Deborah A. Hall PhD - d.hall@ihr.mrc.ac.uk
MRC Institute of Hearing Research
University Park
Nottingham , NG7 2RD, UK
Christopher J. Plack PhD
Department of Psychology,
Lancaster University
Lancaster, LA2 8 QT, UK
Popular version of paper 2aPP5
Presented Tuesday, June 5, 2007 at 10:25 a.m.
153rd ASA Meeting, Salt Lake City, UT
Imagine listening to a piece of orchestral music. The violins set the scene with an opening note, and then a lone trumpet calls. We are able to clearly distinguish between the two instrumental sounds, and yet we can judge that the musicians are playing the same note. Pitch is the most important perceptual dimension of Western music. It is defined as the auditory attribute of sound according to which sounds can be ordered on a scale from low to high. Not only is pitch essential to the appreciation of music, but it also forms one of our dominant auditory sensations. Pitch conveys prosodic information in English and semantic information in tonal languages such as Mandarin, and pitch is also one of the main cues that allow us to separate sounds arising from different sound sources (for example, when two people are speaking at once).
In the laboratory, we can synthesize many different types of pitch-evoking sounds by manipulating the acoustic cues for pitch. The fact that listeners can match these different sounds simply on the basis of their pitch suggests to us that we should be able to identify neurons whose response is governed, not by the simple physical properties of the sound, but by its pitch. Our research investigates where in the auditory brain this neural code might exist. The University of Nottingham (UK) is a world-leading center for neuroimaging research, and here we have used magnetic resonance imaging to provide detailed images of the patterns of neural activity associated with listening to a range of different pitch sounds.
Up to now, the evidence has pointed to a small region in the human auditory brain which is referred to as "lateral Heschl’s gyrus." Some researchers have suggested that this region might function as a general pitch center. Surprisingly, our results appear to contradict this assumption. We have found that, while the one type of pitch sound that has been used most often in experiments of this sort (iterated-ripple noise) does engage lateral Heschl’s gyrus, the other pitch sounds produced larger responses in other brain regions. Typically, we found the pitch response in a part of the auditory brain that was located posterior to lateral Heschl’s gyrus. Therefore the generalized representation of pitch appears to be formed relatively late in the auditory processing stream, probably in the posterior part of the auditory brain.
So the next time you listen to your favorite piece of Mahler, just pause for a moment to think about all those complex brain processes working behind the scenes for you to enjoy the music.