Possible roles of orbitofrontal-amygdala loop in modulation of basal ganglia activation

In the last years research on emotion focused on the role of amygdala-orbitofrontal loops in learning associations between internal states of the organism and external context, and in modulating choice behaviour. Amygdala is now thought to participate actively in current reward value-response learning. Furthermore, amygdala seems to act as an effector of choice behaviour elaboration in orbitofrontal cortex. The influence of amygdala-orbitofrontal loop in reward behaviours and choice behaviours probably passes through its output connections to corticostriatal loop (input from basolateral nuclei of amygdala to nucleus accumbens). At the same time, amygdala modulates hypothalamus and brain stem arousal and controls such systems through pathways mainly running from the amygdala’s central nucleus to brain stem. Habit learning does not require amygdala’s processing. Overall, these findings gives evidence of the existence of two different systems involved in reward-based behaviour, one more dynamic and related to the mapping between the actual context and inner states, and the other, more stable and acquired over long periods of time, relatively independent of actual inners states.