Over the last years functional MRI has become the primary method for non-invasive assessment of brain activity. Its application in deep brain structures, however, is still limited. Here we report on two studies showing that the use of optimum sequence parameters combined with physiological artefact correction allow activation in human amygdala and hypothalamus to be robustly detected.
Study I (focused on the amygdala region) included 50 healthy subjects (25 females) who were asked to identify facial emotions in validated visual stimuli. FMRI was performed using high-resolution gradient-recalled EPI. Analysis in SPM aimed at assessing brain activation to all five emotions (happy, sad, fear, anger, disgust) and neutral expressions. Study II was aimed at revealing arousal-specific modulation of hypothalamic activation using visual stimuli containing funny, neutral or sad scenes, respectively, in a group of 20 participants (4 females). Analysis was also performed in SPM.
Application of the optimized, high-resolution protocol enabled reliable measurement of bilateral amygdala activation during the processing of all basic emotions and neutral expressions. ANOVA of hypothalamic fMRI revealed significant modulation of activation over stimulus valence, and post-hoc testing showed significantly higher activation in both sad and funny as compared to neutrally valenced stimuli.
Robust and reliable bilateral amygdala and hypothalamus activation was detected in our studies, reflecting the importance of applying optimized protocols when imaging ventral brain function. To improve sensitivity and specificity to enable individual diagnosis, further advances are needed, requiring more sensitive coils and higher field strength. Potential clinical applications include sleep, eating and emotional disorders.