Research reveals the default network brain mechanism of ruminant thinking

Recently, Yan chaogan research group, Key Laboratory of behavioral science, Institute of psychology, Chinese Academy of Sciences, published a meta-analysis paper entitled regulation and the default mode network: meta-analysis of brain imaging students and implications for expression in neuroimage, a journal of brain imaging This paper discusses the role of the three subsystems of the default network in rumination The results show that rumination and the default network, especially the core subsystem and the activation of the dorsomedial prefrontal leaf system are closely related Ruminant thinking is a specific mode of response, which refers to the individual's repeated thinking on the causes, effects and consequences of negative life events Although ruminant thinking is a cross diagnosis phenomenon, it is closely related to depression Previous studies have shown that ruminant thinking is related to the severity of major depressive disorder (MDD), which can predict the occurrence and duration of depression In addition, even healthy individuals, the more ruminant thinking, the more likely they are to suffer from depression, and ruminant thinking can predict the recurrence of depression in patients with major depression In recent years, the default mode network has attracted the attention of clinical neuroscientists who study depression It is closely related to self-related processing, which is helpful to understand the neural mechanism of ruminant thinking in patients with major depression In addition, some studies have found that the functional abnormality of default network is closely related to ruminant thinking In recent years, Andrew Hanna et al Proposed that the default network can be divided into three subsystems with different functions: core subsystem, including medial prefrontal cortex and posterior cingulate gyrus, which is mainly involved in self-related processing and coordination of the interaction between the other two subsystems; dorsal system Media temporal cortex subsystem (dmPFC subsystem), including dorsomedial prefrontal lobe, temporal parietal joint area, lateral temporal lobe and temporal pole, plays an important role in the processing of mental and psychological theory; medial temporal lobe subsystem (MTL) Subsystem), including ventral prefrontal lobe, posterior part of inferior parietal lobule, postcortical cortex, parahippocampal and hippocampal structure, is closely related to autobiographical memory In the past, researchers used a variety of paradigms to explore the role of default network in ruminant thinking They found that the key brain areas of default network, such as medial prefrontal lobe, posterior cingulate belt, dorsal medial prefrontal lobe, showed activation, and also found that the rostral anterior cingulate belt, caudate nucleus, amygdala and insula also showed abnormal activation Although researchers in the past are increasingly interested in ruminant thinking, there is no consistent understanding of the neural mechanism of ruminant thinking The possible reasons include the differences in sample size, demographic variables and clinical characteristics of patients in different studies Meta analysis of ruminant thinking is of great significance to understand the neural mechanism of ruminant thinking, but there is no relevant research at present Therefore, the researchers conducted a meta-analysis of brain imaging research related to ruminant thinking in order to integrate the results of different studies, so as to provide a comprehensive information for understanding the neural mechanism of ruminant thinking In this study, SDM (signed differential mapping) software was used to make a meta-analysis of brain imaging research of ruminant thinking PubMed was used to retrieve the ruminant brain imaging studies up to April 20, 2019, and 14 studies meeting the screening criteria were selected The coordinate information reported in these studies was sorted out and then put into SDM for correlation analysis After comparing ruminant thinking with distracted or controlled conditions, brain voxel clumps related to ruminant thinking are obtained (Figure 1) Due to the important role of the default network in ruminant thinking, this study uses the brain template (left side of Figure 2) proposed by Andrew Hanna et al., 2014 on the division of the default network subsystem to investigate the number of ruminant thinking related voxels overlapped with the default network subsystem The results showed that 49.7% of voxels related to ruminant thinking were located in the core subsystem, 18.2% in the dorsomedial prefrontal leaf system, and 7.3% in the medial temporal leaf system At the same time, z-values of ruminant thinking related voxels located in these three subsystems were extracted, and the results further confirmed that the core subsystem showed the highest consistent activation (right side of Figure 2) In order to further verify this finding, the study uses 11 ROIs (region of) defined by Andrew Hanna et al Interest), and then project these ROIs to the three subsystems of the default network (left side of Figure 3), and extract their Z values The results further verify that the core subsystem and medial temporal leaf system have a greater impact on ruminant thinking (right side of Figure 3) In addition, the study further investigated the distribution of ruminant thinking related voxels on these brain networks by using the seven network partition proposed by Yeo et al., 2011 By calculating the distribution proportion of ruminant thinking related voxels in the seven networks, it is found that 31.3% of the default network voxels are related to ruminant thinking, while the proportion of other networks is less than 10% (left side of Figure 4) In this study, the voxels activated by ruminant thinking were further classified according to the seven network partition, and the percentage of voxels in each network in all significant voxels was calculated The results showed that 66.2% of all voxels related to ruminant thinking were divided into default networks, while the voxels divided into other networks were less than 10% (right side of Figure 4) The results show that the default network is the potential neural mechanism of ruminant thinking, especially the core subsystem and the dorsomedial prefrontal leaf system, which is most closely related to ruminant thinking These two brain networks play an important role in the process of intellectualization and self correlation The results are consistent with the existing hypothesis about ruminant thinking, that is, individuals trapped in ruminant thinking mainly focus on their current psychological state and autobiographical memory related to it, but rarely think about the future The results are consistent with the previous study on ruminant thinking of depression patients and healthy control group, that is, depression patients show abnormal activation of medial prefrontal lobe, posterior cingulate gyrus, dorsal medial prefrontal lobe and temporal lobe compared with healthy control group In addition, it was also found that the activity of medial temporal lobe decreased with the increase of prefrontal lobe activation This is consistent with the finding that the medial temporal lobe is less active in ruminant thinking These results suggest that enhancing the activation of medial temporal lobe by promoting the mental construction of current and future novel stimuli may be a potential target for the treatment of depression Similarly, repetitive transcranial magnetic stimulation (rTMS) can inhibit the activities of the dorsomedial prefrontal leaf system, thus weakening the related processing of patients' psychological theory can also be used as a potential mechanism for the treatment of depression In conclusion, the results of this study provide evidence from neuroscience for the reduction of ruminant thinking and the treatment of depression (BIOON Com)