The neural mechanisms of recognition memory: an investigation of study and test brain activity and their influence on memory outcomes

• Author / Creator

  Chen, Yun

• The ability to remember is fundamental to human cognition. The recognition memory paradigm has been widely used to investigate memory-related processes at both study and test phase. Two types of recognition memory are examined here, item and associative recognition memory. In an item recognition task, participants are instructed to remember a list of items (i.e., A, B, C, D …), then they are asked to make old-new judgments regarding the items: “probe (B), old or new?” In an associative recognition task, participants are instructed to remember a list of pairs (i.e., A-B, C-D, E-F, …), then they are asked to make intact-rearranged judgments regarding item-pairs: “probe (C-D), intact or rearranged”. The intact probes are composed of identical pairs from study (A-B), and the rearranged probes are composed of studied items from different study pairs (A-F). With electroencephalographic (EEG) methods, one can identify brain activity related to successful encoding and retrieval. At study, encoding processes are measured by the subsequent memory effect comparing brain activity related to later-remembered and later-forgotten. At test, retrieval processes are measured by the old/new effect comparing brain activity related to correctly identified targets (hits) and correctly identified lures (correct rejections), and the retrieval success effect comparing brain activity related to correctly identified targets (hits) and misidentified targets (misses). The objective of the four studies presented in this dissertation was to examine whether specific brain-activity features reflect recognition-memory encoding and retrieval processes, and to determine whether those features explain individual differences in memory performance. I measured event-related potentials (ERPs) and oscillatory activity during both study and test phase to explore the neural mechanisms of recognition memory. By using an individual-difference approach, one can ask whether these brain-activity measures reflect common or distinct processes. Using the ERP method, prior research has suggested many cognitive processes reflected in memory-related ERP features. Some of those proposed cognitive processes indexed by memory-related ERP features at study resemble other proposed cognitive processes indexed ERP features at test. In the first and the third studies, I asked whether the ERP features during study were functionally correlated with other ERP features during test, and in turn, influence memory performance. Some study ERP features were indeed correlated with test ERP features across participants; however, only a subset of those study-test ERP features explained individual differences in memory performance. Using the oscillation method, prior research has identified changes in theta oscillations (4-8 Hz) and alpha oscillations (~10 Hz) to be crucial for memory functioning. In the second and fourth studies, I investigated the function of theta and alpha oscillations during memory encoding and retrieval. The two studies examined whether these oscillations were functionally correlated with the memory-related ERP features, and in turn, influence memory performance. Theta oscillations correlated with memory performance across participants, and while alpha oscillations correlated with ERP measures across participants, but did not explain the individual difference in memory performance. Taking an alternative approach to exploring the functions of brain activity in recognition memory tasks, the studies presented here revealed relationships between ERP features and oscillation measures and their influence on individual memory performance. Although the neural mechanisms for recognition memory are complex, the results suggest a possible unified neural mechanism encompassing both ERP features and oscillations for both item and associative recognition memory.

• Subjects / Keywords

  • Recognition memory
  • EEG oscillations
  • Event related potentials

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3J38KX6X

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.