BRAIN ACTIVITY DURING DECISION MAKING TASK PERFORMANCE IN PATIENTS WITH MAJOR DEPRESSIVE DISORDER

Major Depressive Disorder (MDD) is associated with altered emotion processing and disrupted neural dynamics. Depressed individuals often exhibit a negative bias in cognition, tending to focus on or overreact to negative outcomes, alongside diminished reactivity to positive stimuli. The aim of the study was to define changes in the largest Lyapunov Exponent (LE) during emotion induction in patients with MDD and healthy participants.
Participants were 60 MDD patients (mean age=26.6, SD = 7.4) and 60 healthy controls (mean age= 25.3, SD = 6.4). EEG was recorded during a decision-making task with positive and negative feedback by using Neurosoft. EEG preprocessing was performed using EEGLAB and TISEAN package (Wolf et al., 1985). LE was computed for each trial per each channel and averaged by condition and brain region.
Two-way mixed-design ANOVA with group as a between-subjects factor and feedback condition as a within-subjects factor revealed a significant main effect of group and condition (p<0.001). Healthy individuals demonstrated more complex brain activity than patients, and negative emotional feedback increases brain signal complexity in both groups. Regional analyses identified frontal and parietal cortices as primary sites of group differences.
Findings suggest that MDD is characterized by reduced EEG complexity, particularly in emotionally aversive contexts, and that LE may serve as a task-sensitive biomarker of altered neural dynamics in depression.
Funding. This research was funded by the Committee of Science of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. BR27198099).