Figure 2.

A, Mean fMRI time courses during the dual-stream selective attention experiment (across all subjects and hemispheres, n = 12) smoothed with a Gaussian (half-width = 8 s). Time courses were extracted from all voxels of primary auditory cortex labeled as preferring 250 Hz (light gray) and 4000 Hz (dark gray) in each subject and hemisphere based on individual subject tonotopic mappings. The responses of 4000 Hz-preferring voxels increased during attend high blocks and decreased during attend low blocks, and vice versa for 250 Hz-preferring voxels. B, Frequency attention. Bars show the mean difference in response between attend high and attend low blocks across all voxel bins in primary auditory cortex with all frequency preferences. C, Spatial attention. Bars show the mean difference in response between attend contralateral and attend ipsilateral blocks. D, Modulation in single-stream experiment. Bars show the mean difference in response between high and low blocks measured in separate scans in which the stimulus physically alternated between high-only and low-only streams. Note change in y-axis scale. Comparing the amplitudes in B and C, feature-selective attention outweighed effects of spatial attention by a factor of ∼5. Comparing the amplitudes of B and D, frequency attention modulation was 18.6% as large as stimulus-driven modulation in 250 Hz voxels and 56.2% as large in 4000 Hz voxels, a robust modulatory effect. Error bars show SEM across all subjects and hemispheres, n = 12.