Comparative functional connectivity of core brain regions between implicit and explicit memory tasks underlying negative emotion in general anxiety disorder
Shin-Eui Park 1, Yun-Hyeon Kim 2, Jong-Chul Yang 3, 4, Gwang-Woo Jeong 2*
1Advanced Institute of Aging Science, Chonnam National University, 2Department of Radiology Chonnam National University Medical School,, 3Department of Psychiatry, Jeonbuk National University Medical School,, 44Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital
Received: December 8, 2020; Revised: February 26, 2021; Accepted: February 27, 2021; Published online: February 27, 2021.
© The Korean College of Neuropsychopharmacology. All rights reserved.

To investigate not only differential patterns of functional connectivity of core brain regions between implicit and explicit verbal memory tasks underlying negatively evoked emotional condition, but also correlations of functional connectivity(FC) strength with clinical symptom severity in patients with generalized anxiety disorder(GAD).
Thirteen patients with GAD and 13 healthy controls(HC) underwent functional MRI for memory tasks with negative emotion words.
Clinical symptom and its severities of GAD were potentially associated with abnormalities of task-based FC with core brain regions and distinct FC patterns between implicit vs. explicit memory processing in GAD were potentially well discriminated. Outstanding FC in implicit memory task includes positive connections of precentral gyus(PrG) to inferior frontal gyrus and inferior parietal gyrus(IPG), respectively, in encoding period; a positive connection of amygdala(Amg) to globus pallidus as well as a negative connection of Amg to cerebellum in retrieval period. Meanwhile, distinct FC in explicit memory included a positive connection of PrG to inferior temporal gyrus(ITG) in encoding period; a positive connection of the anterior cingulate gyrus to superior frontal gyrus in retrieval period. Especially, there were positive correlation between GAD-7 scores and FC of PrG-IPG(r2=0.324, p=0.042) in implicit memory encoding, and FC of PrG-ITG(r2=0.378, p=0.025) in explicit memory encoding.
This study clarified differential patterns of brain activation and relevant FC between implicit and explicit verbal memory tasks underlying negative emotional feelings in GAD. These findings will be helpful for an understanding of distinct brain functional mechanisms associated with clinical symptom severities in GAD.
Keywords: Explicit memory, Implicit memory, Functional connectivity, General anxiety disorder, Negative emotion