Perception of musical pitch in developmental prosopagnosia.

Studies of developmental prosopagnosia have often shown that developmental prosopagnosia differentially affects human face processing over non-face object processing. However, little consideration has been given to whether this condition is associated with perceptual or sensorimotor impairments in other modalities. Comorbidities have played a role in theories of other developmental disorders such as dyslexia, but studies of developmental prosopagnosia have often focused on the nature of the visual recognition impairment despite evidence for widespread neural anomalies that might affect other sensorimotor systems. We studied 12 subjects with developmental prosopagnosia with a battery of auditory tests evaluating pitch and rhythm processing as well as voice perception and recognition. Overall, three subjects were impaired in fine pitch discrimination, a prevalence of 25% that is higher than the estimated 4% prevalence of congenital amusia in the general population. This was a selective deficit, as rhythm perception was unaffected in all 12 subjects. Furthermore, two of the three prosopagnosic subjects who were impaired in pitch discrimination had intact voice perception and recognition, while two of the remaining nine subjects had impaired voice recognition but intact pitch perception. These results indicate that, in some subjects with developmental prosopagnosia, the face recognition deficit is not an isolated impairment but is associated with deficits in other domains, such as auditory perception. These deficits may form part of a broader syndrome which could be due to distributed microstructural anomalies in various brain networks, possibly with a common theme of right hemispheric predominance.

Voice selectivity in the temporal voice area despite matched low-level acoustic cues.

In human listeners, the temporal voice areas (TVAs) are regions of the superior temporal gyrus and sulcus that respond more to vocal sounds than a range of nonvocal control sounds, including scrambled voices, environmental noises, and animal cries. One interpretation of the TVA's selectivity is based on low-level acoustic cues: compared to control sounds, vocal sounds may have stronger harmonic content or greater spectrotemporal complexity. Here, we show that the right TVA remains selective to the human voice even when accounting for a variety of acoustical cues. Using fMRI, single vowel stimuli were contrasted with single notes of musical instruments with balanced harmonic-to-noise ratios and pitches. We also used "auditory chimeras", which preserved subsets of acoustical features of the vocal sounds. The right TVA was preferentially activated only for the natural human voice. In particular, the TVA did not respond more to artificial chimeras preserving the exact spectral profile of voices. Additional acoustic measures, including temporal modulations and spectral complexity, could not account for the increased activation. These observations rule out simple acoustical cues as a basis for voice selectivity in the TVAs.

Sensitivity to musical emotions in congenital amusia.

The emotional experience elicited by music is largely dependent on structural characteristics such as pitch, rhythm, and dynamics. We examine here to what extent amusic adults, who have experienced pitch perception difficulties all their lives, still maintain some ability to perceive emotions from music. Amusic and control participants judged the emotions expressed by unfamiliar musical clips intended to convey happiness, sadness, fear and peacefulness (Experiment 1A). Surprisingly, most amusic individuals showed normal recognition of the four emotions tested here. This preserved ability was not due to some peculiarities of the music, since the amusic individuals showed a typical deficit in perceiving pitch violations intentionally inserted in the same clips (Experiment 1B). In Experiment 2, we tested the use of two major structural determinants of musical emotions: tempo and mode. Neutralization of tempo had the same effect on both amusics' and controls' emotional ratings. In contrast, amusics did not respond to a change of mode as markedly as controls did. Moreover, unlike the control participants, amusics' judgments were not influenced by subtle differences in pitch, such as the number of semitones changed by the mode manipulation. Instead, amusics showed normal sensitivity to fluctuations in energy, to pulse clarity, and to timbre differences, such as roughness. Amusics even showed sensitivity to key clarity and to large mean pitch differences in distinguishing happy from sad music. Thus, the pitch perception deficit experienced by amusic adults had only mild consequences on emotional judgments. In sum, emotional responses to music may be possible in this condition.

Modulation of the startle reflex by pleasant and unpleasant music.

The issue of emotional feelings to music is the object of a classic debate in music psychology. Emotivists argue that emotions are really felt in response to music, whereas cognitivists believe that music is only representative of emotions. Psychophysiological recordings of emotional feelings to music might help to resolve the debate, but past studies have failed to show clear and consistent differences between musical excerpts of different emotional valence. Here, we compared the effects of pleasant and unpleasant musical excerpts on the startle eye blink reflex and associated body markers (such as the corrugator and zygomatic activity, skin conductance level and heart rate). The startle eye blink amplitude was larger and its latency was shorter during unpleasant compared with pleasant music, suggesting that the defensive emotional system was indeed modulated by music. Corrugator activity was also enhanced during unpleasant music, whereas skin conductance level was higher for pleasant excerpts. The startle reflex was the response that contributed the most in distinguishing pleasant and unpleasant music. Taken together, these results provide strong evidence that emotions were felt in response to music, supporting the emotivist stance.