The role of transcranial magnetic stimulation in understanding attention-related networks in single subjects

Predicting responses of neuromodulation and psychotherapies for major depressive disorder: A coordinate-based meta-analysis of functional magnetic resonance imaging studies

This meta-analysis synthesized resting-state functional connectivity (FC) patterns associated with treatment responses in Major Depressive Disorder (MDD). We evaluated studies from 2013 to 2023 that reported pre-treatment FC (i.e., 'biomarker' analysis) and/or treatment-induced FC alterations (i.e., 'longitudinal effects') in three treatments (i.e., transcranial magnetic stimulation, electroconvulsive therapy, psychotherapy), and further associated these patterns with gene expression, neurotransmitter distributions, and symptomatology. From 57 studies covering 1726 patients, the 'biomarker' results revealed significant rs-FC patterns in the Default Mode Network (DMN) and Frontoparietal Network (FPN). 'Longitudinal effects' were characterized by altered DMN connectivity. Psychotherapy primarily affected the visual network and DMN. Gene expression profiles explained 38.5 % and 56.0 % of the variance in 'biomarker' and 'longitudinal' results, respectively. The meta-analysis correlated with neurotransmitter distributions (e.g., serotonin, dopamine) and MDD-related terms ('interaction', 'emotional', 'negative'). These findings indicate that baseline FC within the DMN and FPN is crucial for predicting treatment responses, and the core mechanisms may involve restoring the DMN. This work may enhance our understanding of MDD pathophysiology and help guide personalized interventions.

Resting-state microstate dynamics abnormalities in children with ADHD and co-occurring sleep problems

OBJECTIVES

Children with attention-deficit/hyperactivity disorder often experience sleep problems, exacerbating symptoms, and cognitive deficits. However, the neurophysiological mechanisms underlying such deficits remained unclear. This study aims to use resting-state microstate analysis to investigate the neurophysiological characteristics in children with ADHD and sleep problems and explore whether neurophysiological abnormalities are associated with sleep problems.

METHODS

Five-minute eyes-closed resting-state EEG data were collected in 34 children with both ADHD and sleep problems, 32 children with ADHD without sleep problems, and 22 healthy controls aged 6-12 years. Participants' parents completed the ADHD Rating Scale, Behavioral Rating Inventory of Executive Function, and Children's Sleep Habits Questionnaire. Five minutes of eyes-closed resting-state EEG data were collected, and agglomerative hierarchical clustering was used for microstate analysis. ANCOVAs, adjusted for sex and IQ, were used to compare ADHD symptoms, executive function, and microstate parameters across groups. Pearson partial correlations, controlling for sex and IQ, examined the association between microstate parameters and sleep problems.

RESULTS

Children with both ADHD and sleep problems exhibited more severe inattentive (20.4 ± 3.1 vs 18.0 ± 3.4, p < 0.05) and total symptoms (14.3 ± 6.0 vs 13.0 ± 5.3, p < 0.05), along with greater deficits in emotional regulation (1.88 ± 0.58 vs 1.60 ± 0.42, p < 0.05, organizational of materials 2.56 ± 0.41 vs 2.20 ± 0.55, p < 0.05, behavioral regulation (1.88 ± 0.40 vs 1.70 ± 0.36, p < 0.05), and global executive function (2.14 ± 0.30 vs 1.95 ± 0.30, p < 0.05), compared to children with ADHD without sleep problems. Moreover, Both ADHD groups exhibited significantly reduced microstate D occurrence and lower transition probability from microstate C to D compared to healthy controls (all p < 0.05). Additionally, no significant correlation was found between sleep problems and microstate parameters in all three groups after adjustment (all p > 0.05).

CONCLUSIONS

Children with both ADHD and sleep problems showed greater symptom severity and more pronounced executive function deficits compared to children with ADHD without sleep problems and healthy controls. Additionally, both ADHD groups showed overlapping atypical microstate parameters, suggesting children with co-occurring ADHD and sleep problems may share similar aberrant neurophysiological characteristics with children with ADHD alone. Resting-state EEG microstate parameters may serve as a sensitive tool for assessing sleep problems in children with ADHD, distinguishing them from typically developing children.

Change in striatal functional connectivity networks across 2 years due to stimulant exposure in childhood ADHD: results from the ABCD sample

Widely prescribed for Attention-Deficit/Hyperactivity Disorder (ADHD), stimulants (e.g., methylphenidate) have been studied for their chronic effects on the brain in prospective designs controlling dosage and adherence. While controlled approaches are essential, they do not approximate real-world stimulant exposure contexts where medication interruptions, dosage non-compliance, and polypharmacy are common. Brain changes in real-world conditions are largely unexplored. To fill this gap, we capitalized on the observational design of the Adolescent Brain Cognitive Development (ABCD) study to examine effects of stimulants on large-scale bilateral cortical networks' resting-state functional connectivity (rs-FC) with 6 striatal regions (left and right caudate, putamen, and nucleus accumbens) across two years in children with ADHD. Bayesian hierarchical regressions revealed associations between stimulant exposure and change in rs-FC of multiple striatal-cortical networks, affiliated with executive and visuo-motor control, which were not driven by general psychotropic medication. Of these connections, three were selective to stimulants versus stimulant naive: reduced rs-FC between caudate and frontoparietal network, and between putamen and frontoparietal and visual networks. Comparison with typically developing children in the ABCD sample revealed stronger rs-FC reduction in stimulant-exposed children for putamen and frontoparietal and visual networks, suggesting a normalizing effect of stimulants. 14% of stimulant-exposed children demonstrated reliable reduction in ADHD symptoms, and were distinguished by stronger rs-FC reduction between right putamen and visual network. Thus, stimulant exposure for a two-year period under real-world conditions modulated striatal-cortical functional networks broadly, had a normalizing effect on a subset of networks, and was associated with potential therapeutic effects involving visual attentional control.

Change in Striatal Functional Connectivity Networks Across Two Years Due to Stimulant Exposure in Childhood ADHD: Results from the ABCD Sample

Widely prescribed for Attention-Deficit/Hyperactivity Disorder (ADHD), stimulants (e.g., methylphenidate) have been studied for their chronic effects on the brain in prospective designs controlling dosage and adherence. While controlled approaches are essential, they do not approximate real-world stimulant exposure contexts where medication interruptions, dosage non-compliance, and polypharmacy are common. Brain changes in real-world conditions are largely unexplored. To fill this gap, we capitalized on the observational design of the Adolescent Brain Cognitive Development (ABCD) study to examine effects of stimulants on large-scale bilateral cortical networks' resting-state functional connectivity (rs-FC) with 6 striatal regions (left and right caudate, putamen, and nucleus accumbens) across two years in children with ADHD. Bayesian hierarchical regressions revealed associations between stimulant exposure and change in rs-FC of multiple striatal-cortical networks, affiliated with executive and visuo-motor control, which were not driven by general psychotropic medication. Of these connections, three were selective to stimulants versus stimulant naive: reduced rs-FC between caudate and frontoparietal network, and between putamen and frontoparietal and visual networks. Comparison with typically developing children in the ABCD sample revealed stronger rs-FC reduction in stimulant-exposed children for putamen and frontoparietal and visual networks, suggesting a normalizing effect of stimulants. 14% of stimulant-exposed children demonstrated reliable reduction in ADHD symptoms, and were distinguished by stronger rs-FC reduction between right putamen and visual network. Thus, stimulant exposure for a two-year period under real-world conditions modulated striatal-cortical functional networks broadly, had a normalizing effect on a subset of networks, and was associated with potential therapeutic effects involving visual attentional control.

Systematic review on effects of experimental orthodontic tooth displacement on brain activation assessed by fMRI

BACKGROUND

Orthodontic treatment is often accompanied by discomfort and pain in patients, which are believed to be a result of orthodontic tooth displacement caused by the mechanical forces exerted by the orthodontic appliances on the periodontal tissues. These lead to change blood oxygen level dependent response in related brain regions.

OBJECTIVE

This systematic review aims to assess the impact of experimental orthodontic tooth displacement on alterations in central nervous system activation assessed by tasked based and resting state fMRI.

MATERIALS AND METHODS

A literature search was conducted using online databases, following PRISMA guidelines and the PICO framework. Selected studies utilized magnetic resonance imaging to examine the brain activity changes in healthy participants after the insertion of orthodontic appliances.

RESULTS

The initial database screening resulted in 791 studies. Of these, 234 were duplicates and 547 were deemed irrelevant considering the inclusion and exclusion criteria. Of the ten remaining potential relevant studies, two were excluded during full-text screening. Eight prospective articles were eligible for further analysis. The included studies provided evidence of the intricate interplay between orthodontic treatment, pain perception, and brain function. All of the participants in the included studies employed orthodontic separators in short-term experiments to induce tooth displacement during the early stage of orthodontic treatment. Alterations in brain activation were observed in brain regions, functional connectivity and brain networks, predominantly affecting regions implicated in nociception (thalamus, insula), emotion (insula, frontal areas), and cognition (frontal areas, cerebellum, default mode network).

CONCLUSIONS

The results suggest that orthodontic treatment influences beyond the pain matrix and affects other brain regions including the limbic system. Furthermore, understanding the orthodontically induced brain activation can aid in development of targeted pain management strategies that do not adversely affect orthodontic tooth movement. Due to the moderate to serious risk of bias and the heterogeneity among the included studies, further clinical trials on this subject are recommended.

Enhancing cognitive control with transcranial magnetic stimulation in subject-specific frontoparietal networks

BACKGROUND

Cognitive control processes, including those involving frontoparietal networks, are highly variable between individuals, posing challenges to basic and clinical sciences. While distinct frontoparietal networks have been associated with specific cognitive control functions such as switching, inhibition, and working memory updating functions, there have been few basic tests of the role of these networks at the individual level.

METHODS

To examine the role of cognitive control at the individual level, we conducted a within-subject excitatory transcranial magnetic stimulation (TMS) study in 19 healthy individuals that targeted intrinsic ("resting") frontoparietal networks. Person-specific intrinsic networks were identified with resting state functional magnetic resonance imaging scans to determine TMS targets. The participants performed three cognitive control tasks: an adapted Navon figure-ground task (requiring set switching), n-back (working memory), and Stroop color-word (inhibition).

OBJECTIVE

Hypothesis: We predicted that stimulating a network associated with externally oriented control [the "FPCN-B" (fronto-parietal control network)] would improve performance on the set switching and working memory task relative to a network associated with attention (the Dorsal Attention Network, DAN) and cranial vertex in a full within-subjects crossover design.

RESULTS

We found that set switching performance was enhanced by FPCN-B stimulation along with some evidence of enhancement in the higher-demand n-back conditions.

CONCLUSION

Higher task demands or proactive control might be a distinguishing role of the FPCN-B, and personalized intrinsic network targeting is feasible in TMS designs.

In the face of ambiguity: intrinsic brain organization in development predicts one's bias toward positivity or negativity

Exacerbated negativity bias, including in responses to ambiguity, represents a common phenotype of internalizing disorders. Individuals differ in their propensity toward positive or negative appraisals of ambiguity. This variability constitutes one's valence bias, a stable construct linked to mental health. Evidence suggests an initial negativity in response to ambiguity that updates via regulatory processes to support a more positive bias. Previous work implicates the amygdala and prefrontal cortex, and regions of the cingulo-opercular system, in this regulatory process. Nonetheless, the neurodevelopmental origins of valence bias remain unclear. The current study tests whether intrinsic brain organization predicts valence bias among 119 children and adolescents (6 to 17 years). Using whole-brain resting-state functional connectivity, a machine-learning model predicted valence bias (r = 0.20, P = 0.03), as did a model restricted to amygdala and cingulo-opercular system features (r = 0.19, P = 0.04). Disrupting connectivity revealed additional intra-system (e.g. fronto-parietal) and inter-system (e.g. amygdala to cingulo-opercular) connectivity important for prediction. The results highlight top-down control systems and bottom-up perceptual processes that influence valence bias in development. Thus, intrinsic brain organization informs the neurodevelopmental origins of valence bias, and directs future work aimed at explicating related internalizing symptomology.

The self and conscious experience

The primary determinant of the self (S) is the conscious experience (CE) we have of it. Therefore, it does not come as a surprise that empirical research on S mainly resorts to the CE (or lack of CE) that subjects have of their S. What comes as a surprise is that empirical research on S does not tackle the problem of how CE contributes to building S. Empirical research investigates how S either biases the cognitive processing of stimuli or is altered through a wide range of means (meditation, hypnosis, etc.). In either case, even for different reasons, considerations of how CE contributes to building S are left unspecified in empirical research. This article analyzes these reasons and proposes a theoretical model of how CE contributes to building S. According to the proposed model, the phenomenal aspect of consciousness is produced by the modulation-engendered by attentional activity-of the energy level of the neural substrate (that is, the organ of attention) that underpins attentional activity. The phenomenal aspect of consciousness supplies the agent with a sense of S and informs the agent on how its S is affected by the agent's own operations. The phenomenal aspect of consciousness performs its functions through its five main dimensions: qualitative, quantitative, hedonic, temporal, and spatial. Each dimension of the phenomenal aspect of consciousness can be explained by a specific aspect of the modulation of the energy level of the organ of attention. Among other advantages, the model explains the various forms of S as outcomes resulting from the operations of a single mechanism and provides a unifying framework for empirical research on the neural underpinnings of S.