Making a saccade enhances Stroop and Simon conflict control

Anti-saccade can be used as a screening tool for early cognitive impairment: a correlation study based on anti-saccade parameters and cognitive function

BACKGROUND

Eye movement tasks, especially anti-saccade tasks, have been used to assess cognitive function in patients with neuropsychiatric disorders. Although it has been shown that individuals with cognitive impairment perform worse on anti-saccades tasks, there is a lack of systematic evaluation of the sensitivity of parameters of anti-saccades to assess different subtypes of cognitive impairment.

METHODS

A total of 158 participants were enrolled in this study, consisting of 66 men and 92 women, with an average age of 50.2 ± 10 years. The comparison of pro-saccade reaction time, anti-saccade reaction time, and error rates in the saccade task between individuals with cognitive impairments and a normal group was conducted. Furthermore, we systematically analyzed the correlations between the performance in neurological function tests (Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Stroop) and these anti-saccade parameters. Especially, the correlation between these parameters and cognitive function in different domains of the MoCA task were also evaluated.

RESULTS

The pro-saccade reaction time, anti-saccade reaction time and error rate were negatively correlated with the MMSE and MoCA scores (P < 0.001), and positively correlated with the time used in Stroop tasks. Among them, the error rate had the strongest correlation with the performance of MMSE, MoCA and Stroop tasks (MoCA: P < 0.0001, r2 = -0.608; MMSE: P < 0.0001, r2 = -0.344; Stroop: P < 0.0001, r2 = 0.455). Among the seven cognitive domains examined by the MoCA task, error rates had relatively high correlations with visuospatial/executive (P < 0.0001, r2 = -0.4660) and delayed recall (P < 0.0001, r2 = -0.4228) compared to naming, language (P = 0.0004, r2 = -0.0788), attention (P = 0.0004, r2 = -0.0780), abstraction (P < 0.0001, r2 = -0.1515), orientation (P < 0.0001, r2 = -0.1075). Moreover, pro-saccade reaction time, anti-saccade reaction time and error rate of people with high MoCA scores were significantly higher than those of people with low MoCA scores, which can be used to identify people with mild cognitive impairment.

CONCLUSIONS

Our study's results provide valuable clinical evidence supporting the effectiveness of anti-saccades in assessing cognitive impairment, which is beneficial for screening and timely clinical intervention in individuals with specific cognitive impairment.

Diagnosis of schizophrenia by integrated saccade scores and associations with psychiatric symptoms, and functioning

Eye movement as a neurobiological biomarker of schizophrenia. We aim to estimate diagnostic accuracy of integrated pro/antisaccade eye movement measurements to discriminate between healthy individuals and schizophrenic patients. We compared the eye movement performance of 85 healthy individuals and 116 schizophrenia-stable patients during prosaccade and antisaccade tasks. The difference eye movement measurements were accumulated by stepwise discriminant analysis to produce an integrated score. Finally, the diagnostic value of the integrated score was calculated by the receiver operating characteristic (ROC) area under the curve (AUC), and the best sensitivity and specificity were calculated based on the given cutoff values. Using discriminant analysis, an integrated score included the residual gain and latency (step) during the prosaccade test, the error rate, and the corrected error rate during the antisaccade test. We found that the integrated score could well classify schizophrenia patients and healthy individuals with an accuracy of 80.6%. In the ROC, Youden's index was 0.634 (sensitivity = 81.0%, specificity = 82.4%) and AUC was 0.871. There were significant difference patterns of correlation between the severity of psychiatric symptoms and daily functioning and diagnostic eye movement measurements. Using only 2 saccade tasks to discriminate well between schizophrenia patients and healthy controls, suggesting that abnormalities in saccade behavior is a potential biomarker and efficient diagnostic tool for identifying schizophrenia. The underlying neuropathologic mechanisms associated with abnormal saccades may provide insights into the intervention and diagnosis of schizophrenia.

Volition motivates cognitive performance at the response-execution level by attenuating task-irrelevant motor activations

Humans express volition by making voluntary choices which, relative to forced choices, can motivate cognitive performance in a variety of tasks. However, a task that requires the generation of motor responses on the basis of external sensory stimulation involves complex underlying cognitive processes, e.g., pre-response processing, response selection, and response execution. The present study investigated how these underlying processes are facilitated by voluntary choice-making. In five experiments, participants were free or forced to choose a task-irrelevant picture from two alternatives, and then completed a conflict task, i.e., Flanker, Stroop, Simon, Stroop-Simon, or Flanker-Simon task, where the conflict effect could occur at different processing levels. Results consistently showed that responses in all tasks were generally faster after voluntary (vs. forced) choices. Importantly, the conflict effect at the response-execution level (i.e., the Simon effect), but not the conflict effect at the pre-response and response-selection levels (i.e., the Flanker and Stroop effects), was reduced by the voluntary choice-making. Model fitting revealed that the peak amplitude of automatic motor activations in the response-execution conflict was smaller after voluntary (vs. forced) choices. These findings suggest that volition motivates subsequent cognitive performance at the response-execution level by attenuating task-irrelevant motor activations.

The benefit of making voluntary choices generalizes across multiple effectors

It has been shown that cognitive performance could be improved by expressing volition (e.g., making voluntary choices), which necessarily involves the execution of action through a certain effector. However, it is unclear if the benefit of expressing volition can generalize across different effectors. In the present study, participants made a choice between two pictures either voluntarily or forcibly, and subsequently completed a visual search task with the chosen picture as a task-irrelevant background. The effector for choosing a picture could be the hand (pressing a key), foot (pedaling), mouth (commanding), or eye (gazing), whereas the effector for responding to the search target was always the hand. Results showed that participants responded faster and had a more liberal response criterion in the search task after a voluntary choice (vs. a forced choice). Importantly, the improved performance was observed regardless of which effector was used in making the choice, and regardless of whether the effector for making choices was the same as or different from the effector for responding to the search target. Eye-movement data for oculomotor choice showed that the main contributor to the facilitatory effect of voluntary choice was the post-search time in the visual search task (i.e., the time spent on processes after the target was found, such as response selection and execution). These results suggest that the expression of volition may involve the motor control system in which the effector-general, high-level processing of the goal of the voluntary action plays a key role.

Investigating the relationship between inhibitory control and dietary adherence among patients with type 2 diabetes mellitus based on subjective and objective measures

BACKGROUND

Dietary management has been recommended as the cornerstone of type 2 diabetes mellitus (T2DM) management. However, low adherence to dietary recommendations has been identified in both developed and developing countries. Previous research suggests that inhibitory control influences eating behavior, but few studies have been conducted in patients with T2DM. Thus, we aimed to explore the relationship between inhibitory control and dietary adherence among patients with T2DM.

METHODS

A total of 393 patients with T2DM from the endocrinology departments of three tertiary hospitals in China were enrolled by the convenience sampling method. Dietary adherence was measured by the Dietary Behavior Adherence Scale for Patients with Type 2 Diabetes Mellitus. Additionally, inhibitory control was subjectively measured by the Behavior Rating Inventory of Executive Function-Adult version (BRIEF-A) and objectively assessed by the stop signal task (SST) and the Stroop task. The relationship between inhibitory control and dietary adherence was analyzed using Pearson correlation analysis and hierarchical regression analysis.

RESULTS

Subjectively measured inhibitory control had a significant predictive effect for dietary adherence after controlling for demographic and clinical variables. Adding the inhibitory control variable to the regression equation resulted in the following values: overall model F (19, 373) = 7.096, p < 0.001, increase in R2 value by 0.069, change in F (1, 373) = 35.219, p < 0.001. Similarly, the performance of the Stroop task had a significant predictive effect for dietary adherence to some foods, i.e., carbohydrate and fat. Adding the Stroop effect variable to the regression equation resulted in the following values: overall model F (19, 81) = 2.848, p = 0.005, increase in R2 value by 0.060, change in F (1, 81) = 8.137, p = 0.006.

CONCLUSIONS

Inhibitory control was a predictor of dietary adherence in patients with T2DM. Future interventions should investigate whether inhibitory control training results in the improvement of dietary adherence in patients with T2DM.