Representation of Sound Categories in Auditory Cortical Maps Functional magnetic resonance imaging (fMRI) was used to investigate the representation of sound categories in human auditory cortex. Experiment 1 investigated the representation of prototypical (good) and nonprototypical (bad) examples of a vowel sound. Listening to prototypical examples of a vowel resulted in less auditory cortical activation than did listening ... Research Article
Research Article  |   February 01, 2004
Representation of Sound Categories in Auditory Cortical Maps
 
Author Affiliations & Notes
  • Frank H. Guenther
    Boston University and Massachusetts Institute of Technology, Cambridge
  • Alfonso Nieto-Castanon
    Boston University
  • Satrajit S. Ghosh
    Boston University
  • Jason A. Tourville
    Boston University and Center for Morphometric Analysis, Massachusetts General Hospital, Charlestown
  • Contact author: Frank Guenther, PhD, Department of Cognitive and Neural Systems, Boston University, 677 Beacon Street, Boston, MA 02115. e-mail: guenther@cns.bu.edu
Article Information
Hearing & Speech Perception / Acoustics / Healthcare Settings / International & Global / Attention, Memory & Executive Functions / Speech, Voice & Prosody / Speech / Research Articles
Research Article   |   February 01, 2004
Representation of Sound Categories in Auditory Cortical Maps
Journal of Speech, Language, and Hearing Research, February 2004, Vol. 47, 46-57. doi:10.1044/1092-4388(2004/005)
History: Received December 9, 2002 , Accepted June 4, 2003
 
Journal of Speech, Language, and Hearing Research, February 2004, Vol. 47, 46-57. doi:10.1044/1092-4388(2004/005)
History: Received December 9, 2002; Accepted June 4, 2003
Web of Science® Times Cited: 68

Functional magnetic resonance imaging (fMRI) was used to investigate the representation of sound categories in human auditory cortex. Experiment 1 investigated the representation of prototypical (good) and nonprototypical (bad) examples of a vowel sound. Listening to prototypical examples of a vowel resulted in less auditory cortical activation than did listening to nonprototypical examples. Experiments 2 and 3 investigated the effects of categorization training and discrimination training with novel nonspeech sounds on auditory cortical representations. The 2 training tasks were shown to have opposite effects on the auditory cortical representation of sounds experienced during training: Discrimination training led to an increase in the amount of activation caused by the training stimuli, whereas categorization training led to decreased activation. These results indicate that the brain efficiently shifts neural resources away from regions of acoustic space where discrimination between sounds is not behaviorally important (e.g., near the center of a sound category) and toward regions where accurate discrimination is needed. The results also provide a straightforward neural account of learned aspects of perceptual distortion near sound categories: Sounds from the center of a category are more difficult to discriminate from each other than sounds near category boundaries because they are represented by fewer cells in the auditory cortical areas.

Acknowledgments
We thank Julie Goodman, Jennifer Holmes, Fatima Husain, Bruce Rosen, David Kennedy, Andrew Worth, and Mark Shiffer for their assistance. We also thank the Massachusetts General Hospital NMR Center for the use of their facilities. This research was supported by National Institute on Deafness and Other Communication Disorders Grant R01 DC02852 (F. Guenther, Principal Investigator).
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