Fig. 1.
Task and imaging protocol. A, A series of neutral faces (top row) was paired with odors (middle row) that varied in pleasantness. Under 50% reinforcement, only one-half of all faces were paired with odor. A brightening of a cross-hair (bottom row, +) was used to prompt the subject to sniff. The four faces and three odors comprised seven different event types and are depicted schematically. See Materials and Methods for abbreviations and further details.B, Functional images were acquired in an oblique orientation tilted at 30°. On the left, the plane of acquisition and the effective brain coverage are shown overlaid on a subject's sagittal T1-weighted scan. The resulting echoplanar image (z = −22) averaged from 15 subjects is shown beside an image obtained using a standard (untilted) acquisition sequence (average of 11 subjects). Preservation of signal is apparent in the basal frontal and medial temporal lobes. Signal dropout is also diminished in lateral posterior temporal areas.