Neural oscillations involved in self-referential processing

Human adults remember better trait words that are referenced to the self than those referenced to others. To investigate whether non-phase-locked neural oscillations engage in the self-reference effect, we recorded electroencephalogram (EEG) from healthy adults during trait judgments of the self and a familiar other. The wavelet analysis was used to calculate non-phase-locked time–frequency power associated with encoding of trait adjectives referenced to the self or the familiar other at theta (5–7 Hz), alpha (8–13 Hz), beta (14–27 Hz) and gamma (28–40 Hz) bands. We found that, relative to other-referential traits, self-referential traits induced event-related synchronization of theta-band activity over the frontal area at 700–800 ms and of alpha-band activity over the central area at 400–600 ms. In contrast, event-related desynchronization associated with self-referential traits was observed in beta-band activity over the central–parietal area at 700–800 ms and in gamma-band activity over the fronto-central area at 500–600 ms. Moreover, valence of traits referenced to the self and self-relevance of traits respectively led to modulations of theta/alpha- and beta/gamma-band activity. Finally, event-related synchronization of frontal theta-band activity at 700–800 ms positively correlated with the self-reference effect observed during memory retrieval. Our results indicate that non-phase-locked neural activity is involved in self-reflexive thinking. In addition, low and high-frequency neural oscillations play different roles in emotional and cognitive aspects of self-reference processing.

Research highlights
► Self-referential traits induce theta/alpha synchronization compared to other-referential traits;
► Self-referential traits induce beta/gamma desynchronization compared to other-referential traits;
► Valence and self-relevance modulate low and high-frequency activities respectively; and
► Theta-band activity positively correlates with the self-reference effect in memory.