Altered proactive control in adults with ADHD: Evidence from event-related potentials during cued task switching

Mind-wandering does not always rhyme with proactive functioning! Changes in the temporal dynamics of the mPFC-mediated theta oscillations during moments of mind-wandering

The reduced engagement of the cognitive control network has been documented widely during mind-wandering (MW). However, it remains unknown how MW affects the neural dynamics of cognitive control processes. From this perspective, we explored neural dynamics mediated by the medial prefrontal cortex (mPFC). Their engagement can be both transient (or reactive) and anticipated (or proactive). A total of fortyseven healthy subjects (37 females) were engaged in a long-lasting sustained-attention Go/NoGo task. Subjective probes were used to detect MW episodes. Channel-based EEG time-frequency analysis was performed to measure the theta oscillations, an index of the mPFC activity. The theta oscillations were computed immediately after conflictual NoGo trials to explore the reactive engagement of the mPFC. Proactive control was measured on the Go trials preceded the NoGo. Behaviorally, periods of MW were associated with an increase in errors and in RT variability in comparison to on-task periods. The analysis of the frontal midline theta power (MFθ) revealed that MW periods were associated with lower anticipated/proactive engagement and similar transient/reactive engagement of mPFC-mediated processes. Moreover, the communication between the mPFC and the DLPFC, as revealed by the poorer theta synchronization between these two regions, was also impaired during MW periods. Our results provide new insights about performance impairment during MW. They could be an important step in improving the existing understanding of the altered performances that are reported for some disorders that are known to be associated with excessive MW.

The metacontrol hypothesis as diagnostic framework of OCD and ADHD: A dimensional approach based on shared neurobiological vulnerability

Obsessive-compulsive disorder (OCD) and attention-deficit hyperactivity disorder (ADHD) are multi-faceted neuropsychiatric conditions that in many aspects appear to be each other's antipodes. We suggest a dimensional approach, according to which these partially opposing disorders fall onto a continuum that reflects variability regarding alterations of cortico-striato-thalamo-cortical (CSTC) circuits and of the processing of neural noise during cognition. By using theoretical accounts of human cognitive metacontrol, we develop a framework according to which OCD can be characterized by a chronic bias towards exaggerated cognitive persistence, equivalent to a high signal-to-noise ratio (SNR)-which facilitates perseverative behaviour but impairs mental flexibility. In contrast, ADHD is characterized by a chronic bias towards inflated cognitive flexibility, equivalent to a low SNR-which increases behavioural variability but impairs the focusing on one goal and on relevant information. We argue that, when pharmacology is not feasible, novel treatments of these disorders may involve methods to manipulate the signal-to-noise ratio via non-invasive brain stimulation techniques, in order to normalize the situational imbalance between cognitive persistence and cognitive flexibility.

Two sides of the same coin: ADHD affects reactive but not proactive inhibition in children

Children with attention-deficit/hyperactivity disorder (ADHD) present a deficit in inhibitory control. Still, it remains unclear whether it comes from a deficit in reactive inhibition (ability to stop the action in progress), proactive inhibition (ability to exert preparatory control), or both.We compared the performance of 39 children with ADHD and 42 typically developing children performing a Simon choice reaction time task. The Simon task is a conflict task that is well-adapted to dissociate proactive and reactive inhibition. Beyond classical global measures (mean reaction time, accuracy rate, and interference effect), we used more sophisticated dynamic analyses of the interference effect and accuracy rate to investigate reactive inhibition. We studied proactive inhibition through the congruency sequence effect (CSE).Our results showed that children with ADHD had impaired reactive but not proactive inhibition. Moreover, the deficit found in reactive inhibition seems to be due to both a stronger impulse capture and more difficulties in inhibiting impulsive responses. These findings contribute to a better understanding of how ADHD affects inhibitory control in children.

What Has Been Learned from Using EEG Methods in Research of ADHD?

Electrophysiological recording methods, including electroencephalography (EEG) and magnetoencephalography (MEG), have an unparalleled capacity to provide insights into the timing and frequency (spectral) composition of rapidly changing neural activity associated with various cognitive processes. The current chapter provides an overview of EEG studies examining alterations in brain activity in ADHD, measured both at rest and during cognitive tasks. While EEG resting state studies of ADHD indicate no universal alterations in the disorder, event-related studies reveal consistent deficits in attentional and inhibitory control and consequently inform the proposed cognitive models of ADHD. Similar to other neuroimaging measures, EEG research indicates alterations in multiple neural circuits and cognitive functions. EEG methods - supported by the constant refinement of analytic strategies - have the potential to contribute to improved diagnostics and interventions for ADHD, underlining their clinical utility.

Slower adaptation of control strategies in individuals with high impulsive tendencies

Flexible use of reactive and proactive control according to environmental demands is the key to adaptive behavior. In this study, forty-eight adults performed ten blocks of an AX-CPT task to reveal the strength of proactive control by the calculation of the proactive behavioral index (PBI). They also filled out the UPPS questionnaire to assess their impulsiveness. The median-split method based on the global UPPS score distribution was used to categorize participants as having high (HI) or low (LI) impulsiveness traits. The analyses revealed that the PBI was negatively correlated with the UPPS scores, suggesting that the higher is the impulsiveness, the weaker the dominance of proactive control processes. We showed, at an individual level, that the PBI increased across blocks and suggested that this effect was due to a smaller decrease in reactive control processes. Notably, the PBI increase was slower in the HI group than in the LI group. Moreover, participants who did not adapt to task demands were all characterized as high impulsive. Overall, the current study demonstrates that (1) impulsiveness is associated with less dominant proactive control due to (2) slower adaptation to task demands (3) driven by a stronger reliance on reactive processes. These findings are discussed in regards to pathological populations.

External rewards and positive stimuli promote different cognitive control engagement strategies in children

In everyday life, children often need to engage control in emotionally or motivationally relevant contexts. This study disentangled and directly compared the respective influences of external rewards and positive stimuli on childhood cognitive control. We expected external rewards to promote proactive cognitive control and positive stimuli to impair proactive control, especially in younger age. EEG data were recorded while children (5-6 years old and 9-10 years old) and adults completed a cued task-switching paradigm in three conditions: positive-stimulus, external-reward and control conditions. Provision of reward resulted in more accurate but slower responses, and more pronounced cue-locked posterior positivity, potentially suggesting general proactive mobilisation of attention (i.e., readiness). Despite no effects on behaviour, the presentation of positive stimuli was unexpectedly associated with a greater cue-locked extended slow-wave when task cues were presented ahead of targets (i.e. proactive-control possible) in younger children, suggesting greater proactive cue preparation. In contrast to our hypothesis, both external rewards and positive stimuli seem to promote different types of proactive approaches in children.