A Neuroimaging Study On The Resilence Effect Of Beliefs On Familial Risk For Developing Major Depressive Disorder

Exploring the neuromechanism of depression and its risk factors have become a hot research topic in the domain of psychology and cognitive science in recent years.Depression is an epidemiological psychiatric illness.Scientists have realized that familial and environmental factors are important factors for the development of depression.Researchers have reported that heredofamilial factors can lead to a significant increase of the risk for developing depression.The pathogenesis of depression is very complex,and it is actually not totally clear yet.Therefore,investigating the neuromechanism that may fight for the onset of depression is crucial.Beliefs is a subjective emotional experience.Its resistance to the development of depression has received more and more attention.Many studies have reported that beliefs may provide a resilence to the onset of depression.However,only a few researchers have explored the neurobiological mechanisms underlying the relationship between beliefs and depression.Therefore,this thesis expects to use a quantitative and efficient method--magnetic resonance imaging（MRI）technology to study the neuromechanism of beliefs’resilence effect to the onset of depression.MRI has been widely used in cognitive neuroscience and clinical research as a probing approach for exploring the brain due to its advantages of noninvasive,multi-parameter and multi-modal imaging capability.At present,neuroimaging research on depression based on MRI mainly focuses on brain function and structure.Meanwhile,as a developing research method,MRI has room to be improved.This thesis employs ellipsoidal area ratio（EAR）,an index based on diffusion tensor imaging（DTI）,to study the white matter（WM）integrity differences in brain regions related to the familial risk of developing depression and to explore the neural mechanism of beliefs in inhibiting the pathogenesis of depression.This thesis has developed a novel method for quantifying local brain volume changes--the improved volume preserved warping（iVPW）,to investigate the impact of beliefs on the local brain volume,that may alter subjective psychological experience,and consequently reducing the risk of developing depression in the population at high familial risk for developing the disease.The first section of this thesis examines the resilence effect of beliefs on developing depression based on EAR.DTI data were collected from 122 2^nd and 3^rd generation offspring of 1^st generation depressed or non-depressed parents,and 99 of the 122 had useful data（53 high-risk,HR;46 low-risk,LR）.According to the importance of beliefs reported by the individuals,the above two groups were further divided into two sub-groups,i.e.,the high importance（HI）sub-groups and low importance（LI）sub-groups.We examined WM integrity differences associated with familial risk for developing depression across the groups of high and low importance of beliefs（HI/LI）.WM integrity differences between the risk groups in the vicinity to the brain regions known to be associated with familial risk for developing depression including the precuneus,frontal lobe,and temporal lobe were non-significant or less significant within the HI group than those found within the LI group.The findings suggest that beliefs may affect WM integrity in brain regions associated with familial risk for developing depression,potentially conferring resilience to onset of depression among individuals at high familial risk for developing the disorder.The second section of this thesis proposes a method for measuring local brain volume and its changes,named improred volume preserved warping（iVPW）.The traditional volume preserved warping（VPW）method decomposes the whole deformation field,which registers a subject image to template space,into a global and a local deformation field,and uses the local deformation field for measuring local brain volumes.However,the deformation fields’decomposition is not unique,and hence the measurement of local brain volume changes cannot be certain,as it depends entirely on the strategy employed to generate the deformation field for spatial normalization of the individual image to the target template.Therefore,these measurements in local brain volumes can be highly unreliable.In this thesis,we propose the iVPW method to resolve this problem.The new method no longer requires isolating the global and local deformation fields from a whole deformation field that normalizes a brain from one space to the other.Experiments based on SPM and FSL,which are spatial normalization methods most popularly employed,using synthetic data and real imaging data acquired from a Schizophrenia study showed that iVPW may achieve consistent results no matter what methods were used.This demonstrated that iVPW is method independent,and it is a stable and reliable method for measuring local brain volumes.The third section of this thesis further examines the resilence effect of beliefs on developing depression based on measuring local brain volumes using the iVPW method.T1-weighted（T1-W）imaging data were collected from 132 2^ndand 3^rd generation offspring of 1^st generation depressed or non-depressed parents,among whom 82 had useful data（43 HR,39 LR）.The individuals were grouped in the same way as the first section.We examined local brain volume differences in brain regions associated with familial risk for developing depression within the groups of high and low importance of beliefs（HI/LI）.Significant differences of local brain volume were identified between the HI and LI groups.Local brain volume differences between the risk groups in brain regions associated with familial risk for developing depression in the left superior frontal gyrus,middle frontal gyrus were non-significant or less significant in the HI group than those in the LI group.More importantly,the above results strongly echo the results in the first section where the DTI study was performed.In summary,individuals at high familial risk for developing depression typically share a neural signature that is similar that can be found in those at low familial risk,as long as they take beliefs as highly important.The findings suggest that beliefs may affect local brain volume in brain regions associated with familial risks for developing depression,potentially conferring a resilience effect to the onset of depression among individuals at high familial risk for developing the disorder.Subjective experiences mediated by beliefs may exert long‐lasting changes in brain structure,which in turn will lead to a resilience effect to developing depression.All these results also indicate that the iVPW has a high application value in depression studies,and the measurement of local brain volumes using iVPW actually has provided a new approach to future depression research studies.