Neural signatures of test-depressed encoding: Dynamic modulations in the memory encoding network and anterior cingulate cortex

Authors

Jian Zhu, Pamela J. LaMontagne, Reza Habib*

Department of Psychology, Southern Illinois University, Carbondale, Illinois, United States of America

Abstract

Although previous behavioral studies have demonstrated that restudying already-learned items is mnemonically ineffective, the neural mechanisms underlying this phenomenon remain largely unknown. Here, functional magnetic resonance imaging (fMRI) was used to assess neural changes during a multi-trial associative learning task where participants repeatedly studied and were tested on unrelated English word pairs. The results revealed that the brain network involved in the initial encoding of the word pairs was less activated when participants restudied previously learned ones, supporting a pattern that we refer to as test-depressed encoding (TDE). More distinctively, the dorsal anterior cingulate cortex (dACC) showed greater activation when restudying learned vs. unlearned word pairs, suggesting dACC-mediated cognitive control of TDE. Functional connectivity analysis further consistently showed that the memory encoding network had a weakened neural coupling within itself, but an enhanced coupling with dACC under TDE. Together, the present work is the first to demonstrate that these dynamic modulations in regional activity and connectivity may reflect the neural foundation for TDE.

Keywords: encoding, testing, repeated study, subsequent memory, fMRI

PAGES:127-146

doi:10.24193/cbb.2018.22.09

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