Short- and long-term memory for pitch and non-pitch contours: Insights from congenital amusia.
Congenital amusia is a neurodevelopmental disorder characterized by deficits in music perception, including discriminating and remembering melodies and melodic contours. As non-amusic listeners can perceive contours in dimensions other than pitch, such as loudness and brightness, our present study investigated whether amusics' pitch contour deficits also extend to these other auditory dimensions. Amusic and control participants performed an identification task for ten familiar melodies and a short-term memory task requiring the discrimination of changes in the contour of novel four-tone melodies. For both tasks, melodic contour was defined by pitch, brightness, or loudness. Amusic participants showed some ability to extract contours in all three dimensions. For familiar melodies, amusic participants showed impairment in all conditions, perhaps reflecting the fact that the long-term memory representations of the familiar melodies were defined in pitch. In the contour discrimination task with novel melodies, amusic participants exhibited less impairment for loudness-based melodies than for pitch- or brightness-based melodies, suggesting some specificity of the deficit for spectral changes, if not for pitch alone. The results suggest pitch and brightness may not be processed by the same mechanisms as loudness, and that short-term memory for loudness contours may be spared to some degree in congenital amusia.