SEMINAR: Representation of spectral contrast in auditory cortex

The Seminar: The role of early auditory processing may be to extract some elementary features from an acoustic mixture in order to organize the auditory scene. To accomplish this task, the central auditory system may rely on the fact that sensory objects are often composed of spectral edges, i.e. regions where the stimulus energy changes abruptly over frequency. The processing of acoustic stimuli may benefit from a mechanism enhancing the internal representation of spectral edges. While the visual system is thought to rely heavily on this mechanism (enhancing spatial edges), it is still unclear whether a related process plays a significant role in audition. We investigated the cortical representation of spectral edges, using acoustic stimuli composed of multi-tone pips whose time-averaged spectral envelope contained suppressed or enhanced regions. Importantly, the stimuli were designed such that neural responses properties could be assessed as a function of stimulus frequency during stimulus presentation. Our results suggest that the representation of acoustic spectral edges is enhanced in the auditory cortex, and that this enhancement is sensitive to the characteristics of the spectral contrast profile, such as depth, sharpness and width.

The Speaker: Arnaud Norena undertook his PhD at the University of Lyon, France (1998-2001) before accepting a Post Doctorate position at the University of Calgary, Canada (2001-2003). He returned to the University of Lyon in (2003-2007) as an Assistant Professor. Since 2007 he has been an Assistant Professor at the Universite de Provence, France.