Attention regulation in women with ADHD and women with bipolar disorder: An ex-Gaussian approach

Ex-Gaussian vector metric and similarity index applied to reaction time analysis

In psychology and cognitive neuroscience, reaction time (RT) series and their ex-Gaussian distributions are commonly used as scalar quantities to explore the time course of attentional processes. However, we propose that such attentional processes can also be analyzed using an "ex-Gaussian vector", defined by successive triads of ex-Gaussian sigma, tau, and mu parameters from RT series. This geometrical object may help characterize interindividual differences between congruent and incongruent stimuli in the attentional Stroop task within a group of participants. To test these hypotheses, we calculated the similarity index of these geometrical objects in young adults without detectable neurological disorders. Our findings show that during two weeks of continuous Stroop task application, each participant displayed distinct ex-Gaussian RT vectors in a Cartesian 3D plot. Furthermore, our study found that the similarity index between ex-Gaussian RT vectors was significantly higher for incongruent stimuli than for congruent stimuli.

Impaired emotional response inhibition among adolescents with bipolar depression: evidence from event-related potentials and behavioral performance

BACKGROUND

Impaired inhibition of inappropriate responses in the emotional context is a core feature in patients with bipolar disorder. However, there has been little research exploring the underlying mechanism of impaired response inhibition for emotional stimuli in adolescents with bipolar depression. To explore this issue, we employed event-related potentials (ERPs) to investigate the underlying neuroelectrophysiological mechanisms of inhibition of inappropriate emotional stimuli in adolescents with bipolar depression.

METHODS

Twenty-five adolescents with bipolar depression and nineteen healthy controls completed an emotional Go/No-Go task during electroencephalography recording. Reaction time (RT), reaction time variability (RTV), discriminability, and response bias were measured as behavioral performance indicators. ERP components, theta-band oscillation and inter-trial coherence (ITC) were compared between the two groups.

RESULTS

Behavioral performance analysis found that adolescents with bipolar depression showed smaller d' values, and larger RT and RTV, than healthy controls. Nogo-P3 amplitude was decreased in adolescents with bipolar depression in comparison with healthy controls. Theta-band oscillation and ITC for emotional stimuli were also reduced in adolescents with bipolar depression. Pearson correlation analysis showed there was a negative correlation between the Nogo-P3 amplitude induced by negative trials and RTV in adolescents with bipolar depression.

CONCLUSION

Our findings suggest that adolescents with bipolar depression exhibit abnormal response inhibition in the emotional context. Impaired attentional function and discrimination of emotional information are related to the failure of behavioral inhibition in negative emotional contexts, and attenuated P3 amplitude and theta-band oscillation could be an electrophysiological indicator for this impairment.

Differences in Ex-Gaussian Parameters from Response Time Distributions Between Individuals with and Without Attention Deficit/Hyperactivity Disorder: A Meta-analysis

Attention Deficit Hyperactivity Disorder (ADHD) is one of the most prevalent neurodevelopmental disorders in childhood and adolescence. Differences in reaction times (RT) in cognitive tasks have been consistently observed between ADHD and typical participants. Instead of estimating means and standard deviations, fitting non-symmetrical distributions like the ex-Gaussian, characterized by three parameters (µ, σ, and τ), account for the whole RT distributions. A meta-analysis is performed with all the available literature using ex-Gaussian distributions for comparisons between individuals with ADHD and controls. Results show that τ and σ are generally greater for ADHD samples, while µ tends to be larger for typical groups but only for younger ages. Differences in τ are also moderated by ADHD subtypes. τ and σ show, respectively, quadratic and linear relationships with inter-stimulus intervals from Continuous Performance Test and Go/No Go tasks. Furthermore, tasks and cognitive domains influence the three parameters. Interpretations of ex-Gaussian parameters and clinical implications of these findings are also discussed. Fitting ex-Gaussian distributions to RT data is a useful way to explore differences between individuals with ADHD and healthy controls.

Exploring the steps of learning: computational modeling of initiatory-actions among individuals with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is characterized by difficulty in acting in a goal-directed manner. While most environments require a sequence of actions for goal attainment, ADHD was never studied in the context of value-based sequence learning. Here, we made use of current advancements in hierarchical reinforcement-learning algorithms to track the internal value and choice policy of individuals with ADHD performing a three-stage sequence learning task. Specifically, 54 participants (28 ADHD, 26 controls) completed a value-based reinforcement-learning task that allowed us to estimate internal action values for each trial and stage using computational modeling. We found attenuated sensitivity to action values in ADHD compared to controls, both in choice and reaction-time variability estimates. Remarkably, this was found only for first-stage actions (i.e., initiatory actions), while for actions performed just before outcome delivery the two groups were strikingly indistinguishable. These results suggest a difficulty in following value estimation for initiatory actions in ADHD.

Event-related brain-oscillatory and ex-Gaussian markers of remission and persistence of ADHD

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) often persists into adolescence and adulthood, but the processes underlying persistence and remission remain poorly understood. We previously found that reaction time variability and event-related potentials of preparation-vigilance processes were impaired in ADHD persisters and represented markers of remission, as ADHD remitters were indistinguishable from controls but differed from persisters. Here, we aimed to further clarify the nature of the cognitive-neurophysiological impairments in ADHD and of markers of remission by examining the finer-grained ex-Gaussian reaction-time distribution and electroencephalographic (EEG) brain-oscillatory measures in ADHD persisters, remitters and controls.

METHODS

A total of 110 adolescents and young adults with childhood ADHD (87 persisters, 23 remitters) and 169 age-matched controls were compared on ex-Gaussian (mu, sigma, tau) indices and time-frequency EEG measures of power and phase consistency from a reaction-time task with slow-unrewarded baseline and fast-incentive conditions ('Fast task').

RESULTS

Compared to controls, ADHD persisters showed significantly greater mu, sigma, tau, and lower theta power and phase consistency across conditions. Relative to ADHD persisters, remitters showed significantly lower tau and theta power and phase consistency across conditions, as well as lower mu in the fast-incentive condition, with no difference in the baseline condition. Remitters did not significantly differ from controls on any measure.

CONCLUSIONS

We found widespread impairments in ADHD persisters in reaction-time distribution and brain-oscillatory measures. Event-related theta power, theta phase consistency and tau across conditions, as well as mu in the more engaging fast-incentive condition, emerged as novel markers of ADHD remission, potentially representing compensatory mechanisms in individuals with remitted ADHD.

Early neurophysiological stimulus processing during a performance-monitoring task differentiates women with bipolar disorder from women with ADHD

Adults with attention-deficit/hyperactivity disorder (ADHD) or bipolar disorder (BD) may display similar cognitive impairments and clinical symptoms, which might reflect shared mechanisms. Initial evidence indicates disorder-specific and overlapping neurophysiological alterations using event-related potentials (ERPs) in individuals with BD or ADHD during attentional tasks, but it is unknown whether impairments generalize across other processes and tasks. We conduct the first comparison between women with ADHD (n = 20), women with BD (n = 20) and control women (n = 20) on ERPs from a performance-monitoring flanker task. The BD group showed a significantly attenuated frontal ERP of conflict monitoring (N2) compared to the ADHD group across both low-conflict (congruent) and high-conflict (incongruent) task conditions, and compared to controls in the high-conflict condition. However, when controlling for an earlier attentional ERP (frontal N1), which was significantly reduced in participants with BD compared to participants with ADHD and controls, N2 group differences were no longer significant. These results indicate that ERP differences in conflict monitoring may be attributable to differences in earlier attentional processes. These findings identify neural differences in early attention between BD and ADHD which precede conflict monitoring processes, potentially pointing to distinct neural mechanisms implicated in the two disorders.