The comparison of effects of emotional expressions on learning the reward between healthy individuals and patients with major depressive disorder

INTRODUCTION: One of the core criteria of major depressive disorder (MDD) is anhedonia. The reward processing system should be examined to assess this finding, which is important in the diagnosis, treatment and prognosis of this disease. Besides, understanding the emotional stimuli correctly is at the top of the social cognitive skills which ensures the individuals to maintain their social relations in a healthy way. Depressed individuals tend to interpret emotional stimuli negatively. This situation negatively affects the social relations of the individuals and this negativity of the social relations lead to the increase of the depressive symptoms. The evaluation of emotional stimuli and reward processing together, knowing how neural reflections are; would increase the success on diagnosis, treatment and the prediction of prognosis. AIM: In this study it is aimed to assess the effect of emotional stimuli on learning the signal which leads to reward or punishment in major depressive disorder, which is one of the most important heatlh problems of society nowadays. It is also aimed to evaluate the assessment of reward- punishment sensitivity, to determine the change of the neural reflections of both reward-punishment process and emotional process in depressed individuals. HYPOTHESIS: The success on learning the cue that will bring the reward which is shown after face expressions with negative emotions is higher in depressed patients compared to the face expressions with positive emotions or neutral face expressions. Depressed individuals have lower reward awareness than healthy individuals. METHOD: Our study was completed with 33 people in the patient group and 32 people in the healthy control group. During the psychiatric examinations of the participants SCID-I (Structured Clinical Interview for DSM IV), Hamilton Depression Rating Scale (HAM-D 17), Beck Depression Inventory, Physical Anhedonia Scale, Social Anhedonia Scale, Behavioural Inhibition Scale/ Behavioural Activation Scale (BIS/BAS) were applied. Within a maximum of 1 week duration after the psychiatric examinations and scale applications of participants, their structural and functional imaging by 3-Tesla Magnetic Resonance Device was completed. It was required from individuals in the task which is applied to the participants during MRI screening to predict the number which is written behind a closed card to be higher or lower than five. They were ordered to make this prediction due to the probabilistic cue they would see before. Individuals gained money for their correct predictions, lost money for their wrong predictions or for no responded situations. In this task, individuals had seen facial expressions with emotions (happy, neutral, sad) for a short duration before the probabilistic cue. However during the education before the application of MRI it was emphasized that those faces were completely independent from the value of the card and that they need to focus their attention on the probabilistic cue. The data of the imaging were seperated into two parts as the period of probablistic cue and the period of feedback and they were included in the analysis. RESULTS: The scores of HAM-D-17, physical anhedonia and social anhedonia in the patients were significantly higher than the control group (p <0,001). When the subscales of behavioral inhibition-activation scale were controlled, the reward sensitivity was found to be significantly higher in the control group (p = 0.015). In the behavioral data, there was no statistically significant difference between groups in net score, which means the total amount of money rest, and number of correct answers. When the main effects of behavioral data were examined, significant main effect was determined between the values of the probabilities independent of the emotion and the group (p<0,001). In addition, statistically significant negative correlation was found between the net score and the behavioral inhibition score in the subscale of BIS/BAS scale (p<0,05). In the imaging results, when the main effect of emotion is examined in the probabilistic cue period significant activation regions were observed in the right FG, right pCC and right parahippocampus (F=11,66; F=11,11; F=8,60 p <0.001 uncorr respectively). In the probabilistic cue period after experiencing sad face, region of activation in the right caudate nucleus and right amygdala were detected in the patients group (t=4,41; t=3,79 p<0,001 uncorr respectively). In the control group, during the same cue regions of activation in bilateral superior and medial frontal gyrus (t=4,31; t=3,78 p<0,001 uncorr, respectively) were observed. During the feedback period, main effect of feedback is found significant in the caudate nucleus, putamen (F=59,57; F=46,73 p<0,001 FEW respectively), aCC, pCC and orbitofrontal corteks (OFC) (F=30,39; F=29,31; F=39,48 p=0.005 FWE, p=0.001 FEW p<0.001 FWE, respectively). In the control group the activation in these regions was meaningful when they received a reward. This data is due to the decrease of activation in these regions in the patient group. CONCLUSION: In our study, neural reflections between depressed individuals and healthy individuals were found to be different, although there is no difference in learning the probabilistic cue according to the emotion in behavioral data. In depressed individuals, during negative emotions, increased activation is observed in regions of memory, attention, and learning roles. In similar regions activation was found decreased during the reward and positive emotions. This data suggests that, depressive individuals learn and record negative emotions. In addition to this, their sensitivity to reward has decreased. It can be said that the neural basis of these symptoms may be due to dysregulation of the striatum and putamen, amygdala, OFC, aCC and pCC. Remembering these data will help to predict prognosis and affect treatment strategies during clinical evaluation.