On the role of the human amygdala : Mapping functions and individual variations using fMRI

Abstract

Decades of research have demonstrated a role for the amygdala in various psychiatric and neurological disorders. Still, the functional role of this brain structure and the biological mechanisms causing individual variation in amygdala function is not fully elucidated. In the present thesis we investigated a new and alternative role for the human amygdala in encoding or calculation of an event’s relevance. Amygdala activity was measured using functional MRI while subjects performed tasks encompassing high and low relevant stimuli. Secondly, we searched for biological mechanisms, i.e. gene variants, causing individual variation in amygdala functional activity by combining genome-wide data and functional imaging phenotypes from a Norwegian sample. We have made novel and important findings which imply that amygdala is important for relevance detection. Futher, we found a genome-wide significant association with a gene variant possibly affecting the expression of monoamines (i.e. dopamine and noradrenalin) within the amygdala. Thus, the individual’s response to relevant events may depend on genetic variation within monoaminergic signaling pathways. Disproportional encoding or calculation of relevance may be an important component in the observed social and cognitive impairments among patients with amygdala pathology. If so, one could speculate that pharmacological agents, which normalize amygdala function, may also reduce these impairments.