Neurocognitive subprocesses of working memory performance.
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ABSTRACT:
SUBMITTER: Lenartowicz A
PROVIDER: S-EPMC8563426 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Working memory is linked to the functions of the frontal areas, in which neural activity is mediated by dopaminergic and serotonergic tones. However, there is no consensus regarding how the dopaminergic and serotonergic systems influence working memory subprocesses. The present study used an imaging genetics approach to examine the interaction between neurochemical functions and working memory performance. We focused on functional polymorphisms of the catechol-O-methyltransferase (COMT) Val(158)Met and serotonin 2A receptor (HTR2A) -1438G/A genes, and devised a delayed recognition task to isolate the encoding, retention, and retrieval processes for visual information. The COMT genotypes affected recognition accuracy, whereas the HTR2A genotypes were associated with recognition response times. Activations specifically related to working memory were found in the right frontal and parietal areas, such as the middle frontal gyrus (MFG), inferior frontal gyrus (IFG), anterior cingulate cortex (ACC), and inferior parietal lobule (IPL). MFG and ACC/IPL activations were sensitive to differences between the COMT genotypes and between the HTR2A genotypes, respectively. Structural equation modeling demonstrated that stronger connectivity in the ACC-MFG and ACC-IFG networks is related to better task performance. The behavioral and fMRI results suggest that the dopaminergic and serotonergic systems play different roles in the working memory subprocesses and modulate closer cooperation between lateral and medial frontal activations.
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Project description:Recent work has begun to shed light on the neural correlates and possible mechanisms of polygenic risk for schizophrenia. Here, we map a schizophrenia polygenic risk profile score (PRS) based on genome-wide association study significant loci onto variability in the activity and functional connectivity of a frontoparietal network supporting the manipulation versus maintenance of information during a numerical working memory (WM) task in healthy young adults (n = 99, mean age = 19.8). Our analyses revealed that higher PRS was associated with hypoactivity of the dorsolateral prefrontal cortex (dlPFC) during the manipulation but not maintenance of information in WM (r2 = .0576, P = .018). Post hoc analyses revealed that PRS-modulated dlPFC hypoactivity correlated with faster reaction times during WM manipulation (r2 = .0967, P = .002), and faster processing speed (r2 = .0967, P = .003) on a separate behavioral task. These PRS-associated patterns recapitulate dlPFC hypoactivity observed in patients with schizophrenia during central executive manipulation of information in WM on this task.
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Project description:BackgroundWorking memory, as a complex system, consists of two independent components: manipulation and maintenance process, which are defined as executive control and storage process. Previous studies mainly focused on the overall effect of transcranial direct current stimulation (tDCS) on working memory. However, little has been known about the segregative effects of tDCS on the sub-processes within working memory.MethodTranscranial direct current stimulation, as one of the non-invasive brain stimulation techniques, is being widely used to modulate the cortical activation of local brain areas. This study modified a spatial n-back experiment with anodal and cathodal tDCS exertion on the right dorsolateral prefrontal cortex (DLPFC), aiming to investigate the effects of tDCS on the two sub-processes of working memory: manipulation (updating) and maintenance. Meanwhile, considering the separability of tDCS effects, we further reconfirmed the causal relationship between the right DLPFC and the sub-processes of working memory with different tDCS conditions.ResultsThe present study showed that cathodal tDCS on the right DLPFC selectively improved the performance of the modified 2-back task in the difficult condition, whereas anodal tDCS significantly reduced the performance of subjects and showed an speeding-up tendency of response time. More precisely, the results of discriminability index and criterion showed that only cathodal tDCS enhanced the performance of maintenance in the difficult condition. Neither of the two tDCS conditions affected the performance of manipulation (updating).ConclusionThese findings provide evidence that cathodal tDCS of the right DLPFC selectively affects maintenance capacity. Besides, cathodal tDCS also serves as an interference suppressor to reduce the irrelevant interference, thereby indirectly improving the working memory capacity. Moreover, the right DLPFC is not the unique brain regions for working memory manipulation (updating).
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Project description:Individuals differ in how they perceive, remember, and think. There is evidence for the existence of distinct subgroups that differ in cognitive performance within the older population. However, it is less clear how individual differences in cognition in old age are linked to differences in brain-based measures. We used latent-profile analysis on n-back working-memory (WM) performance to identify subgroups in a large sample of older adults (n = 181; age = 64-68 years). Our analysis identified one larger normal subgroup with higher performance (n = 113; 63%), and a second smaller subgroup (n = 55; 31%) with lower performance. The low-performing subgroup showed weaker load-dependent BOLD modulation and lower connectivity within the fronto-parietal network (FPN) as well as between FPN and striatum during n-back, along with lower FPN connectivity at rest. This group also exhibited lower FPN structural integrity, lower frontal dopamine D2 binding potential, inferior performance on offline WM tests, and a trend-level genetic predisposition for lower dopamine-system efficiency. By contrast, this group exhibited relatively intact episodic memory and associated brain measures (i.e., hippocampal volume, structural, and functional connectivity within the default-mode network). Collectively, these data provide converging evidence for the existence of a group of older adults with impaired WM functioning characterized by reduced cortico-striatal coupling and aberrant cortico-cortical integrity within FPN.
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Project description:Inhibitory control processes are known to be modulated by working memory demands. However, the neurobiological mechanisms behind these modulations are inconclusive. One important system to consider in this regard is the locus coeruleus (LC) norepinephrine (NE) system. In the current study the role of the LC-NE system by means of pupil diameter recordings that are integrated with neurophysiological (EEG) and source localization data were examined. A combined mental-rotation Go/Nogo task was used. The results show that increases in working memory load complicate response inhibition processes. On a neurophysiological level these effects were reflected by specific modulations in event-related potentials (ERPs) reflecting motor inhibition processes (i.e., Nogo-P3). Attentional selection processes (reflected by the P1 and N1) as well as pre-motor inhibition or conflict monitoring processes (reflected by the Nogo-N2) were not affected. Activity of the LC-NE systems, as indexed by the pupil diameter data, predicted neurophysiological processes selectively in the Nogo-P3 time range. Source localization analyses suggest that this modulation occurs in the right middle and inferior frontal gyrus. The study provides evidence that the LC-NE system is an important neurobiological system modulating the effects of working memory load on response inhibition processes. More specifically, it modulates a subset of dissociable cognitive processes that are related to prefrontal cortical regions. Hum Brain Mapp 38:68-81, 2017. © 2016 Wiley Periodicals, Inc.
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Project description:BACKGROUND:Attention-deficit/hyperactivity disorder (ADHD) is associated with working memory (WM) deficits. However, WM is a multiprocess construct that can be impaired through several pathways, leaving the source of WM impairments in ADHD unresolved. In this study, we aim to replicate, in an independent sample, previously reported deficits in component processes of WM deficits in ADHD and expand to consider their implications for neurocognitive outcomes. METHODS:In 119 children (7-14 years old, 85 with ADHD), we used electroencephalography measures to quantify component processes during performance of a spatial working memory task. We quantified stimulus encoding using alpha range (8-12 Hz) power; vigilance by the P2 event-related potential to cues; and WMmaintenance by occipital-alpha and frontal-theta (4-7 Hz) power. These measures were evaluated against metrics of executive function, ADHD symptoms, and academic achievement. RESULTS:Encoding alpha-power decreases and cue P2 amplitude were attenuated in ADHD, whereas occipital-alpha power during maintenance was significantly greater in ADHD, consistent with a compensatory response to weak encoding. Weak alpha modulation during encoding was associated with poorer reading comprehension and executive function, as well as enhanced ADHD symptoms. Previously reported effects in frontal-theta power failed to replicate. CONCLUSIONS:Stimulus encoding, a component process of WM coupled to alpha modulation, is impaired in ADHD, and, unlike WM maintenance or vigilance processes, has implications outside of the laboratory via a relationship with executive function, and, to a weaker extent, reading comprehension.
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Project description:The ability to manipulate information in working memory is a key factor in cognitive development. Here, we used event-related functional MRI to test the hypothesis that developmental improvements in manipulation, relative to pure maintenance, are associated with increased recruitment of dorsolateral (DL) prefrontal cortex (PFC) and superior parietal cortex. Three age groups (8-12 years old, 13-17 years old, and 18-25 years old) performed an object-working memory task with separate maintenance and manipulation conditions. We found that 8- to 12-year-olds did not perform the task as well as adolescents or adults, particularly on trials requiring manipulation in addition to maintenance. In this study, no age differences were observed in the activation profile of ventrolateral PFC, a region associated with online maintenance. In contrast, unlike the older participants, 8- to 12-year-olds failed to recruit right DL PFC and bilateral superior parietal cortex during the delay period for manipulation relative to maintenance. This group difference was observed specifically during the delay period, while participants reordered items in working memory, and could not be accounted for by group differences in performance. Across participants, activation levels in right DL PFC and superior parietal cortex, but not ventrolateral PFC, were positively correlated with performance on manipulation trials. These results indicate that increased recruitment of right DL PFC and bilateral parietal cortex during adolescence is associated with improvements in the ability to work with object representations.
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Project description:Human immunodeficiency virus (HIV) continues to have adverse effects on cognition and the brain in many infected people, despite a reduced incidence of HIV-associated dementia with combined antiretroviral therapy (cART). Working memory is often affected, along with attention, executive control, and cognitive processing speed. Verbal working memory (VWM) requires the interaction of each of the cognitive component processes along with a phonological loop for verbal repetition and rehearsal. HIV-related functional brain response abnormalities during VWM are evident in functional MRI (fMRI), though the neural substrate underlying these neurocognitive deficits is not well understood. The current study addressed this by comparing 24 HIV+ to 27 demographically matched HIV-seronegative (HIV-) adults with respect to fMRI activation on a VWM paradigm (n-back) relative to performance on two standardized tests of executive control, attention and processing speed (Stroop and Trail Making A-B). As expected, the HIV+ group had deficits on these neurocognitive tests compared to HIV- controls, and also differed in neural response on fMRI relative to neuropsychological performance. Reduced activation in VWM task-related brain regions on the 2-back was associated with Stroop interference deficits in HIV+ but not with either Trail Making A or B performance. Activation of the posterior cingulate cortex (PCC) of the default mode network during rest was associated with Hopkins Verbal Learning Test-2 (HVLT-2) learning in HIV+. These effects were not observed in the HIV- controls. Reduced dynamic range of neural response was also evident in HIV+ adults when activation on the 2-back condition was compared to the extent of activation of the default mode network during periods of rest. Neural dynamic range was associated with both Stroop and HVLT-2 performance. These findings provide evidence that HIV-associated alterations in neural activation induced by VWM demands and during rest differentially predict executive-attention and verbal learning deficits. That the Stroop, but not Trail Making was associated with VWM activation suggests that attentional regulation difficulties in suppressing interference and/or conflict regulation are a component of working memory deficits in HIV+ adults. Alterations in neural dynamic range may be a useful index of the impact of HIV on functional brain response and as a fMRI metric in predicting cognitive outcomes.
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Project description:Fluctuations in attentional control can lead to failures of working memory (WM), in which the subject is no better than chance at reporting items from a recent display. In three experiments, we used a whole-report measure of visual WM to examine the impact of feedback on the rate of failures. In each experiment, subjects remembered an array of colored items across a blank delay, and then reported the identity of items using a whole-report procedure. In Experiment 1, we gave subjects simple feedback about the number of items they correctly identified at the end of each trial. In Experiment 2, we gave subjects additional information about the cumulative number of items correctly identified within each block. Finally, in Experiment 3, we gave subjects weighted feedback in which poor trials resulted in lost points and consistent successful performance received "streak" points. Surprisingly, simple feedback (Exp. 1) was ineffective at improving average performance or decreasing the rate of poor-performance trials. Simple cumulative feedback (Exp. 2) modestly decreased poor-performance trials (by 7 %). Weighted feedback produced the greatest benefits, decreasing the frequency of poor-performance trials by 28 % relative to baseline performance. This set of results demonstrates the usefulness of whole-report WM measures for investigating the effects of feedback on WM performance. Further, we showed that only a feedback structure that specifically discouraged lapses using negative feedback led to large reductions in WM failures.
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Project description:Alpha band (8-12 Hz) phase dynamics in the visual cortex are thought to reflect fluctuations in cortical excitability that influences perceptual processing. As such, visual stimuli are better detected when their onset is concurrent with specific phases of the alpha cycle. However, it is unclear whether alpha phase differentially influences cognitive performance at specific times relative to stimulus onset (i.e., is the influence of phase maximal before, at, or after stimulus onset?). To address this, participants performed a delayed-recognition, working memory (WM) task for visual motion direction during two separate visits. The first visit utilized functional magnetic resonance (fMRI) imaging to identify neural regions associated with task performance. Replicating previous studies, fMRI data showed engagement of visual cortical area V5, as well as a prefrontal cortical region, the inferior frontal junction (IFJ). During the second visit, transcranial magnetic stimulation (TMS) was applied separately to both the right IFJ and right V5 (with the vertex as a control region) while electroencephalography (EEG) was simultaneously recorded. During each trial, a single pulse of TMS (spTMS) was applied at one of six time points (-200, -100, -50, 0, 80, 160 ms) relative to the encoded stimulus onset. Results demonstrated a relationship between the phase of the posterior alpha signal prior to stimulus encoding and subsequent response times to the memory probe two seconds later. Specifically, spTMS to V5, and not the IFJ or vertex, yielded faster response times, indicating improved WM performance, when delivered during the peak, compared to the trough, of the alpha cycle, but only when spTMS was applied 100 ms prior to stimulus onset. These faster responses to the probe correlated with decreased early event related potential (ERP) amplitudes (i.e., P1) to the probe stimuli. Moreover, participants that were least affected by spTMS exhibited greater functional connectivity between V5 and fronto-parietal regions. These results suggest that posterior alpha phase indexes a critical time period for motion processing in the context of WM encoding goals, which occurs in anticipation of stimulus onset.
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