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Andrew Clouter, Kimron Shapiro, Simon Hanslmayr; Gluing Memories via Oscillations: Theta phase synchronization drives associative memory formation in humans . Journal of Vision 2016;16(12):151. doi: 10.1167/16.12.151.
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© 2017 Association for Research in Vision and Ophthalmology.
The objective was to investigate the effects of neural synchrony between visual and auditory processing regions on associative memory for multisensory information. On a cellular level episodic memory formation is likely mediated by fast acting long-term potentiation which relies on the fine grained timing of neural activity. Brain oscillations, especially theta oscillations in the hippocampus, orchestrate such timing, and are a likely "gluing mechanism" for human memories. In the first experiment, in the encoding phase, all participants were shown short (3-second) videos that were luminance modified with a 4 Hz sine wave, with an accompanying audio clip that had been amplitude modulated with a 4 Hz sine wave. The phase offset (i.e. synchrony) between the audio clip and the video was 0, 90, 180, or 270 degrees. In a second experiment, the videos and sounds were modulated at 4 Hz, 1.7 Hz (delta), and 10.5 Hz (alpha). On each trial, participants rated how well the audio clip suited the contents of the video clip. Each of six blocks contained 16 audio-video pairings (four at each phase angle), and was followed by a brief distractor task and an associative recognition test. We expected that associative memory performance would vary as a function of synchrony, with better performance when the video and audio clips were both presented in synchrony compared to out-of-synchrony. Our results were in line with our expectations. We demonstrated that the formation of multisensory memories rely on the exact timing of a particular oscillatory phase that corresponds to the human hippocampal theta oscillation. This effect was observed at theta, but not at a slower (delta) or a faster (alpha) frequency. Our results therefore provide direct evidence for a causal role of theta phase synchronization for the formation of human memories.
Meeting abstract presented at VSS 2016
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