Gamma-band sensory stimulation enhances episodic memory retrieval
Poster No:
1067
Submission Type:
Abstract Submission
Authors:
Benjamin Griffiths1, Katharina Duecker1, Daniel Weinert2, Ole Jensen1, Tobias Staudigl2
Institutions:
1University of Birmingham, Birmingham, West Midlands, 2Ludwig-Maximilians-Universität München, Munich, Bavaria
First Author:
Co-Author(s):
Introduction:
Enhanced gamma activity (30-100Hz) coincides with successful episodic memory retrieval, but it remains unknown whether this oscillatory activity is a cause or a consequence of the retrieval process. We aim to address this question of causality.
Methods:
32 human participants completed a paired associates memory task whilst undergoing visual sensory stimulation (at 65Hz, 43.3Hz and 32.5Hz) during episodic memory retrieval. MEG activity was simultaneously recorded. The impact of sensory stimulation on memory performance was quantified using multi-level logistic regression models. The MEG data was preprocessed to attenuate noise and analysed using two approaches: (i) a standard time-frequency decomposition using wavelets, and (ii) a time-series average computed by locking the MEG data to each light pulse delivered during sensory stimulation. Non-parametric permutation tests were used to assess statistical significance and correct for multiple comparisons.
Results:
In the behavioural data, both 68Hz and 34Hz sensory stimulation enhanced memory recall above a baseline condition where no sensory stimulation was applied. Only a small proportion of participants (~10%) could perceive the 65Hz visual flicker, suggesting 65Hz sensory stimulation is imperceptible. In the time-frequency analysis, 68Hz and 44Hz stimulation produced narrowband increases in spectral power within their respective bands over occipital sensors. In contrast, 34Hz stimulation produced narrowband increases in power at both 34Hz and 68Hz over occipital sensors. In the analysis of the peak-locked time-series data, the 34Hz condition produced two oscillations superimposed over one another: a 34Hz oscillation that principally arose over occipital sensors, and a spatially- and statistically distinct 68Hz oscillation over parietal sensors.
Conclusions:
These results suggest imperceptible sensory stimulation enhances recall, providing a novel and entirely unintrusive means of tackling mnemonic issues. This appears to be achieved by 34Hz and 68Hz stimulation both enhancing an endogenous 68Hz gamma oscillation, suggesting that this gamma activity plays a causal role in episodic memory retrieval. Furthermore, the observation that subharmonic frequencies can modulate endogenous gamma activity suggests that non-linear interactions exist between endogenous brain activity and exogenous stimulation, opening new avenues for future neuro-stimulation interventions.
Brain Stimulation:
Non-Invasive Stimulation Methods Other 2
Learning and Memory:
Long-Term Memory (Episodic and Semantic) 1
Modeling and Analysis Methods:
EEG/MEG Modeling and Analysis
Novel Imaging Acquisition Methods:
MEG
Keywords:
MEG
Memory
1|2Indicates the priority used for review
