Cerebral Cortex Advance Access originally published online on September 24, 2007
Cerebral Cortex 2008 18(6):1350-1360; doi:10.1093/cercor/bhm166
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Temporal Dynamics of Adaptation to Natural Sounds in the Human Auditory Cortex
1 Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan, 2 Institute of Medical Psychology, Johann-Wolfgang-Goethe University, 60528 Frankfurt am Main, Germany, 3 Department of Health Sciences, Faculty of Medicine, Nagoya University, Higashi-ku, Nagoya 461-8673, Japan
Address correspondence to Christian F. Altmann, Institute of Medical Psychology, Heinrich-Hoffmann-Strasse 10, 60528 Frankfurt am Main, Germany. Email: C.Altmann{at}med.uni-frankfurt.de.
We aimed at testing the cortical representation of complex natural sounds within auditory cortex by conducting 2 human magnetoencephalography experiments. To this end, we employed an adaptation paradigm and presented subjects with pairs of complex stimuli, namely, animal vocalizations and spectrally matched noise. In Experiment 1, we presented stimulus pairs of same or different animal vocalizations and same or different noise. Our results suggest a 2-step process of adaptation effects: first, we observed a general item-unspecific reduction of the N1m peak amplitude at 100 ms, followed by an item-specific amplitude reduction of the P2m component at 200 ms after stimulus onset for both animal vocalizations and noise. Multiple dipole source modeling revealed the right lateral Heschl's gyrus and the bilateral superior temporal gyrus as sites of adaptation. In Experiment 2, we tested for cross-adaptation between animal vocalizations and spectrally matched noise sounds, by presenting pairs of an animal vocalization and its corresponding or a different noise sound. We observed cross-adaptation effects for the P2m component within bilateral superior temporal gyrus. Thus, our results suggest selectivity of the evoked magnetic field at 200 ms after stimulus onset in nonprimary auditory cortex for the spectral fine structure of complex sounds rather than their temporal dynamics.
Key Words: animal vocalizations complex sounds MEG repetition suppression