Enhanced Impulsive Action Selection in Middle-Aged Adults-Insights From an Oculomotor Simon Task

Continuous subcutaneous apomorphine infusion does not impair the dynamics of cognitive action control in mild to moderate Parkinson's disease

INTRODUCTION

Continuous subcutaneous apomorphine infusion (CSAI) is increasingly used in Parkinson's disease (PD), notably in patients contraindicated for subthalamic deep brain stimulation. Although it has been suggested that CSAI is safe regarding cognition, few studies have actually investigated its effect, especially on cognitive control which is a crucial process for goal-directed behavior. More specifically, its impact on the dynamics of cognitive action control, as reflected by the activation and suppression of impulsive responses, has yet to be investigated, which is the objective of the present study.

METHODS

We compared cognitive action control between baseline (M0) and 6 months (M6) after the start of add-on CSAI by administering an oculomotor Simon task to 20 patients with mild to moderate PD. We used the activation-suppression model to determine whether CSAI had an effect on either the impulsive errors made in conflict situations or the suppression of these responses.

RESULTS

We found no difference between M0 and M6 in the congruence effect regarding either reaction time or accuracy, indicating that overall conflict resolution was not influenced by CSAI. Furthermore, the rate of fast errors in the conflict situation and the last slope of the delta plots (reflecting the strength of impulsive response suppression) were unaffected by the treatment. The 95% confidence intervals calculated for the treatment effect on both of these measures fell below the range of usual meaningful effects.

CONCLUSION

We found no difference between M0 and M6, which strongly suggests that CSAI does not impair the dynamics of cognitive action control.

Auditory stimulus has a larger effect on anticipatory postural adjustments in older than young adults during choice step reaction

PURPOSE

The study aim was to compare the influence of an auditory stimulus (AS) on anticipatory postural adjustments (APAs) between young and older adults during a choice step reaction.

METHODS

Sixteen young and 19 older adults stepped forward in response to a visual imperative stimulus of an arrow. We used a choice reaction time (CRT) task and a Simon task which consisted of congruent and incongruent conditions. The direction of the presented arrow and its spatial location matched in the congruent condition while they did not in the incongruent condition. The AS was presented randomly and simultaneously with the visual stimulus. Incorrect weight shifts before lifting off the foot, termed APA errors, stepping errors, temporal parameters, and APA amplitudes were analyzed.

RESULTS

The APA error rate was higher in trials with than without AS in all task conditions for the older group, while this increase occurred only in the incongruent condition for the young group. The stepping error rate was also increased in the presence of AS in the incongruent condition for the older group. Reaction times were faster with AS in both groups. The APA amplitude of erroneous APA trials became larger with AS in the incongruent condition for both groups, and this effect appeared greater for the older group.

CONCLUSIONS

The effect of AS on APAs is larger in the elderly during a choice step reaction. In the presence of incongruent visual information, this effect becomes even greater, potentially inducing not only APA errors but also stepping errors.

Impulsive oculomotor action selection in Parkinson's disease

The effects of Parkinson's disease (PD) on the dynamics of impulsive action selection and suppression have recently been studied using distributional analyses, but with mixed results, especially for selection. Furthermore, some authors have suggested that impulsivity, regarded as a personality trait, shares common features with behavioral tasks' measures. The current study was designed to clarify the impact of PD on impulsive action selection and suppression, and investigate the link between cognitive action control and self-reported impulsivity. We administered an oculomotor version of the Simon task to 32 patients with PD and 32 matched healthy controls (HC), and conducted distributional analyses in accordance with the activation-suppression model. Patients and HC also filled out the Barratt Impulsiveness Scale (BIS) questionnaire. Results showed that patients with PD were faster overall and exhibited a greater congruence effect than HC. They also displayed enhanced impulsive action selection. By contrast, the suppression of impulsive responses was similar across both groups. Furthermore, patients had higher impulsivity scores, which were correlated with higher impulsive action selection and higher suppression. Our study yielded two interesting findings. First, PD resulted in a higher number of fast errors. The activation-suppression model suggests that patients with PD are more susceptible to the impulsive action selection induced by the irrelevant stimulus dimension. Second, impulsive action selection and suppression were both associated with trait impulsivity, as measured by the BIS, indicating that these two aspects of impulsivity share common features.