ELUCIDATING DYNAMIC BRAIN INTERACTIONS WITH ACROSS-SUBJECTS CORRELATIONAL ANALYSES OF POSITRON EMISSION TOMOGRAPHIC DATA - THE FUNCTIONAL CONNECTIVITY OF THE AMYGDALA AND ORBITOFRONTAL CORTEX DURING OLFACTORY TASKS

Covariance analyses of positron emission tomography (PET) data are use d increasingly to elucidate the functional connectivity between brain regions during different cognitive tasks. Functional connectivity may be estimated by examining the covariance between regions over time or across subjects. In functional brain-mapping studies, across-subjects covariance matrices derived from within-task (nonsubtracted) and betwe en-task (subtracted) data characterize different. complementary aspect s of functional interactions. The authors conditions (aversive olfacti on, odor detection, and resting with eyes closed) to illustrate the st rengths and limitations of across-subjects covariance analyses based o n subtracted and nonsubtracted data. This example underscores the dyna mic nature of connectivity between the amygdalae and orbitofrontal cor tices and highlights the importance of including data from resting con ditions in covariance analyses.