Effects of feature-selective attention on auditory pattern and location processing.

Recent neuroimaging studies have suggested that spatial versus nonspatial changes in acoustic stimulation are processed along separate cortical pathways. However, it has remained unclear in how far change-related responses are modulated by selective attention. Thus, we aimed at testing effects of feature-selective attention on the cortical representation of pattern and location of complex natural sounds using human functional magnetic resonance imaging (fMRI) adaptation. We consecutively presented the following pairs of animal vocalizations: (a) two identical animal vocalizations, (b) same animal vocalizations at different locations, (c) different animal vocalizations at the same location, and (d) different animal vocalizations at different locations. Subjects underwent this stimulation under two different task conditions requiring either to match sound identity or location. We observed significant fMRI adaptation effects within the bilateral superior temporal sulcus (STS), planum temporale (PT) and right anterior insula for location changes. For pattern changes, we found adaptation effects within the bilateral superior temporal lobe, in particular along the superior temporal gyrus (STG), PT and posterior STS, the bilateral anterior insula and inferior frontal areas. While the adaptation effects within the pattern-selective temporal lobe areas were robust to task requirements, adaptation within the more posterior location-selective areas was modulated by feature-specific attention. In contrast, inferior frontal cortex and anterior insular exhibited adaptation effects mainly during the location matching task. Given that the location matching task was significantly more difficult than the pattern matching, our data suggest that frontal and insular regions were modulated by task difficulty rather than feature-specific attention.