| Background:Schizophrenia is a severe mental disorder in the field of psychiatry,in which patients may suffer from cognitive deficit of various degrees,(inhibition of thoughts,delusions,or lack thereof),perceptual disorder(perceiving stimuli that is absent in objective surrounding,including auditory,visual,tactile,and olfactory hallucinations);these perceptual disorder may in term,induce secondary,subject-specific cognitive,emotional,or behavioral display that is systemic and highly related to the content of thoughts,yet extremely inharmonious and dissociative to external environment.Due to the complexity of the disorder,family,or even patients themselves may frequently have trouble to express the experience accurately and objectively;therefore,if a psychiatrist fail to discover indepth symptoms,and only focused on superficial displays,patients are likely to be diagnosed with mood disorders based on superficial symptoms.For example,hypothymia,decreased decisive and executive ability,and hindered social skill may lead to diagnosis in affective spectrum,rather than psychotic spectrum.Recent studies have suggested that schizophrenia patients may display differently in neuropsychological examination,cerebral function,task-induced cerebral perfusion and electorphysiological measures compared to healthy controls.Patients are likely to be defective in any segment of cognitive task,including perception,retrieval,planning,and execution,which may ultimately limit patients’ ability to provide feedback to stimuli in an appropriate and timely manner.In this study,in order to examine patients’ cognitive capacity and cerebral function,we have combined functional magnetic resonance imaging(fMRI)technique with N-back working memory task to obtain participants’ cognitive and neuroimaging data.Furthermore,based on their performance,we may analyze how cognitive function may affect cerebral activation and encephalic connectivity.Objective:① Observe the difference between schizophrenia patients and healthy controls in the aspect of working memory;② Analyze the pattern of activation differences between schizophrenia patients and controls while performing the same task;③ Discover whether there is a different pattern of connectivity when using the same brain region as region of interest between schizophrenia patients and controls;④ Examine how interaction of diagnosis and task performance may affect the effective connectivity pattern.Method:① Acquire all participants’ resting state and structural state neuroimaging data by applying standard T1,T2,and EPI sequence,and obtain task state image using 3D-Bravo T1 sequence while undergoing N-back task;② Transform the number of hits and false alarms of N-back task into hit rate(H%)and false alarm rate(F%),further standardize and calibrate the hit rate(H%)and false alarm rate(F%)into standard score,and calculate all participants’ performance score(d’0-back,d’0;d’2-back,d’2)using calibrated score;③ Manually examine all participants’ imaging data,and perform preprocessing using Matlab 2013;④ Select participants data with applicable images(no morphological or graphic abnormalities such as artifact and missing section),with head movement not exceeding 3 millimeter or 3° in x,y,or z axis;⑤Select 45 patients and control who are matching in age,gender,education received,and d’0 score,and further divide the participants of each group into"better-performing" and "worse-performing" subgroups based on the group average of d’2 score,and use diagnosis and performance as grouping variable,perform repeated measure of analysis of variance(RMANOVA)analysis for general linear model estimation,and perform alpha-sim correction using REST;⑥ Select region of interest base on general linear model result,select region of interest as seed points and perform psychophysiological interaction(PPI)analysis to examine within group and between group functional connectivity differences,as well as examining functional connectivity pattern under the influence of diagnosis × performance.Result:① While both group have similar performance in 0-back task,patients with schizophrenia performed significantly worse than controls;② Patients displayed significant deactivation in right medial cingular cortex,and significant activation in right inferior parietal lobule,but the degree of activation/deactivation was significantly weaker than controls;between group activation difference suggest that patients may have similar patterns of cerebral activation and deactivation,but differ in magnitude;③ The right medial frontal gyrus(MFG)has a positive interaction with right angular gyrus,and left MFG has negative interaction with left fusiform gyrus.Both interaction style suggested complementary interaction,④ MFG of both left and right hemisphere have negative interaction with left fusiform gyrus,suggesting its role in the N-back task,or its connection to the factors of N-back task.Conclusion:With d’ as controlled index,suggesting that there is no difference of attention capacity between group,patients may still perform worse on cognitive skills of higher ranks,including short term memory consolidation and retrieval.Moreover,in d’2-d’0 activation difference,we may see similar activation/deactivation patterns between patients and controls,yet,activation/deactivation among patients displays a weaker magnitude,suggesting cerebral activation/deactivation deficiencies among patients.The N-back task requires participants to differentiate the rules,and make decisions based on the rules as stimuli were perceived;the left fusiform gyrus is responsible for differentiation,while angular gyrus is capable of decision making.Both regions displayed connectivity in complementary nature while interacting with the seed point from the same side,suggesting there may be possibility of functional lateralization.Moreover,both seed points interact with left fusiform gyrus with negative interactivity,suggesting left fusiform gyrus may have a response to N-back and its cognitive factor. |
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