Neural Representations of Perceptual Reorganization in the Musical Scale Illusion

The auditory system organizes complex acoustic input into coherent perceptual streams, yet how neural responses relate to physical stimulus structure and reported perception when the two diverge remains unclear. We investigated perceptual reorganization using the scale illusion, in which interleaved tone sequences presented separately to the two ears are typically heard as continuous melodic streams.Thirty participants listened to illusory, zigzag, and continuous sequences during EEG recording and reported whether each sequence sounded continuous or zigzag. Temporal response function models characterized neural encoding and reconstruction of amplitude-envelope (envelope) and pitch-change magnitude features. We tested whether neural responses during illusory listening corresponded more closely to reference patterns associated with the physical zigzag structure or reported continuous organization. Illusory sequences were predominantly categorized as Continuous and elicited longer RTs than non-illusory sequences. Encoding models revealed delayed pitch-change magnitude responses in the illusory condition, whereas envelope latencies remained comparatively stable. For pitch-change magnitude, reconstruction correlations computed over the full sequence exceeded chance levels estimated separately for each reference, with higher correlations for the continuous reference. Envelope correlations exceeded neither chance level, despite a small relative preference for the zigzag reference. These findings show that neural response timing and relative correspondence with the tested reference patterns depend on the modeled feature during the scale illusion. The reconstruction result concerns correlations across complete sequences and does not establish continuous tracking of the perceived melody.