A neurocomputational account of reward and novelty processing and effects of psychostimulants in attention deficit hyperactivity disorder

Regional brain structure at the intersection of novelty-seeking trait and anxiety

The interplay between novelty-seeking (NS) and anxiety is critical in decision-making and adaptive behaviour, yet its neuroanatomical underpinnings remain poorly understood. Given that NS reflects a propensity for exploration and risk-taking, while anxiety modulates threat sensitivity, understanding their interaction may provide insight into neural mechanisms underlying approach-avoidance behaviour. In this study, we investigated the association between regional grey matter (GM) structure, NS, anxiety, and their interaction using voxel-based morphometry (VBM) and source-based morphometry (SBM). Structural MRI data from 50 healthy participants were analysed in relation to NS (Tridimensional Personality Questionnaire) and anxiety (State-Trait Anxiety Inventory). Key findings revealed that NS alone was not associated with GM structure potentially due to more stringent inclusion criteria than previous studies. In contrast, trait anxiety correlated with increased subcallosal gyrus volume in VBM and was negatively associated with SBM-derived components encompassing the temporal and frontal cortices (e.g., left inferior temporal gyrus, inferior frontal gyrus, middle temporal gyrus, left middle frontal gyrus). Importantly, a significant NS-anxiety interaction emerged in the left inferior frontal gyrus (LIFG) GM volume (GMV) in VBM, suggesting a structural basis for the modulation of exploratory behaviour by anxiety. No significant interaction effects were observed in SBM analyses. These findings provide novel insights into the neural correlates of reward-related decision-making and anxiety regulation. The LIFG, in particular, may represent a key region where NS and anxiety converge to shape behaviour. Given its role in impulse control and harm avoidance, these results highlight the potential for targeted interventions aimed at modulating prefrontal circuits in impulsivity-related disorders.

Contingency-based flexibility mechanisms through a reinforcement learning model in adults with attention-deficit/hyperactivity disorder and obsessive-compulsive disorder

BACKGROUND AND AIMS

Impaired cognitive flexibility is associated with the characteristic symptomatology of ADHD and OCD. However, the mechanisms underlying learning and flexibility under uncertainty in adults with OCD or ADHD remain unclear. This study aimed to identify the mechanisms underlying contingency-based flexibility in a sample of adults with ADHD or OCD, using probabilistic learning reversal task, functional near-infrared spectroscopy, and computational modelling.

METHODS

148 Spanish-speaking adults (43 OCD, 53 ADHD and 52 healthy controls) completed a probabilistic learning reversal task. Previously, we obtained a resting-state functional connectivity (rsFC) record between several frontoparietal network regions using functional near-infrared spectroscopy. Contingency-based flexibility was explored by reinforcement learning model in combination with a Bayesian Generalized Logistic Model (GLM). The reinforcement learning parameters included reward and punishment learning rates (feedback sensitivity), and inverse temperature (decision consistency). Bayesian GLM parameters were defined to measure final accuracy, learning and speed of learning.

RESULTS

We found that the groups showed optimal performance in the discrimination block and a higher performance of healthy controls compared to patients in the reversal block. Model parameters predicted task performance differently by phase and group. In the discrimination block, while the performance of healthy controls was predicted by a combination of parameters such as high inverse temperature and punishment learning rate together with low values of reward learning rate, in the case of the clinical groups it was only by high inverse temperature. In the reversal block, the performance of OCD was predicted by high punishment learning rate and that of ADHD by low reward learning rate; in contrast, the performance of healthy controls was also predicted by a combination of parameters with high punishment learning rate and inverse temperature as predictors. We found the rsFC between the left and right posterior parietal cortex appears to credibly predict performance in the discrimination block in healthy controls.

CONCLUSIONS

These results suggest that OCD and ADHD in adults could be associated with poor behavioral adaptation when reinforcement-punishment contingencies changed. The difficulties observed in ADHD and OCD likely stem from different underlying mechanisms that affect both learning and switching processes. Findings highlighted how OCD appears to show greater sensitivity to punishment when there is uncertainty about the behavior-outcome association. Instead, the ADHD group can be guided by sensitivity to reinforcement. Interhemispheric rsFC posterior parietal cortex could be important for optimal learning of the task.

Perceptual Novelty Drives Early Exploration in a Bottom-Up Manner

Children are more likely than adults to explore new options, but is this due to a top-down epistemic-uncertainty-driven process or a bottom-up novelty-driven process? Given immature cognitive control, children may choose a new option because they are more susceptible to the automatic attraction of perceptual novelty and have difficulty disengaging from it. This hypothesis is difficult to test because perceptual novelty is intertwined with epistemic uncertainty. To address this problem, we designed a new n-armed bandit task to fully decouple novelty and epistemic uncertainty. By having adults and 4- to 6-year-olds perform the task, we found that perceptual novelty predominated 4-year-olds' (but not adults' or older children's) decisions even when it had no epistemic uncertainty and had the lowest reward value. Additionally, 4-year-olds showed such a novelty preference only when the option's novelty was directly observable, but not when it could only be anticipated, providing new evidence that perceptual novelty alone can drive elevated exploration in early development in a bottom-up manner.

Attention-deficit/hyperactivity disorder-related psychomotor activity and altered neuronal activity in the medial prefrontal cortex and striatum in the A53T mouse model of Parkinson's disease and other synucleinopathies: Findings from an "endophenotype" approach

Attention-Deficit/Hyperactivity Disorder (ADHD) is associated with an increased risk of Parkinson's disease (PD) and other synucleinopathies later in life. The severity of the ADHD phenotype may play a significant role in this association. There is no indication that any of the existing animal models can unify these disorders. Using the Open Field Test, amphetamine-challenge test, Western blot and immunohistochemical analysis of neuronal activity markers (c-Fos, FosB and ΔFosB) we performed a deliberate neurobehavioral characterization of 6-month-old hemizygous A53T carriers (A53T+) of the JAX006823 strain, evaluating the utility of this transgenic mouse model of PD and other synucleinopathies in ADHD/PD continuum research. Adhering to the "endophenotype" approach, non-transgenic littermates (A53T-) and C57BL/6J mice (used to maintain the colony) were examined with A53T+ mice, to differentiate between biomarkers of transgenicity and endophenotypic traits related to the genetic background of the strain. Obtained results revealed that increased behavioral and acute striatal response to novelty, increased basal neuronal activity of the ventromedial prefrontal cortex and rate-dependent calming effect of amphetamine were endophenotypic characteristics of the strain. Increased acute response of the medial prefrontal cortex to novelty and chronic increase in neuronal activity of the striatum appeared as the mark of transgenicity. To the best of our knowledge, this is the first study to indicate external validity of a transgenic mouse model of PD and other synucleinopathies with the neurobehavioral pathology associated with ADHD, hinting at its potential in preclinical research of ADHD/PD continuum. The full capacity of the model remains to be explored.

Listening habits and subjective effects of background music in young adults with and without ADHD

Adults listen to an average of 20.7 hours of music per week, according to a study conducted across 26 countries. Numerous studies indicate that listening to music can have beneficial effects on cognitive performance and emotional well-being. Music listening habits may vary depending on individual needs and listening contexts. However, a limited number of studies have specifically examined the patterns of background music usage during various more or less cognitive activities, especially among individuals with attentional difficulties related to ADHD. This study primarily aimed to compare music listening habits during daily activities that are more and less cognitive (e.g., studying, problem-solving versus cleaning, engaging in sports) between neurotypical young adults and those screened for ADHD (respondents who were identified as likely having ADHD based on the number of self-reported symptoms). To achieve this, 434 young adults aged 17 to 30 responded to an online survey. The results indicate that certain listening habits differ significantly between the neurotypical and ADHD-screened groups. The ADHD-screened group reports significantly more background music listening during less cognitive activities and while studying, compared to the neurotypical group. The results also reveal a difference in the proportion of individuals preferring stimulating music between the groups: ADHD-screened individuals report significantly more frequent listening to stimulating music, regardless of the activity type (more or less cognitive). Other aspects of music listening are common to both groups. Regardless of the group, more respondents reported preferring to listen to relaxing, instrumental, familiar and self-chosen music during more cognitive activities, whereas for less cognitive activities, more individuals mentioned preferring to listen to music that is stimulating, with lyrics, familiar and self-chosen. Overall, the results confirm that most young adults listen to music during their daily activities and perceive positive effects from this listening.

Effects of game-based digital therapeutics on attention deficit hyperactivity disorder in children and adolescents as assessed by parents or teachers: a systematic review and meta-analysis

Attention-deficit/hyperactivity disorder (ADHD) is a childhood-onset disorder characterized by pharmacological and non-pharmacological interventions. Despite the available treatment options and prevention measures, conventional treatments have several limitations. Digital therapeutics (DTx) like EndeavorRx® is an emerging alternative to overcome these limitations. EndeavorRx® is the first FDA-approved, game-based DTx approved for the treatment of pediatric ADHD. We investigated the effects of game-based DTx in randomised controlled trials (RCTs) on children and adolescents with ADHD. In this systematic review and meta-analysis, we searched PubMed, Embase, and PsycINFO databases up to January 2022. The protocol was registered (CRD42022299866). The assessor was defined as parents and teachers. The primary outcome was differences in inattention reported by the assessor, and the secondary outcome was differences in hyperactivity and hyperactivity/impulsivity reported by the assessor and the relative comparisons between game-based DTx, medicine, and control with indirect meta-analysis. Game-based DTx improved inattention more than the control upon assessment by assessors (standard mean difference (SMD) 0.28, 95% confidence interval (CI) 0.14-0.41; SMD 0.21, 95% CI 0.03-0.39, respectively), while medication improved inattention more than game-based DTx (SMD - 0·62, 95% CI - 1·04 to - 0·20) upon assessment by the teacher. Game-based DTx improved hyperactivity/impulsivity than the control upon assessment by assessors (SMD 0.28, 95% CI 0.03-0.53; SMD 0.30, 95% CI 0.05-0.55, respectively), and medication improved hyperactivity/impulsivity significantly than game-based DTx upon assessment by the teacher. Hyperactivity has not been reported extensively. As a result, game-based DTx had a more significant effect than the control, however medication was more effective.

Motor System-Dependent Effects of Amygdala and Ventral Striatum Lesions on Explore-Exploit Behaviors

Deciding whether to forego immediate rewards or explore new opportunities is a key component of flexible behavior and is critical for the survival of the species. Although previous studies have shown that different cortical and subcortical areas, including the amygdala and ventral striatum (VS), are implicated in representing the immediate (exploitative) and future (explorative) value of choices, the effect of the motor system used to make choices has not been examined. Here, we tested male rhesus macaques with amygdala or VS lesions on two versions of a three-arm bandit task where choices were registered with either a saccade or an arm movement. In both tasks we presented the monkeys with explore-exploit tradeoffs by periodically replacing familiar options with novel options that had unknown reward probabilities. We found that monkeys explored more with saccades but showed better learning with arm movements. VS lesions caused the monkeys to be more explorative with arm movements and less explorative with saccades, although this may have been due to an overall decrease in performance. VS lesions affected the monkeys' ability to learn novel stimulus-reward associations in both tasks, while after amygdala lesions this effect was stronger when choices were made with saccades. Further, on average, VS and amygdala lesions reduced the monkeys' ability to choose better options only when choices were made with a saccade. These results show that learning reward value associations to manage explore-exploit behaviors is motor system dependent and they further define the contributions of amygdala and VS to reinforcement learning.

Salience and hedonic experience as predictors of central stimulant treatment response in ADHD - A resting state fMRI study

BACKGROUND

Roughly 20-30% of patients with Attention-deficit/hyperactivity disorder (ADHD) fail to respond to central stimulant (CS) medication. Genetic, neuroimaging, biochemical and behavioral biomarkers for CS response have been investigated, but currently there are no biomarkers available for clinical use that help identify CS responders and non-responders.

METHODS

In the present paper, we studied if incentive salience and hedonic experience evaluated after a single-dose CS medication could predict response and non-response to CS medication. We used a bipolar visual analogue 'wanting' and 'liking' scale to gauge incentive salience and hedonic experience in 25 healthy controls (HC) and 29 ADHD patients. HC received 30 mg methylphenidate (MPH) and ADHD patients received either MPH or lisdexamphetamine (LDX) as selected by their clinician, with dosage individually determined for optimal effect. Clinician-evaluated global impression - severity (CGI-S) and improvement (CGI-I) and patient-evaluated improvement (PGI-I) were used to assess response to CS medication. Resting state functional magnetic resonance imaging (fMRI) was conducted before and after single-dose CS to correlate wanting and liking scores to changes in functional connectivity.

RESULTS

Roughly 20% of the ADHD patients were CS non-responders (5 of 29). CS responders had significantly higher incentive salience and hedonic experience scores compared to healthy controls and CS non-responders. Resting state fMRI showed that wanting scores were significantly associated to changes in functional connectivity in ventral striatum including nucleus accumbens.

CONCLUSION

Incentive salience and hedonic experience evaluated after a single-dose CS medication segregate CS responders and non-responders, with corresponding neuroimaging biomarkers in the brain reward system.

The computational psychiatry of antisocial behaviour and psychopathy

Antisocial behaviours such as disobedience, lying, stealing, destruction of property, and aggression towards others are common to multiple disorders of childhood and adulthood, including conduct disorder, oppositional defiant disorder, psychopathy, and antisocial personality disorder. These disorders have a significant negative impact for individuals and for society, but whether they represent clinically different phenomena, or simply different approaches to diagnosing the same underlying psychopathology is highly debated. Computational psychiatry, with its dual focus on identifying different classes of disorder and health (data-driven) and latent cognitive and neurobiological mechanisms (theory-driven), is well placed to address these questions. The elucidation of mechanisms that might characterise latent processes across different disorders of antisocial behaviour can also provide important advances. In this review, we critically discuss the contribution of computational research to our understanding of various antisocial behaviour disorders, and highlight suggestions for how computational psychiatry can address important clinical and scientific questions about these disorders in the future.

Biological Predictors of Treatment Response in Adult Attention Deficit Hyperactivity Disorder (ADHD): A Systematic Review

Background: Attention-deficit/hyperactivity disorder (ADHD) is a highly prevalent condition with onset in childhood and in many cases persisting into adulthood. Even though an increasing number of studies have investigated the efficacy of pharmacotherapy in the management of adult ADHD, few authors have tried to identify the biological predictors of treatment response. Objectives: To summarize the available data about the biological markers of treatment response in adults affected by ADHD. Methods: A search on the main biomedical and psychological archives (PubMed, Embase, Scopus, and PsycINFO) was performed. Manuscripts in English, published up to May 2022 and having the biological predictors of treatment response in adults with ADHD as their main topic, were included. Results: A total of 3855 articles was screened. Twenty-two articles were finally included. Most of the manuscripts studied neuroimaging and electrophysiological factors as potential predictors of treatment response in adult ADHD patients. No reliable markers were identified until now. Promising findings on this topic regard genetic polymorphisms in snap receptor (SNARE) proteins and default mode network-striatum connectivity. Conclusions: Even though some biological markers seem promising for the prediction of treatment response in adults affected by ADHD, further studies are needed to confirm the available data in the context of precision medicine.

Striatal dopamine dissociates methylphenidate effects on value-based versus surprise-based reversal learning

Psychostimulants such as methylphenidate are widely used for their cognitive enhancing effects, but there is large variability in the direction and extent of these effects. We tested the hypothesis that methylphenidate enhances or impairs reward/punishment-based reversal learning depending on baseline striatal dopamine levels and corticostriatal gating of reward/punishment-related representations in stimulus-specific sensory cortex. Young healthy adults (N = 100) were scanned with functional magnetic resonance imaging during a reward/punishment reversal learning task, after intake of methylphenidate or the selective D_2/3-receptor antagonist sulpiride. Striatal dopamine synthesis capacity was indexed with [¹⁸F]DOPA positron emission tomography. Methylphenidate improved and sulpiride decreased overall accuracy and response speed. Both drugs boosted reward versus punishment learning signals to a greater degree in participants with higher dopamine synthesis capacity. By contrast, striatal and stimulus-specific sensory surprise signals were boosted in participants with lower dopamine synthesis. These results unravel the mechanisms by which methylphenidate gates both attention and reward learning.

The mechanisms underpinning the variability in methylphenidate’s effects on cognition remain unclear. Here, the authors show that such effects reflect changes in striatal dopamine-related output gating of task-relevant cortical signals, and that these changes depend on baseline dopamine synthesis capacity.

Chronic Administrations of Guanfacine on Mesocortical Catecholaminergic and Thalamocortical Glutamatergic Transmissions

It has been established that the selective α2A adrenoceptor agonist guanfacine reduces hyperactivity and improves cognitive impairment in patients with attention-deficit/hyperactivity disorder (ADHD). The major mechanisms of guanfacine are considered to involve the activation of the postsynaptic α2A adrenoceptor of glutamatergic pyramidal neurons in the frontal cortex, but the effects of chronic guanfacine administration on catecholaminergic and glutamatergic transmissions associated with the orbitofrontal cortex (OFC) are yet to be clarified. The actions of guanfacine on catecholaminergic transmission, the effects of acutely local and systemically chronic (for 7 days) administrations of guanfacine on catecholamine release in pathways from the locus coeruleus (LC) to OFC, the ventral tegmental area (VTA) and reticular thalamic-nucleus (RTN), from VTA to OFC, from RTN to the mediodorsal thalamic-nucleus (MDTN), and from MDTN to OFC were determined using multi-probe microdialysis with ultra-high performance liquid chromatography. Additionally, the effects of chronic guanfacine administration on the expression of the α2A adrenoceptor in the plasma membrane fraction of OFC, VTA and LC were examined using a capillary immunoblotting system. The acute local administration of therapeutically relevant concentrations of guanfacine into the LC decreased norepinephrine release in the OFC, VTA and RTN without affecting dopamine release in the OFC. Systemically, chronic administration of therapeutically relevant doses of guanfacine for 14 days increased the basal release of norepinephrine in the OFC, VTA, RTN, and dopamine release in the OFC via the downregulation of the α2A adrenoceptor in the LC, OFC and VTA. Furthermore, systemically, chronic guanfacine administration did not affect intrathalamic GABAergic transmission, but it phasically enhanced thalamocortical glutamatergic transmission. The present study demonstrated the dual actions of guanfacine on catecholaminergic transmission-acute attenuation of noradrenergic transmission and chronic enhancement of noradrenergic transmission and thalamocortical glutamatergic transmission. These dual actions of guanfacine probably contribute to the clinical effects of guanfacine against ADHD.

What is the Effect of Stimulus Complexity on Attention to Repeating and Changing Information in Autism?

Slower habituation to repeating stimuli characterises Autism, but it is not known whether this is driven by difficulties with information processing or an attentional bias towards sameness. We conducted eye-tracking and presented looming geometrical shapes, clocks with moving arms and smiling faces, as two separate streams of stimuli (one repeating and one changing), to 7–15 years old children and adolescents (n = 103) with Autism, ADHD or co-occurring Autism+ADHD, and neurotypical children (Study-1); and to neurotypical children (n = 64) with varying levels of autistic traits (Study-2). Across both studies, autistic features were associated with longer looks to the repeating stimulus, and shorter looks to the changing stimulus, but only for more complex stimuli, indicating greater difficulty in processing complex or unpredictable information.

Cognitive characterization of adult attention deficit hyperactivity disorder by domains: a systematic review

Attention deficit hyperactivity disorder (ADHD) is reportedly the most frequent neurodevelopmental disorder diagnosed during childhood, and it is recognized as a common condition in adulthood. We review the evidence to help identify cognitive domains associated to deficits in adult ADHD. A systematic review with narrative synthesis was performed, assessing studies on adult ADHD, neuropsychology and research on involved cognitive domains in adults 18+ years old with an established diagnosis of ADHD, in seven electronic databases (PubMed, PsychInfo, WebOfScience, Embase, Scopus, OvidSPMedline, and Teseo), and Worldcat and OpenGrey grey literature databases. 93 studies were included for this review, encompassing findings from a total 5574 adults diagnosed only with ADHD, medication-naïve or non-medicated at the moment of the assessment and 4880 healthy controls. Adults diagnosed with ADHD may show, when compared to healthy controls, a cognitive profile characterized by deficits across all attention modalities, processing speed, executive function (mainly working memory and inhibition with emphasis on reward delay and interference control), verbal memory, reading skills, social cognition and arithmetic abilities. A cognitive characterization of adult ADHD by domains is established beyond the sole consideration of attention and executive function problems. Along with these, verbal memory, language (mainly reading), social cognition and arithmetic abilities may also contribute to a more comprehensive characterization of the cognitive profile in adult ADHD.

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.

Shifting uncertainty intolerance: methylphenidate and attention-deficit hyperactivity disorder

Risk evaluation is a critical component of decision making. Risk tolerance is relevant in both daily decisions and pathological disorders such as attention-deficit hyperactivity disorder (ADHD), where impulsivity is a cardinal symptom. Methylphenidate, a commonly prescribed drug in ADHD, improves attention but has mixed reports on risk-based decision making. Using a double-blinded placebo protocol, we studied the risk attitudes of ADHD patients and age-matched healthy volunteers while performing the 2-step sequential learning task and examined the effect of methylphenidate on their choices. We then applied a novel computational analysis using the hierarchical drift-diffusion model to extract parameters such as threshold ('a'-amount of evidence accumulated before making a decision), drift rate ('v'-information processing speed) and response bias ('z' apriori bias towards a specific choice) focusing specifically on risky choice preference. Critically, we show that ADHD patients on placebo have an apriori bias towards risky choices compared to controls. Furthermore, methylphenidate enhanced preference towards risky choices (higher apriori bias) in both groups but had a significantly greater effect in the patient population independent of clinical scores. Thus, methylphenidate appears to shift tolerance towards risky uncertain choices possibly mediated by prefrontal dopaminergic and noradrenergic modulation. We emphasise the utility of computational models in detecting underlying processes. Our findings have implications for subtle yet differential effects of methylphenidate on ADHD compared to healthy population.

Unravelling the effects of methylphenidate on the dopaminergic and noradrenergic functional circuits

Functional magnetic resonance imaging (fMRI) can be combined with drugs to investigate the system-level functional responses in the brain to such challenges. However, most psychoactive agents act on multiple neurotransmitters, limiting the ability of fMRI to identify functional effects related to actions on discrete pharmacological targets. We recently introduced a multimodal approach, REACT (Receptor-Enriched Analysis of functional Connectivity by Targets), which offers the opportunity to disentangle effects of drugs on different neurotransmitters and clarify the biological mechanisms driving clinical efficacy and side effects of a compound. Here, we focus on methylphenidate (MPH), which binds to the dopamine transporter (DAT) and the norepinephrine transporter (NET), to unravel its effects on dopaminergic and noradrenergic functional circuits in the healthy brain at rest. We then explored the relationship between these target-enriched resting state functional connectivity (FC) maps and inter-individual variability in behavioural responses to a reinforcement-learning task encompassing a novelty manipulation to disentangle the molecular systems underlying specific cognitive/behavioural effects. Our main analysis showed a significant MPH-induced FC increase in sensorimotor areas in the functional circuit associated with DAT. In our exploratory analysis, we found that MPH-induced regional variations in the DAT and NET-enriched FC maps were significantly correlated with some of the inter-individual differences on key behavioural responses associated with the reinforcement-learning task. Our findings show that main MPH-related FC changes at rest can be understood through the distribution of DAT in the brain. Furthermore, they suggest that when compounds have mixed pharmacological profiles, REACT may be able to capture regional functional effects that are underpinned by the same cognitive mechanism but are related to engagement of distinct molecular targets.

Using Mobile Electroencephalography and Actigraphy to Diagnose Attention-Deficit/Hyperactivity Disorder: Case-Control Comparison Study

BACKGROUND

Children with attention-deficit/hyperactivity disorder (ADHD), a neurobehavioral disorder, display behaviors of inattention, hyperactivity, or impulsivity, which can affect their ability to learn and establish proper family and social relationships. Various tools are currently used by child and adolescent psychiatric clinics to diagnose, evaluate, and collect information and data. The tools allow professional physicians to assess if patients need further treatment, following a thorough and careful clinical diagnosis process.

OBJECTIVE

We aim to determine potential indicators extracted from a mobile electroencephalography (EEG) device (Mindset; NeuroSky) and an actigraph (MotionWatch 8; CamNtech) and to validate them for diagnosis of ADHD. The 3 indicators are (1) attention, measured by the EEG; (2) meditation, measured by the EEG; and (3) activity, measured by the actigraph.

METHODS

A total of 63 participants were recruited. The case group comprised 40 boys and 9 girls, while the control group comprised 5 boys and 9 girls. The groups were age matched. The test was divided into 3 stages-pretest, in-test, and posttest-with a testing duration of 20 minutes each. We used correlation analysis, repeated measures analysis of variance, and regression analysis to investigate which indicators can be used for ADHD diagnosis.

RESULTS

With the EEG indicators, the analysis results show a significant correlation of attention with both hit reaction time (RT) interstimulus interval (ISI) change (r=-0.368; P=.003) and hit standard error (SE) ISI change (r=-0.336; P=.007). This indicates that the higher the attention of the participants, the smaller both the hit RT change and the hit SE ISI change. With the actigraph indicator, confidence index (r=0.352; P=.005), omissions (r=0.322; P=.01), hit RT SE (r=0.393; P=.001), and variability (r=0.351; P=.005) were significant. This indicates that the higher the activity amounts, the higher the impulsive behavior of the participants and the more target omissions in the continuous performance test (CPT). The results show that the participants with ADHD present a significant difference in activity amounts (P<0.001). The actigraph outperforms the EEG in screening ADHD.

CONCLUSIONS

When the participants with ADHD are stimulated under restricted conditions, they will present different amounts of activity than in unrestricted conditions due to participants' inability to exercise control over their concentration. This finding could be a new electronic physiological biomarker of ADHD. An actigraph can be used to detect the amount of activity exhibited and to help physicians diagnose the disorder in order to develop more objective, rapid auxiliary diagnostic tools.

Low self-control and aggression exert serial mediation between inattention/hyperactivity problems and severity of internet gaming disorder features longitudinally among adolescents

OBJECTIVES

We examined serial mediating roles of low self-control and aggression in explaining relationships between levels of inattention and hyperactivity problems (IHPs) and severity of Internet gaming disorder (IGD) features when exposed to online games among adolescents without Attention deficit hyperactivity disorder (ADHD) stratified by gender using three-wave longitudinal study.

METHOD

The sample comprised a total of 1,732 family dyads from a study that was conducted among seventh graders without diagnoses of ADHD at baseline. Levels of IHPs were assessed by the parent reported Korean version of the ADHD rating scale at baseline (wave1). Severity of IGD features was assessed by the Internet Game Use-Elicited Symptom Screen (IGUESS) at wave3. Both levels of self-control (wave1) and aggression (wave2) were assessed by self-report. The mediating role of low self-control and aggression in the relationships between level of IHPs and severity of IGD were evaluated using serial mediation analysis separately for each gender.

RESULTS

Levels of IHPs were related directly to severity of IGD features in both genders. The indirect effects via low self-control were also significant in both genders, however, the indirect effects via aggression was significant only in women. The serial mediation effect via low self-control and aggression between levels of IHPs and IGD features was significant in both genders (men, coefficient:0.009, 95%CI 0.005-0.019; women, coefficient:0.010, 95%CI:0.005-0.026).

CONCLUSION

We revealed a possible mechanism underlying a serial mediation chain from low self-control to aggression explaining the effects of IHPs on severity of IGD features. However, this conclusion should be taken with a caution, because the effect sizes were very low.

The neurobehavioral mechanisms of motivational control in attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) poses debilitating impairments in the neurobehavioral systems governing reward-related processes-key to the control of motivated behaviors. Individuals with ADHD may rely on a motivational control system that favors cue-driven habits-rooted in the posterior putamen-over caudate and prefrontal cortex-driven goal-directed behaviors. We examined the neurobehavioral correlates of motivational control in ADHD. Twenty-five adults with ADHD and 25 neurotypicals underwent fMRI while training on two stimulus-response-outcome associations. A devaluation procedure followed, whereby they were selectively satiated on one of the snack outcomes, decreasing its value. A subsequent extinction test determined outcome-sensitivity (i.e., whether responses towards devalued snack diminished). Despite behavioral similarities, the ADHD group displayed a distinct neural signature marked by enhanced posterior putamen activation as a function of training. This region also displayed diminished functional connectivity with the dorsal anterior cingulate cortex, which is associated with top-down control. Our whole-brain analysis yielded ADHD-specific posterior putamen and opercular/insular cortex activity over the course of training-regions associated with stimulus-sensitivity and maladaptively rigid behaviors, respectively. Neural comparisons also identified hyper-recruitment of the hippocampus in the ADHD group. These results highlight corticostriatal discrepancies in ADHD, possibly serving as a biomarker of the disorder.

Subcortical Substrates of Explore-Exploit Decisions in Primates

The explore-exploit dilemma refers to the challenge of deciding when to forego immediate rewards and explore new opportunities that could lead to greater rewards in the future. While motivational neural circuits facilitate learning based on past choices and outcomes, it is unclear whether they also support computations relevant for deciding when to explore. We recorded neural activity in the amygdala and ventral striatum of rhesus macaques as they solved a task that required them to balance novelty-driven exploration with exploitation of what they had already learned. Using a partially observable Markov decision process (POMDP) model to quantify explore-exploit trade-offs, we identified that the ventral striatum and amygdala differ in how they represent the immediate value of exploitative choices and the future value of exploratory choices. These findings show that subcortical motivational circuits are important in guiding explore-exploit decisions.