Decoupling of reaction time-related default mode network activity with cognitive demand

The angular gyrus serves as an interface between the non-lexical reading network and the semantic system: evidence from dynamic causal modeling

Understanding encoded language, such as written words, requires multiple cognitive processes that act in a parallel and interactive fashion. These processes and their interactions, however, are not fully understood. Various conceptual and methodical approaches including computational modeling and neuroimaging have been applied to better understand the neural underpinnings of these complex processes in the human brain. In this study, we tested different predictions of cortical interactions that derived from computational models for reading using dynamic causal modeling. Morse code was used as a model for non-lexical decoding followed by a lexical-decision during a functional magnetic resonance examination. Our results suggest that individual letters are first converted into phonemes within the left supramarginal gyrus, followed by a phoneme assembly to reconstruct word phonology, involving the left inferior frontal cortex. To allow the identification and comprehension of known words, the inferior frontal cortex then interacts with the semantic system via the left angular gyrus. As such, the left angular gyrus is likely to host phonological and semantic representations and serves as a bidirectional interface between the networks involved in language perception and word comprehension.

Inflammation Disrupts the Brain Network of Executive Function after Cardiac Surgery

OBJECTIVE

To investigate postoperative functional connectivity (FC) alterations across impaired cognitive domains and their causal relationships with systemic inflammation.

BACKGROUND

Postoperative cognitive dysfunction commonly occurs after cardiac surgery, and both systemic and neuroinflammation may trigger its development. Whether FC alterations underlying deficits in specific cognitive domains after cardiac surgery are affected by inflammation remains unclear.

METHODS

Seventeen patients, who underwent cardiac valve replacement, completed a neuropsychological test battery and brain MRI scan before surgery and on days 7 and 30 after surgery compared to age-matched healthy controls. Blood samples were taken for tumor necrosis factor-a and interleukin-6 measurements. Seed-to-voxel FC of the left dorsolateral prefrontal cortex (DLPFC) was examined. Bivariate correlation and linear regression models were used to determine the relationships among cognitive function, FC alterations, and cytokines.

RESULTS

Executive function was significantly impaired after cardiac surgery. At day 7 follow-up, the surgical patients, compared to the controls, demonstrated significantly decreased DLPFC FC with the superior parietal lobe and attenuated negative connectivity in the default mode network, including the angular gyrus and posterior cingulate cortex. The left DLPFC enhanced the connectivity in the right DLPFC and posterior cingulate cortex, all of which were related to the increased tumor necrosis factor-a and decreased executive function up to day 7 after cardiac surgery.

CONCLUSIONS

The decreased FC of executive control network and its anticorrelation with the default mode network may contribute to executive function deficits after cardiac surgery. Systemic inflammation may trigger these transient FC changes and executive function impairments.

Cognitive control inhibition networks in adulthood are impaired by early iron deficiency in infancy

Iron deficiency, a common form of micronutrient deficiency, primarily affects children and women. The principal cause of iron deficiency is undernutrition in low-income countries and malnutrition in middle to upper income regions. Iron is a key element for myelin production, neuronal metabolism, and dopamine functions. Iron deficiency in early life can alter brain development and exert long-lasting effects. Control inhibition is an executive function that involves several brain regions, including the prefrontal cortex and caudate and sub-thalamic nuclei. Dopamine is the prevalent neurotransmitter underlying cognitive inhibition. We followed cohort study participants who had iron deficiency anemia in infancy as well non-anemic controls. At 22 years of age, the participants were subjected to functional magnetic resonance imaging (fMRI) to evaluate the correlation between functional connectivity and performance on an inhibitory cognitive task (Go/No-Go). We hypothesized that former iron deficient anemic (FIDA) participants demonstrate less strength in functional connectivity compared with controls (C). There were not significant group differences in the behavioral results in terms of accuracy and response time. A continuous covariate interaction analysis of functional connectivity and the Go/No-Go scores demonstrated significant differences between the FIDA and C groups. The FIDA participants demonstrated less strength in connectivity in brain regions related to control inhibition, including the medial temporal lobe, impairment in the integration of the default mode network (indicating decreased attention and alertness), and an increase in connectivity in posterior brain areas, all of which suggest slower circuitry maturation. The results support the hypothesis that FIDA young adults show differences in the connectivity of networks related to executive functions. These differences could increase their vulnerability to develop cognitive dysfunctions or mental disorders in adulthood.

The Effects of Exergame on Attention in Children with Attention Deficit Hyperactivity Disorder (Preprint)

BACKGROUND

Despite growing evidence showing the effects of exercise and cognitive trainings on enhancing attention, little is known about the combined effects of exergame on attention in children with attention deficit/hyperactivity disorder (ADHD). Exergame, a form of exercise using a video game, has both cognitive stimulation and physical activity components and has been shown to improve cognitive function in children.

OBJECTIVE

The purpose of this study was to investigate the effect of exergaming on attention and to compare the effect induced by exergaming with the effect of aerobic exercise on attention in children with ADHD.

METHODS

In all, 30 children with ADHD, aged 8-12 years, were randomly divided into an exergaming group (EXG; n=16) or a bicycle exercise group (BEG; n=14). Before and after the 4-week intervention, the Frankfurter Aufmerksamkeits-Inventar (FAIR; Frankfurt Attention Inventory) test was administrated, and event-related potentials during the Go/No-go task was measured to assess attention.

RESULTS

After intervention, both the EXG and BEG had significantly increased selective attention and continuous attention (all P<.001), as well as self-control on the FAIR test (EXG: P=.02 and BEG: P=.005). Similarly, both the EXG and BEG had significantly reduced response time on the Go/No-go test (all P<.001). For the Go response, the N2 amplitude (frontocentral maximal negativity) was significantly increased in Fz (midfrontal line) in the EXG (P=.003) but was not changed in the BEG (P=.97). Importantly, the N2 amplitude in Fz was significantly greater in the EXG compared to the BEG (Go: P=.001 and No-go: P=.008).

CONCLUSIONS

Exergaming has the comparable effects to bicycle exercise to enhance attention in children with ADHD, suggesting that exergaming can be used as an alternative treatment for children with ADHD.

TRIAL REGISTRATION

Clinical Research Information Service KCT0008239; https://tinyurl.com/57e4jtnb.

Effects of creative expression program on the event-related potential and task reaction time of elderly with mild cognitive impairment

Objectives

This study aimed to evaluate the effects of a 16-week creative expression intervention program (CrExp) on the event-related potential (ERP) and task reaction time in older individuals with mild cognitive impairment (MCI).

Methods

This study is a randomized controlled clinical trial conducted in the Memory Center of Fujian Provincial hospital. Thirty-six MCI patients were randomly distributed into two groups. One group underwent a 16-week creative expression program (CrExp, n = 18) and the other performed as a control group (CG, n = 18) by general social activities. The amplitude and latency of ERP-P300 from the central (Cz), parietal (Pz), frontal (Fz) cortices and task reaction time (RT) were assessed at baseline, post-interventi on, and 24-week follow-up.

Results

The CrExp group showed greater differences than CG of P300 latency in Cz (F = 4.37, P = 0.015), Pz (F = 2.78, P = 0.009), Fz (F = 6.45, P = 0.031) brain area after 16 weeks of intervention and in Fz (F = 3.23, P = 0.028), Cz (F = 3.79, P = 0.024), and Pz (F = 5.60, P = 0.036) at 24 weeks follow-up. Also, we analyzed the task reaction time between two groups and found that a shorten reaction time at post-intervention (F = 4.47, P = 0.011) and 24 weeks follow-up (F = 3.12, P = 0.007) in the CrExp group. However, there was no difference in P300 amplitude in either brain area between the two groups.

Conclusion

The electrophysiological results of the creative expression cognitive therapy group were more obvious than those of the general cognitive therapy group, and the latency and task reaction time may be considered as supported parameters in diagnosing the effects during non-drug therapy intervention in clinical practice.

Alteration in topological properties of brain functional network after 2-year high altitude exposure: A panel study

INTRODUCTION

High altitude (HA) exposure leads to cognitive impairment while the underlying mechanism is still unclear. Brain functional network is crucial for advanced functions, and its alteration is implicated in cognitive decline in multiple diseases. The aim of current study was to investigate the topological changes in HA-exposed brain functional network.

METHODS

Based on Shaanxi-Tibet immigrant cohort, neuropsychological tests and resting-state functional MRI were applied to evaluate the participants' cognitive function and functional connection (FC) changes, respectively. GRETNA toolbox was used to construct the brain functional network. The gray matter was parcellated into 116 anatomically defined regions according to Automated Anatomical Labeling atlas. Subsequently, the mean time series for each of the 116 regions were extracted and computed for Pearson's correlation coefficients. The relation matrix was further processed and seen as brain functional network. Correlation between functional network changes and neuropsychological results was also examined.

RESULTS

The cognitive performance was impaired by HA exposure as indicated by neuropsychological test. HA exposure led to alterations of degree centrality and nodal efficiency in multiple brain regions. Moreover, two subnetworks were extracted in which the FCs significantly decreased after exposure. In addition, the alterations in FCs within above two subnetworks were significantly correlated with changes of memory and reaction time.

CONCLUSIONS

Our results suggest that HA exposure modulates the topological property of functional network and FCs of some important regions, which may impair the attention, perception, memory, motion ignition, and modulation processes, finally decreasing cognitive performance in neuropsychological tests.

Parasympathetic arousal-related cortical activity is associated with attention during cognitive task performance

Parasympathetic arousal is associated with states of heightened attention and well-being. Arousal may affect widespread cortical and subcortical systems across the brain, however, little is known about its influence on cognitive task processing and performance. In the current study, healthy adult participants (n ​= ​20) underwent multi-band echo-planar imaging (TR ​= ​0.72 ​s) with simultaneous pulse oximetry recordings during performance of the Multi Source Interference Task (MSIT), the Oddball Task (OBT), and during rest. Processing speed on both tasks was robustly related to heart rate (HR). Participants with slower HR responded faster on both the MSIT (33% variance explained) and the OBT (25% variance explained). Within all participants, trial-to-trial fluctuations in processing speed were robustly related to the heartbeat-stimulus interval, a metric that is dependent both on the concurrent HR and the stimulus timing with respect to the heartbeat. Models examining the cardiac-BOLD response revealed that a distributed set of regions showed arousal-related activity that was distinct for different task conditions. Across these cortical regions, activity increased with slower HR. Arousal-related activity was distinct from task-evoked activity and it was robust to the inclusion of additional physiological nuisance regressors into the models. For the MSIT, such arousal-related activity occurred across visual and dorsal attention network regions. For the OBT, this activity occurred within fronto-parietal regions. For rest, arousal-related activity also occurred, but was confined to visual regions. The pulvinar nucleus of the thalamus showed arousal-related activity during all three task conditions. Widespread cortical activity, associated with increased parasympathetic arousal, may be propagated by thalamic circuits and contributes to improved attention. This activity is distinct from task-evoked activity, but affects cognitive performance and therefore should be incorporated into neurobiological models of cognition and clinical disorders.

Spontaneous default network activity reflects behavioral variability independent of mind-wandering

The brain's default mode network (DMN) is highly active during wakeful rest when people are not overtly engaged with a sensory stimulus or externally oriented task. In multiple contexts, increased spontaneous DMN activity has been associated with self-reported episodes of mind-wandering, or thoughts that are unrelated to the present sensory environment. Mind-wandering characterizes much of waking life and is often associated with error-prone, variable behavior. However, increased spontaneous DMN activity has also been reliably associated with stable, rather than variable, behavior. We aimed to address this seeming contradiction and to test the hypothesis that single measures of attentional states, either based on self-report or on behavior, are alone insufficient to account for DMN activity fluctuations. Thus, we simultaneously measured varying levels of self-reported mind-wandering, behavioral variability, and brain activity with fMRI during a unique continuous performance task optimized for detecting attentional fluctuations. We found that even though mind-wandering co-occurred with increased behavioral variability, highest DMN signal levels were best explained by intense mind-wandering combined with stable behavior simultaneously, compared with considering either single factor alone. These brain-behavior-experience relationships were highly consistent within known DMN subsystems and across DMN subregions. In contrast, such relationships were absent or in the opposite direction for other attention-relevant networks (salience, dorsal attention, and frontoparietal control networks). Our results suggest that the cognitive processes that spontaneous DMN activity specifically reflects are only partially related to mind-wandering and include also attentional state fluctuations that are not captured by self-report.