The aim of this study is to use fMRI in order to characterize amygdaloid-complex function in human olfaction.
This aim will be achieved through the following specific aims: 1. To discern which subunits of the human amygdaloid complex are involved in olfactory processing, and which are not. The amygdala is not one homogeneous nucleus, but rather a group of structures, referred to as the amygdaloid complex. State-of-the-art neuroimaging methods (event related design combined with high-field-strength high-resolution fMRI) will be used to determine which portion of the amygdaloid complex is involved in olfactory processing in humans. 2. To test the hypothesis that the amygdaloid complex is encoding the intensity of odorants. A major underlying theme on the role of the amygdala in the encoding of sensory input is that it is encoding stimulus intensity. This hypothesis will be directly addressed by measuring with fMRI the amygdala response to various concentrations (intensities) of odorants regardless of valance. 3. To test the hypothesis that the amygdaloid complex is encoding the valance of odorants. A competing to the above underlying theme on the role of the amygdala in the encoding of sensory input, is that it is encoding stimulus valance. This hypothesis will be directly addressed by measuring with fMRI the amygdala response to different odorants varying in valance but not intensity. Achievement of the above aims will pose a significant contribution to the systems-level characterization of the human olfactory system. This study will both pinpoint a component of primary olfactory cortex in humans, and elucidate its role in olfactory processing. In addition, this study will have used olfaction (as opposed to vision and audition) as a path by which to probe the role of the amygdala in sensory processing in general. In that, this study will further our understanding of human brain function, opening avenues to the understanding of the healthy brain and treatment of the diseased brain.