Neural Correlates Of Abnormal Causal Attribution Of Depressed Patients:Evidence From The FMRI Study

Causal attribution is a process that individuals explain and summarize the reasons of their behavior and life events in daily life. It is very important for the construction of individual emotion and cognition schemata. The reason of the episode of depression, on the one hand, is that patients has a cognitive diathesis interacting with negative life events; the other hand, it also has a close relation with their frequently-used attributed style. There are many behavior researches about the attributed style of the depressed patients, but there are few researches on the neuroimaging. It is not very clear that the abnormality of the attributed style of the patients is due to the changes of the brain structure or the dysfunction in the combination of the brain structure and function. We hope to be able to find the characteristics of attributed style in brain of the patients from the perspective of neuroimaging, in order to make up for the shortage of this field. So our paper was to find biomarker on the brain about the abnormal attributed style through exploring the characteristic of the brain structure and function of the patients.This study included two experiments, the first experiments mainly was exploring the characteristic of the brain structure on the attribution of the patients. Firstly, we compared the difference in the brain gray matter volume between the depression group and control group; then we applied the multiple regression method VBM to conduct correlation analysis between the attribution style questionnaire scores and the gray matter volume of brain structure of the patients and normal individuals. The results of behavior showed that, there were both self-serving bias on the attribution questionnaire scores of the two groups. However, the self-serving bias of the depressed group was not as large as the tendency of the bias of the normal group, and the scores of the negative life events from the depressed patients was higher than that of the normal group. It indicated that the depressed patients had a tendency to approaching to the non self-serving bias. MRI results showed that the gray matter volume of the right superior frontal gyrus of the depressed group was decreased; the depressed group showed more negative, the volume of the right superior frontal gyrus was more decreased; the normal group showed more positive, the smaller of the amygdala volume. Structure results showed that the right superior frontal gyrus had the atrophy in the brain structure of the depressed patients. The abnormal attributed style was associated with the volume of right superior frontal gyrus. There might be different relations in the amygdala volume with the degree of the cognitive bias of the depressed and normal groups.The experiment2was by fMRI technique with the attribution paradigm to explore the abnormalities of brain function in the attributed style of the depressed patients. The experiment was conducted with the improved classical attribution paradigm. We used the sentences of the description on the positive and negative life events as the experimental stimulus pictures, comparing the brain activation of the two groups in self-serving and non self-serving attribution and further to conduct the key analysis on the non self-serving attribution of the negative events between the two groups. Behavior results reported that, the attribution questionnaire scores of the normal group showed a self-serving attribution bias, however, the attribution questionnaire scores of the depressed group showed a balanced tendency between the self-serving and non self-serving. It had implied that the depressed patients would form a non self-serving bias differing from the normal individuals. The multivariate ANOVA results showed that, there existed a significant interaction on the two factor design:2(depressed/normal group)×2(positive/negative score). The fMRI results showed that, on the condition of the self-serving and non self-serving attribution of the depressed patients, the inferior frontal gyrus and middle temporal gyrus exhibited the higher activation. It illustrated that the attributed style of the depressed patients was associated with the abnormal activation of the frontal-temporal network. While processing the negative events with the self-serving attribution style singly, the depressed patients had an increased activation at the right inferior parietal lobe, and the activation degree was positively correlated with the duration of illness of the patients. This suggested that the activation of the inferior parietal lobe might be a brain biomarker of the abnormal attributed style in depressed patients, and also a marker of the keep the depressed symptoms. This study, however, exist some shortages:for instance, the medicine taking or not had not been strictly controlled, this would influence the results because of the remission of the disease; the age span of the patients was too large, we didn’t distinguish between the young depression and the old depression; the experiment materials of the life events were not involved a wide range, etc.Above all, as for the attributed characteristics, depressed patients displayed an abnormal non self-serving attribution bias not only in behavior, but also displayed a brain activation patterns differing from normal group in the MRI neuroimaging. This suggested that the activation of the inferior parietal lobe might be associated with the abnormal attributed style in depressed patients, and also with the duration of the depressed symptoms. More importantly, for the realistic significance, this research had provided a constructive suggestion for the prevention of the mental diseases and the treatment and recoverment of the depression. It promoted that the treatment direction of the depression was to facilitating the patients explaining their behavior in a more positive way and forming a positive self-serving attribution style.