The relationship of lyrics and tunes in the processing of unfamiliar songs: a functional magnetic resonance adaptation study

Abstract

The cognitive relationship between lyrics and tunes in song is currently under debate, with some researchers arguing that lyrics and tunes are represented as separate components, while others suggest that they are processed in integration. The present study addressed this issue by means of a functional magnetic resonance adaptation paradigm during passive listening to unfamiliar songs. The repetition and variation of lyrics and/or tunes in blocks of six songs was crossed in a 2 x 2 factorial design to induce selective adaptation for each component. Reductions of the hemodynamic response were observed along the superior temporal sulcus and gyrus (STS/STG) bilaterally. Within these regions, the left mid-STS showed an interaction of the adaptation effects for lyrics and tunes, suggesting an integrated processing of the two components at prelexical, phonemic processing levels. The degree of integration decayed toward more anterior regions of the left STS, where the lack of such an interaction and the stronger adaptation for lyrics than for tunes was suggestive of an independent processing of lyrics, perhaps resulting from the processing of meaning. Finally, evidence for an integrated representation of lyrics and tunes was found in the left dorsal precentral gyrus (PrCG), possibly relating to the build-up of a vocal code for singing in which musical and linguistic features of song are fused. Overall, these results demonstrate that lyrics and tunes are processed at varying degrees of integration (and separation) through the consecutive processing levels allocated along the posterior-anterior axis of the left STS and the left PrCG.

Figure 1.

Experimental design. The repetition or variation of lyrics and/or tunes within blocks of six songs was crossed in a 2 × 2 factorial design.

Figure 2.

A, Adaptation effects for lyric repetition. Left, Main effect of the factorial design [(S_TD_L + D_TD_L) − (D_TS_L + S_TS_L)]. Right, Simple effects of lyric repetition when tunes varied (D_TD_L − D_TS_L) (top), or when tunes were simultaneously repeated (S_TD_L − S_TS_L) (bottom; see Results for details). The inset depicts stronger adaptation for the repetition of lyrics than of tunes [2 × (S_TD_L − D_TS_L)]. B, Adaptation effects for tune repetition. Left, Main effect of the factorial design [(D_TS_L + D_TD_L) − (S_TD_L + S_TS_L)]. Right, Simple effects of tune repetition when lyrics varied [D_TD_L − S_TD_L] (top), or when lyrics were simultaneously repeated [D_TS_L − S_TS_L] (bottom). No brain region showed stronger adaptation for tunes than for lyrics [2 × (D_TS_L − S_TD_L)] (data not shown). C, Interaction of lyrics × tunes [(S_TD_L + D_TS_L) − (D_TD_L + S_TS_L)]. Bar diagrams depict the percentage signal change of the peak voxels in the four conditions relative to baseline. Error bars indicate one SEM. *p < 0.05, **p < 0.01, ***p < 0.001. For illustration, data are presented at a threshold of p < 0.001 (uncorrected, cluster size ≥5 voxels).

Figure 3.

Posterior–anterior gradient of integration.