Association between ADHD symptoms and inhibition-related brain activity using functional near-infrared spectroscopy (fNIRS)

fNIRS Classification of Adults with ADHD Enhanced by Feature Selection

Adult attention deficit hyperactivity disorder (ADHD), a prevalent psychiatric disorder, significantly impacts social, academic, and occupational functioning. However, it has been relatively less prioritized compared to childhood ADHD. This study employed a functional near-infrared spectroscopy (fNIRS) during verbal fluency tasks in conjunction with machine learning (ML) techniques to differentiate between healthy controls (N=75) and ADHD individuals (N=120). Efficient feature selection in high-dimensional fNIRS datasets is crucial for improving accuracy. To address this, we propose a hybrid feature selection method that combines a wrapper-based and embedded approach, termed Bayesian-Tuned Ridge RFECV (BTR-RFECV). The proposed method facilitated streamlined feature selection and hyperparameter tuning in high-dimensional data, thereby reducing the number of features while enhancing accuracy. HbO features from the combined frontal and temporal regions were key, with the models achieving precision (89.89%), recall (89.74%), F-1 score (89.66%), accuracy (89.74%), MCC (78.36%), and GDR (88.45%). The outcomes of this study highlight the promising potential of combining fNIRS with ML as diagnostic tools in clinical settings, offering a pathway to significantly reduce manual intervention.

Transcutaneous auricular vagus nerve stimulation as a potential therapy for attention deficit hyperactivity disorder: modulation of the noradrenergic pathway in the prefrontal lobe

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by developmental impairments, inattention, motor hyperactivity, and impulsivity. Currently, there is no effective intervention that can completely cure it. One of the pathogenic mechanisms of ADHD involves abnormalities in the norepinephrine (NE) pathway within the prefrontal cortex (PFC). In recent years, transcutaneous auricular vagus nerve stimulation (taVNS), a non-invasive neuromodulation technique, has demonstrated promising potential in the treatment of neurological and psychiatric disorders. However, its application in the management of ADHD remains relatively unexplored. Previous studies have shown that taVNS exerts therapeutic effects on attention, cognition, arousal, perception, and behavioral regulation primarily through activating the vagus nerve conduction pathway, specifically targeting the nucleus tractus solitarius - locus coeruleus - NE pathway. These findings have led to the hypothesis that taVNS may be an effective intervention for ADHD, with NE and its pathway playing a pivotal role in this context. Therefore, this review comprehensively examines the correlation between NE pathway alterations in the PFC and ADHD, the mechanism of action of taVNS, and the potential role of the NE pathway in treating ADHD with taVNS, aiming to provide a theoretical foundation for clinical applications.

Baseline brain volume predicts home-based transcranial direct current stimulation effects on inattention in adults with attention-deficit/hyperactivity disorder

BACKGROUND

Home-based transcranial direct current stimulation (Hb-tDCS) is a non-invasive brain stimulation technique that utilizes low-intensity electric currents delivered via scalp electrodes to modulate brain activity. It holds significant promise for addressing inattention in adults with attention-deficit/hyperactivity disorder (ADHD). However, its effectiveness varies among individuals, and predicting outcomes remains uncertain, partially due to the influence of individual differences in ADHD-related brain anatomy.

METHODS

We analyzed data from a subsample, composed by twenty-nine adult patients with ADHD, of the Treatment of Inattention Symptoms in Adult Patients with ADHD (TUNED) trial. Fourteen patients underwent active anodal right cathodal left dorsolateral prefrontal cortex (DLPFC) Hb-tDCS for 4 weeks and fifteen received sham-related tDCS intervention. Inattention outcome was evaluated at both baseline and endpoint (4th week). Baseline structural measures of the DLPFC, anterior cingulate cortex (ACC) and subcortical structures, previously associated with ADHD, were quantified. Several linear mixed models, with a three-way interaction between the fixed predictors brain volume or thickness, time, and treatment were calculated. Multiple comparison corrections were applied using the Benjamini-Hochberg method.

RESULTS

Baseline volume of the left DLPFC regions middle frontal gyrus (t (25) = 3.33, p-adjusted = 0.045, Cohen's d = 1.33, 95% CI = [0.45, 2.19]), inferior frontal gyrus (orbital part) (t (25) = 3.10, p-adjusted = 0.045, Cohen's d = 1.24, 95% CI = [0.37, 2.08]), and of the left ACC supragenual (t (25) = 3.15, p-adjusted = 0.045, Cohen's d = 1.26, 95% CI = [0.39, 2.11]) presented significant association with the inattentive score improvement only in the active tDCS group. More specifically, the smaller these regions were, the more the symptoms improved following anodal right cathodal left DLPFC Hb-tDCS.

CONCLUSION

Hb-tDCS was associated with greater improvement in brain areas related to attention regulation. Brain MRI can be potentially used to predict clinical response to tDCS in ADHD adults.

Neural Mechanisms of Inhibition in Scientific Reasoning: Insights from fNIRS

This study examines the impact of response and semantic inhibition on scientific reasoning using fNIRS data from 30 students (15 male, 15 female). Utilizing Go/Nogo and Stroop-like tasks within a modified speeded-reasoning task, it was found that inhibition significantly influences scientific reasoning. Specifically, slower responses and lower accuracy on incongruent statements were linked to increased activity in bilateral dorsolateral prefrontal cortex (DLPFC) and pre-supplementary motor area (pre-SMA). The research shows that both DLPFC and pre-SMA are associated with overcoming misconceptions in scientific reasoning. The findings suggest that understanding inhibitory mechanisms can enhance educational strategies to improve critical thinking and scientific literacy.

Abnormal prefrontal cortical activation during the GO/NOGO and verbal fluency tasks in adult patients with comorbid generalized anxiety disorder and attention-deficit/hyperactivity disorder: An fNIRS study

Generalized anxiety disorder (GAD) and adult attention-deficit/hyperactivity disorder (ADHD) are commonly reported comorbidities. Adult GAD patients with comorbid ADHD are often underdiagnosed and undertreated. To explore the clinical value of functional near-infrared spectroscopy (fNIRS) data for assisting in the accurate diagnosis of ADHD in individuals with GAD, haemoglobin (HbO) concentration changes in the prefrontal cortex (PFC) were detected via fNIRS in 49 patients with both GAD and ADHD, 46 patients with GAD, and 34 healthy controls (HCs) during a verbal fluency task (VFT) and a GO/NOGO task. The correlations between PFC fNIRS data and the severity of inattention and hyperactivity symptoms assessed using the adult ADHD Self-Report Scale (ASRS) were analyzed. Our results showed that, during the GO/NOGO task, channels in the left dorsolateral PFC (channels 28 and 29) were hyperactivated, while channels in the medial PFC (channels 36, 37, and 47) were hypoactivated in participants with ADHD and GAD compared with those with GAD alone. During the VFT, compared with the HC group, both the ADHD + GAD group and the GAD group exhibited significantly decreased HbO activation in the medial PFC (channels 37, 38, and 48) and in the left ventrolateral PFC (channel 39); moreover, no difference was found between the ADHD + GAD group and the GAD group. Activation in the left dorsolateral PFC (channels 28 and 29) during the GO/NOGO task showed a significant positive correlation with ASRS-inattention scores. Our results indicated that fNIRS data collected during the GO/NOGO task may help to distinguish patients with comorbid GAD and ADHD from those with GAD alone.

Using fNIRS to evaluate ADHD medication effects on neuronal activity: A systematic literature review

Background

Functional near infrared spectroscopy (fNIRS) is a relatively non-invasive and inexpensive functional neuroimaging technique that has shown promise as a method for understanding the differences in neuronal activity associated with various neurodevelopmental conditions, including ADHD. Additionally, fNIRS has been suggested as a possible tool to understand the impact of psychotropic medications on brain activity in individuals with ADHD, but this approach is still in its infancy.

Objective

The purpose of this systematic literature review was to synthesize the extant research literature on the use of fNIRS to assess the effects of ADHD medications on brain activity in children and adolescents with ADHD.

Methods

A literature search following Preferred Reporting Items for Systematic Literature Reviews and Meta-Analyses (PRISMA) guidelines was conducted for peer-reviewed articles related to ADHD, medication, and fNIRS in PsychInfo, Scopus, and PubMed electronic databases.

Results

The search yielded 23 published studies meeting inclusion criteria. There was a high degree of heterogeneity in terms of the research methodology and procedures, which is explained in part by the distinct goals and approaches of the studies reviewed. However, there was also relative consistency in outcomes among a select group of studies that demonstrated a similar research focus.

Conclusion

Although fNIRS has great potential to further our understanding of the effects of ADHD medications on the neuronal activity of children and adolescents with ADHD, the current research base is still relatively small and there are limitations and methodological inconsistencies that should be addressed in future studies.