Two fiber pathways connecting amygdala and prefrontal cortex in humans and monkeys

The interactions between amygdala and prefrontal cortex are pivotal to many neural processes involved in learning, decision-making, emotion, and social regulation. The broad functional role of amygdala-prefrontal interplay may reflect the diversity of its anatomical connections. Little, however, is known of the structural wiring linking amygdala and prefrontal cortex in humans. Using diffusion imaging techniques, we reconstructed connections between amygdala, anterior temporal and prefrontal cortex in human and macaque brains. First, by studying macaques we were able to assess which aspects of connectivity known from tracer studies could be identified with diffusion imaging. Second, by comparing diffusion imaging results in humans and macaques we were able to estimate amygdala-prefrontal connection patterns in humans and compare them with those in the monkey. We observed a prominent and well-preserved bifurcation of connections between amygdala and frontal lobe into two fiber networks – an amygdalofugal path and an uncinate fascicle path – in both species.