ADHD, Smoking Withdrawal, and Inhibitory Control: Results of a Neuroimaging Study with Methylphenidate Challenge

"I Found Comfort in Exercising": Exploring Experiences With Exercise for Adults With Attention-Deficit/Hyperactivity Disorder

Little is known about how adults with attention-deficit/hyperactivity disorder (ADHD) experience exercise, resulting in a lack of recommendations for supporting this population. We aimed to explore how adults with ADHD experience exercise as a management tool before and after diagnosis and how and why individuals experience issues related to exercise dependence. Fifteen active adults with a diagnosis of ADHD participated in semistructured interviews. Three overarching themes were identified: (a) exercise as a necessity for ADHD, reflecting the need to exercise before a formal ADHD diagnosis, and use of exercise as a management tool postdiagnosis; (b) goals and achievements to live by, reflecting how exercise patterns revolved around a need to make progress toward targets; and (c) activity or exercise: a roller coaster journey, covering the ups and downs of exercise journeys. This article highlights the importance of exercise for adults to manage ADHD and how this can be encouraged and supported.

Corticostriatal causality analysis in children and adolescents with attention-deficit/hyperactivity disorder

AIM

The effective connectivity between the striatum and cerebral cortex has not been fully investigated in attention-deficit/hyperactivity disorder (ADHD). Our objective was to explore the interaction effects between diagnosis and age on disrupted corticostriatal effective connectivity and to represent the modulation function of altered connectivity pathways in children and adolescents with ADHD.

METHODS

We performed Granger causality analysis on 300 participants from a publicly available Attention-Deficit/Hyperactivity Disorder-200 dataset. By computing the correlation coefficients between causal connections between striatal subregions and other cortical regions, we estimated the striatal inflow and outflow connection to represent intermodulation mechanisms in corticostriatal pathways.

RESULTS

Interactions between diagnosis and age were detected in the superior occipital gyrus within the visual network, medial prefrontal cortex, posterior cingulate gyrus, and inferior parietal lobule within the default mode network, which is positively correlated with hyperactivity/impulsivity severity in ADHD. Main effect of diagnosis exhibited a general higher cortico-striatal causal connectivity involving default mode network, frontoparietal network and somatomotor network in ADHD compared with comparisons. Results from high-order effective connectivity exhibited a disrupted information pathway involving the default mode-striatum-somatomotor-striatum-frontoparietal networks in ADHD.

CONCLUSION

The interactions detected in the visual-striatum-default mode networks pathway appears to be related to the potential distraction caused by long-term abnormal information input from the retina in ADHD. Higher causal connectivity and weakened intermodulation may indicate the pathophysiological process that distractions lead to the impairment of motion planning function and the inhibition/control of this unplanned motion signals in ADHD.

Exercise Dependency and Overuse Injuries in Attention Deficit Hyperactivity Disorder

ABSTRACT

Attention deficit hyperactivity disorder (ADHD) is a common condition, but current medications have limitations, pushing a drive for alternative approaches. Different exercise-focused approaches have shown promise, but concern has also been raised about individuals with ADHD showing greater risk of addiction, including exercise dependency. Using an online survey, we examined current exercise practices, including exercise dependency and the presence of overuse injury, which could result from overexercising, in 114 adults with ADHD. We found that most were regularly exercising. None were classified as exercise dependent, but 38.9% were deemed symptomatic nondependent. Hyperactive-impulsive symptoms were a predictor of the level of exercise withdrawal experienced, and the co-occurrence of autism spectrum disorder was associated with greater risk of overuse injuries. The data indicate that ADHD may confer some greater risk of exercise dependency, aligning with previous studies investigating other addictions and suggesting further research is critical.

Response Inhibition and Interference Control in Adult Attention Deficit Hyperactivity Disorder

Introduction

Among the executive functions affected in attention deficit hyperactivity disorder (ADHD), inhibitory control is one of the primary areas of impairment, characterized by components that include response inhibition and interference control. Determining the impaired inhibitory control components will be useful in the differential diagnosis and treatment of ADHD. The present study aimed to investigate response inhibition and interference control abilities of adults with ADHD.

Methods

The study included 42 adults diagnosed with ADHD and 43 healthy controls. The stop-signal task (SST) and Stroop test were used for assessing the response inhibition and interference control, respectively. Multivariate analysis of covariance was used for comparing the ADHD and healthy control groups in terms of their SST and Stroop test scores, wherein the age and education level of the participants were taken as covariables. The relationship between SST and Stroop Test and Barratt Impulsiveness Scale-11 (BIS-11) was tested by Pearson correlation analysis. Mann-Whitney U test was used for comparing the test scores between those who were administered with psychostimulants among the adults with ADHD and those who were not.

Results

Response inhibition was observed to be impaired in adults with ADHD compared with the healthy controls, whereas no difference regarding interference control was observed. As per the Barratt Impulsiveness Scale-11 (BIS-11), a weak and moderately negative relationship was found between the stop signal delay and the attentional, motor, non-planning scores, and total scores and a weak positive relationship was found between the stop-signal reaction time and the attentional, motor, non-planning scores, and total scores. A significant improvement was observed in the response inhibition skills of the adults with ADHD who had received methylphenidate treatment compared to those who had not, and the former also showed lower impulsivity levels as measured by the BIS-11.

Conclusions

It should be noted that response inhibition and interference control, which are considered under the umbrella of inhibitory control, may exhibit different characteristics in adult individuals diagnosed with ADHD and this is important for differential diagnosis. An improvement was observed in the response inhibition of adults with ADHD caused by psychostimulant treatment, which was associated with positive outcomes that were also noticeable by the patients. Understanding the underlying neurophysiological mechanisms of the condition would further facilitate the development of appropriate treatments.

Subcortical structures and visual divergent thinking: a resting-state functional MRI analysis

An increasing number of studies have found that a few, specific subcortical regions are involved in creative visual divergent thinking. In addition, creative thinking is heavily reliant on the fronto-striatal dopaminergic pathways. This study aimed to explore whether spontaneous fluctuations in the subcortex, which contribute to our creative abilities, showed significant differences between individuals with different levels of creativity based on resting-state functional magnetic resonance imaging data. We calculated subcortical regions' seed-wise and dynamic functional connectivity (dFC), and then examined the differences between the high and low visual creativity groups. Furthermore, the topological properties of the subcortical network were measured, and their relationship with creative visual divergent thinking was calculated using brain-behavior correlation analyses. The results showed that functional connectivity (FC) between the putamen, pallidum, and thalamus indicated group differences within the subcortex. Whole-brain FC results showed group differences across subcortical (i.e., the thalamus and pallidum) and cerebral regions (i.e., the insula, middle frontal gyrus, and middle temporal gyrus). In addition, subcortical FC demonstrated a positive correlation with visual divergent thinking scores across the pallidum, putamen, and thalamus. Our findings provide novel insights into the relationship between visual divergent thinking and the activities of the subcortex. It is likely that not only fronto-striatal dopaminergic pathways, but also "motor" pathways, are involved in creative visual divergent thinking processing.

A Novel Knowledge Distillation-Based Feature Selection for the Classification of ADHD

Attention Deficit Hyperactivity Disorder (ADHD) is a brain disorder with characteristics such as lack of concentration, excessive fidgeting, outbursts of emotions, lack of patience, difficulty in organizing tasks, increased forgetfulness, and interrupting conversation, and it is affecting millions of people worldwide. There is, until now, not a gold standard test using which an ADHD expert can differentiate between an individual with ADHD and a healthy subject, making accurate diagnosis of ADHD a challenging task. We are proposing a Knowledge Distillation-based approach to search for discriminating features between the ADHD and healthy subjects. Learned embeddings from a large neural network, trained on the functional connectivity features, were fed to one hidden layer Autoencoder for reproduction of the embeddings using the same connectivity features. Finally, a forward feature selection algorithm was used to select a combination of most discriminating features between the ADHD and the Healthy Controls. We achieved promising classification results for each of the five individual sites. A combined accuracy of 81% in KKI, 60% Peking, 56% in NYU, 64% NI, and 56% OHSU and individual site wise accuracy of 72% in KKI, 60% Peking, 73% in NYU, 70% NI, and 71% OHSU were obtained using our extracted features. Our results also outperformed state-of-the-art methods in literature which validates the efficacy of our proposed approach.

Attention-deficit/hyperactivity disorder and the explore/exploit trade-off

The ability to maximize rewards and minimize the costs of obtaining them is vital to making advantageous explore/exploit decisions. Exploratory decisions are theorized to be greater among individuals with attention-deficit/hyperactivity disorder (ADHD), potentially due to deficient catecholamine transmission. Here, we examined the effects of ADHD status and methylphenidate, a common ADHD medication, on explore/exploit decisions using a 6-armed bandit task. We hypothesized that ADHD participants would make more exploratory decisions than controls, and that MPH would reduce group differences. On separate study days, adults with (n = 26) and without (n = 23) ADHD completed the bandit task at baseline, and after methylphenidate or placebo in counter-balanced order. Explore/exploit decisions were modeled using reinforcement learning algorithms. ADHD participants made more exploratory decisions (i.e., chose options without the highest expected reward value) and earned fewer points than controls in all three study days, and methylphenidate did not affect these outcomes. Baseline exploratory choices were positively associated with hyperactive ADHD symptoms across all participants. These results support several theoretical models of increased exploratory choices in ADHD and suggest the unexplained variance in ADHD decisions may be due to less value tracking. The inability to suppress actions with little to no reward value may be a key feature of hyperactive ADHD symptoms.

Does methylphenidate use affect sperm parameters in patients undergoing infertility investigation? A retrospective analysis of 9769 semen samples

OBJECTIVES

Methylphenidate (MPH) is the most widely prescribed therapy for attention deficit hyperactivity disorder. Animal studies have shown a potential adverse effect of MPH exposure on male fertility. We examined the impact of MPH on human male sperm parameters.

DESIGN

Sperm parameters of 9769 samples from patients 18 years of age or older, collected as part of the basic evaluation of couples referred to the Infertility Clinic were analyzed retrospectively. We divided the study population into three groups according to MPH purchasing information: MPH purchased ≤ 90 days prior to sperm analysis-current users (n = 83), MPH purchased > 90 days prior to sperm analysis-past users (n = 293), and MPH-naïve patients (n = 9393).

METHODS

All sperm samples were analyzed by the same laboratory technician team for the following routine parameters: semen volume, sperm concentration, percentage of motile sperm, and percentage of normal morphology according to World Health Organization. The analysis of the samples was completed by evaluation of total sperm count, total sperm motility, and percentage of fast and slow motile cells. Sperm morphology was evaluated by a laboratory technician using methodological examination according to the strict Kruger-Tygerberg criteria.

RESULTS

Methylphenidate exposure did not affect sperm morphology but was associated with increased sperm concentration as well as increased total sperm count and total sperm motility among current and past users compared with MPH-naïve patients. In particular, progressive motility and total motile sperm count were significantly increased following MPH use. A multivariate analysis adjusting for age and current smoking was conducted, further supporting a positive correlation between current MPH use and increased values of total sperm count and total sperm motility.

LIMITATIONS

Our study has several inherent weaknesses, foremost of which is its retrospective nature. Another notable weakness is that medication purchasing data may not accurately reflect MPH exposure in the study population. Patients may be purchasing MPH and not taking it as prescribed.

CONCLUSIONS

In the present study, we could not demonstrate a negative impact of methylphenidate treatment on sperm parameters in adults with ADHD. Hence, we may assume that methylphenidate does not negatively affect male fertility.

Associations Between Smoking Abstinence, Inhibitory Control, and Smoking Behavior: An fMRI Study

Nicotine addiction is associated with dysregulated inhibitory control (IC), mediated by corticothalamic circuitry including the right inferior frontal gyrus (rIFG). Among sated smokers, worse IC task performance and greater IC-related rIFG activity have been shown to be associated with greater relapse vulnerability. The present study investigated the effects of smoking abstinence on associations between IC task performance, rIFG activation, and smoking behavior. Smokers (N = 26, 15 female) completed an IC task (Go/Go/No-go) during fMRI scanning followed by a laboratory-based smoking relapse analog task (SRT) on two visits: once when sated and once following 24 h of smoking abstinence. During the SRT, smokers were provided with monetary rewards for incrementally delaying smoking. A significant main effect of No-go accuracy on latency to smoke during the SRT was observed when collapsing across smoking states (abstinent vs. sated). Similarly, a significant main effect of IC-related activation in rIFG on SRT performance was observed across states. The main effect of state, however, was non-significant in both of these models. Furthermore, the interaction between smoking state and No-go accuracy on SRT performance was non-significant, indicating a similar relationship between IC and lapse vulnerability under both sated and abstinent conditions. The state X rIFG activation interaction on SRT performance was likewise non-significant. Post-hoc whole brain analyses indicated that abstinence resulted in greater IC-related activity in the right middle frontal gyrus (MFG) and insula. Activation during IC in these regions was significantly associated with decreased No-go accuracy. Moreover, greater abstinence induced activity in right MFG during IC was associated with smoking sooner on the SRT. These findings are bolstered by the extant literature on the effects of nicotine on executive function and also contribute novel insights on how individual differences in behavioral and neuroimaging measures of IC may influence relapse propensity independent of smoking state.

Reduced Activation in the Pallidal-Thalamic-Motor Pathway Is Associated With Deficits in Reward-Modulated Inhibitory Control in Adults With a History of Attention-Deficit/Hyperactivity Disorder

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) symptoms persist into adulthood and are associated with functional impairments. Neuroimaging studies of reward-modulated inhibitory control can identify potential objective markers of impairment and may deepen our understanding of why probands engage in costly behaviors leading to adverse outcomes. The study aimed to identify reward-modulated inhibitory control neural circuitries, their association with ADHD symptoms, and real-world implications of a decreased capacity to engage in reward-modulated inhibitory control.

METHODS

A total of 106 adults (90% male) with rigorous childhood diagnoses of ADHD were scanned with functional magnetic resonance imaging during the Monetary Incentive Go/NoGo task. Adulthood symptoms of inattention and hyperactivity/impulsivity based on self- and informant report were assessed. The number of lifetime attempts taken to quit smoking were also assessed as an exemplar real-world outcome.

RESULTS

Hyperactivity/impulsivity was negatively associated with activation in the pallidum and primary motor cortex when inhibiting a previously rewarded Go stimulus that yielded a small immediate reward in order to obtain a larger reward later on. Reduced recruitment of the pallidal-thalamic-motor circuit mediated the negative association between hyperactivity/impulsivity and reward-modulated inhibitory control accuracy. Reduced pallidum activation, in response to reward-modulated inhibitory control, was also associated with more attempts made to successfully quit smoking.

CONCLUSIONS

Probands with persistent hyperactivity/impulsivity symptoms have alterations in brain regions that calculate the value of inhibiting an action that yields an immediate reward in order to obtain delayed larger rewards. This deficit results in poor inhibitory control on basic tasks and during real-world behaviors that rely on similar processes.

Increased subjective and reinforcing effects of initial nicotine exposure in young adults with attention deficit hyperactivity disorder (ADHD) compared to matched peers: results from an experimental model of first-time tobacco use

Individuals with attention deficit hyperactivity disorder (ADHD) are at increased risk for adverse cigarette smoking outcomes, and little is known about factors underlying this risk. This study sought to evaluate the effects of initial nicotine exposure in young adults with and without ADHD using a novel paradigm of exposure to model initial smoking experiences. Participants were young adult nonsmokers (n = 61 ADHD, n = 75 Control) between the ages of 18-25 years (inclusive) who reported never having smoked a full cigarette, and no tobacco use in the prior 3 years. Participants were exposed to three different blinded doses of intranasally administered nicotine (0, 0.5, 1.0 mg) across three separate fixed dose experimental sessions. In subsequent sessions, participants were given the opportunity to self-administer nicotine under two different conditions-high and low cognitive demand. Physiological, subjective, and reinforcing effects of nicotine were the main outcomes. Nicotine plasma levels, and no group differences in effects of nicotine on heart rate or blood pressure, confirmed comparable dosing exposure across groups. ADHD participants reported significantly greater dizziness following nicotine, and greater pleasant subjective effects across all conditions, compared to non-ADHD non-smokers. There were no group differences on subjective reports of bad or unpleasant effects. Subsequent nicotine self-administration was significantly higher among non-smokers with ADHD, and their choices of nicotine were not influenced by cognitive condition. There are meaningful differences between young adults with and without ADHD with respect to the initial subjective and reinforcing effects of nicotine; and interventions to prevent use should start prior to typical age of experimentation among ADHD patients.

Fronto-parietal engagement in response inhibition is inversely scaled with attention-deficit/hyperactivity disorder symptom severity

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A novel Go/No-go task points to a critical role for the IPS in response inhibition.

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IPS engagement in response inhibition is scaled back with ADHD symptom severity.

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Fronto-parietal connectivity increases when response inhibition is challenging.

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Connectivity modulation is also scaled back with ADHD symptom severity.

Background

Impaired response inhibition is one of the most consistent findings in attention deficit hyperactivity disorder (ADHD). However, the underlying brain mechanisms are not clear. This study aimed to underpin atypical inhibition-related brain activation and connectivity patterns in ADHD using a novel Go/No-go task design, and to determine its association with clinical symptoms of the disorder.

Methods

Forty-eight adults with ADHD performed a Go/No-go task in which target frequency was manipulated during functional MRI. Specific inhibition-related brain activation was correlated with ADHD symptom severity, to assess the relationship of individual differences in engagement of inhibition-related brain circuits with the magnitude of every-day functioning impairments. Finally, generalized psychophysical interaction analyses were carried out to examine whether not only engagement but also functional connectivity between regions implicated in response inhibition is related to symptom severity.

Results

We found no evidence for the expected parietal modulation by increased demand for inhibition at the group-level results. However, this lack of modulation was mediated by individual differences in ADHD symptom severity – increased engagement of the intraparietal sulcus (IPS) in inhibition-demanding events was evident in individuals with less severe symptoms but dissipated with increase in symptomatology. Similarly, functional connectivity between the IPS and the right inferior frontal gyrus (rIFG) was elevated under high inhibitory demand conditions, but this effect diminished with increased symptom severity.

Conclusions

The results highlight the importance of IPS engagement in response inhibition and suggest that IPS modulation may be driven by top-down control from the IFG. Moreover, the current findings force the point of treating ADHD as a continuum whereby brain correlates are scaled with severity of the disorder, and point to the potential use of individual differences in the modulation of IPS activation and connectivity as a neuromarker of ADHD.