ABSTRACT
Objective To explore mechanisms of sustained and transient effects in encoding processes of emotional memory by examining activation of amygdala via functional MRI and to provide evidence for understanding the underlying neural mechanism related to emotional memory disorders further. Methods Twenty two subjects (aged from 20 to 24 years old) participated in the study and mixed blocked/event-related design was adopted. Sixty negatively emotional pictures and sixty neutral scene pictures were used. Functional MRI scanning was performed while subjects were doing encoding tasks. Behavioral data were acquired during retrieval. Correlation analyses of functional MRI data and simples paired t -test of behavioral performance were performed with SPM2 and SPSS13.0 statistical software,respectively. Results Significant differences of behavioral performance ( t= 2.791,P= 0.01 ) was found between emotional (3.15 ± 0.14) and neutral (2.25 ± 0.08 ) pictures. A whole-brain voxelwise correlation analysis between functional MRI and emotional enhancement effect indicated that the transient effect of emotional enhancement of memory involved the left amygdala, left hippocampus and left lateral orbitofrontal cortex, while the sustained effect involved the right amygdala, right hippocampus, right inferior frontal gyrus, right medial and lateral orbitofrontal cortex. Region of interest analysis demonstrated that the sustained effect was related to the right amygdala (r= 0.50, P = 0.019 ), which was different from transient effect ( Z = 1.655, P = 0.049 ),while the transient effect was correlated with the left amygdala (r=0.65, P=0.001 ) ,which was different from sustained effect( Z= 2.512, P=0.006). Conclusion Different neural mechanisms are involved in sustained and transient effects of emotional memory encoding. The right amygdala is responsible for sustained effect and the left amygdala is responsible for transient effect ,respectively. The results confirm and extend the model of the left-transient/right-sustained effect.