Modulation of cerebellum-dependent learning by amygdala central nucleus efferent pathways

The brain learns associations when certain stimuli in the environment are able to stand out from others. How the brain knows which stimuli to pay attention to depends on a multitude of factors, not only in the environment, but also in the state arousal. The research presented here causally investigates how a forebrain region, the amygdala, can modulate learning in a hindbrain region, the cerebellum. The amygdala has been shown across several species to be necessary in storing cued fear memories. The cerebellum has been shown across several species to be necessary in learning discrete motor movements. To date, the framework offered to understand how these two regions interact has been fear and avoidance learning accelerate learning in the cerebellum. We demonstrate that the amygdala has a long-term role in facilitating learning in the cerebellum in non-threatening (non-fearful) contexts. By optically controlling activity of amygdala neurons, we modulate how quickly the cerebellum learns. We also extended this manipulation to specific connections the amygdala has with other brain areas and found we were able to modulate in different ways how the cerebellum learns.

Overall, the amygdala through its connections with other brain regions can amplify the stimuli used in cerebellum-dependent learning. In one amygdala connection, this is accomplished by enhancing sensory detection, thereby learning predictive values of stimuli faster. In another amygdala connection, learning can be modulated by changing the state of vigilance or attention. We found this modulatory role to be relevant to amygdala-cerebellum interaction in the early and late stages of learning.