, or without, the requirement to chew gum. Self‐rated measures of mood were taken both pre‐ and post‐task. As expected, the vigilance task produced a time‐dependent performance decrement indexed via decreases in target detections and lengthened correct reaction times (RTs), and a reduction in post‐task self‐rated alertness scores. The declines in both performance and subjective alertness were attenuated in the chewing‐gum group. In particular, correct RTs were significantly shorter following the chewing of gum in the latter stages of the task. Additionally, the gradients of decline for target detection and incline for correct RTs were both attenuated for the chewing‐gum group. These findings are consistent with the data of Tucha and Simpson (2011), Appetite, 56, 299–301, who showed beneficial effects of chewing gum in the latter stages of a 30 min visual attention task, and extend their data to a task that necessitates the continuous updating of order memory. It is noteworthy that our data contradict the claim (Kozlov, Hughes, & Jones, 2012, Q. J. Exp. Psychology, 65, 501–513) that chewing gum negatively impacts short‐term memory task performance.     

Task-set inertia and memory-consolidation bottleneck in dual tasks

Three dual-task experiments examined the influence of processing a briefly presented visual object for deferred verbal report on performance in an unrelated auditory-manual reaction time (RT) task. RT was increased at short stimulus-onset asynchronies (SOAs) relative to long SOAs, showing that memory consolidation processes can produce a functional processing bottleneck in dual-task performance. In addition, the experiments manipulated the spatial compatibility of the orientation of the visual object and the side of the speeded manual response. This cross-task compatibility produced relative RT benefits only when the instruction for the visual task emphasized overlap at the level of response codes across the task sets (Experiment 1). However, once the effective task set was in place, it continued to produce cross-task compatibility effects even in single-task situations (“ignore” trials in Experiment 2) and when instructions for the visual task did not explicitly require spatial coding of object orientation (Experiment 3). Taken together, the data suggest a considerable degree of task-set inertia in dual-task performance, which is also reinforced by finding costs of switching task sequences (e.g., AC → BC vs. BC → BC) in Experiment 3.     

Intelligence and reaction times in the Hick, Sternberg and Posner paradigms

The relationship between psychometric intelligence and reaction times (RTs) in three well-known elementary cognitive tasks (Hick simple and choice reaction time task, Sternberg's short-term memory scanning, Posner's letter matching) was studied in a sample of 116 participants. In conformity with other studies mean RTs and intraindividual variabilities (SDs) of RT were correlated significantly with Raven's Advanced Progressive Matrices (APM). On the basis of the mental speed theory the processing measures or component scores (like slopes in the Hick and Sternberg paradigm and the NI-PI measure in the Posner task) should give the most substantial relationships with intelligence. However, as in other previous studies these measures displayed rather low, albeit significant, relationships with intelligence, which was probably due to the low reliability of these parameters. For the Posner paradigm, we proposed alternative approaches to compute an indicator for long-term memory (LTM) access that gave substantial correlations with intelligence. We conclude that LTM access is significantly associated with psychometric intelligence, whereas up to now there has been no unequivocal evidence for a substantial relationship between short-term memory access in the Sternberg task and intelligence.