Neural Oscillations associated with Encoding Strategies
We rely on our long-term memory (LTM) system to remember a wide range of information. However, we know from experience, whether forgetting a necessary item on a grocery list or answers to a test question, we are not always able to accurately recall that information. What determines how well information is stored in LTM? One factor is how memory stimuli are encoded. Encoding strategies are designed to help counteract failures by providing memory cues that are associated with the to-be-remembered information. This line of research aims to understand the underlying neural signatures involved in utilizing encoding strategies. Normatively effective strategies, or more elaborative strategies (e.g., sentence-linking and imagery), often lead to a better memory performance for verbal information. These strategies typically require the participant to consider the meaning of the to-be-remembered. For example, sentence-linking allows the participant to connect the to-be-remembered information to other to-be-remembered words (e.g., linking the words “DOG” and “BREAD” together as “my dog, Miller, likes to steal bread from the counter”), which increases the association in long-term memory. On the other hand, normatively less effective strategies, or less elaborative strategies (e.g., rehearsing a word repeatedly), are associated with lower performance compared to when people report using the normatively effective strategies (Dunlosky & Kane, 2007, Turley-Ames & Whitfield, 2003). Rehearsal, for instance, only requires the participant internally repeat the information to keep it active in memory but does not require the participant to make associations between the to-be-remembered information and long-term memory (Craik & Watkins, 1973; Richardson, 1998).
Strategies mentioned above can counteract retrieval failures by providing memory cues during encoding. Past literature evaluated the behavioral accuracy of strategies, but less is known about the associated neural oscillations. The current research addressed this gap using time-frequency analyses of electroencephalography (EEG) recorded during a paired-associates memory task. Word pairs that were later correctly recalled exhibited higher theta power (4 – 7 Hz) during encoding than those that were later forgotten (see Figure 1). Further, bands of alpha (8 - 12 Hz) and beta power (17 - 27 Hz) showed greater power for less effective strategies during encoding (see Figure 2). Results are consistent with prior work proposing a role for theta oscillations in encoding. It is plausible beta recruitment is associated with an internal rehearsal loop whereas alpha increases with number of maintained items. Thus, the current data can speak to potential differences in the "effortfulness" of employing effective compared to less effective strategies.
Brain activity during the encoding period while participants later A) correctly recalled words and B) incorrectly recalled words. Frequency (Hz) is plotted on the Y-axis and time from the start of the remember period (ms) is on the X-axis. Trials where participants later recalled words correctly showed more theta (4-7 Hz) power than trials where participants were later incorrect.
Brain activity during the encoding period while participants used A) Effective strategies and B) Less Effective strategies. Frequency (Hz) is plotted on the Y-axis and time from the start of the remember period (ms) is on the X-axis. Less effective strategies required more alpha power (8-12 Hz) and beta power (17-27 Hz) than effective strategies.
(* denotes current or former undergraduate author)
Bell, T. J., Anguiano, A., Krehbiel, K., Zakrzewski, A. C., Wisniewski, M. G., & Bailey, H. (2022, November). Neural Oscillations Differentiate Effective and Less Effective Strategies. Poster to be presented at Psychonomics. Boston, Massachusetts.
Bell, T. J., *Krehbiel, K., *Harper, A. & Bailey, H. (2022, April). Neural Oscillations in Memory Strategies. Talk presented at Midwestern Psychological Association. Chicago, IL.