Sigma power and encoding strength in sleep-based and retrieval-mediated memory consolidation

Poster Session E - Monday, April 15, 2024, 2:30 – 4:30 pm EDT, Sheraton Hall ABC
Also presenting in Data Blitz Session 4 - Saturday, April 13, 2024, 1:00 – 2:30 pm EDT, Sheraton Hall EF.

Hayley Caldwell¹ (hayley.caldwell@mymail.unisa.edu.au), Alex Chatburn¹, Kurt Lushington¹; ¹University of South Australia

Emerging evidence suggests that memory consolidation can be achieved during wake, using repeated retrieval training, rather than only during sleep. However, the neural mechanisms of sleep-based and retrieval-mediated consolidation have never been directly compared. Sigma activity, which is important for sleep-based consolidation’s enhancement of initially weakly encoded memories, may be involved in this selective enhancement in both consolidation states. To test this, we compared the interaction of sigma band (~12-15 Hz) power and encoding strength across different memory interventions. Participants (N=22, 18-31 years) learnt different object-word pairs in each of 3 sessions, completed an immediate recognition test, then experienced 1 of 3 120-minute interventions: (i) retrieval training (repeated cued-recall); (ii) restudy (repeated viewing, eliciting no consolidation); or (iii) a nap opportunity. After 45 minutes, participants were given a delayed recognition test. It was hypothesised that sleep and retrieval training, but not restudy, would enhance weakly encoded memories, when sigma power was high. We instead found that across all conditions, high sigma power stabilised the initial encoding strength, and low sigma power lead to the deterioration of initially strongly encoded memories, χ2(1)=5.11, p=.024, β=1.06. This suggests that sigma activity may represent a unifying mechanism of stabilising initial memory strength, across different brain states and learning paradigms. Our research is the first to investigate sigma activity’s influence on memories during wake. Further research is required to determine sigma activity’s specific influence on memories, involving their qualitative, inter-item, and longitudinal changes, to uncover if it is involved in state-independent consolidation, or paradigm-independent learning.

Topic Area: LONG-TERM MEMORY: Other