Neural correlates of spatial working memory load in a delayed match-to-sample saccade task

Patients with schizophrenia exhibit impairments in working memory that often appear in attenuated form in persons at high risk for the illness. The authors hypothesized that deviations in task-related brain activation and deactivation would occur in persons with an at-risk mental state performing a working memory task that entailed the maintenance and manipulation of letters. Participants at ultra high risk for developing psychosis (N=60), identified using the Comprehensive Assessment of At-Risk Mental States, and healthy comparison subjects (N=38) 14 to 29 years of age underwent functional MRI while performing a verbal working memory task. Group differences in brain activation were identified using analysis of covariance. The two groups did not show significant differences in speed or accuracy of performance, even after accounting for differences in education. Irrespective of task condition, at-risk participants exhibited significantly less activation than healthy comparison subjects in the left anterior insula. During letter manipulation, at-risk persons exhibited greater task-related deactivation within the default-mode network than comparison subjects. Region-of-interest analysis in the at-risk group revealed significantly greater right dorsolateral prefrontal cortex activation during manipulation of letters. Despite comparable behavioral performance, at-risk participants performing a verbal working memory task exhibited altered brain activation compared with healthy subjects. These findings demonstrate an altered pattern of brain activation in at-risk persons that contains elements of reduced function as well as compensation.

Event Abstract Back to Event Age differences in the reliance on executive resources during updating working memory depend on memory load Michel Isingrini1*, Lucie Angel1, Severine Fay1, Laurence Taconnat1, Patrick Lemaire2 and Badiaa Bouazzaoui1 1 University of Tours - Research Center on Cognition and Learning, Psychology, France 2 University of Aix-Marseille, Psychology, France In this study, the rationale of the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH; Reuter-Lorenz & Cappell, 2008) was used to investigate how executive control is involved when young and older adults accomplish an updating working-memory task. We hypothesized that the functional neural CRUNCH mechanisms would be reflected at a cognitive level by an executive CRUNCH-like mechanism that would be highlighted through correlations between performance on cognitive and executive function measures that would interact with levels of task difficulty during adulthood. Correlational and regression approaches were used to test the hypothesis that age-related differences in the correlation between working memory and executive control vary as a function of memory load. Consistent with CRUNCH predictions, we found that executive control was more used at lower memory loads by older adults and at higher memory loads in young adults. We also found that executive and speed factors are two significant resources involved in UWMT performance for both young and older adults, but that these resources are differently involved as a function of age and load level. Moreover, executive functioning appeared as the only predictor paralleling the expected CRUNCH pattern. Finally, as regard, that in conditions in which they relied on executive control, older adults were able to obtain as good performance as young adults, we discuss the possibility that greater reliance on executive resources may serve as a compensatory mechanism in older adults. Overall, these results support the validity of the CRUNCH model as an account of age-related differences in executive control engagement. Keywords: Aging, executive functions, Updating, Working memory load, CRUNCH model Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Cognition and Executive Processes Citation: Isingrini M, Angel L, Fay S, Taconnat L, Lemaire P and Bouazzaoui B (2015). Age differences in the reliance on executive resources during updating working memory depend on memory load. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00125 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Prof. Michel Isingrini, University of Tours - Research Center on Cognition and Learning, Psychology, Tours, France, isingrini@univ-tours.fr Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Michel Isingrini Lucie Angel Severine Fay Laurence Taconnat Patrick Lemaire Badiaa Bouazzaoui Google Michel Isingrini Lucie Angel Severine Fay Laurence Taconnat Patrick Lemaire Badiaa Bouazzaoui Google Scholar Michel Isingrini Lucie Angel Severine Fay Laurence Taconnat Patrick Lemaire Badiaa Bouazzaoui PubMed Michel Isingrini Lucie Angel Severine Fay Laurence Taconnat Patrick Lemaire Badiaa Bouazzaoui Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Neural effects of cognitive control load on auditory selective attention

An increase in concurrent working memory load has been shown to amplify the attentional blink. The present study investigated the temporal locus of this phenomenon, by using a dual rapid serial visual presentation paradigm that enabled the measurement of lateralized event-related potentials. The P3 component was shown to be affected by both working memory load and the lag between the target stimuli, consistent with current models of temporal attention and a functional explanation of the P3 in terms of memory consolidation. P3 amplitude was reduced for short target lags and high memory loads. The P2 component was affected by lag only, and not memory load. Importantly, the N2pc component was modulated also by both lag and memory load. The results showed that early attentional processing (as marked by the N2pc) was suppressed by increased involvement of working memory, a phenomenon not well predicted by many current theories of temporal attention.

We examined the effects of chronic unilateral lesions to either the inferior parietal lobe, or to the dorsolateral prefrontal cortex including the frontal eye fields (FEFs), upon human visual perception and saccades in temporal-order-judgment (TOJ) tasks. Two visual events were presented on each trial, one in each hemifield at various stimulus onset asynchronies (SOAs). In the saccade task, patients moved their eyes to whichever stimulus attracted gaze first. In the perceptual-manual task, they pressed a button to indicate which stimulus was perceived first. Frontal patients showed appropriate TOJs for visual targets in both tasks. Parietal patients showed appropriate TOJs in the perceptual-manual but not the saccade task; their saccades tended to be ipsilesional unless the contralesional target led substantially. This reveals a bias in saccade choice after parietal damage that cannot be attributed to deficient visual perception. These results challenge previous claims that only anterior lesions produce motoric spatial biases in humans. However, they are in accord with recent neurophysiological evidence for parietal involvement in saccade generation, and also with suggestions that visuomotor transformations in the parietal lobe serving direct spatial motor responses can dissociate from conscious perception as indicated by indirect arbitrary responses.

Intelligent technologies have shifted operator tasks from physical to cognitive demands, making it crucial to understand the impact of task load on visual search tasks. This study examined the effects of auditory working memory and visual perceptual load on inspection tasks using electroencephalography, electrooculography, and electromyography (EMG). Working memory load was varied by an N‐back task, and perceptual load by interference presence. Results indicated: (1) Excessive auditory working memory load induces interference suppression, with event‐related potential P300 and P200 amplitudes indicating sensitivity to perceptual load; (2) Delta, theta, alpha, and low beta band power spectral densities (PSDs) are sensitive to working memory load, with alpha being most sensitive; (3) Eye blink rate (EBR) increases with working memory load; (4) EMG activity detection may not effectively detect working memory load despite observed trends; (5) Strong positive correlations exist within PSD bands and between P300/P200 amplitudes at certain electrodes, with significant correlations between different modality indicators, such as negative correlations between EBR and low beta band PSD and positive correlations between root mean square, integrated EMG (iEMG), and F4 electrode P300 amplitude.

Error monitoring is essential for detecting errors and may facilitate behavioral adjustments that can reduce or prevent future errors. At times, error monitoring must occur while individuals are engaged in other, cognitively demanding tasks that might consume processing resources necessary for error monitoring. Here, we set out to determine whether concurrent working memory (WM) load interferes with error monitoring, as measured using event-related potentials, the error-related negativity (Ne/ERN), and error positivity (Pe). Fifty-four participants (n = 33 female) completed an arrowhead flanker task, with trials presented under low (2 letter) or high (6 letter) WM load. Participants were required to hold letter strings in memory and to recall these letters at the end of a set of flanker trials. Results showed that WM load reduced the Pe but did not affect the Ne/ERN. Therefore, WM load appeared to attenuate later, more elaborated stages of error processing, though initial error detection was unaffected. Additionally, high WM load slowed reaction times overall, but did not lead to a significant increase in errors. As such, slower responses may have helped participants maintain comparable accuracy for low-load versus high-load trials. Overall, results indicate that WM load interferes with the evaluation of error significance, which could interfere with behavioral adaptations over time.

The present study examined how native phonological and phonetic factors in non-native speech perception (Perceptual Assimilation Model [PAM]: Best, 1995) affect non-native imitation of Thai tones by Thai-naïve Mandarin and Vietnamese participants, and how memory load and stimulus variability shift the balance between phonological versus phonetic modes (Automatic Selective Perception model [ASP]: Strange, 2011) in imitation. Although overall imitation was quite good, native phonological influences, as reflected in Categorised versus Uncategorised assimilation types in a prior perception study with the same participants (Chen, Antoniou, & Best, 2023), constrained non-native tone imitations. Residual perceptual sensitivity to phonetic differences between the target stimuli and native tones, as reflected in percent choice and goodness ratings in assimilation, also affected imitation. Effects of stimulus variability and memory load were restricted and interacted with specific tones for each participant group. Imitations were generally more accurate under low memory load, constant talker and vowel conditions, consistent with a more phonetic mode of perception. Imitation accuracy decreased under high memory load, variable talker and vowel conditions, consistent with a more phonological mode of perception. Results support the PAM and ASP accounts of native phonological and phonetic effects in non-native perception and extend them to non-native tone imitation.

Recent studies have shown that spontaneous pre-stimulus fluctuations in brain activity affect higher-order cognitive processes, including risky decision-making, cognitive flexibility, and aesthetic judgments. However, there is currently no direct evidence to suggest that pre-choice activity influences value-based decisions that require self-control. We examined the impact of fluctuations in pre-choice activity in key regions of the reward system on self-control in food choice. In the functional magnetic resonance imaging (fMRI) scanner, 49 participants made 120 food choices that required self-control in high and low working memory load conditions. The task was designed to ensure that participants were cognitively engaged and not thinking about upcoming choices. We defined self-control success as choosing a food item that was healthier over one that was tastier. The brain regions of interest (ROIs) were the ventral tegmental area (VTA), putamen, nucleus accumbens (NAc), and caudate nucleus. For each participant and condition, we calculated the mean activity in the 3-s interval preceding the presentation of food stimuli in successful and failed self-control trials. These activities were then used as predictors of self-control success in a fixed-effects logistic regression model. The results indicate that increased pre-choice VTA activity was linked to a higher probability of self-control success in a subsequent food-choice task within the low-load condition, but not in the high-load condition. We posit that pre-choice fluctuations in VTA activity change the reference point for immediate (taste) reward evaluation, which may explain our finding. This suggests that the neural context of decisions may be a key factor influencing human behavior.

BackgroundCompromised object‐based spatial navigation and spatio‐cognitive map navigation are critical early indicators of Alzheimer's Disease. Distinct neural processes, such as the interaction between posterior parietal cortices and lateral entorhinal cortex, are significant for egocentric object‐based processing, while the retrosplenial cortex (RSC) and hippocampus interaction is important for allocentric map processing. Identifying the mechanisms underlying cognitive impairment can help engage dysfunctional circuits and improve rehabilitation through closed‐loop stimulation paradigms. In this study, we explore these circuits with a passive cognitive task that evaluates cortical energy distribution and increases working memory load, while participants navigate in real‐world settings. We hypothesize that ego‐ versus allocentric navigation performance decline under high memory load may reveal early damage in relevant circuits, which could serve as clinical markers.MethodParticipants navigated five standardized paths with varying stress loads (high and low) while performing a Digit Numbering Task (DNT). An auditory mismatch negativity paradigm was also used to assess cortical energy distribution. Behavioral data were collected with electroencephalography for N = 24 (age>55, 14 males, MCI=12) subjects, screened as control or MCI using the Mini‐Mental State Exam.ResultsA significant difference was observed in DNT accuracy between groups (control: 68.9±38.8, MCI=52.3±42.1, p = 0.04*). No significant differences were found between the two groups for egocentric or allocentric performance across working memory loads. However, allocentric performance was significantly worse in MCI (67.14±54.47, 88.96±53.23, p = 0.0013**). The energy factor, measured as the difference in cortical potentials for deviant and standard trials, was higher for MCI in the parietal region (mu for control= ‐1.016, MCI= ‐2.34 microV, p = 0.0036).ConclusionThe poorer allocentric performance in MCI suggests RSC involvement, offering a potential biomarker for closed‐loop stimulation. Additionally, the increased energy factor observed in the parietal area may indicate compensatory mechanisms in MCI or inefficient resource management. Future work will validate these findings using high‐resolution source localization methodologies.

Using the n-back task, we recently identified, in young subjects, a positive-negative event related potential component (PN(wm)) in a time-range window between 140 and 280 ms after stimulus onset representing an electrophysiological correlate of working memory load. To evaluate age-related electrophysiological changes in working memory processing, we applied the same neuropsychological paradigm and compared densities of the PN(wm) component in 17 young (mean age: 26) and 17 healthy elderly individuals (mean age: 75). Both age groups displayed a PN(wm) component during the two working memory tasks. For the 1-back task, densities were similar in both young and elderly individuals. In contrast, PN(wm) densities increased with higher memory load (2-back>1-back) in the younger but not in the older group. This difference was mainly observed over parietal electrodes suggesting an impaired activation of neural generators within this brain region. The present results are consistent with the hypothesis of decreased brain reserve in the elderly and provide evidence for age-related deficits in the recruitment of posterior cortical neurons with increasing working memory load.

The classic account of the load theory (LT) of attention suggests that increasing cognitive load leads to greater processing of task-irrelevant stimuli due to competition for limited executive resource that reduces the ability to actively maintain current processing priorities. Studies testing this hypothesis have yielded widely divergent outcomes. The inconsistent results may, in part, be related to variability in executive capacity (EC) and task difficulty across subjects in different studies. Here, we used a cross-modal paradigm to investigate whether augmented working memory (WM) load leads to increased early distracter processing, and controlled for the potential confounders of EC and task difficulty. Twenty-three young subjects were engaged in a primary visual WM task, under high and low load conditions, while instructed to ignore irrelevant auditory stimuli. Demands of the high load condition were individually titrated to make task difficulty comparable across subjects with differing EC. Event-related potentials (ERPs) were used to measure neural activity in response to stimuli presented in both the task relevant modality (visual) and task-irrelevant modality (auditory). Behavioral results indicate that the load manipulation and titration procedure of the primary visual task were successful. ERPs demonstrated that in response to visual target stimuli, there was a load-related increase in the posterior slow wave, an index of sustained attention and effort. Importantly, under high load, there was a decrease of the auditory N1 in response to distracters, a marker of early auditory processing. These results suggest that increased WM load is associated with enhanced attentional engagement and protection from distraction in a cross-modal setting, even after controlling for task difficulty and EC. Our findings challenge the classic LT and offer support for alternative models.

We recently showed that transcranial magnetic stimulation (TMS) over the right parietal eye fields disrupts memory of object features and locations across saccades. We applied TMS over the frontal eye fields (FEF) as subjects compared the feature details of visual targets presented either within a single eye fixation (Fixation Task) or across a saccade (Saccade Task). TMS pulses were randomly delivered at one of 3 time intervals around the time of the saccade, or at equivalent times in the Fixation Task. A No-TMS control confirmed that subjects could normally retain approximately 3 visual features. TMS in the Fixation Task had no effect compared with No-TMS, but differences among TMS times were found during right FEF stimulation. TMS over either the right or left FEF disrupted memory performance in the Saccade Task when stimulation coincided most closely with the saccade. The capacity to compare pre-and postsaccadic features was reduced to 1-2 objects, as expected if the spatial aspect of memory was disrupted. These findings suggest that the FEF plays a role in the spatial processing involved in trans-saccadic memory of visual features. We propose that this process employs saccade-related feedback signals similar to those observed in spatial updating.

The dual‐process theory that two different systems of thought coexist in creative thinking has attracted considerable attention. In the field of creative thinking, divergent thinking (DT) is the ability to produce multiple solutions to open‐ended problems in a short time. It is mainly considered an associative and fast process. Meanwhile, insight, the new and unexpected comprehension of close‐ended problems, is frequently marked as a deliberate and time‐consuming thinking process requiring concentrated effort. Previous research has been dedicated to revealing their separate neural mechanisms, while few studies have compared their differences and similarities at the brain level. Therefore, the current study applied Activation Likelihood Estimation to decipher common and distinctive neural pathways that potentially underlie DT and insight. We selected 27 DT studies and 30 insight studies for retrospective meta‐analyses. Initially, two single analyses with follow‐up contrast and conjunction analyses were performed. The single analyses showed that DT mainly involved the inferior parietal lobe (IPL), cuneus, and middle frontal gyrus (MFG), while the precentral gyrus, inferior frontal gyrus (IFG), parahippocampal gyrus (PG), amygdala (AMG), and superior parietal lobe were engaged in insight. Compared to insight, DT mainly led to greater activation in the IPL, the crucial part of the default mode network. However, insight caused more significant activation in regions related to executive control functions and emotional responses, such as the IFG, MFG, PG, and AMG. Notably, the conjunction analysis detected no overlapped areas between DT and insight. These neural findings implicate that various neurocognitive circuits may support DT and insight.

The efferent connections of the cerebral cortex to paramedial tegmental and basilar pons were studied in the monkey by using the retrograde and orthograde capabilities of the horseradish peroxidase (HRP) technique. Six capuchin monkeys (Cebus apella) received transcannular pontine HRP gel implants to retrogradely label the cells of origin of corticopontine projections. Four additional capuchin monkeys, one rhesus (Macaca mulatta), and one cynomolgus (Macaca fascicularis) monkey, received HRP gel implants in premotor (area 6), frontal eye field (FEF, area 8), superior (area 5), and inferior (area 7) parietal lobules to orthogradely label the course and termination of corticopontine projections, and thus to confirm the retrograde studies. The brains were processed according to the tetramethylbenzidine (TMB) protocol of Mesulam ('78) and studied with darkfield microscopy. Premotor (area 6) frontal cortex and FEF (area 8) were found to be the main sources of cortical inputs to the ipsilateral paramedian basilar pons, whereas FEF, dorsal prefrontal convexity, and dorsal medial prefrontal (granular frontal association) cortex were the main sources of bilateral projections to the paramedian pontine tegmentum. The medial portion of the nucleus reticularis tegmenti pontis (NRTP), considered to be a tegmental extension of the basilar pontine gray, also received its principal cortical input from the frontal lobe. Parietal cortex, on the other hand, was observed to project to lateral NRTP and lateral basilar pons. Although the possibility exists of convergence of frontal and parietal eye field efferents in the NRTP, the frontal eye field and prefrontal cortex appear to be the principal source of cortical projections to the paramedian pontine tegmentum, which contains the physiologically defined PPRF (paramedian pontine reticular formation), an important preoculomotor center. The results are discussed primarily with regard to their significance for potential cortical influence on the oculomotor system.