Expectancy Effects in Feedback Processing are Explained Primarily by Time-frequency Delta not Theta.

•FN is sensitive to outcome valence but not expectancy; valence effects are driven by loss-sensitive theta and gain-sensitive delta.•P300 is sensitive to outcome expectancy for gain outcomes only; expectancy effects are driven by delta, not theta.•Theta band activity is sensitive to the most salient stimulus feature: outcome valence.•Delta band activity is modulated by valence as well as a more complex characteristic: outcome expectancy.