Unsmoothed functional MRI of the human amygdala and bed nucleus of the stria terminalis during processing of emotional faces.

Functional neuroimaging of the human amygdala has been of great interest to uncover the neural underpinnings of emotions, mood, motivation, social cognition, and decision making, as well as their dysfunction in psychiatric disorders. Yet, several factors limit in vivo imaging of amygdalar function, most importantly its location deep within the temporal lobe adjacent to air-filled cavities that cause magnetic field inhomogeneities entailing signal dropouts. Additionally, the amygdala and the extended amygdalar region consist of several substructures, which have been assigned different functions and have important implications for functional and effective connectivity studies. Here we show that high-resolution ultra-high field fMRI at 7T can be used to overcome these fundamental challenges for acquisition and can meet some of the demands posed by the complex neuroanatomy and -physiology in this region. Utilizing the inherently high SNR, we use an optimized preprocessing and data analysis strategy to demonstrate that imaging of the (extended) amygdala is highly reliable and robust. Using unsmoothed single-subject data allowed us to differentiate brain activation during processing of emotional faces in the central and basolateral amygdala and, for the first time, in the bed nucleus of the stria terminalis (BNST), which is critically involved in the neural mechanisms of anxiety and threat monitoring. We also provide a quantitative assessment of single subject sensitivity, which is relevant for connectivity studies that rely on time course extraction of functionally-defined volumes of interest.