ERPs and Theta-Oscillations Indicating Memory for Music in a Short 20-Minute EEG Paradigm

Abstract

An intriguing characteristic of semantic memory for music, that is, long-term memory of a musical piece itself, is its preservation in the face of cognitive decline, whether through normative or disease-impacted aging [1]. The goal of this project is to assess which markers of memory for music can be elicited in a 20-minute long, non-invasive EEG paradigm, potentially suitable for use with patient populations. The N400 and P600 event-related potentials (ERPs) are elicited when a violation of semantic memory-based expectations occurs [2]. In addition, theta (5-9 Hz) oscillations have been found to increase as people repeatedly listen to the same musical piece [3], indicative of musical semantic memory.

We collected 64-channel EEG data from 39 healthy volunteers (M = 32.3, SD = 15.8) while they listened to 34 short melodies (17 familiar melodies validated on 41 other participants, 17 novel melodies composed in the familiar songs’ style). Both sets of melodies were modified to contain 40 semantic violation notes. EEG data were preprocessed in MATLAB using EEGLAB. N400 and P600 ERPs were quantified as mean amplitudes in posterior regions of interest time-locked to violations and unchanged notes [2]. Theta oscillatory activity was analyzed at the beginning of each melody on frontal electrode sites [3].

Repeated-measures ANOVAs on ERP difference wave amplitudes revealed that in familiar melodies, significantly larger N400 (F(1, 38) = 5.37, p < .05) and P600 (F(1, 38) = 9.90, p < .01) components were elicited than in novel melodies. For theta oscillations, there was significant interaction between melody type and electrode sites (F(2, 64) = 3.92, p < .05), such that theta-oscillatory power in the fronto-midline region was higher in familiar compared to novel melodies.

Our results show that 20 minutes suffice to establish ERPs which significantly differ between familiar and novel melodies, demonstrating the utility of this shortened paradigm for assessing semantic memory for music. Significant N400 amplitudes in novel melodies suggest that repetition of musical phrases within a song may facilitate short-term memory retention, while the P600, purely responsive to violations in known melodies, may serve as a marker for long-term semantic memory of music. Higher theta-power in fronto-midline regions for familiar melodies suggests that oscillatory activity may indicate long-term memory within the first four seconds of a song. These results add to ongoing discussions regarding a semantic, experience-dependent P600 effect and a re-interpretation of the N400 component as a marker of memory retrieval processes, as well as theta oscillation’s relationship to long-term musical memory.

References

[1] A. D. Vanstone and L. L. Cuddy, “Musical Memory in Alzheimer Disease,” Aging, Neuropsychology, and Cognition, vol. 17, no. 1, pp. 108–128, Dec. 2009. doi:  10.1080/13825580903042676.

[2] R. A. Miranda and M. T. Ullman, “Double dissociation between rules and memory in music: An event-related potential study,” NeuroImage, vol. 38, no. 2, pp. 331–345, Nov. 2007. doi: 10.1016/j.neuroimage.2007.07.034

[3] A. Malekmohammadi, S. K. Ehrlich, and G. Cheng, “Modulation of theta and gamma oscillations during familiarization with previously unknown music,” Brain Research, vol. 1800, p. 148198, Feb. 2023. doi: 10.1016/j.brainres.2022.148198