The Journal of Neuroscience, August 15, 1998, 18(16):6388-6394
The Functional Anatomy of Sound Intensity Discrimination
Pascal
Belin1,
Stephen
McAdams2, 3,
Bennet
Smith2,
Sophie
Savel2, 3,
Lionel
Thivard1,
Séverine
Samson4, and
Yves
Samson1, 5
1 Groupe de Neurologie, Service Hospitalier
Frédéric Joliot, DRM-CEA, F-91406 Orsay cedex, France,
2 Institut de Recherche et de Coordination
Acoustique/Musique, F-75004 Paris, France, 3 Laboratoire de
Psychologie Expérimentale (Centre National de la Recherche
Scientifique), Université René Descartes, Équipe de
Neuropsychologie et Langage, F-75006 Paris, France,
4 Université Charles de Gaulle Lille III, BP 149, F-59653 Villeneuve d'Asq cedex, France, and 5 Service des
Urgences Cérébro-Vasculaires, Hôpital de la
Salpêtrière, F-75651 Paris cedex 13, France
The human neuroanatomical substrate of sound intensity
discrimination was investigated by combining psychoacoustics and
functional neuroimaging. Seven normal subjects were trained to detect
deviant sounds presented with a slightly higher intensity than a
standard harmonic sound, using a Go/No Go paradigm. Individual
psychometric curves were carefully assessed using a three-step
psychoacoustic procedure. Subjects were scanned while passively
listening to the standard sound and while discriminating changes in
sound intensity at four different performance levels (d' = 1.5, 2.5, 3.5, and 4.5). Analysis of regional cerebral blood flow data
outlined activation, during the discrimination conditions, of a right
hemispheric frontoparietal network already reported in other studies of
selective or sustained attention to sensory input, and in which
activity appeared inversely proportional to intensity discriminability.
Conversely, a right posterior temporal region included in secondary
auditory cortex was activated during discrimination of sound intensity
independently of performance level. These findings suggest that
discrimination of sound intensity involves two different cortical
networks: a supramodal right frontoparietal network responsible for
allocation of sensory attentional resources, and a region of secondary
auditory cortex specifically involved in sensory computation of sound
intensity differences.
Key words:
audition; attention; intensity discrimination; functional
neuroimaging; psychoacoustics; human; performance level
Copyright © 1998 Society for Neuroscience 0270-6474/98/18166388-07$05.00/0