Low Memory Load Research Articles

Working memory regulates trait anxiety-related threat processing biases.

High trait anxious individuals tend to show biased processing of threat. Correlational evidence suggests that executive control could be used to regulate such threat-processing. On this basis, we hypothesized that trait anxiety-related cognitive biases regarding threat should be exaggerated when executive control is experimentally impaired by loading working memory. In Study 1, 68 undergraduates read ambiguous vignettes under high and low working memory load; later, their interpretations of these vignettes were assessed via a recognition test. Trait anxiety predicted biased interpretation of social threat vignettes under high working memory load, but not under low working memory load. In Study 2, 53 undergraduates completed a dot probe task with fear-conditioned Japanese characters serving as threat stimuli. Trait anxiety predicted attentional bias to the threat stimuli but, again, this only occurred under high working memory load. Interestingly however, actual eye movements toward the threat stimuli were only associated with state anxiety, and this was not moderated by working memory load, suggesting that executive control regulates biased threat-processing downstream of initial input processes such as orienting. These results suggest that cognitive loads can exacerbate trait anxiety-related cognitive biases, and therefore represent a useful tool for assessing cognitive biases in future research. More importantly, since biased threat-processing has been implicated in the etiology and maintenance of anxiety, poor executive control may be a risk factor for anxiety disorders. (PsycINFO Database Record

Processing of negative stimuli facilitates event-based prospective memory only under low memory load

ABSTRACTEvent-based prospective memory (PM) is related to the ability to execute a previously planned action at the appropriate situation. Previous literature showed enhanced performance when emotional stimuli are used as PM targets. However, it was entirely unexplored whether this effect is susceptible to prospective memory load (PML), related to the number of target events that are relevant for the pending PM task. Here we presented participants with angry or neutral faces for an identity judgment (ongoing task). A different number of faces, depending on low vs. high levels of PML, served as PM targets. The results showed better PM performance following negative than neutral targets, but only under low levels of PML. This indicates that the bottom-up facilitation driven by negative stimuli serving as PM targets dramatically depends on the available attention resources allocated for monitoring the incoming information.

Analyze the beta waves of electroencephalogram signals from young musicians and non-musicians in major scale working memory task

Electroencephalograms can record wave variations in any brain activity. Beta waves are produced when an external stimulus induces logical thinking, computation, and reasoning during consciousness. This work uses the beta wave of major scale working memory N-back tasks to analyze the differences between young musicians and non-musicians. After the feature analysis uses signal filtering, Hilbert-Huang transformation, and feature extraction methods to identify differences, k-means clustering algorithm are used to group them into different clusters. The results of feature analysis showed that beta waves significantly differ between young musicians and non-musicians from the low memory load of working memory task.

The Role of Cognitive Load in Intentional Forgetting Using the Think/No-Think Task.

We investigated the role of cognitive control in intentional forgetting by manipulating working memory load during the think/no-think task. In two experiments, participants learned a series of cue-target word pairs and were asked to recall the target words associated with some cues or to avoid thinking about the target associated with other cues. In addition to this, participants also performed a modified version of the n-back task which required them to respond to the identity of a single target letter present in the currently presented cue word (n=0 condition, low working memory load), and in either the previous cue word (n=1 condition, high working memory load, Experiment 1) or the cue word presented two trials previously (n=2 condition, high working memory load, Experiment 2). Participants' memory for the target words was subsequently tested using same and novel independent probes. In both experiments it was found that although participants were successful at forgetting on both the same and independent-probe tests in the low working memory load condition, they were only successful at forgetting on the same-probe test in the high working memory load condition. We argue that our findings suggest that the high load working memory task diverted attention from direct suppression and acted as an interference-based strategy. Thus, when cognitive resources are limited participants can switch between the strategies they use to prevent unwanted memories from coming to mind.

Executive control and working memory are involved in sub-second repetitive motor timing

The nature of the relationship between timing and cognition remains poorly understood. Cognitive control is known to be involved in discrete timing tasks involving durations above 1 s, but has not yet been demonstrated for repetitive motor timing below 1 s. We examined the latter in two continuation tapping experiments, by varying the cognitive load in a concurrent task. In Experiment 1, participants repeated a fixed three finger sequence (low executive load) or a pseudorandom sequence (high load) with either 524-, 733-, 1024- or 1431-ms inter-onset intervals (IOIs). High load increased timing variability for 524 and 733-ms IOIs but not for the longer IOIs. Experiment 2 attempted to replicate this finding for a concurrent memory task. Participants retained three letters (low working memory load) or seven letters (high load) while producing intervals (524- and 733-ms IOIs) with a drum stick. High load increased timing variability for both IOIs. Taken together, the experiments demonstrate that cognitive control processes influence sub-second repetitive motor timing.

Retro-dimension-cue benefit in visual working memory.

In visual working memory (VWM) tasks, participants’ performance can be improved by a retro-object-cue. However, previous studies have not investigated whether participants’ performance can also be improved by a retro-dimension-cue. Three experiments investigated this issue. We used a recall task with a retro-dimension-cue in all experiments. In Experiment 1, we found benefits from retro-dimension-cues compared to neutral cues. This retro-dimension-cue benefit is reflected in an increased probability of reporting the target, but not in the probability of reporting the non-target, as well as increased precision with which this item is remembered. Experiment 2 replicated the retro-dimension-cue benefit and showed that the length of the blank interval after the cue disappeared did not influence recall performance. Experiment 3 replicated the results of Experiment 2 with a lower memory load. Our studies provide evidence that there is a robust retro-dimension-cue benefit in VWM. Participants can use internal attention to flexibly allocate cognitive resources to a particular dimension of memory representations. The results also support the feature-based storing hypothesis.

State orientation and memory load impair prospective memory performance in older compared to younger persons

ABSTRACTA modified event-based paradigm of prospective memory was applied to investigate intention initiation in older and younger participants under high versus low memory load (subsequent episodic word recall vs. recognition). State versus action orientation, a personality dimension related to intention enactment, was also measured. State-oriented persons show a superiority effect for the storage of intentions in an explicit format but have a paradoxical deficit in their actual enactment. We predicted an interaction between aging, personality, and memory load, with longer intention-initiation latencies and higher omission rates for older state-oriented participants under high memory load. Results were consistent with predictions and are interpreted according to current personality and prospective memory models of aging.

Motor creativity: the roles of attention breadth and working memory in a divergent doing task

ABSTRACTWe evaluated the dual-pathway model to creativity in a motor context. The model describes separate flexibility and persistence pathways that are affected differently by breadth of attention and working memory. Motor creativity was tested using a divergent doing task. In Experiment 1 participants performed the divergent doing task after attention was broadened, narrowed or not manipulated. In Experiment 2, the divergent doing task was performed with a low or high working memory load. We found that a broad attention increased flexibility but not persistence. Also originality was unaffected. Taxing working memory did not affect persistence, flexibility or originality. The results provide partial support for the dual-pathway model in motor creativity. Discusion focusses on increased demands for the appropriatness of a solution in divergent doing relative to divergent thinking and to degree to which this implies a more general shortcoming of the dual-pathway model.

Oscillation Phase Locking and Late ERP Components of Intracranial Hippocampal Recordings Correlate to Patient Performance in a Working Memory Task.

In working memory tasks, stimulus presentation induces a resetting of intracranial temporal lobe oscillations in multiple frequency bands. To further understand the functional relevance of this phenomenon, we investigated whether working memory performance depends on the phase precision of ongoing oscillations in the hippocampus. We recorded intra-hippocampal local field potentials in individuals performing a working memory task. Two types of trials were administered. For high memory trials presentation of a list of four letters (“List”) was followed by a single letter memory probe (“Test”). Low memory load trials, consisting of four identical letters (AAAA) followed by a probe with the same letter (A), were interspersed. Significant phase locking of ongoing oscillations across trials, estimated by the Pairwise Phase Consistency Index (PPCI) was observed in delta (0.5–4 Hz), theta (5–7 Hz), and alpha (8–12 Hz) bands during stimulus presentation and recall but was increased in low memory load trials. Across patients however, higher delta PPCIs during recall in the left hippocampus were associated with faster reaction times. Because phase locking could also be interpreted as a consequence of a stimulus evoked potential, we performed event related potential analysis (ERP) and examined the relationship of ERP components with performance. We found that both amplitude and latency of late ERP components correlated with both reaction time and accuracy. We propose that, in the Sternberg task, phase locking of oscillations, or alternatively its ERP correlate, synchronizes networks within the hippocampus and connected structures that are involved in working memory.

Influence of pharmacological manipulations of NMDA and cholinergic receptors on working versus reference memory in a dual component odor span task

Developed as a tool to assess working memory capacity in rodents, the odor span task (OST) has significant potential to advance drug discovery in animal models of psychiatric disorders. Prior investigations indicate OST performance is impaired by systemic administration of N-methyl-d-aspartate receptor (NMDA-r) antagonists and is sensitive to cholinergic manipulations. The present study sought to determine whether an impairment in OST performance can be produced by systemic administration of the competitive NMDA-r antagonist 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP; 3, 10, 17 mg/kg i.p.) in a unique dual-component variant of the OST, and whether this impairment is ameliorated by nicotine (0.75 mg/kg i.p.). Male Sprague-Dawley rats were trained to asymptotic level of performance on a 24-trial two-comparison incrementing nonmatching to sample OST. In addition, rats were administered a two-comparison olfactory reference memory (RM) task, which was integrated into the OST. The RM task provided an assessment of the effects of drug administration on global behavioral measures, long-term memory and motivation. Several measures of working memory (span, longest run, and accuracy) were dose dependently impaired by CPP without adversely affecting RM. Analysis of drug effects across trial blocks demonstrated a significant impairment of performance even at low memory loads, suggesting a CPP-induced deficit of olfactory short-term memory that is not load-dependent. Although nicotine did not ameliorate CPP-induced impairments in span or accuracy, it did block the impairment in longest run produced by the 10 mg/kg dose of CPP. Overall, our results indicate that performance in our 24 odor two-comparison OST is capacity dependent and that CPP impaired OST working, but not reference, memory.

Temporal dynamics of visual working memory

The involvement of the human cerebellum in working memory has been well established in the last decade. However, the cerebro-cerebellar network for visual working memory is not as well defined. Our previous fMRI study showed superior and inferior cerebellar activations during a block design visual working memory task, but specific cerebellar contributions to cognitive processes in encoding, maintenance and retrieval have not yet been established. The current study examined cerebellar contributions to each of the components of visual working memory and presence of cerebellar hemispheric laterality was investigated. 40 young adults performed a Sternberg visual working memory task during fMRI scanning using a parametric paradigm. The contrast between high and low memory load during each phase was examined. We found that the most prominent activation was observed in vermal lobule VIIIb and bilateral lobule VI during encoding. Using a quantitative laterality index, we found that left-lateralized activation of lobule VIIIa was present in the encoding phase. In the maintenance phase, there was bilateral lobule VI and right-lateralized lobule VIIb activity. Changes in activation in right lobule VIIIa were present during the retrieval phase. The current results provide evidence that superior and inferior cerebellum contributes to visual working memory, with a tendency for left-lateralized activations in the inferior cerebellum during encoding and right-lateralized lobule VIIb activations during maintenance. The results of the study are in agreement with Baddeley's multi-component working memory model, but also suggest that stored visual representations are additionally supported by maintenance mechanisms that may employ verbal coding.

Transfer after Working Memory Updating Training.

During the past decade, working memory training has attracted much interest. However, the training outcomes have varied between studies and methodological problems have hampered the interpretation of results. The current study examined transfer after working memory updating training by employing an extensive battery of pre-post cognitive measures with a focus on near transfer. Thirty-one healthy Finnish young adults were randomized into either a working memory training group or an active control group. The working memory training group practiced with three working memory tasks, while the control group trained with three commercial computer games with a low working memory load. The participants trained thrice a week for five weeks, with one training session lasting about 45 minutes. Compared to the control group, the working memory training group showed strongest transfer to an n-back task, followed by working memory updating, which in turn was followed by active working memory capacity. Our results support the view that working memory training produces near transfer effects, and that the degree of transfer depends on the cognitive overlap between the training and transfer measures.

Categorical Perception of Topological Relations between Objects

In many types of perception, change are easier to spot a when they are categorical - crossing thresholds between blue and green, or between oblique and straight. Here we show that categorical perception applies powerfully to topological relations between two objects. We showed two pairs of simple objects to participants, and asked them to detect potential changes to the distances between the objects across a 1 second delay. Participants (N=15) were far better at detecting changes that crossed categorical thresholds (M=88%), e.g., from touching to intersecting or from intersecting to containing, compared to changes of equal size that did not cross these boundaries (M=73%) (p < .001). With large memory loads, participants appear to rely heavily on abstract and efficient categorical representations of interobject relations. But under conditions of low memory load, this advantage may be hidden to us. When participants were asked to detect changes to only a single pair, performance for categorical changes (M=93%) and non-categorical changes (M=88%) was more similar (though still significantly different, p = .005). A significant interaction between categorical status and memory load (p < .001) confirmed that the effect was far stronger when load was higher. Previous research shows that humans are skilled at encoding and remembering categorical information. Here we show that this broader principle applies to the perception of spatial relations between objects - a key area of visual processing that has received surprisingly little attention. Meeting abstract presented at VSS 2015

Reading comprehension in children with Down syndrome.

Two studies aimed to investigate the reading comprehension abilities of 14 readers with Down syndrome aged 6 years 8 months to 13 years relative to those of typically developing children matched on word reading ability, and to investigate how these abilities were associated with reading accuracy, listening comprehension, phonological awareness and vocabulary knowledge. Study 1 confirmed significantly poorer passage-reading comprehension than the typically developing group. In an experimental task, readers with Down syndrome understood fewer written sentences than the typical group and, contrary to prediction, received no advantage from printed sentences compared to spoken sentences, despite the lower memory load. Reading comprehension was associated with listening comprehension, word reading and phonological awareness in DS. Vocabulary knowledge was also associated with reading comprehension, mediated by word reading and nonverbal cognitive abilities. Study 2 investigated the longitudinal relationships between reading and language measures in the readers with DS over around 22 months. Time 1 listening comprehension and phonological awareness predicted Time 2 reading comprehension but there was no evidence that reading or reading comprehension predicted Time 2 language scores or phonological awareness, and no evidence that readers had acquired greater depth of vocabulary.

Neural correlates of visuospatial working memory in attention-deficit/hyperactivity disorder and healthy controls

Impaired visuospatial working memory (VSWM) is suggested to be a core neurocognitive deficit in attention-deficit/hyperactivity disorder (ADHD), yet the underlying neural activation patterns are poorly understood. Furthermore, it is unclear to what extent age and gender effects may play a role in VSWM-related brain abnormalities in ADHD. Functional magnetic resonance imaging (fMRI) data were collected from 109 individuals with ADHD (60% male) and 103 controls (53% male), aged 8–25 years, during a spatial span working memory task. VSWM-related brain activation was found in a widespread network, which was more widespread compared with N-back tasks used in the previous literature. Higher brain activation was associated with higher age and male gender. In comparison with controls, individuals with ADHD showed greater activation in the left inferior frontal gyrus (IFG) and the lateral frontal pole during memory load increase, effects explained by reduced activation on the low memory load in the IFG pars triangularis and increased activation during high load in the IFG pars opercularis. Age and gender effects did not differ between controls and individuals with ADHD. Results indicate that individuals with ADHD have difficulty in efficiently and sufficiently recruiting left inferior frontal brain regions with increasing task difficulty.

Attention allocation: Relationships to general working memory or specific language processing

Attention allocation, updating working memory, and language processing are interdependent cognitive tasks related to the focused direction of limited resources, refreshing and substituting information in the current focus of attention, and receiving/sending verbal communication, respectively. The current study systematically examined the relationship among executive attention, working memory executive skills, and language abilities while adjusting for individual differences in short-term memory. School-age children completed a selective attention task requiring them to recall whether a presented shape was in the same place as a previous target shape shown in an array imposing a low or high working memory load. Results revealed a selective attention cost when working above but not within memory span capacity. Measures of general working memory were positively related to overall task performance, whereas language abilities were related to response time. In particular, higher language skills were associated with faster responses under low load conditions. These findings suggest that attentional control and storage demands have an additive impact on working memory resources but provide only limited evidence for a domain-general mechanism in language learning.

A long-term fatty fish intervention improved executive function in inpatients with antisocial traits and a history of alcohol and drug abuse.

The aim of the present study was to investigate the effects of fatty fish consumption on cognitive functioning in a group of inpatients characterized by antisocial behavior. Eighty-three male forensic inpatients participated in this study. Participants were randomly assigned into a Fish or a Control group (e.g., meat, chicken, pork). One decision-making task, the Iowa Gambling Task (IGT), and one planning task, the Tower of Hanoi (ToH), were administered before (pre-test) and at the end of the intervention period (post-test). For the IGT the Fish group showed improved performance from pre- to post- test. Moreover, the Fish group showed significantly better performance than the Control group on the IGT at post-test. The Fish group also demonstrated improved performance from pre- to post-test on the ToH; however, this was limited to participants with a history of substance abuse. Further, the improvement was only significant for tasks with high working memory load (5-7 move problems), and not for tasks with low working memory load (1-4 move problems). The Control group showed no improvement on any of the tasks regardless of alcohol or drug abuse history. The present study suggests that regular fatty fish consumption may improve executive functions in forensic inpatients with antisocial traits and a history of substance abuse. Thus, the current results may have important implications with regard to health care interventions.

Age-related changes in brain activity are specific for high order cognitive processes during successful encoding of information in working memory.

Memory capacity suffers an age-related decline, which is supposed to be due to a generalized slowing of processing speed and to a reduced availability of processing resources. Information encoding in memory has been demonstrated to be very sensitive to age-related changes, especially when carried out through self-initiated strategies or under high cognitive demands. However, most event-related potentials (ERP) research on age-related changes in working memory (WM) has used tasks that preclude distinction between age-related changes in encoding and retrieval processes. Here, we used ERP recording and a delayed match to sample (DMS) task with two levels of memory load to assess age-related changes in electrical brain activity in young and old adults during successful information encoding in WM. Age-related decline was reflected in lower accuracy rates and longer reaction times in the DMS task. Beside, only old adults presented lower accuracy rates under high than low memory load conditions. However, effects of memory load on brain activity were independent of age and may indicate an increased need of processing after stimulus classification as reflected in larger mean voltages in high than low load conditions between 550 and 1000 ms post-stimulus for young and old adults. Regarding age-related effects on brain activity, results also revealed smaller P2 and P300 amplitudes that may signal the existence of an age dependent reduction in the processing resources available for stimulus evaluation and categorization. Additionally, P2 and N2 latencies were longer in old than in young participants. Furthermore, longer N2 latencies were related to greater accuracy rates on the DMS task, especially in old adults. These results suggest that age-related slowing of processing speed may be specific for target stimulus analysis and evaluation processes. Thus, old adults seem to improve their performance the longer they take to evaluate the stimulus they encode in visual WM.

Real-time state estimation in a flight simulator using fNIRS.

Working memory is a key executive function for flying an aircraft. This function is particularly critical when pilots have to recall series of air traffic control instructions. However, working memory limitations may jeopardize flight safety. Since the functional near-infrared spectroscopy (fNIRS) method seems promising for assessing working memory load, our objective is to implement an on-line fNIRS-based inference system that integrates two complementary estimators. The first estimator is a real-time state estimation MACD-based algorithm dedicated to identifying the pilot’s instantaneous mental state (not-on-task vs. on-task). It does not require a calibration process to perform its estimation. The second estimator is an on-line SVM-based classifier that is able to discriminate task difficulty (low working memory load vs. high working memory load). These two estimators were tested with 19 pilots who were placed in a realistic flight simulator and were asked to recall air traffic control instructions. We found that the estimated pilot’s mental state matched significantly better than chance with the pilot’s real state (62% global accuracy, 58% specificity, and 72% sensitivity). The second estimator, dedicated to assessing single trial working memory loads, led to 80% classification accuracy, 72% specificity, and 89% sensitivity. These two estimators establish reusable blocks for further fNIRS-based passive brain computer interface development.

Hearing loss impacts neural alpha oscillations under adverse listening conditions.

Degradations in external, acoustic stimulation have long been suspected to increase the load on working memory (WM). One neural signature of WM load is enhanced power of alpha oscillations (6–12 Hz). However, it is unknown to what extent common internal, auditory degradation, that is, hearing impairment, affects the neural mechanisms of WM when audibility has been ensured via amplification. Using an adapted auditory Sternberg paradigm, we varied the orthogonal factors memory load and background noise level, while the electroencephalogram was recorded. In each trial, participants were presented with 2, 4, or 6 spoken digits embedded in one of three different levels of background noise. After a stimulus-free delay interval, participants indicated whether a probe digit had appeared in the sequence of digits. Participants were healthy older adults (62–86 years), with normal to moderately impaired hearing. Importantly, the background noise levels were individually adjusted and participants were wearing hearing aids to equalize audibility across participants. Irrespective of hearing loss (HL), behavioral performance improved with lower memory load and also with lower levels of background noise. Interestingly, the alpha power in the stimulus-free delay interval was dependent on the interplay between task demands (memory load and noise level) and HL; while alpha power increased with HL during low and intermediate levels of memory load and background noise, it dropped for participants with the relatively most severe HL under the highest memory load and background noise level. These findings suggest that adaptive neural mechanisms for coping with adverse listening conditions break down for higher degrees of HL, even when adequate hearing aid amplification is in place.