| Backgrounds and Objectives Emotional memory is also called emotion arousalepisodic memory, which is a type of episodic memory. Emotional event is more easily tobe remembered, which is so-called emotion enhancement effect. The elder usually havedecrease of general cognitive ability in various degrees, but emotional enhancementeffect still exists. Previous studies about emotional memory often concentrated ontask-related functional imaging MRI (fMRI); resting-state fMRI has been widely usedin recent years. Functional connectivity has been characterized by spatiallyinterconnected regions with organization in specific connectivity patterns and thestrength of the connection, which is non-directional. Analysis of functional connectionwith resting-state fMRI has been widely used in the functional network of the humansensorimotor function, cognitive and emotional mechanisms. Currently there have a fewreports about the relationship between emotional memory network and other networksby using resting-state fMRI, while no report about the study related to age-relatedchanges of emotional memory network by using resting-state fMRI. Previous studieswith resting-state fMRI indicated that structural and functional network significantlychange with aging. Normal aging might thus be associated with changes in thesmall-world properties of brain functional networks. To explore age-related differencesof emotional memory network, small-word properties of emotional memory networks ofthe young and the old will be investigated by using resting-state fMRI in our study.Correlation between the network efficiency and behavioral performance will beexamined as well. Materials and Methods Forty eight healthy older subjects (21males, aged from55to78years old) and forty healthy younger subjects (20males, aged from20to32yearsold) were involved in this study. Sixty emotion pictures were used as experimentalmaterials, including30emtional and30neutral pictures; both encoding and retrievalperiod were invovled in the experimental process. Behavioral performance was recordedand resting-state functional MR data were acquired via3.0T MRI. MATLAB7.12ã€AFNIand SPSS13.0were used for statistical analysis of fMRI and behavioral data.Results (1) The behavioral results indicated that the younger has higher accuracythan the older in reaction to emotional and neutral pictures as well as shorter in themean reaction time (p<0.05). Both of two groups have a high mean accuracy rates foremotional pictures. In the young, the accuracies of emotional (r2=0.22, p<0.05) andneutral (r2=0.18; p<0.05) pictures are positively correlated with the age. In the old, theaccuracy of neutral (r2=0.32, p<0.05) pictures is negatively correlated with the age,while positively correlated to enhancement effect of emotion memory (r2=0.17,p<0.05). Correct rate of emotional pictures changes with a linear trend across theoverall age, and neutral pictures with a parabola, and enhancement effects of emotionalmemory with a U-shaped curve.(2) Resting-state fMRI results suggested that there are age-related diffferences inresting-state functional connectivity networks of emotional memory between the youngand the old group. In contrast to the young group, the long-range functional connectivitybetween the medial temporal lobe and the frontal cortex/or parietal cortex significantlydecrease in the elderly group, while the short-rang functional connectivity in severalmedial temporal lobe regions significantly increased. There are also age-related changesin network efficiency and behavioral performance between the two groups. The globalefficiency of the young group is significantly higher than the old group which weresignificant differences (p<0.01), while the local efficiency was generally comparable between the two groups. The behavioral performance was positively correlated with thelocal efficiency of the young group while the behavioral performance was positivelycorrelated with the global efficiency of the old group. In the young group,5regionswere designated as the global hubs, including right amygdale, left fusiform gyrus, rightmiddle frontal gyrus, right DMPFC and right insula. In the old group,3regions wereidentified as the global hubs, including bilateral amygdale and right middle frontalgyrus.Conclusions (1) The emotion memory ability in the old is significantly declined,but the emotion enhancement effect still exists.(2) There are age-related diffferences in resting-state functional connectivity networksof emotional memory. It can be observed that correlations decreased among long-rangefunctional connections, along with an increase among short-range functionalconnections with increasing age.(3) Moreover, the small-world properties and node betweenness centrality showedsignficant changes with normal aging. The global efficiency of the young group wassignificantly higher than that of the old group, and there was no significant differencebetween the local efficiency of the two groups. The emotional memory of the youngeradults depends more on local efficiency, while older adults tend to the global efficiency.There were differences in the number and location of the node betweenness betweentwo groups and global hub function of the left amygdale demonstrated compensatoryincrease. Backgrounds and Objectives Depression is a kind of mood disease which ishazard to human health and emotional behaviors, with a yearly increase in morbidity.Depression has a character of "negative bias effect" in emotional memory, which inconsistent with "Mood-congruent memory" theory. The core symptom of depression isremarkableness and long-lasting abnormally low mood clinically. Depression ischaracterized by persistent negative emotion including sadness, guilt, and worthlessness,and further by ruminating thoughts, cognitive impairments, and somatic complaints.Previous studies about the abnormal regions of depression often concentrated ontask-related functional imaging MRI (fMRI) and resting-state fMRI has been used less.Neruoimaging studies indicated that these various symptoms are accompanied byabnormal activity in several brain regions and abnormal emotion regulation circuitsinvolving in these symptoms mainly located in limbic-cortical-striatal-pallidal-thalamicneural pathway in depression. As a major part of this circuit, amygdala, hippocampus,thalamus and prefrontal lobe play an important role in emotion regulation andconduction. Late-life depression is associated with more severe impairment in verballearning and memory and motor networks than depression in earlier adult life. By now,there have no report about the study late-life depression of emotion memory network. Toexplore the disorder of emotion regulation circuits in depression, differences infunctional connectivity of emotional memory network between late-life depression andhealthy controls were investigated by resting-state fMRI. Materials and Methods Eighteen late life depression subjects (7males, aged from55to84years old) and twenty four healthy controls (14males, aged from57to82yearsold) were involved in our study. Two hundred and forty pictures were used in thisexperiment. There were4kinds of pictures involving fear, happy, sad, and neutral scene,60pictures for each emotion category. Both encoding and retrieval period were invovledin the experimental process. Behavioral performance was recorded and functional MRdata were acquired via3.0T MRI scanner. MATLAB7.12, AFNI and SPSS13.0wereused for statistical analysis of fMRI and behavioral data.Results (1) The behavioral results indicated that the performances of four pictureswere worse in depression than healthy controls. The performance of fear was the bestand happy was the worst in depression, which difference was marginally significant(P=0.055). The performance of fear was the best and sad is worst in the healthy controls.There was significant difference between the fear/sad and others (P<0.05). Theperformance of happy was worse than sad in depression and the performance of sad wasworse than happy in healthy controls. There was interaction of happy and sadperformance between depression and controls (P<0.05).(2) Resting-state fMRI results suggested that there were diffferences in functionalconnectivity networks of emotional memory between depression and healthy controls:compared with the healthy controls, changes in functional connectivity had been shownbetween specific region pairs in depression, such as decreased left amygdala-rightthalamus connectivity, right amygdala-left inferior frontal gyrus connectivity,supramarginal gyrus-dorsomedial prefrontal cortex/ACC connectivity, middle temporalgyrus-middle frontal gyrus connectivity and thalamus-inferior frontal gyrus/left frontaleye fields connectivity; while increased left hippocampus-left middle temporal gyrusconnectivity, right hippocampus-ventromedial prefrontal cortex/ACC/right frontal eyefields connectivity, left middle temporal gyrus-left fusiform gyrus/left frontal eye fields connectivity, right insula-right middle temporal gyrus/right frontal eye fieldsconnectivity and right thalamus-left caudate connectivity. In the depression group,4regions were designated as the global hubs, including left amygdale, right hippocampus,right middle frontal gyrus, and right insula. In the healthy control group,6regions wereidentified as the global hubs, including bilateral amygdale and middle frontal gyrus,right anterior inferior parietal lobe and right insula.Conclusions (1) The cognitive ability in depression is declined compared withhealthy controls, but there exists "negative bias effect" in emotional memory.(2) There are differences in functional connectivity of emotional memory networkbetween depression and healthy controls and our findings further confirm thatdepression may be associated with disorder in emotion regulation circuits.(3) There were differences in the number and location of the node betweenness betweentwo groups and global hub function of the right amygdale and left inferior frontal gyrusdemonstrated decrease while right hippocampus compensatory increase. |
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